build: update gnulib submodule to latest

bison: allow trivially copyable C++ YYLTYPE
Problem reported by James K. Lowden in: https://lists.gnu.org/r/bison-patches/2026-07/msg00000.html * data/skeletons/yacc.c: In C++, check that YYLTYPE is trivially copyable if this is not already known. But skip the check in older compilers.
2026-08-08 10:15:14 +00:00 · 2026-07-30 08:36:29 -07:00 · 2026-07-21 12:52:53 -07:00 · 2026-07-21 12:52:53 -07:00 · 2026-07-21 12:52:53 -07:00 · 2026-07-21 12:52:53 -07:00
321 changed files with 31149 additions and 8430 deletions
@@ -1 +1,2 @@
-
+*.at   diff=autotest
+*.texi diff=texinfo
@@ -0,0 +1,12 @@
+# To use this gitconfig file, run
+#
+# git config --local include.path ../.gitconfig
+#
+# It adds an `[include]` section in .git/config.
+# See <https://git-scm.com/docs/git-config#_includes>.
+
+[diff "autotest"]
+        xfuncname = "^((m4_define|m4_pushdef|AT_SETUP).*)$"
+
+[diff "texinfo"]
+        xfuncname = "^@node .*$"
@@ -1,10 +1,19 @@
+*.a
+*.bak
+*.diff
+*.exe
 *.log
 *.o
+*.orig
+*.out
+*.output
 *.pdf
+*.rej
 *.stamp
+*.tmp
 *.trs
 *~
-.deps
+.deps/
 .dirstamp
 /*.cache
 /*.flc
@@ -20,11 +29,9 @@
 /Makefile.in
 /README-release
 /_*
-/a.exe
-/a.out
 /aclocal.m4
-/b.out
 /bison-*
+/build-aux/move-if-change
 /conf[0-9]*
 /confdefs*
 /config.log
@@ -1 +1 @@
-3.6.1
+3.8.2
@@ -29,12 +29,13 @@ jobs:
        clone: true
      dist: bionic
      script:
-        - sudo apt-get install -qq autoconf automake autopoint flex gettext graphviz help2man m4 texinfo
+        - sudo apt-get install -qq autoconf automake autopoint flex gettext gperf graphviz help2man m4 texinfo
        - autoconf --version
        - automake --version
        - autopoint --version
        - dot -V
        - gettext --version
+        - gperf --version
        - help2man --version
        - makeinfo --version
        - m4 --version
@@ -43,12 +44,15 @@ jobs:
        - git fetch --unshallow || true
        - git submodule update --init --recursive

+        # As of 2021-08, we don't have Autoconf 2.71 on Ubuntu.
+        - sed -i 's/AC_PREREQ(\[2\.71])/AC_PREREQ([2.69])/g' configure.ac
        - ./bootstrap
        - ./configure --enable-gcc-warnings || { cat config.log && false; }
        - make -j2
        - make -j2 dist-xz
        # Can help understanding why we get "dirty" tarballs.
        - git status
+        - git diff
        - dist=$(echo bison*.xz)

        # Unfortunately we cannot deterministically know the name of the tarball without the full
@@ -69,55 +73,57 @@ jobs:

    # Start with three completely different environments, to get errors asap.

-    - name: "GCC 10 -O3"
+    - name: "GCC 11 -O3"
      stage: check
      os: linux
      dist: bionic
-      addons: &gcc10
+      addons: &gcc11
        apt:
          sources:
            # See https://github.com/travis-ci/apt-source-safelist/issues/410.
            - sourceline: 'ppa:ubuntu-toolchain-r/test'
-          packages: g++-10
+          packages: g++-11
      env:
-        - CC=gcc-10
-        - CXX=g++-10
+        - CC=gcc-11
+        - CXX=g++-11
        - CONFIGUREFLAGS='CPPFLAGS=-DNDEBUG CFLAGS=-O3 CXXFLAGS=-O3'

    # ASAN is time consuming, and we timeout the 50min granted by
    # Travis if we run all the tests in one go.  Run in two parts.
-    - name: "Clang 10 libc++ and ASAN part 1"
+    - name: "Clang 11 libc++ and ASAN part 1"
      stage: check
      os: linux
      dist: bionic
-      addons: &clang10
+      addons: &clang11
        apt:
          sources:
            # See https://github.com/travis-ci/apt-source-safelist/issues/410.
            - sourceline: 'ppa:ubuntu-toolchain-r/test'
-            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
          packages:
-            - clang-10
-            - libc++-10-dev
-            - libc++abi-10-dev
+            - clang-11
+            - libc++-11-dev
+            - libc++abi-11-dev
      env:
        # Do not use ASAN with ubuntu's libc++: https://bugs.llvm.org/show_bug.cgi?id=17379
-        - CC='clang-10 -fsanitize=address'
-        - CXX='clang++-10 -fsanitize=address -stdlib=libc++'
+        - CC='clang-11 -fsanitize=address'
+        - CXX='clang++-11 -fsanitize=address -stdlib=libc++'
        - PART=1

-    - name: "Clang 10 libc++ and ASAN part 2"
+    - name: "Clang 11 libc++ and ASAN part 2"
      stage: check
      os: linux
      dist: bionic
-      addons: *clang10
+      addons: *clang11
      env:
        # Do not use ASAN with ubuntu's libc++: https://bugs.llvm.org/show_bug.cgi?id=17379
-        - CC='clang-10 -fsanitize=address'
-        - CXX='clang++-10 -fsanitize=address -stdlib=libc++'
+        - CC='clang-11 -fsanitize=address'
+        - CXX='clang++-11 -fsanitize=address -stdlib=libc++'
        - PART=2

+    # See https://github.com/simd-everywhere/simde/blob/master/.travis.yml
+    # and https://software.intel.com/content/www/us/en/develop/documentation/get-started-with-intel-oneapi-render-linux/top/configure-your-system.html.
    - name: "ICC"
      stage: check
      os: linux
@@ -126,7 +132,7 @@ jobs:
        - CC=icc
        - CXX=icpc
      install:
-        - source /opt/intel/inteloneapi/compiler/latest/env/vars.sh
+        - source /opt/intel/oneapi/compiler/latest/env/vars.sh
      addons:
        apt:
          sources:
@@ -135,49 +141,69 @@ jobs:
          packages:
          - intel-oneapi-icc

-    - name: "ARM64: GCC 10 -O3 part 1"
+    - name: "ARM64: GCC 11 -O2 part 1"
      stage: check
      os: linux
      arch: arm64
      dist: bionic
-      addons: *gcc10
+      addons: *gcc11
      env:
-        - CC=gcc-10
-        - CXX=g++-10
-        - CONFIGUREFLAGS='CPPFLAGS=-DNDEBUG CFLAGS=-O3 CXXFLAGS=-O3'
+        - CC=gcc-11
+        - CXX=g++-11
+        - CONFIGUREFLAGS='CPPFLAGS=-DNDEBUG CFLAGS=-O2 CXXFLAGS=-O2'
        - PART=1

-    # GCC10 on PPC seems to be buggy.
-    # E.g., https://travis-ci.org/github/akimd/bison/jobs/687812428.
-    - name: "PPC64le: GCC 9 part 1"
+    - name: "PPC64le: GCC 11 -O2 part 1"
      stage: check
      os: linux
      arch: ppc64le
      dist: bionic
-      addons: *gcc10
+      addons:
+        apt:
+          sources:
+            # See https://github.com/travis-ci/apt-source-safelist/issues/410.
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+          packages: g++-11
      env:
-        - CC=gcc-9
-        - CXX=g++-9
-        - CONFIGUREFLAGS='CFLAGS=-O3 CXXFLAGS=-O3'
+        - CC=gcc-11
+        - CXX=g++-11
+        - CONFIGUREFLAGS='CFLAGS=-O2 CXXFLAGS=-O2'
        - PART=1

-    - name: "s390x: GCC 10 part 1"
+    - name: "s390x: GCC 11 -O2 part 1"
      stage: check
      os: linux
      arch: s390x
      dist: bionic
-      addons: *gcc10
+      addons: *gcc11
      env:
-        - CC=gcc-10
-        - CXX=g++-10
-        - CONFIGUREFLAGS='CFLAGS=-O3 CXXFLAGS=-O3'
+        - CC=gcc-11
+        - CXX=g++-11
+        - CONFIGUREFLAGS='CFLAGS=-O2 CXXFLAGS=-O2'
        - PART=1

    ## ----- ##
    ## GCC.  ##
    ## ----- ##

-    - name: "GCC 9 with sanitizers part 1"
+    - name: "GCC 10 with sanitizers part 1"
+      stage: check
+      os: linux
+      dist: bionic
+      addons:
+        apt:
+          sources:
+            # See https://github.com/travis-ci/apt-source-safelist/issues/410.
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+          packages: g++-10
+      env:
+        - CC='gcc-10 -fsanitize=undefined,address -fno-omit-frame-pointer'
+        - CXX='g++-10 -fsanitize=undefined,address -fno-omit-frame-pointer'
+        - CONFIGUREFLAGS='CFLAGS=-O1 CXXFLAGS=-O1'
+        - PART=1
+
+    # With glr2.cc, we run out of time with the full test suite.
+    - name: "GCC 9 part 1"
      stage: check
      os: linux
      dist: bionic
@@ -188,12 +214,12 @@ jobs:
            - sourceline: 'ppa:ubuntu-toolchain-r/test'
          packages: g++-9
      env:
-        - CC='gcc-9 -fsanitize=undefined,address -fno-omit-frame-pointer'
-        - CXX='g++-9 -fsanitize=undefined,address -fno-omit-frame-pointer'
-        - CONFIGUREFLAGS='CFLAGS=-O1 CXXFLAGS=-O1'
+        - CC=gcc-9
+        - CXX=g++-9
        - PART=1

-    - name: "GCC 8"
+    # With glr2.cc, we run out of time with the full test suite.
+    - name: "GCC 8 part 1"
      stage: check
      os: linux
      dist: bionic
@@ -203,6 +229,7 @@ jobs:
      env:
        - CC=gcc-8
        - CXX=g++-8
+        - PART=1

    - name: "GCC 7"
      stage: check
@@ -291,7 +318,28 @@ jobs:
    ## Clang.  ##
    ## ------- ##

-    - name: "Clang 9 -O3"
+    - name: "Clang 10 -O3, libc++, part 1"
+      stage: check
+      os: linux
+      dist: bionic
+      addons:
+        apt:
+          sources:
+            # See https://github.com/travis-ci/apt-source-safelist/issues/410.
+            - sourceline: 'ppa:ubuntu-toolchain-r/test'
+            - sourceline: 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - clang-10
+            - libc++-10-dev
+            - libc++abi-10-dev
+      env:
+        - CC='clang-10'
+        - CXX='clang++-10 -stdlib=libc++'
+        - CONFIGUREFLAGS='CPPFLAGS=-DNDEBUG CFLAGS=-O3 CXXFLAGS=-O3'
+        - PART=1
+
+    - name: "Clang 9 and libc++"
      stage: check
      os: linux
      dist: bionic
@@ -309,9 +357,8 @@ jobs:
      env:
        - CC='clang-9'
        - CXX='clang++-9 -stdlib=libc++'
-        - CONFIGUREFLAGS='CPPFLAGS=-DNDEBUG CFLAGS=-O3 CXXFLAGS=-O3'

-    - name: "Clang 8"
+    - name: "Clang 8 and libc++"
      stage: check
      os: linux
      dist: bionic
@@ -325,7 +372,7 @@ jobs:
        - CC=clang-8
        - CXX='clang++-8 -stdlib=libc++'

-    - name: "Clang 7"
+    - name: "Clang 7 and libc++"
      stage: check
      os: linux
      dist: bionic
@@ -24,7 +24,8 @@ and nasty bugs.

 -----

-Copyright (C) 1998-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 1998-2015, 2018-2022, 2025-2026 Free Software Foundation,
+Inc.

 This file is part of Bison, the GNU Compiler Compiler.

@@ -39,4 +40,4 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
@@ -1,7 +1,7 @@
                    GNU GENERAL PUBLIC LICENSE
                       Version 3, 29 June 2007

- Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

@@ -645,7 +645,7 @@ the "copyright" line and a pointer to where the full notice is found.
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.

 Also add information on how to contact you by electronic and paper mail.

@@ -664,11 +664,11 @@ might be different; for a GUI interface, you would use an "about box".
  You should also get your employer (if you work as a programmer) or school,
 if any, to sign a "copyright disclaimer" for the program, if necessary.
 For more information on this, and how to apply and follow the GNU GPL, see
-<http://www.gnu.org/licenses/>.
+<https://www.gnu.org/licenses/>.

  The GNU General Public License does not permit incorporating your program
 into proprietary programs.  If your program is a subroutine library, you
 may consider it more useful to permit linking proprietary applications with
 the library.  If this is what you want to do, use the GNU Lesser General
 Public License instead of this License.  But first, please read
-<http://www.gnu.org/philosophy/why-not-lgpl.html>.
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
@@ -1,6 +1,7 @@
 ## Process this file with automake to produce Makefile.in.

-# Copyright (C) 2001-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2001-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,7 +14,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 AUTOMAKE_OPTIONS = subdir-objects
 ACLOCAL_AMFLAGS = -I m4
@@ -76,6 +77,13 @@ include tests/local.mk
 clean-local:
 	rm -rf $(CLEANDIRS)

+.PHONY: gitsort
+gitsort:
+	cd $(srcdir)							\
+	&& for i in $$(git ls-files '*.gitignore' | grep -v doc); do	\
+	  LC_ALL=C sort $$i -o $$i;					\
+	done
+
 # See comments in build-aux/git-version-gen.  However, we make .version depend
 # on configure so that .version and VERSION/PACKAGE_VERSION stay in sync in the
 # working copy (for example, when you run autoreconf && make).  Allowing these
@@ -131,3 +139,12 @@ gen-ChangeLog:
 # Useful to debug.
 .c.i:
 	$(CC) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -o $@ -E $<
+
+.PHONY: codespell
+CODESPELL = codespell
+codespell:
+	$(AM_V_GEN) cd $(srcdir) \
+	&& $(CODESPELL) \
+	     --regex "[\\w\\-'’\`]+\+*" \
+	     --ignore-words-list "ba,circularly,cloneable,copyable,define'd,dout,froms,iff,ifset,od,ois" \
+	     $$(git ls-files data doc lib src tests)
@@ -36,8 +36,8 @@ to the bison package.

 -----

-Copyright (C) 2002, 2005, 2009-2015, 2018-2020 Free Software Foundation,
-Inc.
+Copyright (C) 2002, 2005, 2009-2015, 2018-2022, 2025-2026 Free Software
+Foundation, Inc.

 This file is part of Bison, the GNU Compiler Compiler.

@@ -52,4 +52,4 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
@@ -7,7 +7,7 @@ simple desk calculators to complex programming languages.

 Bison is upward compatible with Yacc: all properly-written Yacc grammars
 work with Bison with no change.  Anyone familiar with Yacc should be able to
-use Bison with little trouble.  You need to be fluent in C, C++ or Java
+use Bison with little trouble.  You need to be fluent in C, C++, D or Java
 programming in order to use Bison.

 Bison and the parsers it generates are portable, they do not require any
@@ -17,17 +17,18 @@ GNU Bison's home page is https://gnu.org/software/bison/.

 # Installation
 ## Build from git
-Here are basic installation instructions for a repository checkout:
+The [README-hacking.md file](README-hacking.md) is about building, modifying
+and checking Bison.  See its "Working from the Repository" section to build
+Bison from the git repo.  Roughly, run:

    $ git submodule update --init
    $ ./bootstrap

 then proceed with the usual `configure && make` steps.

-The file README-hacking.md is about building, modifying and checking Bison.
-
 ## Build from tarball
-See the file INSTALL for generic compilation and installation instructions.
+See the [INSTALL file](INSTALL) for generic compilation and installation
+instructions.

 Bison requires GNU m4 1.4.6 or later.  See
 https://ftp.gnu.org/gnu/m4/m4-1.4.6.tar.gz.
@@ -41,9 +42,11 @@ installing it.  In that case, do not use `src/bison`: it would use the
 As an experimental feature, diagnostics are now colored, controlled by the
 `--color` and `--style` options.

-To use them, install the libtextstyle library before configuring Bison.  It
-is available from https://alpha.gnu.org/gnu/gettext/, for instance
-https://alpha.gnu.org/pub/gnu/gettext/libtextstyle-0.20.5.tar.gz.
+To use them, install the libtextstyle library, 0.20.5 or newer, before
+configuring Bison.  It is available from https://alpha.gnu.org/gnu/gettext/,
+for instance https://alpha.gnu.org/gnu/gettext/libtextstyle-0.20.5.tar.gz,
+or as part of Gettext 0.21 or newer, for instance
+https://ftp.gnu.org/gnu/gettext/gettext-0.21.tar.gz.

 The option --color supports the following arguments:
 - always, yes: Enable colors.
@@ -60,6 +63,13 @@ To customize the styles, create a CSS file, say `bison-bw.css`, similar to
 then invoke bison with `--style=bison-bw.css`, or set the `BISON_STYLE`
 environment variable to `bison-bw.css`.

+In some diagnostics, bison uses libtextstyle to emit special escapes to
+generate clickable hyperlinks.  The environment variable
+`NO_TERM_HYPERLINKS` can be used to suppress them.  This may be useful for
+terminal emulators which produce garbage output when they receive the escape
+sequence for a hyperlink. Currently (as of 2020), this affects some versions
+of emacs, guake, konsole, lxterminal, rxvt, yakuake.
+
 ## Relocatability
 If you pass `--enable-relocatable` to `configure`, Bison is relocatable.

@@ -77,7 +87,7 @@ for the user-side parser execution).  The requirements between both differ:
 bison needs ngettext, the generated parsers do not.  To simplify the build
 system, neither are installed if ngettext is not supported, even if
 generated parsers could have been localized.  See
-http://lists.gnu.org/archive/html/bug-bison/2009-08/msg00006.html for more
+https://lists.gnu.org/r/bug-bison/2009-08/msg00006.html for more
 details.

 # Questions
@@ -100,8 +110,18 @@ that the range specifies every single year in that closed interval.

 <!--

-Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018-2020 Free
-Software Foundation, Inc.
+LocalWords:  parsers ngettext Texinfo pdf html YYYY ZZZZ ispell american md
+LocalWords:  MERCHANTABILITY GLR LALR IELR submodule init README src bw
+LocalWords:  Relocatability symlinks symlink
+
+Local Variables:
+mode: markdown
+fill-column: 76
+ispell-dictionary: "american"
+End:
+
+Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018-2022,
+2025-2026 Free Software Foundation, Inc.

 This file is part of GNU bison, the GNU Compiler Compiler.

@@ -112,14 +132,4 @@ Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
 Texts.  A copy of the license is included in the "GNU Free
 Documentation License" file as part of this distribution.

-Local Variables:
-mode: markdown
-fill-column: 76
-ispell-dictionary: "american"
-End:
-
-LocalWords:  parsers ngettext Texinfo pdf html YYYY ZZZZ ispell american md
-LocalWords:  MERCHANTABILITY GLR LALR IELR submodule init README src bw
-LocalWords:  Relocatability symlinks symlink
-
 -->
@@ -12,8 +12,8 @@ the problems you encounter.

 -----

-Copyright (C) 2002, 2004, 2009-2015, 2018-2020 Free Software Foundation,
-Inc.
+Copyright (C) 2002, 2004, 2009-2015, 2018-2022, 2025-2026 Free Software
+Foundation, Inc.

 This file is part of GNU Bison.

@@ -28,4 +28,4 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
@@ -2,152 +2,7 @@ This file attempts to describe the rules to use when hacking Bison.
 Don't put this file into the distribution.

 Everything related to the development of Bison is on Savannah:
-http://savannah.gnu.org/projects/bison/.
-
-
-Administrivia
-=============
-
-## If you incorporate a change from somebody on the net:
-First, if it is a large change, you must make sure they have signed the
-appropriate paperwork.  Second, be sure to add their name and email address
-to THANKS.
-
-## If a change fixes a test, mention the test in the commit message.
-
-## Bug reports
-If somebody reports a new bug, mention his name in the commit message and in
-the test case you write.  Put him into THANKS.
-
-The correct response to most actual bugs is to write a new test case which
-demonstrates the bug.  Then fix the bug, re-run the test suite, and check
-everything in.
-
-
-
-Hacking
-=======
-
-## Visible Changes
-Which include serious bug fixes, must be mentioned in NEWS.
-
-## Translations
-Only user visible strings are to be translated: error messages, bits of the
-.output file etc.  This excludes impossible error messages (comparable to
-assert/abort), and all the --trace output which is meant for the maintainers
-only.
-
-## Syntax highlighting
-It's quite nice to be in C++ mode when editing lalr1.cc for instance.
-However tools such as Emacs will be fooled by the fact that braces and
-parens do not nest, as in `[[}]]`.  As a consequence you might be misguided
-by its visual pairing to parens.  The m4-mode is safer.  Unfortunately the
-m4-mode is also fooled by `#` which is sees as a comment, stops pairing with
-parens/brackets that are inside...
-
-## Coding Style
-Do not add horizontal tab characters to any file in Bison's repository
-except where required.  For example, do not use tabs to format C code.
-However, make files, ChangeLog, and some regular expressions require tabs.
-Also, test cases might need to contain tabs to check that Bison properly
-processes tabs in its input.
-
-Prefer "res" as the name of the local variable that will be "return"ed by
-the function.
-
-### Bison
-Follow the GNU Coding Standards.
-
-Don't reinvent the wheel: we use gnulib, which features many components.
-Actually, Bison has legacy code that we should replace with gnulib modules
-(e.g., many ad hoc implementations of lists).
-
-### Skeletons
-We try to use the "typical" coding style for each language.
-
-#### CPP
-We indent the CPP directives this way:
-
-```
-#if FOO
-# if BAR
-#  define BAZ
-# endif
-#endif
-```
-
-Don't indent with leading spaces in the skeletons (it's ok in the grammar
-files though, e.g., in `%code {...}` blocks).
-
-On occasions, use `cppi -c` to see where we stand.  We don't aim at full
-correctness: depending `-d`, some bits can be in the *.c file, or the *.h
-file within the double-inclusion cpp-guards.  In that case, favor the case
-of the *.h file, but don't waste time on this.
-
-Don't hesitate to leave a comment on the `#endif` (e.g., `#endif /* FOO
-*/`), especially for long blocks.
-
-There is no conistency on `! defined` vs. `!defined`.  The day gnulib
-decides, we'll follow them.
-
-#### C/C++
-Follow the GNU Coding Standards.
-
-The `glr.c` skeleton was implemented with `camlCase`.  We are migrating it
-to `snake_case`.  Because we are standardizing the code, it is currently
-inconsistent.
-
-Use `YYFOO` and `yyfoo` for entities that are exposed to the user.  They are
-part of our contract with the users wrt backward compatibility.
-
-Use `YY_FOO` and `yy_foo` for private matters.  Users should not use them,
-we are free to change them without fear of backward compatibility issues.
-
-Use `*_t` for types, especially for `yy*_t` in which case we shouldn't worry
-about the C standard introducing such a name.
-
-#### C++
-Follow the C++ Core Guidelines
-(http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines).  The Google
-ones may be interesting too
-(https://google.github.io/styleguide/cppguide.html).
-
-Our enumerators, such as the kinds (symbol and token kinds), should be lower
-case, but it was too late to follow that track for token kinds, and symbol
-kind enumerators are made to be consistent with them.
-
-Use `*_type` for type aliases.  Use `foo_get()` and `foo_set(v)` for
-accessors, or simply `foo()` and `foo(v)`.
-
-Use the `yy` prefix for private stuff, but there's no need for it in the
-public API.  The `yy` prefix is already taken care of via the namespace.
-
-#### Java
-We follow https://www.oracle.com/technetwork/java/codeconventions-150003.pdf
-and https://google.github.io/styleguide/javaguide.html.  Unfortunately at
-some point some GNU Coding Style was installed in Java, but it's an error.
-So we should for instance stop putting spaces in function calls.  Because we
-are standardizing the code, it is currently inconsistent.
-
-Use a 2-space indentation (Google) rather than 4 (Oracle).
-
-Don't use the "yy" prefix for public members: "getExpectedTokens", not
-"yyexpectedTokens" or "yygetExpectedTokens".
-
-## Commit Messages
-Imitate the style we use.  Use `git log` to get sources of inspiration.
-
-If the changes have a small impact on Bison's generated parser, embed these
-changes in the commit itself.  If the impact is large, first push all the
-changes except those about src/parse-gram.[ch], and then another commit
-named "regen" which is only about them.
-
-## Debugging
-Bison supports tracing of its various steps, via the `--trace` option.
-Since it is not meant for the end user, it is not displayed by `bison
--help`, nor is it documented in the manual.  Instead, run `bison
--trace=help`.
-
+https://savannah.gnu.org/projects/bison/.


 Working from the Repository
@@ -164,27 +19,28 @@ requirements on anyone wishing to build from the just-checked-out sources.
 For example, you have to use the latest stable versions of the maintainer
 tools we depend upon, including:

- Autoconf <http://www.gnu.org/software/autoconf/>
- Automake <http://www.gnu.org/software/automake/>
- Flex <http://www.gnu.org/software/flex/>
- Gettext <http://www.gnu.org/software/gettext/>
- Graphviz <http://www.graphviz.org>
- Gzip <http://www.gnu.org/software/gzip/>
- Help2man <http://www.gnu.org/software/help2man/>
- Perl <http://www.cpan.org/>
- Rsync <http://samba.anu.edu.au/rsync/>
- Tar <http://www.gnu.org/software/tar/>
- Texinfo <http://www.gnu.org/software/texinfo/>
+- Autoconf <https://www.gnu.org/software/autoconf/>
+- Automake <https://www.gnu.org/software/automake/>
+- Flex <https://www.gnu.org/software/flex/>
+- Gettext <https://www.gnu.org/software/gettext/>
+- Gperf <https://www.gnu.org/software/gperf/>
+- Graphviz <https://www.graphviz.org>
+- Gzip <https://www.gnu.org/software/gzip/>
+- Help2man <https://www.gnu.org/software/help2man/>
+- Perl <https://www.cpan.org/>
+- Rsync <https://rsync.samba.org/>
+- Tar <https://www.gnu.org/software/tar/>
+- Texinfo <https://www.gnu.org/software/texinfo/>

-Valgrind <http://valgrind.org/> is also highly recommended, if it supports
-your architecture.
+Valgrind <https://www.valgrind.org/> is also highly recommended, if it
+supports your architecture.

 If you're using a GNU/Linux distribution, the easiest way to install the
 above packages depends on your system.  The following shell command should
 work for Debian-based systems such as Ubuntu:

    sudo apt-get install \
-      autoconf automake autopoint flex graphviz help2man texinfo valgrind
+      autoconf automake autopoint flex gperf graphviz help2man texinfo valgrind

 Bison is written using Bison grammars, so there are bootstrapping issues.
 The bootstrap script attempts to discover when the C code generated from the
@@ -201,7 +57,7 @@ might be needed.

 Obviously, if you are reading these notes, you did manage to check out this
 package from the repository.  For the record, you will find all the relevant
-information on http://savannah.gnu.org/git/?group=bison.
+information on https://savannah.gnu.org/git/?group=bison.

 Bison uses Git submodules: subscriptions to other Git repositories.  In
 particular it uses gnulib, the GNU portability library.  To ask Git to
@@ -283,7 +139,7 @@ Register your changes.

 For a suggestion of what gnulib commit might be stable enough for a formal
 release, see the ChangeLog in the latest gnulib snapshot at
-http://erislabs.net/ianb/projects/gnulib/.
+https://erislabs.net/ianb/projects/gnulib/.

 The Autoconf files we use are currently:
 - m4/m4.m4
@@ -322,6 +178,203 @@ version, compile bison, then force it to recreate the files:
    $ make -C _build


+Administrivia
+=============
+
+## If you incorporate a change from somebody on the net:
+First, if it is a large change, you must make sure they have signed the
+appropriate paperwork.  Second, be sure to add their name and email address
+to THANKS.
+
+## If a change fixes a test, mention the test in the commit message.
+
+## Bug reports
+If somebody reports a new bug, mention his name in the commit message and in
+the test case you write.  Put him into THANKS.
+
+The correct response to most actual bugs is to write a new test case which
+demonstrates the bug.  Then fix the bug, re-run the test suite, and check
+everything in.
+
+
+
+Hacking
+=======
+
+## Visible Changes
+Which include serious bug fixes, must be mentioned in NEWS.
+
+## Translations
+Only user visible strings are to be translated: error messages, bits of the
+.output file etc.  This excludes impossible error messages (comparable to
+assert/abort), and all the --trace output which is meant for the maintainers
+only.
+
+## Vocabulary
+- "lookahead", not "look-ahead".
+- "midrule", not "mid-rule".
+- "nonterminal", not "variable" or "non-terminal" or "non terminal".
+  Abbreviated as "nterm".
+- "shift/reduce" and "reduce/reduce", not "shift-reduce" or "shift reduce",
+  etc.
+
+## Syntax Highlighting
+It's quite nice to be in C++ mode when editing lalr1.cc for instance.
+However tools such as Emacs will be fooled by the fact that braces and
+parens do not nest, as in `[[}]]`.  As a consequence you might be misguided
+by its visual pairing to parens.  The m4-mode is safer.  Unfortunately the
+m4-mode is also fooled by `#` which is sees as a comment, stops pairing with
+parens/brackets that are inside...
+
+## Implementation Notes
+There are several places with interesting details about the implementation:
+- [Understanding C parsers generated by GNU
+Bison](https://www.cs.uic.edu/~spopuri/cparser.html) by Satya Kiran Popuri,
+is a wonderful piece of work that explains the implementation of Bison,
+- [src/gram.h](src/gram.h) documents the way the grammar is represented
+- [src/tables.h](src/tables.h) documents the generated tables
+- [data/README.md](data/README.md) contains details about the m4 implementation
+
+## Coding Style
+Do not add horizontal tab characters to any file in Bison's repository
+except where required.  For example, do not use tabs to format C code.
+However, make files, ChangeLog, and some regular expressions require tabs.
+Also, test cases might need to contain tabs to check that Bison properly
+processes tabs in its input.
+
+Prefer `res` as the name of the local variable that will be "return"ed by
+the function.
+
+In writing arithmetic comparisons, use "<" and "<=" rather than ">" and ">="
+<https://public-inbox.org/git/7vfyw7yebj.fsf_-_@assigned-by-dhcp.cox.net/>.
+
+### Bison
+Follow the GNU Coding Standards.
+
+Don't reinvent the wheel: we use gnulib, which features many components.
+Actually, Bison has legacy code that we should replace with gnulib modules
+(e.g., many ad hoc implementations of lists).
+
+#### Includes
+The `#include` directives follow an order:
+- first section for *.c files is `<config.h>`.  Don't include it in header
+  files
+- then, for *.c files, the corresponding *.h file
+- then possibly the `"system.h"` header
+- then the system headers.
+  Consider headers from `lib/` like system headers (i.e., `#include
+  <verify.h>`, not `#include "verify.h"`).
+- then headers from src/ with double quotes (`#include "getargs.h"`).
+
+Keep headers sorted alphabetically in each section.
+
+See also the [Header
+files](https://www.gnu.org/software/gnulib/manual/html_node/Header-files.html)
+and the [Implementation
+files](https://www.gnu.org/software/gnulib/manual/html_node/Implementation-files.html#Implementation-files)
+nodes of the gnulib documentation.
+
+Some source files are in the build tree (e.g., `src/scan-gram.c` made from
+`src/scan-gram.l`).  For them to find the headers from `src/`, we actually
+use `#include "src/getargs.h"` instead of `#include "getargs.h"`---that
+saves us from additional `-I` flags.
+
+### Skeletons
+We try to use the "typical" coding style for each language.
+
+#### CPP
+We indent the CPP directives this way:
+
+```
+#if FOO
+# if BAR
+#  define BAZ
+# endif
+#endif
+```
+
+Don't indent with leading spaces in the skeletons (it's OK in the grammar
+files though, e.g., in `%code {...}` blocks).
+
+On occasions, use `cppi -c` to see where we stand.  We don't aim at full
+correctness: depending `-d`, some bits can be in the *.c file, or the *.h
+file within the double-inclusion cpp-guards.  In that case, favor the case
+of the *.h file, but don't waste time on this.
+
+Don't hesitate to leave a comment on the `#endif` (e.g., `#endif /* FOO
+*/`), especially for long blocks.
+
+There is no consistency on `! defined` vs. `!defined`.  The day gnulib
+decides, we'll follow them.
+
+#### C/C++
+Follow the GNU Coding Standards.
+
+The `glr.c` skeleton was implemented with `camlCase`.  We are migrating it
+to `snake_case`.  Because we are gradually standardizing the code, it is
+currently inconsistent.
+
+Use `YYFOO` and `yyfoo` for entities that are exposed to the user.  They are
+part of our contract with the users wrt backward compatibility.
+
+Use `YY_FOO` and `yy_foo` for private matters.  Users should not use them,
+we are free to change them without fear of backward compatibility issues.
+
+Use `*_t` for types, especially for `yy*_t` in which case we shouldn't worry
+about the C standard introducing such a name.
+
+#### C++
+Follow the [C++ Core
+Guidelines](https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines).
+The [Google ones](https://google.github.io/styleguide/cppguide.html) may be
+interesting too.
+
+Our enumerators, such as the kinds (symbol and token kinds), should be lower
+case, but it was too late to follow that track for token kinds, and symbol
+kind enumerators are made to be consistent with them.
+
+Use `*_type` for type aliases.  Use `foo_get()` and `foo_set(v)` for
+accessors, or simply `foo()` and `foo(v)`.
+
+Use the `yy` prefix for private stuff, but there's no need for it in the
+public API.  The `yy` prefix is already taken care of via the namespace.
+
+#### Java
+We follow the [Java Code
+Conventions](https://www.oracle.com/technetwork/java/codeconventions-150003.pdf)
+and [Google Java Style
+Guide](https://google.github.io/styleguide/javaguide.html).  Unfortunately
+at some point some GNU Coding Style was installed in Java, but it's an
+error.  So we should for instance stop putting spaces in function calls.
+Because we are standardizing the code, it is currently inconsistent.  Treat
+acronyms as words: `YYLacStack`, not `YYLACStack`.
+
+Use a 2-space indentation (Google) rather than 4 (Oracle).
+
+Don't use the `yy` prefix for public members: `getExpectedTokens`, not
+`yyexpectedTokens` or `yygetExpectedTokens`.  Keep the `yy` prefix though
+for private details.
+
+## Commit Messages
+Imitate the style we use.  Use `git log` to get sources of inspiration.
+
+If the changes have a small impact on Bison's generated parser, embed these
+changes in the commit itself.  If the impact is large, first push all the
+changes except those about src/parse-gram.[ch], and then another commit
+named "regen" which is only about them.
+
+## Debugging
+Bison supports tracing of its various steps, via the `--trace` option.
+Since it is not meant for the end user, it is not displayed by `bison
+--help`, nor is it documented in the manual.  Instead, run `bison
+--trace=help`.
+
+## Documentation
+Use `@option` for options and options with their argument if they have no
+space (e.g., `@option{-Dfoo=bar}`).  However, use `@samp` elsewhere (e.g.,
+`@samp{-I foo}`).
+
+
 Test Suite
 ==========

@@ -331,9 +384,14 @@ examples, and the main test suite.

 ### The Examples
 In examples/, there is a number of ready-to-use examples (see
-examples/README.md).  These examples have small test suites run by `make
-check`.  The test results are in local `*.log` files (e.g.,
-`$build/examples/c/calc/calc.log`).
+[examples/README.md](examples/README.md)).  These examples have small test
+suites run by `make check`.  The test results are in local `*.log` files
+(e.g., `$build/examples/c/calc/calc.log`).
+
+To check only the examples, run `make check-examples`.  To check just one
+example,
+
+    make check-examples TESTS='examples/c/bistromathic/bistromathic.test'

 ### The Main Test Suite
 The main test suite, in tests/, is written on top of GNU Autotest, which is
@@ -348,28 +406,23 @@ contains lots of details that should help diagnosing issues, including build
 issues.  The per-test logs are more convenient when working locally.

 #### TESTSUITEFLAGS
-To run just the main test suite, run `make check-local`.
+To run just the main test suite, run `make check-tests`.

-The default is for make check-local to run all tests sequentially.  This can
-be very time consuming when checking repeatedly or on slower setups.  This
-can be sped up in two ways:
+The default is for `make check-tests` to run all tests sequentially.  This
+can be very time consuming when checking repeatedly or on slower setups.
+This can be sped up in two ways.

-Using -j, in a make-like fashion, for example:
+1. Using -j, in a make-like fashion, for example:

-    $ make check-local TESTSUITEFLAGS='-j8'
+    $ make check-tests TESTSUITEFLAGS='-j8'

-Actually, when using GNU Make, TESTSUITEFLAGS defaults to the -jN passed to
-it, so you may simply run
+When using GNU Make, TESTSUITEFLAGS defaults to the -jN passed to it, so you
+may simply run

-    $ make check-local -j8
+    $ make check-tests -j8

-Running only the tests of a certain category, as specified in the AT files
-with AT_KEYWORDS([[category]]). Categories include:
- c++, for c++ parsers
- deprec, for tests concerning deprecated constructs.
- glr, for glr parsers
- java, for java parsers
- report, for automaton dumps
+2. Running only the tests of a certain category. See
+[tests/README.md](tests/README.md#keywords) for the list of categories.

 To get a list of all the tests (and their keywords for -k), run

@@ -377,11 +430,11 @@ To get a list of all the tests (and their keywords for -k), run

 To run a specific set of tests, use -k (for "keyword"). For example:

-    $ make check-local TESTSUITEFLAGS='-k c++'
+    $ make check-tests TESTSUITEFLAGS='-k c++'

 Both can be combined.

-    $ make check-local TESTSUITEFLAGS='-j8 -k c++'
+    $ make check-tests TESTSUITEFLAGS='-j8 -k c++'

 To rerun the tests that failed:

@@ -393,7 +446,7 @@ added the `[-Wother]` part to all the warnings).  Part of the update can be
 done with a crude tool: `build-aux/update-test`.

 Once you ran the test suite, and therefore have many `testsuite.log` files,
-run, from the source tree:
+run `make update-tests`.  Or, by hand, from the *source* tree:

    $ ./build-aux/update-test $build/tests/testsuite.dir/*/testsuite.log

@@ -409,6 +462,58 @@ Use the `javaexec.sh` script.  For instance to run the parser of test case

    $ sh ./_build/javaexec.sh -cp ./_build/tests/testsuite.dir/504 Calc

+## Using Sanitizers
+Address sanitizer (ASAN) and undefined-behavior sanitizer (UBSAN) are very
+useful.  Here's one way to set them up with GCC 10 on Mac Ports
+
+1. Configure with
+   ```
+   $ ./configure -C --enable-gcc-warnings \
+       CPPFLAGS='-isystem /opt/local/include' \
+       CC='gcc-mp-10 -fsanitize=address -fsanitize=undefined' \
+       CFLAGS='-ggdb' \
+       CXX='g++-mp-10.0 -fsanitize=address -fsanitize=undefined' \
+       CXXFLAGS='-ggdb' \
+       LDFLAGS='-L/opt/local/lib'
+   ```
+
+2. Compile
+
+3. Generate debug symbols:
+
+   ```
+   $ dsymutil src/bison
+   ```
+
+4. Run the tests with leak detection enabled
+   (`ASAN_OPTIONS=detect_leaks=1`).  E.g. for counterexamples:
+   ```
+   $ make check-tests TESTSUITEFLAGS='-j5 -k cex' ASAN_OPTIONS=detect_leaks=1
+   ```
+
+5. You might need a suppression file.  See
+   https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#suppressions.
+   With G++ on a Mac, you might need a suppression file (say `leak.supp`)
+   that contains:
+
+   ```
+   leak:std::clog
+   ```
+
+   and pass the additional flags
+   `LSAN_OPTIONS=suppressions=$PWD/leak.supp,print_suppressions=0`
+
+6. To run the debugger, you might want something like this:
+   ```
+   $ YYDEBUG=1 \
+     UBSAN_OPTIONS=print_stacktrace=1 \
+     LSAN_OPTIONS=suppressions=$PWD/leak.supp,print_suppressions=0 \
+     ASAN_OPTIONS=detect_leaks=1 \
+     lldb -- ./_build/tests/testsuite.dir/712/glr-regr2a ./_build/tests/testsuite.dir/712/input1.txt
+   ```
+
+   In lldb to set a break on ubsan, try `rbreak ^__ubsan_handle_`.
+
 ## make maintainer-check-valgrind
 This target uses valgrind both to check bison, and the generated parsers.

@@ -436,7 +541,7 @@ release:
 - Maybe build with -DGNULIB_POSIXCHECK, which suggests gnulib modules that
  can fix portability issues.  See if you really want to pay attention to
  its warnings; there's no need to obey blindly to it
-  (<http://lists.gnu.org/archive/html/bison-patches/2012-05/msg00057.html>).
+  (<https://lists.gnu.org/r/bison-patches/2012-05/msg00057.html>).

 - Check with `make syntax-check` if there are issues diagnosed by gnulib.

@@ -484,16 +589,57 @@ re-run the tests, run:
    make check


+## Docker
+
+Running old compilers is not very easy.  Docker can be used for some of
+them.  Have a look at .travis.yml for setups.  Move the tarball in `/tmp`
+and run, for instance:
+
+```
+docker run -v /tmp:/tmp -it ubuntu:xenial
+```
+
+This way, the host and guest machines share `/tmp`.
+
+### GCC 4.6
+On Ubuntu Xenial.
+
+```
+apt-get update
+apt-get install software-properties-common
+apt-add-repository -y "ppa:ubuntu-toolchain-r/test"
+apt-get update
+apt-get install -y gcc-4.6 g++-4.6 m4 make
+```
+
+## Stow
+
+If you want to install several versions of Bison using GNU Stow, do
+something like this:
+
+```
+for v in 3.7 3.7.1
+do
+  cd /tmp
+  wget https://ftp.gnu.org/gnu/bison/bison-$v.tar.xz
+  tar xf bison-$v.tar.xz
+  cd bison-$v
+  ./configure --prefix /usr/local/stow/bison-$v
+  make -j4
+  sudo make install
+done
+```

 Release Procedure
 =================

-See README-release.
+See the [README-release file](README-release), created when the package is
+bootstrapped.

 <!--

-Copyright (C) 2002-2005, 2007-2015, 2018-2020 Free Software Foundation,
-Inc.
+Copyright (C) 2002-2005, 2007-2015, 2018-2022, 2025-2026 Free Software
+Foundation, Inc.

 This file is part of GNU Bison.

@@ -508,7 +654,7 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.

 Local Variables:
 mode: markdown
@@ -524,8 +670,10 @@ LocalWords:  symlinks vti html lt POSIX Cc'ed Graphviz Texinfo autoconf jN
 LocalWords:  automake autopoint graphviz texinfo PROG Wother parsers YYFOO
 LocalWords:  TESTSUITEFLAGS deprec struct gnulib's getopt config ggdb yyfoo
 LocalWords:  bitset fsanitize symlink CFLAGS MERCHANTABILITY ispell wrt YY
-LocalWords:  american Administrivia camlCase yy accessors namespace src
-LocalWords:  getExpectedTokens yyexpectedTokens yygetExpectedTokens
-LocalWords:  regen dogfooding Autotest testsuite
+LocalWords:  american Administrivia camlCase yy accessors namespace src hoc
+LocalWords:  getExpectedTokens yyexpectedTokens yygetExpectedTokens parens
+LocalWords:  regen dogfooding Autotest testsuite getargs CPP BAZ endif cppi
+LocalWords:  cpp javaexec cp Calc ASAN UBSAN CPPFLAGS isystem CXX cex Gperf
+LocalWords:  CXXFLAGS LDFLAGS dsymutil gperf

 -->
@@ -14,6 +14,7 @@ Alexandre Duret-Lutz      [email protected]
 Andre da Costa Barros     [email protected]
 Andreas Damm              [email protected]
 Andreas Schwab            [email protected]
+Andrei Malashkin          [email protected]
 Andrew Suffield           [email protected]
 Angelo Borsotti           [email protected]
 Anthony Heading           [email protected]
@@ -34,6 +35,7 @@ Bob Rossi                 [email protected]
 Brandon Lucia             [email protected]
 Brooks Moses              [email protected]
 Bruce Lilly               [email protected]
+Bruno Belanyi             [email protected]
 Bruno Haible              [email protected]
 Charles-Henri de Boysson  [email protected]
 Christian Burger          [email protected]
@@ -46,6 +48,7 @@ Dagobert Michelsen        [email protected]
 Daniel Frużyński          [email protected]
 Daniel Galloway           [email protected]
 Daniel Hagerty            [email protected]
+Daniela Becker            [email protected]
 David Barto               [email protected]
 David J. MacKenzie        [email protected]
 David Kastrup             [email protected]
@@ -59,6 +62,7 @@ Di-an Jan                 [email protected]
 Dick Streefland           [email protected]
 Didier Godefroy           [email protected]
 Don Macpherson            [email protected]
+Dwight Guth               [email protected]
 Efi Fogel                 [email protected]
 Enrico Scholz             [email protected]
 Eric Blake                [email protected]
@@ -78,11 +82,13 @@ Gavin Smith               [email protected]
 Georg Sauthoff            [email protected]
 George Neuner             [email protected]
 Gilles Espinasse          [email protected]
+Giorgos Pap               [email protected]
 Goran Uddeborg            [email protected]
 Guido Trentalancia        [email protected]
 H. Merijn Brand           [email protected]
 Hans Åberg                [email protected]
 Horst Von Brand           [email protected]
+Jacob L. Mandelson        [email protected]
 Jan Nieuwenhuizen         [email protected]
 Jannick                   [email protected]
 Jeff Hammond              [email protected]
@@ -103,14 +109,18 @@ Keith Browne              [email protected]
 Ken Moffat                [email protected]
 Kiyoshi Kanazawa          [email protected]
 Lars Maier                [email protected]
+Lars Wendler              [email protected]
 László Várady             [email protected]
 Laurent Mascherpa         [email protected]
 Lie Yan                   [email protected]
+Maarten De Braekeleer     [email protected]
 Magnus Fromreide          [email protected]
 Marc Autret               [email protected]
 Marc Mendiola             [email protected]
 Marc Schönefeld           [email protected]
 Mark Boyall               [email protected]
+Marko Mäkelä              [email protected]
+Martin Blais              [email protected]
 Martin Jacobs             [email protected]
 Martin Mokrejs            [email protected]
 Martin Nylin              [email protected]
@@ -121,6 +131,7 @@ Michael Catanzaro         [email protected]
 Michael Felt              [email protected]
 Michael Hayes             [email protected]
 Michael Raskin            [email protected]
+Michał Majchrowicz        [email protected]
 Michel d'Hooge            [email protected]
 Michiel De Wilde          [email protected]
 Mickael Labau             [email protected]
@@ -135,6 +146,7 @@ Nick Bowler               [email protected]
 Nicolas Bedon             [email protected]
 Nicolas Burrus            [email protected]
 Nicolas Tisserand         [email protected]
+Nikita Popov              [email protected]
 Nikki Valen               [email protected]
 Noah Friedman             [email protected]
 Odd Arild Olsen           [email protected]
@@ -170,6 +182,7 @@ Rob Vermaas               [email protected]
 Robert Anisko             [email protected]
 Robert Yang               [email protected]
 Roland Levillain          [email protected]
+Ryan                      [email protected]
 Satya Kiran Popuri        [email protected]
 Sebastian Setzer          [email protected]
 Sebastien Fricker         [email protected]
@@ -180,6 +193,7 @@ Simon Sobisch             [email protected]
 Stefano Lattarini         [email protected]
 Stephen Cameron           [email protected]
 Steve Murphy              [email protected]
+Suhwan Song               [email protected]
 Sum Wu                    [email protected]
 Théophile Ranquet         [email protected]
 Thiru Ramakrishnan        [email protected]
@@ -213,6 +227,7 @@ Wolfram Wagner            [email protected]
 Wwp                       [email protected]
 xolodho                   [email protected]
 Yuichiro Kaneko           [email protected]
+Yuriy Solodkyy            [email protected]
 Zack Weinberg             [email protected]
 江 祖铭                    [email protected]
 長田偉伸                   [email protected]
@@ -228,7 +243,8 @@ End:

 -----

-Copyright (C) 2000-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2000-2015, 2018-2022, 2025-2026 Free Software Foundation,
+Inc.

 This file is part of Bison, the GNU Parser Generator.

@@ -243,4 +259,4 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
@@ -1,15 +1,83 @@
-* Bison 3.7
+* Soon
+** yyerror_range in GLR
+It seems useless that it is based on glr_stack_item, it should be doable
+with location only.
+
+** scan-code
+The default case is scanning char-per-char.
+
+    /* By default, grow the string obstack with the input.  */
+    .|\n        STRING_GROW ();
+
+make it more eager?
+
+** Missing tests
+commit 2c294c132528ede23d8ae4959783a67e9ff05ac5
+Author: Vincent Imbimbo <[email protected]>
+Date:   Sat Jan 23 13:25:18 2021 -0500
+
+    cex: fix state-item pruning
+
+See https://lists.gnu.org/r/bug-bison/2021-01/msg00002.html
+
+** pos_set_set
+The current approach is correct, but with poor performances.  Bitsets need
+to support 'assign' and 'shift'.  And instead of extending POS_SET just for
+the out-of-range new values, we need something like doubling the size.
+
+** glr
+There is no test with "Parse on stack %ld rejected by rule %d" in it.
+
+** yyrline etc.
+Clarify that rule numbers in the skeletons are 1-based.
+
+** Macros in C++
+There are many macros that should obey api.prefix: YY_CPLUSPLUS, YY_MOVE,
+etc.
+
+** yyerrok in Java
+And add tests in calc.at, to prepare work for D.
+
+** YYERROR and yynerrs
+We are missing some cases.  Write a test case, and check all the skeletons.
+
+** Cex
+*** Improve gnulib
+Don't do this (counterexample.c):
+
+// This is the fastest way to get the tail node from the gl_list API.
+gl_list_node_t
+list_get_end (gl_list_t list)
+{
+  gl_list_node_t sentinel = gl_list_add_last (list, NULL);
+  gl_list_node_t res = gl_list_previous_node (list, sentinel);
+  gl_list_remove_node (list, sentinel);
+  return res;
+}
+
+*** Ambiguous rewriting
+If the user is stupid enough to have equal rules, then the derivations are
+harder to read:
+
+    Reduce/reduce conflict on tokens $end, "+", "⊕":
+        2 exp: exp "+" exp .
+        3 exp: exp "+" exp .
+      Example                  exp "+" exp •
+      First derivation         exp ::=[ exp "+" exp • ]
+      Example                  exp "+" exp •
+      Second derivation        exp ::=[ exp "+" exp • ]
+
+Do we care about this?  In color, we use twice the same color here, but we
+could try to use the same color for the same rule.
+
+*** XML reports
+Show the counterexamples.  This is going to be really hard and/or painful.
+Unless we play it dumb (little structure).
+
 ** Bistromathic
- Hitting tab on a line with a syntax error is ugly
-
- Be robust to existing ~/.inputrc
-
 - How about not evaluating incomplete lines when the text is not finished
  (as shells do).

-** Doc
-*** api.header.include
-
 ** Questions
 *** Java
 - Should i18n be part of the Lexer?  Currently it's a static method of
@@ -22,13 +90,6 @@

 - promote YYEOF rather than EOF.

-*** D
- is there a way to attach yysymbol_name to the enum itself?  As we did
-  in Java.
-
- It would be better to have TokenKind as return value.  Can we use
-  reflection to support both output types?
-
 ** YYerror
 https://git.savannah.gnu.org/gitweb/?p=gettext.git;a=blob;f=gettext-runtime/intl/plural.y;h=a712255af4f2f739c93336d4ff6556d932a426a5;hb=HEAD

@@ -39,34 +100,13 @@ enough.
 *** calc.at
 Stop hard-coding "Calc".  Adjust local.at (look for FIXME).

-** Counter example generation
-See https://github.com/akimd/bison/pull/15.
-
-** Clean up
-Rename user_token_number for tokens as "code".  It's not a "user number",
-it's the token code, and the user can control it, but this code always
-exists.
-
-See also USER_NUMBER_UNDEFINED and NUMBER_UNDEFINED.
-
-Rename endtoken as eoftoken.
-
-Also do it in data/skeletons.
-
-Don't rename in Bison 3.6 (it would be logical to do so) because that
-would probably create many conflicts in Vincent's work (see previous point).
-
-** A dev warning for b4_
-Maybe we should check for m4_ and b4_ leaking out of the m4 processing, as
-Autoconf does.  It would have caught overquotation issues.
-
 ** doc
 I feel it's ugly to use the GNU style to declare functions in the doc.  It
 generates tons of white space in the page, and may contribute to bad page
 breaks.

 ** consistency
-token vs terminal, variable vs non terminal.
+token vs terminal.

 ** api.token.raw
 The YYUNDEFTOK could be assigned a semantic value so that yyerror could be
@@ -79,7 +119,7 @@ push parsers on top of pull parser.  Which is currently not relevant, since
 push parsers are measurably slower.

 ** %define parse.error formatted
-How about pushing bistromathics' yyreport_syntax_error as another standard
+How about pushing Bistromathic's yyreport_syntax_error as another standard
 way to generate the error message, and leave to the user the task of
 providing the message formats?  Currently in bistro, it reads:

@@ -147,7 +187,48 @@ Les catégories d'avertissements incluent :

 Line -1 and -3 should mention CATEGORIE, not CATEGORY.

-* Bison 3.8
+* Bison 3.9
+** Rewrite glr.cc (currently glr2.cc)
+*** custom error messages
+
+*** Remove jumps
+We can probably replace setjmp/longjmp with exceptions.  That would help
+tremendously other languages such as D and Java that probably have no
+similar feature.  If we remove jumps, we probably no longer need _Noreturn,
+so simplify `b4_attribute_define([noreturn])` into `b4_attribute_define`.
+
+After discussing with Valentin, it was decided that it's better to stay with
+jumps, since in some places exceptions are ruled out from C++.
+
+*** Coding style
+Move to our coding conventions.  In particular names such as yy_glr_stack,
+not yyGLRStack.
+
+*** yydebug
+It should be a member of the parser object, see lalr1.cc.  Let the parser
+object decide what the debug stream is, rather than open coding std::cerr.
+
+*** Avoid pointers
+There are many places where pointers should be replaced with references.
+Some occurrences were fixed, but now some have improper names:
+
+-yygetToken (int *yycharp, ]b4_namespace_ref[::]b4_parser_class[& yyparser][]b4_pure_if([, glr_stack* yystackp])[]b4_user_formals[)
+yygetToken (int& yycharp, ]b4_namespace_ref[::]b4_parser_class[& yyparser][]b4_pure_if([, glr_stack* yystackp])[]b4_user_formals[)
+
+yycharp is no longer a Pointer.  And yystackp should probably also be a reference.
+
+*** parse.assert
+Currently all the assertions are enabled.  Once we are confident in glr2.cc,
+let parse.assert use the same approach as in lalr1.cc.
+
+*** debug_stream
+Stop using std::cerr everywhere.
+
+*** glr.c
+When glr2.cc fully replaces glr.cc, get rid of the glr.cc scaffolding in
+glr.c.
+
+* Chains
 ** Unit rules / Injection rules (Akim Demaille)
 Maybe we could expand unit rules (or "injections", see
 https://homepages.cwi.nl/~daybuild/daily-books/syntax/2-sdf/sdf.html), i.e.,
@@ -190,18 +271,54 @@ The "automaton" and "set" categories are not so useful.  We should probably
 introduce lr(0) and lalr, just the way we have ielr categories.  The
 "closure" function is too verbose, it should probably have its own category.

-"set" can still be used for summariring the important sets.  That would make
+"set" can still be used for summarizing the important sets.  That would make
 tests easy to maintain.

 *** complain.*
 Rename these guys as "diagnostics.*" (or "diagnose.*"), since that's the
-name they have in gcc, clang, etc.  Likewise for the complain_* series of
+name they have in GCC, clang, etc.  Likewise for the complain_* series of
 functions.

 *** ritem
 states/nstates, rules/nrules, ..., ritem/nritems
 Fix the latter.

+*** m4: slot, type, type_tag
+The meaning of type_tag varies depending on api.value.type.  We should avoid
+that and using clear definitions with stable semantics.
+
+* D programming language
+There's a number of features that are missing, here sorted in _suggested_
+order of implementation.
+
+When copying code from other skeletons, keep the comments exactly as they
+are.  Keep the same variable names.  If you change the wording in one place,
+do it in the others too.  In other words: make sure to keep the
+maintenance *simple* by avoiding any gratuitous difference.
+
+** CI
+Check when gdc and ldc.
+
+** GLR Parser
+This is very ambitious.  That's the final boss.  There are currently no
+"clean" implementation to get inspiration from.
+
+glr.c is very clean but:
+- is low-level C
+- is a different skeleton from yacc.c
+
+glr.cc is (currently) an ugly hack: a C++ shell around glr.c.  Valentin
+Tolmer is currently rewriting glr.cc to be clean C++, but he is not
+finished.  There will be a lot a common code between lalr1.cc and glr.cc, so
+eventually I would like them to be fused into a single skeleton, supporting
+both deterministic and generalized parsing.
+
+It would be great for D to also support this.
+
+The basic ideas of GLR are explained here:
+
+https://www.codeproject.com/Articles/5259825/GLR-Parsing-in-Csharp-How-to-Use-The-Most-Powerful
+
 * Better error messages
 The users are not provided with enough tools to forge their error messages.
 See for instance "Is there an option to change the message produced by
@@ -219,9 +336,8 @@ and older C++ compilers.  Currently the code defaults to defining it to
 define it to the same type as the C ptrdiff_t type.

 * Completion
-Several features are not available in all the backends.
+Several features are not available in all the back-ends.

- lac: D, Java (easy)
 - push parsers: glr.c, glr.cc, lalr1.cc (not very difficult)
 - token constructors: Java, C, D (a bit difficult)
 - glr: D, Java (super difficult)
@@ -236,9 +352,6 @@ $ ./tests/testsuite -l | grep errors | sed q
  38: input.at:1730      errors

 * Short term
-** Get rid of YYPRINT and b4_toknum
-Besides yytoknum is wrong when api.token.raw is defined.
-
 ** Better design for diagnostics
 The current implementation of diagnostics is ad hoc, it grew organically.
 It works as a series of calls to several functions, with dependency of the
@@ -289,7 +402,7 @@ opposite side we have some use of \l, which is graphviz-specific, in what
 should be generic code.

 Little effort seems to have been given to factoring these files and their
-rint{,-xml} counterpart. We would very much like to re-use the pretty format
+print{,-xml} counterpart. We would very much like to re-use the pretty format
 of states from .output for the graphs, etc.

 Since graphviz dies on medium-to-big grammars, maybe consider an other tool?
@@ -356,23 +469,6 @@ It would be a very nice source of inspiration for the other languages.

 Valentin Tolmer is working on this.

-** yychar == YYEMPTY
-The code in yyerrlab reads:
-
-      if (yychar <= YYEOF)
-        {
-          /* Return failure if at end of input.  */
-          if (yychar == YYEOF)
-            YYABORT;
-        }
-
-There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
-But I can't produce the situation where yychar is YYEMPTY here, is it
-really possible?  The test suite does not exercise this case.
-
-This shows that it would be interesting to manage to install skeleton
-coverage analysis to the test suite.
-
 * From lalr1.cc to yacc.c
 ** Single stack
 Merging the three stacks in lalr1.cc simplified the code, prompted for
@@ -414,16 +510,6 @@ undocumented ''features''.  Maybe an empty action ought to be
 presented too.  Shall we try to make a single grammar with all these
 features, or should we have several very small grammars?

-** --report=conflict-path
-Provide better assistance for understanding the conflicts by providing
-a sample text exhibiting the (LALR) ambiguity.  See the paper from
-DeRemer and Penello: they already provide the algorithm.
-
-** Statically check for potential ambiguities in GLR grammars
-See <http://www.lsv.fr/~schmitz/pub/expamb.pdf> for an approach.
-An Experimental Ambiguity Detection Tool ∗ Sylvain Schmitz
-LORIA, INRIA Nancy - Grand Est, Nancy, France
-
 * Extensions
 ** More languages?
 Well, only if there is really some demand for it.
@@ -435,6 +521,9 @@ https://github.com/scfc/bison-php/blob/master/data/lalr1.php
 https://lists.gnu.org/r/bison-patches/2013-09/msg00000.html and following

 ** Multiple start symbols
+Revert a70e75b8a41755ab96ab211a0ea111ac68a4aadd.
+Revert tests: disable "Multistart reports".
+
 Would be very useful when parsing closely related languages.  The idea is to
 declare several start symbols, for instance

@@ -456,12 +545,27 @@ happen with yy_start: stmt | expr).  Then adjust the skeletons so that this
 initial token (YY_START_STMT, YY_START_EXPR) be shifted first in the
 corresponding parse function.

+*** Number of useless symbols
+AT_TEST(
+[[%start exp;
+exp: exp;]],
+[[input.y: warning: 2 nonterminals useless in grammar [-Wother]
+input.y: warning: 2 rules useless in grammar [-Wother]
+input.y:2.8-10: error: start symbol exp does not derive any sentence]])
+
+We should say "1 nonterminal": the other one is $accept, which should not
+participate in the count.
+
+*** Tokens
+Do we want to disallow terminal start symbols?  The limitation is not
+technical.  Can it be useful to someone to "parse" a token?
+
 ** %include
 This is a popular demand.  We already made many changes in the parser that
 should make this reasonably easy to implement.

 Bruce Mardle <[email protected]>
-https://lists.gnu.org/archive/html/bison-patches/2015-09/msg00000.html
+https://lists.gnu.org/r/bison-patches/2015-09/msg00000.html

 However, there are many other things to do before having such a feature,
 because I don't want a % equivalent to #include (which we all learned to
@@ -470,11 +574,11 @@ them together, paying attention to keep separate bits separated, in pseudo
 name spaces.

 ** Push parsers
-There is demand for push parsers in Java and C++.  And GLR I guess.
+There is demand for push parsers in C++.

 ** Generate code instead of tables
 This is certainly quite a lot of work.  See
-http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.50.4539.
+https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.50.4539.

 ** $-1
 We should find a means to provide an access to values deep in the
@@ -514,13 +618,6 @@ XML output for GNU Bison and gcc
 XML output for GNU Bison
   http://yaxx.sourceforge.net/

-** Counterexample generation
-https://lists.gnu.org/archive/html/bug-bison/2016-06/msg00000.html
-http://www.cs.cornell.edu/andru/papers/cupex/
-
-Andrew Myers and Vincent Imbimbo are working on this item, see
-https://github.com/akimd/bison/issues/12
-
 * Coding system independence
 Paul notes:

@@ -584,28 +681,47 @@ to bison. If you're interested, I'll work on a patch.
 Equip the parser with a means to create the (visual) parse tree.


+-----
+
+# LocalWords:  Cex gnulib gl Bistromathic TokenKinds yylex enum YYEOF EOF
+# LocalWords:  YYerror gettext af hb YYERRCODE undef calc FIXME dev yyerror
+# LocalWords:  Autoconf YYUNDEFTOK lexemes parsers Bistromathic's yyreport
+# LocalWords:  const argc yacc yyclearin lookahead destructor Rici incluent
+# LocalWords:  yydestruct yydiscardin catégories d'avertissements sr activé
+# LocalWords:  conflits défaut rr l'alias chaîne n'est attaché un symbole
+# LocalWords:  obsolète règle vide midrule valeurs de intermédiaire ou avec
+# LocalWords:  définies inutilisées priorité associativité inutiles POSIX
+# LocalWords:  incompatibilités tous les autres avertissements sauf dans rp
+# LocalWords:  désactiver CATEGORIE traiter comme des erreurs glr Akim bool
+# LocalWords:  Demaille arith lalr goto struct pathlen nullable ntokens lr
+# LocalWords:  nterm bitsetv ielr ritem nstates nrules nritems yysymbol EQ
+# LocalWords:  SymbolKind YYEMPTY YYUNDEF YYTNAME NUM yyntokens yytname sed
+# LocalWords:  nonterminals yykind yycode YYNAMES yynames init getName conv
+# LocalWords:  TokenKind ival yychar yylval yylexer Tolmer hoc
+# LocalWords:  Sobisch YYPTRDIFF ptrdiff Autotest toknum yytoknum
+# LocalWords:  sym Wother stderr FP fixits xgettext fdiagnostics Graphviz
+# LocalWords:  graphviz VCG bitset xml bw maint yytoken YYABORT deps
+# LocalWords:  YYACCEPT yytranslate nonnegative destructors yyerrlab repo
+# LocalWords:  backends stmt expr yy Mardle baz qux Vadim Maslow CPP cpp
+# LocalWords:  yydebug gcc UCHAR EBCDIC gung PDP NUL Pre Florian Krohm utf
+# LocalWords:  YYACT YYLLOC YYLSP yyval yyvsp yylen yyloc yylsp endif
+# LocalWords:  ispell american
+
 Local Variables:
 mode: outline
 coding: utf-8
 fill-column: 76
+ispell-dictionary: "american"
 End:

-----
-
-Copyright (C) 2001-2004, 2006, 2008-2015, 2018-2020 Free Software
-Foundation, Inc.
+Copyright (C) 2001-2004, 2006, 2008-2015, 2018-2022, 2025-2026 Free
+Software Foundation, Inc.

 This file is part of Bison, the GNU Compiler Compiler.

-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the "GNU Free
+Documentation License" file as part of this distribution.
@@ -0,0 +1,39 @@
+#!/bin/sh
+# Convenience script for regenerating all autogeneratable files that are
+# omitted from the version control repository. In particular, this script
+# also regenerates all aclocal.m4, config.h.in, Makefile.in, configure files
+# with new versions of autoconf or automake.
+
+# Copyright (C) 2003-2026 Free Software Foundation, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# Originally written by Paul Eggert.  The canonical version of this
+# script is maintained as top/autogen.sh in gnulib.  However, to be
+# useful to your package, you should place a copy of it under version
+# control in the top-level directory of your package.  The intent is
+# that all customization can be done with a bootstrap.conf file also
+# maintained in your version control; gnulib comes with a template
+# build-aux/bootstrap.conf to get you started.
+#
+# Alternatively, you can use an autogen.sh script that is specific
+# to your package.
+
+me="$0"
+medir=`dirname "$me"`
+
+# Read the function library and the configuration.
+. "$medir"/bootstrap-funclib.sh
+
+autogen "$@"
@@ -0,0 +1,37 @@
+#!/bin/sh
+# Convenience script for fetching auxiliary files that are omitted from
+# the version control repository of this package.
+
+# Copyright (C) 2003-2026 Free Software Foundation, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+# Originally written by Paul Eggert.  The canonical version of this
+# script is maintained as top/autopull.sh in gnulib.  However, to be
+# useful to your package, you should place a copy of it under version
+# control in the top-level directory of your package.  The intent is
+# that all customization can be done with a bootstrap.conf file also
+# maintained in your version control; gnulib comes with a template
+# build-aux/bootstrap.conf to get you started.
+#
+# Alternatively, you can use an autopull.sh script that is specific
+# to your package.
+
+me="$0"
+medir=`dirname "$me"`
+
+# Read the function library and the configuration.
+. "$medir"/bootstrap-funclib.sh
+
+autopull "$@"
@@ -1,6 +1,7 @@
 # Bootstrap configuration.

-# Copyright (C) 2006-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2006-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,38 +14,43 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 # gnulib modules used by this package.
 gnulib_modules='
-  argmatch array-list assert assure
+  argmatch array-list assert assure attribute
  bitsetv
-  calloc-posix close closeout config-h c-strcase
+  calloc-posix close closeout config-h c-strcase c-strtod
  configmake
  dirname
-  error extensions
-  fdl fopen-safer fstrcmp
+  error execute extensions
+  fopen-safer fstrcmp
  getopt-gnu
  gettext-h git-version-gen gitlog-to-changelog
  gpl-3.0 intprops inttypes isnan javacomp-script
+  hash-map
  javaexec-script
  ldexpl
  libtextstyle-optional
+  linked-list
  malloc-gnu
+  mcel-prefer
  mbfile mbswidth
-  non-recursive-gnulib-prefix-hack
  obstack
  obstack-printf
  perror progname
  quote quotearg
+  rbtreehash-list
  readline
  readme-release
  realloc-posix
  relocatable-prog relocatable-script
  rename
-  spawn-pipe stdbool stpcpy strdup-posix strerror strverscmp
+  spawn-pipe stdbool stpcpy stpncpy strdup-posix strerror strverscmp
+  sys_ioctl
+  termios
  timevar
-  unistd unistd-safer unlink unlocked-io
+  unicodeio unistd unistd-safer unlink unlocked-io
  update-copyright unsetenv verify
  warnings
  winsz-ioctl
@@ -54,7 +60,7 @@ gnulib_modules='
  xconcat-filename
  xhash
  xlist
-  xmemdup0
+  xmap xmemdup0
  xstrndup

  fprintf-posix printf-posix snprintf-posix sprintf-posix
@@ -75,13 +81,23 @@ XGETTEXT_OPTIONS_RUNTIME=$XGETTEXT_OPTIONS'\\\
 --keyword=YY_ \\\
 '

-gnulib_tool_option_extras='--symlink --conditional-dependencies --makefile-name=gnulib.mk --po-base=gnulib-po --po-domain=bison'
+gnulib_tool_option_extras="\
+ --automake-subdir\
+ --automake-subdir-tests\
+ --avoid=mbiterf\
+ --conditional-dependencies\
+ --makefile-name=gnulib.mk\
+ --po-base=gnulib-po\
+ --po-domain=bison\
+ --symlink\
+"
+
+gnulib_extra_files="$gnulib_extra_files build-aux/move-if-change"
+
+gnulib_extra_files="$gnulib_extra_files build-aux/epsf.tex"

 bootstrap_post_import_hook()
 {
-  # Massage lib/gnulib.mk before using it later in the bootstrapping process.
-  build-aux/prefix-gnulib-mk --lib-name="$gnulib_name" "lib/$gnulib_mk"
-
  # Ensure that ChangeLog exists, for automake.
  test -f ChangeLog || touch ChangeLog
 }
@@ -1,30 +1,29 @@
 /announce-gen
 /compile
 /config.guess
+/config.libpath
 /config.rpath
-/config.rpath~
 /config.sub
 /depcomp
 /do-release-commit-and-tag
+/epsf.tex
 /gendocs.sh
 /git-version-gen
 /gitlog-to-changelog
 /gnu-web-doc-update
 /gnupload
+/install-reloc
 /install-sh
 /javacomp.sh.in
 /javaexec.sh.in
+/libtool-reloc
 /mdate-sh
 /missing
-/prefix-gnulib-mk
+/reloc-ldflags
+/relocatable.sh.in
 /test-driver
 /texinfo.tex
 /update-copyright
 /useless-if-before-free
 /vc-list-files
 /ylwrap
-/config.libpath
-/install-reloc
-/reloc-ldflags
-/relocatable.sh.in
-/libtool-reloc
@@ -1,4 +1,5 @@
-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -11,7 +12,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 # Valgrind suppression file for Bison.

@@ -1,4 +1,5 @@
-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -11,7 +12,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 # Valgrind suppression file for Bison.

@@ -2,7 +2,7 @@

 # Generate a release announcement message.

-# Copyright (C) 2007-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2022, 2025-2026 Free Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -1,4 +1,5 @@
-## Copyright (C) 2000-2015, 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2000-2015, 2018-2022, 2025-2026 Free Software
+## Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -11,12 +12,13 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 EXTRA_DIST +=					\
  build-aux/Darwin.valgrind			\
  build-aux/Linux.valgrind			\
  build-aux/cross-options.pl			\
+  build-aux/epsf.tex				\
  build-aux/move-if-change			\
  build-aux/prev-version.txt			\
  build-aux/update-b4-copyright
@@ -1 +0,0 @@
-../gnulib/build-aux/move-if-change
@@ -3,7 +3,8 @@
 # Update b4_copyright invocations or b4_copyright_years definitions to
 # include the current year.

-# Copyright (C) 2009-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2009-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,7 +17,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 use strict;
 use warnings;
@@ -2,7 +2,8 @@

 # In configure.ac, update PACKAGE_COPYRIGHT_YEAR to the current year.

-# Copyright (C) 2010-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2010-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 use strict;
 use warnings;
@@ -2,7 +2,7 @@

 # Update expectations in an Autotest test suite.

-# Copyright (C) 2019-2020 Free Software Foundation, Inc.
+# Copyright (C) 2019-2022, 2025-2026 Free Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -1,5 +1,6 @@
 ## Customize maint.mk                           -*- makefile -*-
-## Copyright (C) 2008-2015, 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2008-2015, 2018-2022, 2025-2026 Free Software
+## Foundation, Inc.

 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -12,7 +13,7 @@
 ## GNU General Public License for more details.

 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 # Update version, then recompile so that tests/bison --version be
 # up-to-date, then compile our parser again with our up-to-date bison.
@@ -42,7 +43,7 @@ url_dir_list = \
 # Tests not to run as part of "make distcheck".
 local-checks-to-skip =			\
  sc_immutable_NEWS			\
-  sc_prohibit_atoi_atof
+  sc_indent

 # The local directory containing the checked-out copy of gnulib used in
 # this release.  Used solely to get a date for the "announcement" target.
@@ -126,7 +127,7 @@ _sed_rm_comments_q = $(subst ','\'',$(_sed_remove_comments))

 _space_before_paren_exempt =? \\n\\$$
 _space_before_paren_exempt = \
-  (^ *\#|(LA)?LR\([01]\)|percent_(code|define)|b4_syncline|m4_(define|init)|symbol)
+  (^ *\#|(LA)?LR\([01]\)|percent_(code|define)|b4_syncline|m4_(define|init))
 # Ensure that there is a space before each open parenthesis in C code.
 sc_space_before_open_paren:
 	@if $(VC_LIST_EXCEPT) | grep -l '\.[ch]$$' > /dev/null; then	\
@@ -156,12 +157,15 @@ exclude = \
 $(call exclude,                                                                 \
  bindtextdomain=^lib/main.c$$                                                  \
  cast_of_argument_to_free=^src/muscle-tab.c$$                                  \
+  error_message_uppercase=etc/bench.pl.in$$                                     \
+  file_system=^doc/Doxyfile.in$$                                                \
  po_check=^tests|(^po/POTFILES.in|.md)$$                                       \
  preprocessor_indentation=^data/|^lib/|^src/parse-gram.[ch]$$                  \
  program_name=^lib/main.c$$                                                    \
  prohibit_always-defined_macros=^data/skeletons/yacc.c$$                       \
  prohibit_always-defined_macros+=?|^src/(parse-gram.c|system.h)$$              \
  prohibit_always-defined_macros+=?|^tests/regression.at$$                      \
+  prohibit_atoi_atof=^(doc|etc|examples|tests)/                                 \
  prohibit_doubled_word=^tests/named-refs.at$$                                  \
  prohibit_magic_number_exit=^doc/bison.texi$$                                  \
  prohibit_magic_number_exit+=?|^tests/(conflicts|regression).at$$              \
@@ -1,6 +1,7 @@
 # Configure template for GNU Bison.                   -*-Autoconf-*-
 #
-# Copyright (C) 2001-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2001-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,14 +14,9 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

-# In order for some versions of Sun Studio to compile our C++ test cases
-# correctly, we need Autoconf 2.64 or better to handle the restrict
-# keyword in at least string.h from gnulib.  We need Autoconf 2.68 or
-# better to avoid a typo in the 'configure --help' entry for the YACC
-# environment variable.
-AC_PREREQ([2.68])
+AC_PREREQ([2.71])
 m4_pattern_forbid([^_?(gl_[A-Z]|AX_|BISON_)])
 m4_pattern_allow([^BISON_USE_NLS$])

@@ -29,7 +25,7 @@ AC_INIT([GNU Bison],
        [[email protected]],
        [],
        [https://www.gnu.org/software/bison/])
-AC_SUBST([PACKAGE_COPYRIGHT_YEAR], [2020])
+AC_SUBST([PACKAGE_COPYRIGHT_YEAR], [2026])
 AC_DEFINE_UNQUOTED([PACKAGE_COPYRIGHT_YEAR], [$PACKAGE_COPYRIGHT_YEAR],
                   [The copyright year for this package])

@@ -54,7 +50,7 @@ AM_SILENT_RULES([yes])
 AC_CONFIG_HEADERS([lib/config.h:lib/config.in.h])

 # Checks for the compiler.
-AC_PROG_CC_STDC
+AC_PROG_CC
 AC_PROG_CXX

 # Gnulib (early checks).
@@ -81,7 +77,8 @@ BISON_CXXSTD([03])
 BISON_CXXSTD([11])
 BISON_CXXSTD([14])
 BISON_CXXSTD([17])
-BISON_CXXSTD([2a])
+BISON_CXXSTD([20])
+BISON_CXXSTD([2b])
 AM_CONDITIONAL([ENABLE_CXX11], [test x"$CXX11_CXXFLAGS" != x])
 AM_CONDITIONAL([ENABLE_CXX14], [test x"$CXX14_CXXFLAGS" != x])
 AC_LANG_POP([C++])
@@ -130,13 +127,17 @@ if test "$enable_gcc_warnings" = yes; then
  warn_common='-Wall -Wextra
    -Wcast-align -Wchar-subscripts
    -fparse-all-comments -Wdocumentation
-    -Wformat -Wimplicit-fallthrough -Wnull-dereference
+    -Wformat -Wimplicit-fallthrough -Wmismatched-dealloc -Wnull-dereference
    -Wno-sign-compare -Wno-tautological-constant-out-of-range-compare
-    -Wpointer-arith -Wshadow
+    -Wpointer-arith -Wshadow -Wstrict-aliasing
+    -Wunused-but-set-variable
    -Wwrite-strings
    -wr188 -wr2259 -wr3179'
-  warn_c='-Wbad-function-cast -Wstrict-prototypes'
-  warn_cxx='-Wextra-semi -Wnoexcept -Wold-style-cast -Wundefined-func-template
+  warn_c='-Wbad-function-cast
+    -Wmissing-prototypes
+    -Wstrict-prototypes'
+  warn_cxx='-Wextra-semi -Wnoexcept -Wsubobject-linkage
+    -Wold-style-cast -Wundefined-func-template
    -Wweak-vtables'
  # Warnings for the test suite only.
  #
@@ -226,6 +227,16 @@ if test "$enable_gcc_warnings" = yes; then
  gl_WARN_ADD([-Wno-deprecated], [WNO_DEPRECATED_CXXFLAGS])
  CXXFLAGS=$save_CXXFLAGS
  AC_LANG_POP([C++])
+
+  AC_DEFINE([lint], [1], [Define to 1 if the compiler is checking for lint.])
+  AH_VERBATIM([FORTIFY_SOURCE],
+    [/* Enable compile-time and run-time bounds-checking, and some warnings,
+        without upsetting glibc 2.15+. */
+     #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
+     # define _FORTIFY_SOURCE 2
+     #endif
+    ])
+  AC_DEFINE([GNULIB_PORTCHECK], [1], [Enable some gnulib portability checks.])
 fi


@@ -246,7 +257,7 @@ AM_CONDITIONAL([ENABLE_JAVA], [test x"$CONF_JAVAC" != x && test x"$CONF_JAVA" !=


 AC_ARG_ENABLE([yacc],
-  [AC_HELP_STRING([--disable-yacc],
+  [AS_HELP_STRING([--disable-yacc],
     [do not build a yacc command or an -ly library])],
  , [enable_yacc=yes])
 AM_CONDITIONAL([ENABLE_YACC], [test "$enable_yacc" = yes])
@@ -283,6 +294,9 @@ AC_C_INLINE
 # gl_EARLY avoids some redundant checks.
 gl_INIT

+# We want ostream_printf and hyperlink support.
+gl_LIBTEXTSTYLE_OPTIONAL([0.20.5])
+
 # Checks for library functions.
 AC_CHECK_FUNCS_ONCE([setlocale])

@@ -1,6 +1,6 @@
 This directory contains data needed by Bison.

-# Directory content
+# Directory Content
 ## Skeletons
 Bison skeletons: the general shapes of the different parser kinds, that are
 specialized for specific grammars by the bison program.
@@ -48,7 +48,7 @@ various formats.
 - xml2xhtml.xsl
  Conversion into XHTML.

-# Implementation note about the skeletons
+# Implementation Notes About the Skeletons

 "Skeleton" in Bison parlance means "backend": a skeleton is fed by the bison
 executable with LR tables, facts about the symbols, etc. and they generate
@@ -73,40 +73,60 @@ skeletons.  If you are to write a new skeleton, please, implement them for
 your language.  Overall, be sure to follow the same patterns as the existing
 skeletons.

+## Vocabulary
+
+We use "formal arguments", or "formals" for short, to denote the declared
+parameters of a function (e.g., `int argc, const char **argv`).  Yes, this
+is somewhat contradictory with `param` in the `%param` directives.
+
+We use "effective arguments", or "args" for short, to denote the values
+passed in function calls (e.g., `argc, argv`).
+
 ## Symbols

 ### `b4_symbol(NUM, FIELD)`
 In order to unify the handling of the various aspects of symbols (tag, type
 name, whether terminal, etc.), bison.exe defines one macro per (token,
 field), where field can `has_id`, `id`, etc.: see
-`prepare_symbols_definitions()` in `src/output.c`.
+`prepare_symbol_definitions()` in `src/output.c`.

-The macro `b4_symbol(NUM, FIELD)` gives access to the following FIELDS:
+NUM can be:
+- `empty` to denote the "empty" pseudo-symbol when it exists,
+- `eof`, `error`, or `undef`
+- a symbol number.
+
+FIELD can be:

 - `has_id`: 0 or 1
-  Whether the symbol has an id.
+  Whether the symbol has an `id`.

- `id`: string
-  If has_id, the id (prefixed by api.token.prefix if defined), otherwise
-  defined as empty.  Guaranteed to be usable as a C identifier.  This is
-  used to define the token kind (i.e., the enum used by the return value of
-  yylex).
+- `id`: string (e.g., `exp`, `NUM`, or `TOK_NUM` with api.token.prefix)
+  If `has_id`, the name of the token kind (prefixed by api.token.prefix if
+  defined), otherwise empty.  Guaranteed to be usable as a C identifier.
+  This is used to define the token kind (i.e., the enum used by the return
+  value of yylex).  Should be named `token_kind`.

 - `tag`: string
-  A human representation of the symbol.  Can be 'foo', 'foo.id', '"foo"' etc.
+  A human readable representation of the symbol.  Can be `'foo'`,
+  `'foo.id'`, `'"foo"'` etc.

- `user_number`: integer
-  The code associated to the `id`.
+- `code`: integer
+  The token code associated to the token kind `id`.
  The external number as used by yylex.  Can be ASCII code when a character,
-  some number chosen by bison, or some user number in the case of
-  %token FOO <NUM>.  Corresponds to yychar in yacc.c.
+  some number chosen by bison, or some user number in the case of `%token
+  FOO <NUM>`.  Corresponds to `yychar` in `yacc.c`.

 - `is_token`: 0 or 1
  Whether this is a terminal symbol.

+- `kind_base`: string (e.g., `YYSYMBOL_exp`, `YYSYMBOL_NUM`)
+  The base of the symbol kind, i.e., the enumerator of this symbol (token or
+  nonterminal) which is mapped to its `number`.
+
 - `kind`: string
-  The symbol kind, i.e., the enumerator of this symbol (token or nonterminal)
-  which is mapping to its `number`.
+  Same as `kind_base`, but possibly with a prefix in some languages.  E.g.,
+  EOF's `kind_base` and `kind` are `YYSYMBOL_YYEOF` in C, but are
+  `S_YYEMPTY` and `symbol_kind::S_YYEMPTY` in C++.

 - `number`: integer
  The code associated to the `kind`.
@@ -136,11 +156,17 @@ The macro `b4_symbol(NUM, FIELD)` gives access to the following FIELDS:
  When api.value.type=union, the generated name for the union member.
  yytype_INT etc. for symbols that has_id, otherwise yytype_1 etc.

- `type`
+- `type`: string
  If it has a semantic value, its type tag, or, if variant are used,
  its type.
  In the case of api.value.type=union, type is the real type (e.g. int).

+- `slot`: string
+  If it has a semantic value, the name of the union member (i.e., bounces to
+  either `type_tag` or `type`).  It would be better to fix our mess and
+  always use `type` for the true type of the member, and `type_tag` for the
+  name of the union member.
+
 - `has_printer`: 0, 1
 - `printer`: string
 - `printer_file`: string
@@ -173,7 +199,7 @@ The data corresponding to the symbol `#POS`, where the current rule has
 Expansion of `$<TYPE>POS`, where the current rule has `RULE-LENGTH` symbols
 on RHS.

-----
+<!--

 Local Variables:
 mode: markdown
@@ -181,7 +207,8 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2002, 2008-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2002, 2008-2015, 2018-2022, 2025-2026 Free Software
+Foundation, Inc.

 This file is part of GNU Bison.

@@ -196,4 +223,6 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+-->
@@ -1,5 +1,5 @@
 /* Default styling rules for Bison when doing terminal output.
-   Copyright (C) 2019-2020 Free Software Foundation, Inc.
+   Copyright (C) 2019-2022, 2025-2026 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -30,5 +30,32 @@
 /* "Sections" in traces (--trace).  */
 .trace0    { color: green; }

+/* Syntax error messages.  */
 .expected   { color: green; }
 .unexpected { color: red; }
+
+
+/* Counterexamples.  */
+
+/* Cex: point in rule.  */
+.cex-dot { color: red; }
+
+/* Cex: coloring various rules.  */
+.cex-0   { color: yellow; }
+.cex-1   { color: green; }
+.cex-2   { color: blue; }
+.cex-3   { color: purple; }
+.cex-4   { color: violet; }
+.cex-5   { color: orange; }
+.cex-6   { color: brown; }
+.cex-7   { color: mauve; }
+.cex-8   { color: #013220; } /* Dark green. */
+.cex-9   { color: #e75480; } /* Dark pink. */
+.cex-10  { color: cyan; }
+.cex-11  { color: orange; }
+
+/* Cex: derivation rewriting steps.  */
+.cex-step { font-style: italic; }
+
+/* Cex: leaves of a derivation.  */
+.cex-leaf { font-weight: 600; }
@@ -1,5 +1,5 @@
-## Copyright (C) 2002, 2005-2015, 2018-2020 Free Software Foundation,
-## Inc.
+## Copyright (C) 2002, 2005-2015, 2018-2022, 2025-2026 Free Software
+## Foundation, Inc.

 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -12,7 +12,7 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 dist_pkgdata_DATA =                             \
  data/README.md                                \
@@ -28,18 +28,19 @@ dist_skeletons_DATA =                           \
  data/skeletons/c.m4                           \
  data/skeletons/glr.c                          \
  data/skeletons/glr.cc                         \
+  data/skeletons/glr2.cc                        \
  data/skeletons/java-skel.m4                   \
  data/skeletons/java.m4                        \
  data/skeletons/lalr1.cc                       \
  data/skeletons/lalr1.java                     \
  data/skeletons/location.cc                    \
  data/skeletons/stack.hh                       \
+  data/skeletons/traceon.m4                     \
  data/skeletons/variant.hh                     \
  data/skeletons/yacc.c

 # Experimental support for the D language.
 dist_skeletons_DATA +=                          \
-  data/skeletons/README-D.txt                   \
  data/skeletons/d-skel.m4                      \
  data/skeletons/d.m4                           \
  data/skeletons/lalr1.d
@@ -1,60 +0,0 @@
-Some usage notes for the D Parser:
-
- it is a port of the Java parser, so interface is very similar.
-
- the lexer class needs to implement the interface 'Lexer' (similar to
-  java). It typically (depending on options) looks like this:
-
-public interface Lexer
-{
-  /**
-   * Method to retrieve the beginning position of the last scanned token.
-   * @return the position at which the last scanned token starts.  */
-  @property YYPosition startPos ();
-
-  /**
-   * Method to retrieve the ending position of the last scanned token.
-   * @return the first position beyond the last scanned token.  */
-  @property YYPosition endPos ();
-
-  /**
-   * Method to retrieve the semantic value of the last scanned token.
-   * @return the semantic value of the last scanned token.  */
-  @property YYSemanticType semanticVal ();
-
-  /**
-   * Entry point for the scanner.  Returns the token identifier corresponding
-   * to the next token and prepares to return the semantic value
-   * and beginning/ending positions of the token.
-   * @return the token identifier corresponding to the next token. */
-  TokenKind yylex ();
-
-  /**
-   * Entry point for error reporting.  Emits an error
-   * referring to the given location in a user-defined way.
-   *
-   * @param loc The location of the element to which the
-   *                error message is related
-   * @param s The string for the error message.  */
-   void yyerror (YYLocation loc, string s);
-}
-
- semantic types are handled by D unions (same as for C/C++ parsers)
-
- the following (non-standard) %defines are supported:
-
-  %define package "<package_name>"
-  %define api.parser.class "my_class_name>"
-  %define position_type "my_position_type"
-  %define location_type "my_location_type"
-
- the following declarations basically work like in C/C++:
-
-  %locations
-  %error-verbose
-  %parse-param
-  %initial-action
-  %code
-  %union
-
- %destructor is not yet supported
@@ -2,8 +2,8 @@

 # Language-independent M4 Macros for Bison.

-# Copyright (C) 2002, 2004-2015, 2018-2020 Free Software Foundation,
-# Inc.
+# Copyright (C) 2002, 2004-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,7 +16,30 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+
+
+# m4_gsub(STRING, RE1, SUBST1, RE2, SUBST2, ...)
+# ----------------------------------------------
+# m4 equivalent of
+#
+#   $_ = STRING;
+#   s/RE1/SUBST1/g;
+#   s/RE2/SUBST2/g;
+#   ...
+#
+# Really similar to m4_bpatsubsts, but behaves properly with quotes.
+# See m4.at's "Generating Comments".  Super inelegant, but so far, I
+# did not find any better solution.
+m4_define([b4_gsub],
+[m4_bpatsubst(m4_bpatsubst(m4_bpatsubst([[[[$1]]]],
+                                        [$2], [$3]),
+                           [$4], [$5]),
+              [$6], [$7])])
+
+# m4_shift2 and m4_shift3 are provided by m4sugar.
+m4_define([m4_shift4], [m4_shift(m4_shift(m4_shift(m4_shift($@))))])


 ## ---------------- ##
@@ -26,7 +49,7 @@
 # b4_generated_by
 # ---------------
 m4_define([b4_generated_by],
-[b4_comment([A Bison parser, made by GNU Bison b4_version.])
+[b4_comment([A Bison parser, made by GNU Bison b4_version_string.])
 ])

 # b4_copyright(TITLE, [YEARS])
@@ -51,7 +74,7 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.])
+along with this program.  If not, see <https://www.gnu.org/licenses/>.])

 b4_comment([As a special exception, you may create a larger work that contains
 part or all of the Bison parser skeleton and distribute that work
@@ -162,7 +185,7 @@ m4_define([b4_error],
 [b4_cat([[@complain][(]$1[@,]$2[@,]$3[@,]$4[]]dnl
 [m4_if([$#], [4], [],
       [m4_foreach([b4_arg],
-                   m4_dquote(m4_shift(m4_shift(m4_shift(m4_shift($@))))),
+                   m4_dquote(m4_shift4($@)),
                   [[@,]b4_arg])])[@)]])])

 # b4_warn(FORMAT, [ARG1], [ARG2], ...)
@@ -238,6 +261,13 @@ m4_define([b4_fatal_at],
 [b4_error([[fatal]], $@)dnl
 m4_exit(1)])

+# b4_canary(MSG)
+# --------------
+# Issue a warning on stderr and in the output.  Used in the test suite
+# to catch spurious m4 evaluations.
+m4_define([b4_canary],
+[m4_errprintn([dead canary: $1])DEAD CANARY($1)])
+

 ## ------------ ##
 ## Data Types.  ##
@@ -309,14 +339,14 @@ number is the opposite.  If YYTABLE_NINF, syntax error.]])
 $1([check], [b4_check])

 $1([stos], [b4_stos],
-   [[YYSTOS[STATE-NUM] -- The (internal number of the) accessing
-symbol of state STATE-NUM.]])
+   [[YYSTOS[STATE-NUM] -- The symbol kind of the accessing symbol of
+state STATE-NUM.]])

 $1([r1], [b4_r1],
-   [[YYR1[YYN] -- Symbol number of symbol that rule YYN derives.]])
+   [[YYR1[RULE-NUM] -- Symbol kind of the left-hand side of rule RULE-NUM.]])

 $1([r2], [b4_r2],
-   [[YYR2[YYN] -- Number of symbols on the right hand side of rule YYN.]])
+   [[YYR2[RULE-NUM] -- Number of symbols on the right-hand side of rule RULE-NUM.]])
 ])


@@ -368,9 +398,9 @@ m4_define([b4_$3_if],
 # b4_FLAG_if(IF-TRUE, IF-FALSE)
 # -----------------------------
 # Expand IF-TRUE, if FLAG is true, IF-FALSE otherwise.
-b4_define_flag_if([defines])            # Whether headers are requested.
 b4_define_flag_if([glr])                # Whether a GLR parser is requested.
 b4_define_flag_if([has_translations])   # Whether some tokens are internationalized.
+b4_define_flag_if([header])             # Whether a header is requested.
 b4_define_flag_if([nondeterministic])   # Whether conflicts should be handled.
 b4_define_flag_if([token_table])        # Whether yytoken_table is demanded.
 b4_define_flag_if([yacc])               # Whether POSIX Yacc is emulated.
@@ -381,6 +411,10 @@ b4_define_flag_if([yacc])               # Whether POSIX Yacc is emulated.
 m4_define([b4_glr_cc_if],
          [m4_if(b4_skeleton, ["glr.cc"], $@)])

+# b4_glr2_cc_if([IF-TRUE], [IF-FALSE])
+# ------------------------------------
+m4_define([b4_glr2_cc_if],
+          [m4_if(b4_skeleton, ["glr2.cc"], $@)])

 ## --------- ##
 ## Symbols.  ##
@@ -415,14 +449,14 @@ m4_define([b4_symbol_token_kind],
 _b4_symbol([$1], [id])])


-# b4_symbol_kind(NUM)
-# -------------------
+# b4_symbol_kind_base(NUM)
+# ------------------------
 # Build the name of the kind of this symbol.  It must always exist,
 # otherwise some symbols might not be represented in the enum, which
 # might be compiled into too small a type to contain all the symbol
 # numbers.
 m4_define([b4_symbol_prefix], [b4_percent_define_get([api.symbol.prefix])])
-m4_define([b4_symbol_kind],
+m4_define([b4_symbol_kind_base],
 [b4_percent_define_get([api.symbol.prefix])dnl
 m4_case([$1],
  [-2],                             [[YYEMPTY]],
@@ -435,16 +469,42 @@ m4_case([$1],
                                    [m4_bpatsubst([$1-][]_b4_symbol([$1], [tag]), [[^a-zA-Z_0-9]+], [_])])])])])


+# b4_symbol_kind(NUM)
+# -------------------
+# Same as b4_symbol_kind, but possibly with a prefix in some
+# languages.  E.g., EOF's kind_base and kind are YYSYMBOL_YYEOF in C,
+# but are S_YYEMPTY and symbol_kind::S_YYEMPTY in C++.
+m4_copy([b4_symbol_kind_base], [b4_symbol_kind])
+
+
+# b4_symbol_slot(NUM)
+# -------------------
+# The name of union member that contains the value of these symbols.
+# Currently, we are messy, this should actually be type_tag, but type_tag
+# has several meanings.
+m4_define([b4_symbol_slot],
+[m4_case(b4_percent_define_get([[api.value.type]]),
+         [union],   [b4_symbol([$1], [type_tag])],
+         [variant], [b4_symbol([$1], [type_tag])],
+         [b4_symbol([$1], [type])])])
+
+
 # b4_symbol(NUM, FIELD)
 # ---------------------
-# Fetch FIELD of symbol #NUM (or "orig NUM").  Fail if undefined.
+# Fetch FIELD of symbol #NUM (or "orig NUM", or "empty").  Fail if undefined.
 #
 # If FIELD = id, prepend the token prefix.
 m4_define([b4_symbol],
-[m4_case([$2],
-         [id],    [b4_symbol_token_kind([$1])],
-         [kind],  [b4_symbol_kind([$1])],
-         [_b4_symbol($@)])])
+[m4_if([$1], [empty], [b4_symbol([-2], [$2])],
+       [$1], [eof],   [b4_symbol([0], [$2])],
+       [$1], [error], [b4_symbol([1], [$2])],
+       [$1], [undef], [b4_symbol([2], [$2])],
+       [m4_case([$2],
+                [id],        [b4_symbol_token_kind([$1])],
+                [kind_base], [b4_symbol_kind_base([$1])],
+                [kind],      [b4_symbol_kind([$1])],
+                [slot],      [b4_symbol_slot([$1])],
+                [_b4_symbol($@)])])])


 # b4_symbol_if(NUM, FIELD, IF-TRUE, IF-FALSE)
@@ -506,7 +566,7 @@ m4_defn([b4_actions_])[]dnl
        break;
    }dnl
 ],
-[YYUSE (m4_default([$2], [yykind]));])dnl
+[b4_use(m4_default([$2], [yykind]));])dnl
 m4_popdef([b4_actions_])dnl
 ])

@@ -516,7 +576,7 @@ m4_popdef([b4_actions_])dnl
 # easier to use with m4_map, but then, use []dnl to suppress the last
 # one.
 m4_define([_b4_symbol_case],
-[case b4_symbol([$1], [number]): b4_symbol_tag_comment([$1])])
+[case b4_symbol([$1], [kind]): b4_symbol_tag_comment([$1])])
 ])


@@ -564,8 +624,8 @@ m4_define([b4_any_token_visible_if],
 m4_define([b4_token_format],
 [b4_token_visible_if([$2],
 [m4_format([[$1]],
-           m4_expand(b4_symbol([$2], [id])),
-           m4_expand(b4_symbol([$2], b4_api_token_raw_if([[number]], [[user_number]]))))])])
+           b4_symbol([$2], [id]),
+           b4_symbol([$2], b4_api_token_raw_if([[number]], [[code]])))])])


 # b4_last_enum_token
@@ -602,11 +662,11 @@ m4_define([_b4_type_action],

 ])])

-# b4_type_foreach(MACRO)
-# ----------------------
+# b4_type_foreach(MACRO, [SEP])
+# -----------------------------
 # Invoke MACRO(SYMBOL-NUMS) for each set of SYMBOL-NUMS for each type set.
 m4_define([b4_type_foreach],
-          [m4_map([$1], m4_defn([b4_type_names]))])
+          [m4_map_sep([$1], [$2], m4_defn([b4_type_names]))])



@@ -727,7 +787,7 @@ m4_define([b4_check_user_names],
 [m4_pushdef([b4_occurrence], b4_occurrence)dnl
 m4_pushdef([b4_user_name], m4_car(b4_occurrence))dnl
 m4_pushdef([b4_start], m4_car(m4_shift(b4_occurrence)))dnl
-m4_pushdef([b4_end], m4_shift(m4_shift(b4_occurrence)))dnl
+m4_pushdef([b4_end], m4_shift2(b4_occurrence))dnl
 m4_ifndef($3[(]m4_quote(b4_user_name)[)],
          [b4_complain_at([b4_start], [b4_end],
                          [[%s '%s' is not used]],
@@ -922,15 +982,18 @@ m4_define([b4_percent_define_flag_if],
 # For example:
 #
 #   b4_percent_define_default([[foo]], [[default value]])
+m4_define([_b4_percent_define_define],
+[m4_define([b4_percent_define(]$1[)], [$2])dnl
+m4_define([b4_percent_define_kind(]$1[)],
+          [m4_default([$3], [keyword])])dnl
+m4_define([b4_percent_define_loc(]$1[)],
+          [[[[<skeleton default value>:-1.-1]],
+            [[<skeleton default value>:-1.-1]]]])dnl
+m4_define([b4_percent_define_syncline(]$1[)], [[]])])
+
 m4_define([b4_percent_define_default],
 [_b4_percent_define_ifdef([$1], [],
-           [m4_define([b4_percent_define(]$1[)], [$2])dnl
-            m4_define([b4_percent_define_kind(]$1[)],
-                      [m4_default([$3], [keyword])])dnl
-            m4_define([b4_percent_define_loc(]$1[)],
-                      [[[[<skeleton default value>:-1.-1]],
-                        [[<skeleton default value>:-1.-1]]]])dnl
-            m4_define([b4_percent_define_syncline(]$1[)], [[]])])])
+                          [_b4_percent_define_define($@)])])


 # b4_percent_define_if_define(NAME, [VARIABLE = NAME])
@@ -940,11 +1003,12 @@ m4_define([b4_percent_define_default],
 # to '_'.
 m4_define([_b4_percent_define_if_define],
 [m4_define(m4_bpatsubst([b4_$1_if], [[-.]], [_]),
-           [b4_percent_define_flag_if(m4_default([$2], [$1]),
-                                      [$3], [$4])])])
+           [b4_percent_define_default([m4_default([$2], [$1])], [[false]])dnl
+b4_percent_define_flag_if(m4_default([$2], [$1]),
+                                     [$3], [$4])])])
+
 m4_define([b4_percent_define_if_define],
-[b4_percent_define_default([m4_default([$2], [$1])], [[false]])
-_b4_percent_define_if_define([$1], [$2], $[1], $[2])])
+[_b4_percent_define_if_define([$1], [$2], $[1], $[2])])


 # b4_percent_define_check_kind(VARIABLE, KIND, [DIAGNOSTIC = complain])
@@ -1050,6 +1114,7 @@ b4_percent_define_if_define([token_ctor], [api.token.constructor])
 b4_percent_define_if_define([locations])     # Whether locations are tracked.
 b4_percent_define_if_define([parse.assert])
 b4_percent_define_if_define([parse.trace])
+b4_percent_define_if_define([posix])


 # b4_bison_locations_if([IF-TRUE])
@@ -1079,14 +1144,18 @@ m4_define([b4_parse_error_bmatch],



+# b4_union_if([IF-UNION-ARE-USED], [IF-NOT])
 # b4_variant_if([IF-VARIANT-ARE-USED], [IF-NOT])
 # ----------------------------------------------
-b4_percent_define_if_define([variant])
+# Depend on whether api.value.type is union, or variant.
+m4_define([b4_union_flag],   [[0]])
 m4_define([b4_variant_flag], [[0]])
 b4_percent_define_ifdef([[api.value.type]],
   [m4_case(b4_percent_define_get_kind([[api.value.type]]), [keyword],
-            [m4_case(b4_percent_define_get([[api.value.type]]), [variant],
-                    [m4_define([b4_variant_flag], [[1]])])])])
+            [m4_case(b4_percent_define_get([[api.value.type]]),
+                     [union],   [m4_define([b4_union_flag],   [[1]])],
+                     [variant], [m4_define([b4_variant_flag], [[1]])])])])
+b4_define_flag_if([union])
 b4_define_flag_if([variant])


@@ -2,7 +2,7 @@

 # C++ skeleton dispatching for Bison.

-# Copyright (C) 2006-2007, 2009-2015, 2018-2020 Free Software
+# Copyright (C) 2006-2007, 2009-2015, 2018-2022, 2025-2026 Free Software
 # Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -16,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 b4_glr_if(             [m4_define([b4_used_skeleton], [b4_skeletonsdir/[glr.cc]])])
 b4_nondeterministic_if([m4_define([b4_used_skeleton], [b4_skeletonsdir/[glr.cc]])])
@@ -2,7 +2,7 @@

 # C++ skeleton for Bison

-# Copyright (C) 2002-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2022, 2025-2026 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +15,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 # Sanity checks, before defaults installed by c.m4.
 b4_percent_define_ifdef([[api.value.union.name]],
@@ -105,11 +105,10 @@ b4_percent_define_default([[api.parser.class]], [[parser]])
 #
 # b4_percent_define_default([[api.location.type]], [[location]])

-b4_percent_define_default([[filename_type]], [[std::string]])
+b4_percent_define_default([[api.filename.type]], [[const std::string]])
 # Make it a warning for those who used betas of Bison 3.0.
 b4_percent_define_default([[api.namespace]], m4_defn([b4_prefix]))

-b4_percent_define_default([[global_tokens_and_yystype]], [[false]])
 b4_percent_define_default([[define_location_comparison]],
                          [m4_if(b4_percent_define_get([[filename_type]]),
                                 [std::string], [[true]], [[false]])])
@@ -193,7 +192,7 @@ m4_define([b4_declare_symbol_enum],
 [[enum symbol_kind_type
      {
        YYNTOKENS = ]b4_tokens_number[, ///< Number of tokens.
-        ]b4_symbol_kind([-2])[ = -2,
+        ]b4_symbol(empty, kind_base)[ = -2,
 ]b4_symbol_foreach([      b4_symbol_enum])dnl
 [      };]])

@@ -207,16 +206,16 @@ m4_define([b4_declare_symbol_enum],

 # b4_value_type_declare
 # ---------------------
-# Declare semantic_type.
+# Declare value_type.
 m4_define([b4_value_type_declare],
 [b4_value_type_setup[]dnl
 [    /// Symbol semantic values.
 ]m4_bmatch(b4_percent_define_get_kind([[api.value.type]]),
 [code],
-[[    typedef ]b4_percent_define_get([[api.value.type]])[ semantic_type;]],
+[[    typedef ]b4_percent_define_get([[api.value.type]])[ value_type;]],
 [m4_bmatch(b4_percent_define_get([[api.value.type]]),
 [union\|union-directive],
-[[    union semantic_type
+[[    union value_type
    {
 ]b4_user_union_members[
    };]])])dnl
@@ -228,11 +227,19 @@ m4_define([b4_value_type_declare],
 # Define the public types: token, semantic value, location, and so forth.
 # Depending on %define token_lex, may be output in the header or source file.
 m4_define([b4_public_types_declare],
-[[#ifndef ]b4_api_PREFIX[STYPE
-]b4_value_type_declare[
+[b4_glr2_cc_if(
+[b4_value_type_declare],
+[[#ifdef ]b4_api_PREFIX[STYPE
+# ifdef __GNUC__
+#  pragma GCC message "bison: do not #define ]b4_api_PREFIX[STYPE in C++, use %define api.value.type"
+# endif
+    typedef ]b4_api_PREFIX[STYPE value_type;
 #else
-    typedef ]b4_api_PREFIX[STYPE semantic_type;
-#endif]b4_locations_if([
+]b4_value_type_declare[
+#endif
+    /// Backward compatibility (Bison 3.8).
+    typedef value_type semantic_type;
+]])[]b4_locations_if([
    /// Symbol locations.
    typedef b4_percent_define_get([[api.location.type]],
                                  [[location]]) location_type;])[
@@ -258,16 +265,16 @@ m4_define([b4_public_types_declare],
    /// Token kinds.
    struct token
    {
-      ]b4_token_enums[
+      ]b4_token_enums[]b4_glr2_cc_if([], [[
      /// Backward compatibility alias (Bison 3.6).
-      typedef token_kind_type yytokentype;
+      typedef token_kind_type yytokentype;]])[
    };

    /// Token kind, as returned by yylex.
-    typedef token::yytokentype token_kind_type;
+    typedef token::token_kind_type token_kind_type;]b4_glr2_cc_if([], [[

    /// Backward compatibility alias (Bison 3.6).
-    typedef token_kind_type token_type;
+    typedef token_kind_type token_type;]])[

    /// Symbol kinds.
    struct symbol_kind
@@ -301,7 +308,7 @@ m4_define([b4_symbol_type_define],
      typedef Base super_type;

      /// Default constructor.
-      basic_symbol ()
+      basic_symbol () YY_NOEXCEPT
        : value ()]b4_locations_if([
        , location ()])[
      {}
@@ -321,15 +328,16 @@ m4_define([b4_symbol_type_define],
      /// Copy constructor.
      basic_symbol (const basic_symbol& that);]b4_variant_if([[

-      /// Constructor for valueless symbols, and symbols from each type.
-]b4_type_foreach([b4_basic_symbol_constructor_define])], [[
+      /// Constructors for typed symbols.
+]b4_type_foreach([b4_basic_symbol_constructor_define], [
+])], [[
      /// Constructor for valueless symbols.
      basic_symbol (typename Base::kind_type t]b4_locations_if([,
                    YY_MOVE_REF (location_type) l])[);

      /// Constructor for symbols with semantic value.
      basic_symbol (typename Base::kind_type t,
-                    YY_RVREF (semantic_type) v]b4_locations_if([,
+                    YY_RVREF (value_type) v]b4_locations_if([,
                    YY_RVREF (location_type) l])[);
 ]])[
      /// Destroy the symbol.
@@ -338,8 +346,32 @@ m4_define([b4_symbol_type_define],
        clear ();
      }

+#if 201103L <= YY_CPLUSPLUS
+      /// Copy assignment.
+      basic_symbol& operator= (const basic_symbol& that)
+      {
+        Base::operator= (that);]b4_variant_if([[
+        ]b4_symbol_variant([this->kind ()], [value], [copy],
+                           [that.value])], [[
+        value = that.value]])[;]b4_locations_if([[
+        location = that.location;]])[
+        return *this;
+      }
+
+      /// Move assignment.
+      basic_symbol& operator= (basic_symbol&& that)
+      {
+        Base::operator= (std::move (that));]b4_variant_if([[
+        ]b4_symbol_variant([this->kind ()], [value], [move],
+                           [std::move (that.value)])], [[
+        value = std::move (that.value)]])[;]b4_locations_if([[
+        location = std::move (that.location);]])[
+        return *this;
+      }
+#endif
+
      /// Destroy contents, and record that is empty.
-      void clear ()
+      void clear () YY_NOEXCEPT
      {]b4_variant_if([[
        // User destructor.
        symbol_kind_type yykind = this->kind ();
@@ -378,10 +410,10 @@ m4_define([b4_symbol_type_define],
      std::string name () const YY_NOEXCEPT
      {
        return ]b4_parser_class[::symbol_name (this->kind ());
-      }]])[
+      }]])[]b4_glr2_cc_if([], [[

      /// Backward compatibility (Bison 3.6).
-      symbol_kind_type type_get () const YY_NOEXCEPT;
+      symbol_kind_type type_get () const YY_NOEXCEPT;]])[

      /// Whether empty.
      bool empty () const YY_NOEXCEPT;
@@ -390,7 +422,7 @@ m4_define([b4_symbol_type_define],
      void move (basic_symbol& s);

      /// The semantic value.
-      semantic_type value;]b4_locations_if([
+      value_type value;]b4_locations_if([

      /// The location.
      location_type location;])[
@@ -405,43 +437,51 @@ m4_define([b4_symbol_type_define],
    /// Type access provider for token (enum) based symbols.
    struct by_kind
    {
-      /// Default constructor.
-      by_kind ();
-
-#if 201103L <= YY_CPLUSPLUS
-      /// Move constructor.
-      by_kind (by_kind&& that);
-#endif
-
-      /// Copy constructor.
-      by_kind (const by_kind& that);
-
      /// The symbol kind as needed by the constructor.
      typedef token_kind_type kind_type;

+      /// Default constructor.
+      by_kind () YY_NOEXCEPT;
+
+#if 201103L <= YY_CPLUSPLUS
+      /// Move constructor.
+      by_kind (by_kind&& that) YY_NOEXCEPT;
+#endif
+
+      /// Copy constructor.
+      by_kind (const by_kind& that) YY_NOEXCEPT;
+
      /// Constructor from (external) token numbers.
-      by_kind (kind_type t);
+      by_kind (kind_type t) YY_NOEXCEPT;
+
+#if 201103L <= YY_CPLUSPLUS
+      /// Copy assignment.
+      by_kind& operator= (const by_kind& that);
+
+      /// Move assignment.
+      by_kind& operator= (by_kind&& that);
+#endif

      /// Record that this symbol is empty.
-      void clear ();
+      void clear () YY_NOEXCEPT;

      /// Steal the symbol kind from \a that.
      void move (by_kind& that);

      /// The (internal) type number (corresponding to \a type).
      /// \a empty when empty.
-      symbol_kind_type kind () const YY_NOEXCEPT;
+      symbol_kind_type kind () const YY_NOEXCEPT;]b4_glr2_cc_if([], [[

      /// Backward compatibility (Bison 3.6).
-      symbol_kind_type type_get () const YY_NOEXCEPT;
+      symbol_kind_type type_get () const YY_NOEXCEPT;]])[

      /// The symbol kind.
      /// \a ]b4_symbol_prefix[YYEMPTY when empty.
      symbol_kind_type kind_;
-    };
+    };]b4_glr2_cc_if([], [[

    /// Backward compatibility for a private implementation detail (Bison 3.6).
-    typedef by_kind by_type;
+    typedef by_kind by_type;]])[

    /// "External" symbols: returned by the scanner.
    struct symbol_type : basic_symbol<by_kind>
@@ -450,10 +490,10 @@ m4_define([b4_symbol_type_define],
      typedef basic_symbol<by_kind> super_type;

      /// Empty symbol.
-      symbol_type () {}
+      symbol_type () YY_NOEXCEPT {}

      /// Constructor for valueless symbols, and symbols from each type.
-]b4_type_foreach([_b4_token_constructor_define])dnl
+]b4_type_foreach([_b4_symbol_constructor_define])dnl
    ])[};
 ]])

@@ -487,7 +527,7 @@ m4_define([b4_public_types_define],
  template <typename Base>
  ]b4_parser_class[::basic_symbol<Base>::basic_symbol (]b4_join(
          [typename Base::kind_type t],
-          [YY_RVREF (semantic_type) v],
+          [YY_RVREF (value_type) v],
          b4_locations_if([YY_RVREF (location_type) l]))[)
    : Base (t)
    , value (]b4_variant_if([], [YY_MOVE (v)])[)]b4_locations_if([
@@ -496,18 +536,20 @@ m4_define([b4_public_types_define],
    (void) v;
    ]b4_symbol_variant([this->kind ()], [value], [YY_MOVE_OR_COPY], [YY_MOVE (v)])])[}]])[

+]b4_glr2_cc_if([], [[
  template <typename Base>
  ]b4_parser_class[::symbol_kind_type
  ]b4_parser_class[::basic_symbol<Base>::type_get () const YY_NOEXCEPT
  {
    return this->kind ();
  }
+]])[

  template <typename Base>
  bool
  ]b4_parser_class[::basic_symbol<Base>::empty () const YY_NOEXCEPT
  {
-    return this->kind () == symbol_kind::]b4_symbol_prefix[YYEMPTY;
+    return this->kind () == ]b4_symbol(empty, kind)[;
  }

  template <typename Base>
@@ -522,30 +564,47 @@ m4_define([b4_public_types_define],
  }

  // by_kind.
-  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind ()
-    : kind_ (symbol_kind::]b4_symbol_prefix[YYEMPTY)
+  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind () YY_NOEXCEPT
+    : kind_ (]b4_symbol(empty, kind)[)
  {}

 #if 201103L <= YY_CPLUSPLUS
-  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (by_kind&& that)
+  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (by_kind&& that) YY_NOEXCEPT
    : kind_ (that.kind_)
  {
    that.clear ();
  }
 #endif

-  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (const by_kind& that)
+  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (const by_kind& that) YY_NOEXCEPT
    : kind_ (that.kind_)
  {}

-  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (token_kind_type t)
+  ]b4_inline([$1])b4_parser_class[::by_kind::by_kind (token_kind_type t) YY_NOEXCEPT
    : kind_ (yytranslate_ (t))
  {}

-  ]b4_inline([$1])[void
-  ]b4_parser_class[::by_kind::clear ()
+#if 201103L <= YY_CPLUSPLUS
+  ]b4_inline([$1])]b4_parser_class[::by_kind&
+  b4_parser_class[::by_kind::by_kind::operator= (const by_kind& that)
  {
-    kind_ = symbol_kind::]b4_symbol_prefix[YYEMPTY;
+    kind_ = that.kind_;
+    return *this;
+  }
+
+  ]b4_inline([$1])]b4_parser_class[::by_kind&
+  b4_parser_class[::by_kind::by_kind::operator= (by_kind&& that)
+  {
+    kind_ = that.kind_;
+    that.clear ();
+    return *this;
+  }
+#endif
+
+  ]b4_inline([$1])[void
+  ]b4_parser_class[::by_kind::clear () YY_NOEXCEPT
+  {
+    kind_ = ]b4_symbol(empty, kind)[;
  }

  ]b4_inline([$1])[void
@@ -561,17 +620,19 @@ m4_define([b4_public_types_define],
    return kind_;
  }

+]b4_glr2_cc_if([], [[
  ]b4_inline([$1])[]b4_parser_class[::symbol_kind_type
  ]b4_parser_class[::by_kind::type_get () const YY_NOEXCEPT
  {
    return this->kind ();
  }
+]])[
 ]])


 # b4_token_constructor_define
 # ----------------------------
-# Define symbol constructors for all the value types.
+# Define make_FOO for all the token kinds.
 # Use at class-level.  Redefined in variant.hh.
 m4_define([b4_token_constructor_define], [])

@@ -582,7 +643,7 @@ m4_define([b4_token_constructor_define], [])
 # sometimes in the cc file.
 m4_define([b4_yytranslate_define],
 [  b4_inline([$1])b4_parser_class[::symbol_kind_type
-  ]b4_parser_class[::yytranslate_ (int t)
+  ]b4_parser_class[::yytranslate_ (int t) YY_NOEXCEPT
  {
 ]b4_api_token_raw_if(
 [[    return static_cast<symbol_kind_type> (t);]],
@@ -594,12 +655,13 @@ m4_define([b4_yytranslate_define],
    {
  ]b4_translate[
    };
-    const int user_token_number_max_ = ]b4_user_token_number_max[;
+    // Last valid token kind.
+    const int code_max = ]b4_code_max[;

    if (t <= 0)
      return symbol_kind::]b4_symbol_prefix[YYEOF;
-    else if (t <= user_token_number_max_)
-      return YY_CAST (symbol_kind_type, translate_table[t]);
+    else if (t <= code_max)
+      return static_cast <symbol_kind_type> (translate_table[t]);
    else
      return symbol_kind::]b4_symbol_prefix[YYUNDEF;]])[
  }
@@ -2,7 +2,8 @@

 # Common code for C-like languages (C, C++, Java, etc.)

-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +16,8 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+

 # _b4_comment(TEXT, OPEN, CONTINUE, END)
 # --------------------------------------
@@ -27,9 +29,10 @@
 #
 # Prefix all the output lines with PREFIX.
 m4_define([_b4_comment],
-[$2[]m4_bpatsubsts(m4_expand([$1]),
-                   [[*]/], [*\\/],
-                   [/[*]], [/\\*], [
+[$2[]b4_gsub(m4_expand([$1]),
+            [[*]/], [*\\/],
+            [/[*]], [/\\*],
+            [
 \(.\)], [
 $3\1])$4])

@@ -2,7 +2,7 @@

 # C skeleton dispatching for Bison.

-# Copyright (C) 2006-2007, 2009-2015, 2018-2020 Free Software
+# Copyright (C) 2006-2007, 2009-2015, 2018-2022, 2025-2026 Free Software
 # Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -16,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 b4_glr_if(             [m4_define([b4_used_skeleton], [b4_skeletonsdir/[glr.c]])])
 b4_nondeterministic_if([m4_define([b4_used_skeleton], [b4_skeletonsdir/[glr.c]])])
@@ -2,8 +2,8 @@

 # C M4 Macros for Bison.

-# Copyright (C) 2002, 2004-2015, 2018-2020 Free Software Foundation,
-# Inc.
+# Copyright (C) 2002, 2004-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_include(b4_skeletonsdir/[c-like.m4])

@@ -58,11 +58,11 @@ m4_define([b4_cpp_guard_close],
 # b4_pull_flag if they use the values of the %define variables api.pure or
 # api.push-pull.
 m4_define([b4_identification],
-[[/* Identify Bison output.  */
-#define YYBISON 1
+[[/* Identify Bison output, and Bison version.  */
+#define YYBISON ]b4_version[

-/* Bison version.  */
-#define YYBISON_VERSION "]b4_version["
+/* Bison version string.  */
+#define YYBISON_VERSION "]b4_version_string["

 /* Skeleton name.  */
 #define YYSKELETON_NAME ]b4_skeleton[]m4_ifdef([b4_pure_flag], [[
@@ -107,27 +107,32 @@ b4_percent_define_default([[api.symbol.prefix]], [[YYSYMBOL_]])
 ## Pure/impure interfaces.  ##
 ## ------------------------ ##

-# b4_lex_formals
-# --------------
+# b4_yylex_formals
+# ----------------
 # All the yylex formal arguments.
 # b4_lex_param arrives quoted twice, but we want to keep only one level.
-m4_define([b4_lex_formals],
-[b4_pure_if([[[[YYSTYPE *yylvalp]], [[&yylval]]][]dnl
-b4_locations_if([, [[YYLTYPE *yyllocp], [&yylloc]]])])dnl
+m4_define([b4_yylex_formals],
+[b4_pure_if([[[b4_api_PREFIX[STYPE *yylvalp]], [[&yylval]]][]dnl
+b4_locations_if([, [b4_api_PREFIX[LTYPE *yyllocp], [&yylloc]]])])dnl
 m4_ifdef([b4_lex_param], [, ]b4_lex_param)])


-# b4_lex
-# ------
+# b4_yylex
+# --------
 # Call yylex.
-m4_define([b4_lex],
-[b4_function_call([yylex], [int], b4_lex_formals)])
+m4_define([b4_yylex],
+[b4_function_call([yylex], [int], b4_yylex_formals)])


 # b4_user_args
 # ------------
 m4_define([b4_user_args],
-[m4_ifset([b4_parse_param], [, b4_args(b4_parse_param)])])
+[m4_ifset([b4_parse_param], [, b4_user_args_no_comma])])
+
+# b4_user_args_no_comma
+# ---------------------
+m4_define([b4_user_args_no_comma],
+[m4_ifset([b4_parse_param], [b4_args(b4_parse_param)])])


 # b4_user_formals
@@ -158,13 +163,20 @@ m4_popdef([$2])dnl
 m4_popdef([$1])dnl
 ])])

+
+# b4_use(EXPR)
+# ------------
+# Pacify the compiler about some maybe unused value.
+m4_define([b4_use],
+[YY_USE ($1)])
+
 # b4_parse_param_use([VAL], [LOC])
 # --------------------------------
-# 'YYUSE' VAL, LOC if locations are enabled, and all the parse-params.
+# 'YY_USE' VAL, LOC if locations are enabled, and all the parse-params.
 m4_define([b4_parse_param_use],
-[m4_ifvaln([$1], [  YYUSE ([$1]);])dnl
-b4_locations_if([m4_ifvaln([$2], [  YYUSE ([$2]);])])dnl
-b4_parse_param_for([Decl], [Formal], [  YYUSE (Formal);
+[m4_ifvaln([$1], [  b4_use([$1]);])dnl
+b4_locations_if([m4_ifvaln([$2], [  b4_use([$2]);])])dnl
+b4_parse_param_for([Decl], [Formal], [  b4_use(Formal);
 ])dnl
 ])

@@ -242,6 +254,18 @@ typedef int_least16_t yytype_int16;
 typedef short yytype_int16;
 #endif

+/* Work around bug in HP-UX 11.23, which defines these macros
+   incorrectly for preprocessor constants.  This workaround can likely
+   be removed in 2023, as HPE has promised support for HP-UX 11.23
+   (aka HP-UX 11i v2) only through the end of 2022; see Table 2 of
+   <https://h20195.www2.hpe.com/V2/getpdf.aspx/4AA4-7673ENW.pdf>.  */
+#ifdef __hpux
+# undef UINT_LEAST8_MAX
+# undef UINT_LEAST16_MAX
+# define UINT_LEAST8_MAX 255
+# define UINT_LEAST16_MAX 65535
+#endif
+
 #if defined __UINT_LEAST8_MAX__ && __UINT_LEAST8_MAX__ <= __INT_MAX__
 typedef __UINT_LEAST8_TYPE__ yytype_uint8;
 #elif (!defined __UINT_LEAST8_MAX__ && defined YY_STDINT_H \
@@ -355,17 +379,27 @@ m4_define([b4_attribute_define],
 #endif

 ]m4_bmatch([$1], [\bnoreturn\b], [[/* The _Noreturn keyword of C11.  */
-]dnl This is an exact copy of lib/_Noreturn.h.
+]dnl This is close to lib/_Noreturn.h, except that we do enable
+dnl the use of [[noreturn]], because _Noreturn is used in places
+dnl where [[noreturn]] works in C++.  We need this in particular
+dnl because of glr.cc which compiles code from glr.c in C++.
+dnl And the C++ compiler chokes on _Noreturn.  Also, we do not
+dnl use C' _Noreturn in C++, to avoid -Wc11-extensions warnings.
 [#ifndef _Noreturn
 # if (defined __cplusplus \
      && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
          || (defined _MSC_VER && 1900 <= _MSC_VER)))
 #  define _Noreturn [[noreturn]]
 # elif ((!defined __cplusplus || defined __clang__) \
-        && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0)  \
-            || 4 < __GNUC__ + (7 <= __GNUC_MINOR__)))
+        && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0) \
+            || (!defined __STRICT_ANSI__ \
+                && (4 < __GNUC__ + (7 <= __GNUC_MINOR__) \
+                    || (defined __apple_build_version__ \
+                        ? 6000000 <= __apple_build_version__ \
+                        : 3 < __clang_major__ + (5 <= __clang_minor__))))))
   /* _Noreturn works as-is.  */
-# elif 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || 0x5110 <= __SUNPRO_C
+# elif (2 < __GNUC__ + (8 <= __GNUC_MINOR__) || defined __clang__ \
+        || 0x5110 <= __SUNPRO_C)
 #  define _Noreturn __attribute__ ((__noreturn__))
 # elif 1200 <= (defined _MSC_VER ? _MSC_VER : 0)
 #  define _Noreturn __declspec (noreturn)
@@ -376,17 +410,23 @@ m4_define([b4_attribute_define],

 ]])[/* Suppress unused-variable warnings by "using" E.  */
 #if ! defined lint || defined __GNUC__
-# define YYUSE(E) ((void) (E))
+# define YY_USE(E) ((void) (E))
 #else
-# define YYUSE(E) /* empty */
+# define YY_USE(E) /* empty */
 #endif

-#if defined __GNUC__ && ! defined __ICC && 407 <= __GNUC__ * 100 + __GNUC_MINOR__
 /* Suppress an incorrect diagnostic about yylval being uninitialized.  */
-# define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN                            \
+#if defined __GNUC__ && ! defined __ICC && 406 <= __GNUC__ * 100 + __GNUC_MINOR__
+# if __GNUC__ * 100 + __GNUC_MINOR__ < 407
+#  define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN                           \
+    _Pragma ("GCC diagnostic push")                                     \
+    _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")
+# else
+#  define YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN                           \
    _Pragma ("GCC diagnostic push")                                     \
    _Pragma ("GCC diagnostic ignored \"-Wuninitialized\"")              \
    _Pragma ("GCC diagnostic ignored \"-Wmaybe-uninitialized\"")
+# endif
 # define YY_IGNORE_MAYBE_UNINITIALIZED_END      \
    _Pragma ("GCC diagnostic pop")
 #else
@@ -466,7 +506,7 @@ m4_define([b4_null], [YY_NULLPTR])
 # -------------------------------------------------------------
 # Define "yy<TABLE-NAME>" whose contents is CONTENT.
 m4_define([b4_integral_parser_table_define],
-[m4_ifvaln([$3], [b4_comment([$3], [  ])])dnl
+[m4_ifvaln([$3], [b4_comment([$3])])dnl
 static const b4_int_type_for([$2]) yy$1[[]] =
 {
  $2
@@ -485,7 +525,7 @@ static const b4_int_type_for([$2]) yy$1[[]] =
 m4_define([b4_symbol(-2, id)],  [b4_api_PREFIX[][EMPTY]])
 m4_define([b4_symbol(-2, tag)], [[No symbol.]])

-m4_if(b4_symbol(0, id), [YYEOF],
+m4_if(b4_symbol(eof, id), [YYEOF],
     [m4_define([b4_symbol(0, id)],  [b4_api_PREFIX[][EOF]])])
 m4_define([b4_symbol(1, id)],  [b4_api_PREFIX[][error]])
 m4_define([b4_symbol(2, id)],  [b4_api_PREFIX[][UNDEF]])
@@ -501,10 +541,11 @@ m4_define([b4_token_define],
 # ----------------
 # Output the definition of the tokens.
 m4_define([b4_token_defines],
-[b4_any_token_visible_if([/* Token kinds.  */
-m4_join([
+[[/* Token kinds.  */
+#define ]b4_symbol(empty, [id])[ -2
+]m4_join([
 ], b4_symbol_map([b4_token_define]))
-])])
+])


 # b4_token_enum(TOKEN-NUM)
@@ -515,7 +556,7 @@ m4_define([b4_token_enum],
    [m4_format([    %-30s %s],
               m4_format([[%s = %s%s%s]],
                         b4_symbol([$1], [id]),
-                         b4_symbol([$1], b4_api_token_raw_if([[number]], [[user_number]])),
+                         b4_symbol([$1], b4_api_token_raw_if([[number]], [[code]])),
                         m4_if([$1], b4_last_enum_token, [], [[,]])),
               [b4_symbol_tag_comment([$1])])])])

@@ -529,7 +570,7 @@ m4_define([b4_token_enums],
 # define ]b4_api_PREFIX[TOKENTYPE
  enum ]b4_api_prefix[tokentype
  {
-    ]b4_symbol([-2], [id])[ = -2,
+    ]b4_symbol(empty, [id])[ = -2,
 ]b4_symbol_foreach([b4_token_enum])dnl
 [  };
  typedef enum ]b4_api_prefix[tokentype ]b4_api_prefix[token_kind_t;
@@ -564,7 +605,7 @@ m4_define([b4_symbol_translate],
 m4_define([b4_symbol_enum],
 [m4_format([  %-40s %s],
           m4_format([[%s = %s%s%s]],
-                     b4_symbol([$1], [kind]),
+                     b4_symbol([$1], [kind_base]),
                     [$1],
                     m4_if([$1], b4_last_symbol, [], [[,]])),
           [b4_symbol_tag_comment([$1])])])
@@ -579,7 +620,7 @@ m4_define([b4_declare_symbol_enum],
 [[/* Symbol kind.  */
 enum yysymbol_kind_t
 {
-  ]b4_symbol_kind([-2])[ = -2,
+  ]b4_symbol(empty, [kind_base])[ = -2,
 ]b4_symbol_foreach([b4_symbol_enum])dnl
 [};
 typedef enum yysymbol_kind_t yysymbol_kind_t;
@@ -621,6 +662,14 @@ m4_define([b4_formal],
 [$1])


+# b4_function_declare(NAME, RETURN-VALUE, [DECL1, NAME1], ...)
+# ------------------------------------------------------------
+# Declare the function NAME.
+m4_define([b4_function_declare],
+[$2 $1 (b4_formals(m4_shift2($@)));[]dnl
+])
+
+

 ## --------------------- ##
 ## Calling C functions.  ##
@@ -658,10 +707,10 @@ m4_define([b4_sync_start], [[#]line $1 $2])
 ## User actions.  ##
 ## -------------- ##

-# b4_case(LABEL, STATEMENTS)
-# --------------------------
+# b4_case(LABEL, STATEMENTS, [COMMENTS])
+# --------------------------------------
 m4_define([b4_case],
-[  case $1:
+[  case $1:m4_ifval([$3], [ b4_comment([$3])])
 $2
 b4_syncline([@oline@], [@ofile@])dnl
    break;])
@@ -720,13 +769,6 @@ yy_symbol_value_print (FILE *yyo,
 ]b4_parse_param_use([yyoutput], [yylocationp])dnl
 [  if (!yyvaluep)
    return;]
-dnl glr.c does not feature yytoknum.
-m4_if(b4_skeleton, ["yacc.c"],
-[[# ifdef YYPRINT
-  if (yykind < YYNTOKENS)
-    YYPRINT (yyo, yytoknum[yykind], *yyvaluep);
-# endif
-]])dnl
 b4_percent_code_get([[pre-printer]])dnl
  YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
  b4_symbol_actions([printer])
@@ -747,7 +789,7 @@ yy_symbol_print (FILE *yyo,
  YYFPRINTF (yyo, "%s %s (",
             yykind < YYNTOKENS ? "token" : "nterm", yysymbol_name (yykind));

-]b4_locations_if([  YY_LOCATION_PRINT (yyo, *yylocationp);
+]b4_locations_if([  YYLOCATION_PRINT (yyo, yylocationp);
  YYFPRINTF (yyo, ": ");
 ])dnl
 [  yy_symbol_value_print (yyo, yykind, yyvaluep]dnl
@@ -934,7 +976,7 @@ struct ]b4_api_PREFIX[LTYPE

 # b4_declare_yylstype
 # -------------------
-# Declarations that might either go into the header (if --defines) or
+# Declarations that might either go into the header (if --header) or
 # in the parser body.  Declare YYSTYPE/YYLTYPE, and yylval/yylloc.
 m4_define([b4_declare_yylstype],
 [b4_value_type_define[]b4_locations_if([
@@ -1004,17 +1046,24 @@ m4_define([b4_yylloc_default_define],
 #endif
 ]])

-# b4_yy_location_print_define
-# ---------------------------
-# Define YY_LOCATION_PRINT.
-m4_define([b4_yy_location_print_define],
+# b4_yylocation_print_define
+# --------------------------
+# Define YYLOCATION_PRINT.
+m4_define([b4_yylocation_print_define],
 [b4_locations_if([[
-/* YY_LOCATION_PRINT -- Print the location on the stream.
+/* YYLOCATION_PRINT -- Print the location on the stream.
   This macro was not mandated originally: define only if we know
   we won't break user code: when these are the locations we know.  */

-# ifndef YY_LOCATION_PRINT
-#  if defined ]b4_api_PREFIX[LTYPE_IS_TRIVIAL && ]b4_api_PREFIX[LTYPE_IS_TRIVIAL
+# ifndef YYLOCATION_PRINT
+
+#  if defined YY_LOCATION_PRINT
+
+   /* Temporary convenience wrapper in case some people defined the
+      undocumented and private YY_LOCATION_PRINT macros.  */
+#   define YYLOCATION_PRINT(File, Loc)  YY_LOCATION_PRINT(File, *(Loc))
+
+#  elif defined ]b4_api_PREFIX[LTYPE_IS_TRIVIAL && ]b4_api_PREFIX[LTYPE_IS_TRIVIAL

 /* Print *YYLOCP on YYO.  Private, do not rely on its existence. */

@@ -1042,19 +1091,23 @@ yy_location_print_ (FILE *yyo, YYLTYPE const * const yylocp)
        res += YYFPRINTF (yyo, "-%d", end_col);
    }
  return res;
- }
+}

-#   define YY_LOCATION_PRINT(File, Loc)          \
-  yy_location_print_ (File, &(Loc))
+#   define YYLOCATION_PRINT  yy_location_print_
+
+    /* Temporary convenience wrapper in case some people defined the
+       undocumented and private YY_LOCATION_PRINT macros.  */
+#   define YY_LOCATION_PRINT(File, Loc)  YYLOCATION_PRINT(File, &(Loc))

 #  else
-#   define YY_LOCATION_PRINT(File, Loc) ((void) 0)
+
+#   define YYLOCATION_PRINT(File, Loc) ((void) 0)
+    /* Temporary convenience wrapper in case some people defined the
+       undocumented and private YY_LOCATION_PRINT macros.  */
+#   define YY_LOCATION_PRINT  YYLOCATION_PRINT
+
 #  endif
-# endif /* !defined YY_LOCATION_PRINT */]],
-[[/* This macro is provided for backward compatibility. */
-# ifndef YY_LOCATION_PRINT
-#  define YY_LOCATION_PRINT(File, Loc) ((void) 0)
-# endif]])
+# endif /* !defined YYLOCATION_PRINT */]])
 ])

 # b4_yyloc_default
@@ -2,7 +2,7 @@

 # D skeleton dispatching for Bison.

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +15,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 b4_glr_if(             [b4_complain([%%glr-parser not supported for D])])
 b4_nondeterministic_if([b4_complain([%%nondeterministic-parser not supported for D])])
@@ -2,7 +2,7 @@

 # D language support for Bison

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,27 +15,36 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.


-# _b4_comment(TEXT, OPEN, CONTINUE, END)
-# --------------------------------------
-# Put TEXT in comment.  Avoid trailing spaces: don't indent empty lines.
-# Avoid adding indentation to the first line, as the indentation comes
-# from OPEN.  That's why we don't patsubst([$1], [^\(.\)], [   \1]).
-#
-# Prefix all the output lines with PREFIX.
-m4_define([_b4_comment],
-[$2[]m4_bpatsubst(m4_expand([[$1]]), [
-\(.\)], [
-$3\1])$4])
+m4_include(b4_skeletonsdir/[c-like.m4])


-# b4_comment(TEXT, [PREFIX])
-# --------------------------
-# Put TEXT in comment.  Prefix all the output lines with PREFIX.
-m4_define([b4_comment],
-[_b4_comment([$1], [$2/* ], [$2   ], [  */])])
+# b4_symbol_action(SYMBOL-NUM, ACTION)
+# ------------------------------------
+# Run the action ACTION ("destructor" or "printer") for SYMBOL-NUM.
+m4_define([b4_symbol_action],
+[b4_symbol_if([$1], [has_$2],
+[b4_dollar_pushdef([yyval],
+                   [$1],
+                   [],
+                   [yyloc])dnl
+    _b4_symbol_case([$1])[]dnl
+b4_syncline([b4_symbol([$1], [$2_line])], [b4_symbol([$1], [$2_file])])dnl
+b4_symbol([$1], [$2])
+b4_syncline([@oline@], [@ofile@])dnl
+        break;
+
+b4_dollar_popdef[]dnl
+])])
+
+
+# b4_use(EXPR)
+# ------------
+# Pacify the compiler about some maybe unused value.
+m4_define([b4_use],
+[])


 # b4_sync_start(LINE, FILE)
@@ -58,6 +67,23 @@ m4_define([b4_percent_define_get3],
          [m4_ifval(m4_quote(b4_percent_define_get([$1])),
                [$2[]b4_percent_define_get([$1])[]$3], [$4])])

+# b4_percent_define_if_get2(ARG1, ARG2, DEF, NOT)
+# -----------------------------------------------
+# Expand to the value of DEF if ARG1 or ARG2 are %define'ed,
+# otherwise NOT.
+m4_define([b4_percent_define_if_get2],
+          [m4_ifval(m4_quote(b4_percent_define_get([$1])),
+                [$3], [m4_ifval(m4_quote(b4_percent_define_get([$2])),
+                      [$3], [$4])])])
+
+# b4_percent_define_class_before_interface(CLASS, INTERFACE)
+# ----------------------------------------------------------
+# Expand to a ', ' if both a class and an interface have been %define'ed
+m4_define([b4_percent_define_class_before_interface],
+          [m4_ifval(m4_quote(b4_percent_define_get([$1])),
+                [m4_ifval(m4_quote(b4_percent_define_get([$2])),
+                      [, ])])])
+

 # b4_flag_value(BOOLEAN-FLAG)
 # ---------------------------
@@ -78,8 +104,10 @@ b4_percent_define_flag_if([api.parser.public],   [public ])dnl
 b4_percent_define_flag_if([api.parser.abstract], [abstract ])dnl
 b4_percent_define_flag_if([api.parser.final],    [final ])dnl
 [class ]b4_parser_class[]dnl
-b4_percent_define_get3([api.parser.extends], [ extends ])dnl
-b4_percent_define_get3([api.parser.implements], [ implements ])])
+b4_percent_define_if_get2([api.parser.extends], [api.parser.implements], [ : ])dnl
+b4_percent_define_get([api.parser.extends])dnl
+b4_percent_define_class_before_interface([api.parser.extends], [api.parser.implements])dnl
+b4_percent_define_get([api.parser.implements])])


 # b4_lexer_if(TRUE, FALSE)
@@ -103,12 +131,12 @@ m4_define([b4_location_type_if],
 # b4_identification
 # -----------------
 m4_define([b4_identification],
-[/** Version number for the Bison executable that generated this parser.  */
-  public static immutable string yy_bison_version = "b4_version";
+[[/** Version number for the Bison executable that generated this parser.  */
+  public static immutable string yy_bison_version = "]b4_version_string[";

  /** Name of the skeleton that generated this parser.  */
-  public static immutable string yy_bison_skeleton = b4_skeleton;
-])
+  public static immutable string yy_bison_skeleton = ]b4_skeleton[;
+]])


 ## ------------ ##
@@ -152,6 +180,9 @@ private static immutable b4_int_type_for([$2])[[]] yy$1_ =
 ## Token kinds.  ##
 ## ------------- ##

+m4_define([b4_symbol(-2, id)],  [[YYEMPTY]])
+b4_percent_define_default([[api.token.raw]], [[true]])
+
 # b4_token_enum(TOKEN-NAME, TOKEN-NUMBER)
 # ---------------------------------------
 # Output the definition of this token as an enum.
@@ -165,18 +196,53 @@ m4_define([b4_token_enum],
 m4_define([b4_token_enums],
 [/* Token kinds.  */
 public enum TokenKind {
-  ]b4_symbol_kind([-2])[ = -2,
+  ]b4_symbol(empty, id)[ = -2,
 b4_symbol_foreach([b4_token_enum])dnl
 }
 ])

+# b4_symbol_translate(STRING)
+# ---------------------------
+# Used by "bison" in the array of symbol names to mark those that
+# require translation.
+m4_define([b4_symbol_translate],
+[[_($1)]])


+# _b4_token_constructor_define(SYMBOL-NUM)
+# ----------------------------------------
+# Define Symbol.FOO for SYMBOL-NUM.
+m4_define([_b4_token_constructor_define],
+[b4_token_visible_if([$1],
+[[
+    static auto ]b4_symbol([$1], [id])[(]b4_symbol_if([$1], [has_type],
+[b4_union_if([b4_symbol([$1], [type]],
+[[typeof(YYSemanticType.]b4_symbol([$1], [type])[]])) [val]])dnl
+[]b4_locations_if([b4_symbol_if([$1], [has_type], [[, ]])[Location l]])[)
+    {
+      return Symbol(TokenKind.]b4_symbol([$1], [id])[]b4_symbol_if([$1], [has_type],
+      [[, val]])[]b4_locations_if([[, l]])[);
+    }]])])
+
+# b4_token_constructor_define
+# ---------------------------
+# Define Symbol.FOO for each token kind FOO.
+m4_define([b4_token_constructor_define],
+[[
+    /* Implementation of token constructors for each symbol type visible to
+     * the user. The code generates static methods that have the same names
+     * as the TokenKinds.
+     */]b4_symbol_foreach([_b4_token_constructor_define])dnl
+])
+
 ## -------------- ##
 ## Symbol kinds.  ##
 ## -------------- ##

-b4_percent_define_default([[api.symbol.prefix]], [[S_]])
+# b4_symbol_kind(NUM)
+# -------------------
+m4_define([b4_symbol_kind],
+[SymbolKind.b4_symbol_kind_base($@)])


 # b4_symbol_enum(SYMBOL-NUM)
@@ -185,7 +251,7 @@ b4_percent_define_default([[api.symbol.prefix]], [[S_]])
 m4_define([b4_symbol_enum],
 [m4_format([    %-30s %s],
           m4_format([[%s = %s,]],
-                     b4_symbol([$1], [kind]),
+                     b4_symbol([$1], [kind_base]),
                     [$1]),
           [b4_symbol_tag_comment([$1])])])

@@ -197,18 +263,47 @@ m4_define([b4_symbol_enum],
 # to use a signed type, which matters for yytoken.
 m4_define([b4_declare_symbol_enum],
 [[  /* Symbol kinds.  */
-  public enum SymbolKind
+  struct SymbolKind
  {
-    ]b4_symbol_kind([-2])[ = -2,  /* No symbol.  */
+    enum
+    {
+    ]b4_symbol(empty, kind_base)[ = -2,  /* No symbol.  */
 ]b4_symbol_foreach([b4_symbol_enum])dnl
-[  };
-]])])
+[    }
+
+    private int yycode_;
+    alias yycode_ this;
+
+    this(int code)
+    {
+      yycode_ = code;
+    }
+
+    /* Return YYSTR after stripping away unnecessary quotes and
+     backslashes, so that it's suitable for yyerror.  The heuristic is
+     that double-quoting is unnecessary unless the string contains an
+     apostrophe, a comma, or backslash (other than backslash-backslash).
+     YYSTR is taken from yytname.  */
+    final void toString(void delegate(const(char)[]) sink) const
+    {
+      immutable string[] yy_sname = @{
+  ]b4_symbol_names[
+      @};]b4_has_translations_if([[
+      /* YYTRANSLATABLE[SYMBOL-NUM] -- Whether YY_SNAME[SYMBOL-NUM] is
+        internationalizable.  */
+      immutable ]b4_int_type_for([b4_translatable])[[] yytranslatable = @{
+  ]b4_translatable[
+      @};]])[
+
+      sink.formattedWrite!"%s"(yy_sname[yycode_]);
+    }
+  }
+]])


-
-# b4-case(ID, CODE)
-# -----------------
-m4_define([b4_case], [    case $1:
+# b4_case(ID, CODE, [COMMENTS])
+# -----------------------------
+m4_define([b4_case], [    case $1:m4_ifval([$3], [ b4_comment([$3])])
 $2
      break;])

@@ -233,6 +328,109 @@ m4_define([b4_location_type], b4_percent_define_ifdef([[location_type]],[b4_perc
 m4_define([b4_position_type], b4_percent_define_ifdef([[position_type]],[b4_percent_define_get([[position_type]])],[YYPosition]))


+## ---------------- ##
+## api.value.type.  ##
+## ---------------- ##
+
+
+# ---------------------- #
+# api.value.type=union.  #
+# ---------------------- #
+
+# b4_symbol_type_register(SYMBOL-NUM)
+# -----------------------------------
+# Symbol SYMBOL-NUM has a type (for union) instead of a type-tag.
+# Extend the definition of %union's body (b4_union_members) with a
+# field of that type, and extend the symbol's "type" field to point to
+# the field name, instead of the type name.
+m4_define([b4_symbol_type_register],
+[m4_define([b4_symbol($1, type_tag)],
+           [b4_symbol_if([$1], [has_id],
+                         [b4_symbol([$1], [id])],
+                         [yykind_[]b4_symbol([$1], [number])])])dnl
+m4_append([b4_union_members],
+m4_expand([m4_format([  %-40s %s],
+                     m4_expand([b4_symbol([$1], [type]) b4_symbol([$1], [type_tag]);]),
+                     [b4_symbol_tag_comment([$1])])]))
+])
+
+
+# b4_type_define_tag(SYMBOL1-NUM, ...)
+# ------------------------------------
+# For the batch of symbols SYMBOL1-NUM... (which all have the same
+# type), enhance the %union definition for each of them, and set
+# there "type" field to the field tag name, instead of the type name.
+m4_define([b4_type_define_tag],
+[b4_symbol_if([$1], [has_type],
+              [m4_map([b4_symbol_type_register], [$@])])
+])
+
+
+# b4_symbol_value_union(VAL, SYMBOL-NUM, [TYPE])
+# ----------------------------------------------
+# Same of b4_symbol_value, but when api.value.type=union.
+m4_define([b4_symbol_value_union],
+[m4_ifval([$3],
+          [(*($3*)(&$1))],
+          [m4_ifval([$2],
+                    [b4_symbol_if([$2], [has_type],
+                                  [($1.b4_symbol([$2], [type_tag]))],
+                                  [$1])],
+                    [$1])])])
+
+
+# b4_value_type_setup_union
+# -------------------------
+# Setup support for api.value.type=union.  Symbols are defined with a
+# type instead of a union member name: build the corresponding union,
+# and give the symbols their tag.
+m4_define([b4_value_type_setup_union],
+[m4_define([b4_union_members])
+b4_type_foreach([b4_type_define_tag])
+m4_copy_force([b4_symbol_value_union], [b4_symbol_value])
+])
+
+
+# _b4_value_type_setup_keyword
+# ----------------------------
+# api.value.type is defined with a keyword/string syntax.  Check if
+# that is properly defined, and prepare its use.
+m4_define([_b4_value_type_setup_keyword],
+[b4_percent_define_check_values([[[[api.value.type]],
+                                  [[none]],
+                                  [[union]],
+                                  [[union-directive]],
+                                  [[yystype]]]])dnl
+m4_case(b4_percent_define_get([[api.value.type]]),
+        [union],   [b4_value_type_setup_union])])
+
+
+# b4_value_type_setup
+# -------------------
+# Check if api.value.type is properly defined, and possibly prepare
+# its use.
+b4_define_silent([b4_value_type_setup],
+[
+# Define default value.
+b4_percent_define_ifdef([[api.value.type]], [],
+[# %union => api.value.type=union-directive
+m4_ifdef([b4_union_members],
+[m4_define([b4_percent_define_kind(api.value.type)], [keyword])
+m4_define([b4_percent_define(api.value.type)], [union-directive])],
+[# no tag seen => api.value.type={int}
+m4_if(b4_tag_seen_flag, 0,
+[m4_define([b4_percent_define_kind(api.value.type)], [code])
+m4_define([b4_percent_define(api.value.type)], [int])],
+[# otherwise api.value.type=yystype
+m4_define([b4_percent_define_kind(api.value.type)], [keyword])
+m4_define([b4_percent_define(api.value.type)], [yystype])])])])
+
+# Set up.
+m4_bmatch(b4_percent_define_get_kind([[api.value.type]]),
+   [keyword], [_b4_value_type_setup_keyword])
+])
+
+
 ## ----------------- ##
 ## Semantic Values.  ##
 ## ----------------- ##
@@ -279,7 +477,7 @@ m4_define([b4_lhs_location],
 # Expansion of @POS, where the current rule has RULE-LENGTH symbols
 # on RHS.
 m4_define([b4_rhs_location],
-[yystack.locationAt ([$1], [$2])])
+[yystack.locationAt (b4_subtract($@))])


 # b4_lex_param
@@ -364,3 +562,66 @@ m4_define([b4_var_decls],
 ], [$@])])
 m4_define([b4_var_decl],
          [    protected $1;])
+
+
+# b4_public_types_declare
+# -----------------------
+# Define the public types: token, semantic value, location, and so forth.
+# Depending on %define token_lex, may be output in the header or source file.
+m4_define([b4_public_types_declare],
+[[
+alias Symbol = ]b4_parser_class[.Symbol;
+alias Value = ]b4_yystype[;]b4_locations_if([[
+alias Location = ]b4_location_type[;
+alias Position = ]b4_position_type[;]b4_push_if([[
+alias PUSH_MORE = ]b4_parser_class[.YYPUSH_MORE;
+alias ABORT = ]b4_parser_class[.YYABORT;
+alias ACCEPT = ]b4_parser_class[.YYACCEPT;]])[]])[
+]])
+
+
+# b4_basic_symbol_constructor_define
+# ----------------------------------
+# Create Symbol struct constructors for all the visible types.
+m4_define([b4_basic_symbol_constructor_define],
+[b4_token_visible_if([$1],
+[[    this(TokenKind token]b4_symbol_if([$1], [has_type],
+[[, ]b4_union_if([], [[typeof(YYSemanticType.]])b4_symbol([$1], [type])dnl
+[]b4_union_if([], [[) ]])[ val]])[]b4_locations_if([[, Location loc]])[)
+    {
+      kind = yytranslate_(token);]b4_union_if([b4_symbol_if([$1], [has_type], [[
+      static foreach (member; __traits(allMembers, YYSemanticType))
+      {
+        static if (is(typeof(mixin("value_." ~ member)) == ]b4_symbol([$1], [type])[))
+        {
+          mixin("value_." ~ member ~ " = val;");
+        }
+      }]])], [b4_symbol_if([$1], [has_type], [[
+      value_.]b4_symbol([$1], [type])[ = val;]])])[]b4_locations_if([
+      location_ = loc;])[
+    }
+]])])
+
+
+# b4_symbol_type_define
+# ---------------------
+# Define symbol_type, the external type for symbols used for symbol
+# constructors.
+m4_define([b4_symbol_type_define],
+[[
+  /**
+    * A complete symbol
+    */
+  struct Symbol
+  {
+    private SymbolKind kind;
+    private Value value_;]b4_locations_if([[
+    private Location location_;]])[
+
+]b4_type_foreach([b4_basic_symbol_constructor_define])[
+    SymbolKind token() { return kind; }
+    Value value() { return value_; }]b4_locations_if([[
+    Location location() { return location_; }]])[
+]b4_token_ctor_if([b4_token_constructor_define])[
+  }
+]])
@@ -1,8 +1,9 @@
-                                                                    -*- C -*-
+#                                                             -*- C -*-

 # GLR skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.


 # If we are loaded by glr.cc, do not override c++.m4 definitions by
@@ -32,7 +33,9 @@ m4_if(b4_skeleton, ["glr.c"],
 m4_define_default([b4_stack_depth_max], [10000])
 m4_define_default([b4_stack_depth_init],  [200])

-
+# Included header.
+b4_percent_define_default([[api.header.include]],
+                          [["@basename(]b4_spec_header_file[@)"]])

 ## ------------------------ ##
 ## Pure/impure interfaces.  ##
@@ -122,7 +125,7 @@ m4_define([b4_rhs_data],
 # --------------------------------------------------
 # Expansion of $$ or $<TYPE>$, for symbol SYMBOL-NUM.
 m4_define([b4_rhs_value],
-[b4_symbol_value([b4_rhs_data([$1], [$2]).yysemantics.yysval], [$3], [$4])])
+[b4_symbol_value([b4_rhs_data([$1], [$2]).yysemantics.yyval], [$3], [$4])])



@@ -145,13 +148,22 @@ m4_define([b4_rhs_location],
 [(b4_rhs_data([$1], [$2]).yyloc)])


+# b4_call_merger(MERGER-NUM, MERGER-NAME, SYMBOL-SUM)
+# ---------------------------------------------------
+m4_define([b4_call_merger],
+[b4_case([$1],
+         [    b4_symbol_if([$3], [has_type],
+                           [yy0->b4_symbol($3, slot) = $2 (*yy0, *yy1);],
+                           [*yy0 = $2 (*yy0, *yy1);])])])
+
+
 ## -------------- ##
 ## Declarations.  ##
 ## -------------- ##

 # b4_shared_declarations
 # ----------------------
-# Declaration that might either go into the header (if --defines)
+# Declaration that might either go into the header (if --header)
 # or open coded in the parser body.  glr.cc has its own definition.
 m4_if(b4_skeleton, ["glr.c"],
 [m4_define([b4_shared_declarations],
@@ -185,13 +197,13 @@ int ]b4_prefix[parse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)],

 # glr.cc produces its own header.
 b4_glr_cc_if([],
-[b4_defines_if(
+[b4_header_if(
 [b4_output_begin([b4_spec_header_file])
 b4_copyright([Skeleton interface for Bison GLR parsers in C],
-             [2002-2015, 2018-2020])[
-]b4_cpp_guard_open([b4_spec_header_file])[
+             [2002-2015, 2018-2022, 2025-2026])[
+]b4_cpp_guard_open([b4_spec_mapped_header_file])[
 ]b4_shared_declarations[
-]b4_cpp_guard_close([b4_spec_header_file])[
+]b4_cpp_guard_close([b4_spec_mapped_header_file])[
 ]b4_output_end[
 ]])])

@@ -202,7 +214,7 @@ b4_copyright([Skeleton interface for Bison GLR parsers in C],

 b4_output_begin([b4_parser_file_name])
 b4_copyright([Skeleton implementation for Bison GLR parsers in C],
-             [2002-2015, 2018-2020])[
+             [2002-2015, 2018-2022, 2025-2026])[
 /* C GLR parser skeleton written by Paul Hilfinger.  */

 ]b4_disclaimer[
@@ -215,7 +227,7 @@ b4_copyright([Skeleton implementation for Bison GLR parsers in C],
 #define YYLTYPE ]b4_api_PREFIX[LTYPE]])])[
 ]m4_if(b4_prefix, [yy], [],
 [[/* Substitute the variable and function names.  */
-#define yyparse ]b4_prefix[parse
+#define ]b4_glr_cc_if([yy_parse_impl], [yyparse])[ ]b4_prefix[]b4_glr_cc_if([_parse_impl], [parse])[
 #define yylex   ]b4_prefix[lex
 #define yyerror ]b4_prefix[error
 #define yydebug ]b4_prefix[debug]]b4_pure_if([], [[
@@ -228,9 +240,11 @@ b4_copyright([Skeleton implementation for Bison GLR parsers in C],
 ]b4_cast_define[
 ]b4_null_define[

-]b4_defines_if([[#include "@basename(]b4_spec_header_file[@)"]],
-               [b4_shared_declarations])[
-]b4_declare_symbol_enum[
+]b4_header_if([[#include ]b4_percent_define_get([[api.header.include]])],
+              [b4_shared_declarations])[
+
+]b4_glr_cc_if([b4_glr_cc_setup],
+              [b4_declare_symbol_enum])[

 /* Default (constant) value used for initialization for null
   right-hand sides.  Unlike the standard yacc.c template, here we set
@@ -293,6 +307,10 @@ static YYLTYPE yyloc_default][]b4_yyloc_default;])[
 # include <setjmp.h>
 # define YYJMP_BUF jmp_buf
 # define YYSETJMP(Env) setjmp (Env)
+/* Pacify GCC <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=21161>.  */
+#if defined __GNUC__ && 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
+# pragma GCC diagnostic ignored "-Wclobbered"
+#endif
 /* Pacify Clang and ICC.  */
 # define YYLONGJMP(Env, Val)                    \
 do {                                           \
@@ -331,8 +349,8 @@ static YYLTYPE yyloc_default][]b4_yyloc_default;])[
   accessed by $0, $-1, etc., in any rule.  */
 #define YYMAXLEFT ]b4_max_left_semantic_context[

-/* YYMAXUTOK -- Last valid token number (for yychar).  */
-#define YYMAXUTOK   ]b4_user_token_number_max[
+/* YYMAXUTOK -- Last valid token kind.  */
+#define YYMAXUTOK   ]b4_code_max[

 /* YYTRANSLATE(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
   as returned by yylex, with out-of-bounds checking.  */
@@ -429,7 +447,7 @@ int yychar;])[

 enum { YYENOMEM = -2 };

-typedef enum { yyok, yyaccept, yyabort, yyerr } YYRESULTTAG;
+typedef enum { yyok, yyaccept, yyabort, yyerr, yynomem } YYRESULTTAG;

 #define YYCHK(YYE)                              \
  do {                                          \
@@ -494,10 +512,11 @@ typedef struct yySemanticOption yySemanticOption;
 typedef union yyGLRStackItem yyGLRStackItem;
 typedef struct yyGLRStack yyGLRStack;

-struct yyGLRState {
+struct yyGLRState
+{
  /** Type tag: always true.  */
  yybool yyisState;
-  /** Type tag for yysemantics.  If true, yysval applies, otherwise
+  /** Type tag for yysemantics.  If true, yyval applies, otherwise
   *  yyfirstVal applies.  */
  yybool yyresolved;
  /** Number of corresponding LALR(1) machine state.  */
@@ -512,24 +531,26 @@ struct yyGLRState {
     *  yynext.  */
    yySemanticOption* yyfirstVal;
    /** Semantic value for this state.  */
-    YYSTYPE yysval;
+    YYSTYPE yyval;
  } yysemantics;]b4_locations_if([[
  /** Source location for this state.  */
  YYLTYPE yyloc;]])[
 };

-struct yyGLRStateSet {
+struct yyGLRStateSet
+{
  yyGLRState** yystates;
  /** During nondeterministic operation, yylookaheadNeeds tracks which
   *  stacks have actually needed the current lookahead.  During deterministic
   *  operation, yylookaheadNeeds[0] is not maintained since it would merely
-   *  duplicate yychar != ]b4_symbol(-2, id)[.  */
+   *  duplicate yychar != ]b4_symbol(empty, id)[.  */
  yybool* yylookaheadNeeds;
  YYPTRDIFF_T yysize;
  YYPTRDIFF_T yycapacity;
 };

-struct yySemanticOption {
+struct yySemanticOption
+{
  /** Type tag: always false.  */
  yybool yyisState;
  /** Rule number for this reduction */
@@ -635,6 +656,13 @@ yysymbol_name (yysymbol_kind_t yysymbol)
 }]])[
 #endif

+/** Left-hand-side symbol for rule #YYRULE.  */
+static inline yysymbol_kind_t
+yylhsNonterm (yyRuleNum yyrule)
+{
+  return YY_CAST (yysymbol_kind_t, yyr1[yyrule]);
+}
+
 #if ]b4_api_PREFIX[DEBUG

 # ifndef YYFPRINTF
@@ -660,7 +688,7 @@ yysymbol_name (yysymbol_kind_t yysymbol)
    YY_IGNORE_USELESS_CAST_END                  \
  } while (0)

-]b4_yy_location_print_define[
+]b4_yylocation_print_define[

 ]b4_yy_symbol_print_define[

@@ -674,6 +702,16 @@ yysymbol_name (yysymbol_kind_t yysymbol)
      }                                                                 \
  } while (0)

+static inline void
+yy_reduce_print (yybool yynormal, yyGLRStackItem* yyvsp, YYPTRDIFF_T yyk,
+                 yyRuleNum yyrule]b4_user_formals[);
+
+# define YY_REDUCE_PRINT(Args)          \
+  do {                                  \
+    if (yydebug)                        \
+      yy_reduce_print Args;             \
+  } while (0)
+
 /* Nonzero means print parse trace.  It is left uninitialized so that
   multiple parsers can coexist.  */
 int yydebug;
@@ -687,6 +725,7 @@ static void yypdumpstack (yyGLRStack* yystackp)

 # define YY_DPRINTF(Args) do {} while (yyfalse)
 # define YY_SYMBOL_PRINT(Title, Kind, Value, Location)
+# define YY_REDUCE_PRINT(Args)

 #endif /* !]b4_api_PREFIX[DEBUG */

@@ -789,9 +828,9 @@ yyfillin (yyGLRStackItem *yyvsp, int yylow0, int yylow1)
 #endif
      yyvsp[i].yystate.yyresolved = s->yyresolved;
      if (s->yyresolved)
-        yyvsp[i].yystate.yysemantics.yysval = s->yysemantics.yysval;
+        yyvsp[i].yystate.yysemantics.yyval = s->yysemantics.yyval;
      else
-        /* The effect of using yysval or yyloc (in an immediate rule) is
+        /* The effect of using yyval or yyloc (in an immediate rule) is
         * undefined.  */
        yyvsp[i].yystate.yysemantics.yyfirstVal = YY_NULLPTR;]b4_locations_if([[
      yyvsp[i].yystate.yyloc = s->yyloc;]])[
@@ -807,14 +846,14 @@ yygetToken (int *yycharp][]b4_pure_if([, yyGLRStack* yystackp])[]b4_user_formals
 {
  yysymbol_kind_t yytoken;
 ]b4_parse_param_use()dnl
-[  if (*yycharp == ]b4_symbol(-2, id)[)
+[  if (*yycharp == ]b4_symbol(empty, id)[)
    {
      YY_DPRINTF ((stderr, "Reading a token\n"));]b4_glr_cc_if([[
 #if YY_EXCEPTIONS
      try
        {
 #endif // YY_EXCEPTIONS
-          *yycharp = ]b4_lex[;
+          *yycharp = ]b4_yylex[;
 #if YY_EXCEPTIONS
        }
      catch (const ]b4_namespace_ref[::]b4_parser_class[::syntax_error& yyexc)
@@ -825,14 +864,14 @@ yygetToken (int *yycharp][]b4_pure_if([, yyGLRStack* yystackp])[]b4_user_formals
          // Map errors caught in the scanner to the undefined token,
          // so that error handling is started.  However, record this
          // with this special value of yychar.
-          *yycharp = ]b4_symbol(1, id)[;
+          *yycharp = ]b4_symbol(error, id)[;
        }
 #endif // YY_EXCEPTIONS]], [[
-      *yycharp = ]b4_lex[;]])[
+      *yycharp = ]b4_yylex[;]])[
    }
-  if (*yycharp <= ]b4_symbol(0, [id])[)
+  if (*yycharp <= ]b4_symbol(eof, [id])[)
    {
-      *yycharp = ]b4_symbol(0, [id])[;
+      *yycharp = ]b4_symbol(eof, [id])[;
      yytoken = ]b4_symbol_prefix[YYEOF;
      YY_DPRINTF ((stderr, "Now at end of input.\n"));
    }
@@ -864,28 +903,31 @@ yyfill (yyGLRStackItem *yyvsp, int *yylow, int yylow1, yybool yynormal)
 *  and top stack item YYVSP.  YYLVALP points to place to put semantic
 *  value ($$), and yylocp points to place for location information
 *  (@@$).  Returns yyok for normal return, yyaccept for YYACCEPT,
- *  yyerr for YYERROR, yyabort for YYABORT.  */
+ *  yyerr for YYERROR, yyabort for YYABORT, yynomem for YYNOMEM.  */
 static YYRESULTTAG
-yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* yyvsp,
-              yyGLRStack* yystackp,
+yyuserAction (yyRuleNum yyrule, int yyrhslen, yyGLRStackItem* yyvsp,
+              yyGLRStack* yystackp, YYPTRDIFF_T yyk,
              YYSTYPE* yyvalp]b4_locuser_formals[)
 {
-  yybool yynormal YY_ATTRIBUTE_UNUSED = yystackp->yysplitPoint == YY_NULLPTR;
-  int yylow;
+  const yybool yynormal YY_ATTRIBUTE_UNUSED = yystackp->yysplitPoint == YY_NULLPTR;
+  int yylow = 1;
 ]b4_parse_param_use([yyvalp], [yylocp])dnl
-[  YYUSE (yyrhslen);
+[  YY_USE (yyk);
+  YY_USE (yyrhslen);
 # undef yyerrok
 # define yyerrok (yystackp->yyerrState = 0)
 # undef YYACCEPT
 # define YYACCEPT return yyaccept
 # undef YYABORT
 # define YYABORT return yyabort
+# undef YYNOMEM
+# define YYNOMEM return yynomem
 # undef YYERROR
 # define YYERROR return yyerrok, yyerr
 # undef YYRECOVERING
 # define YYRECOVERING() (yystackp->yyerrState != 0)
 # undef yyclearin
-# define yyclearin (yychar = ]b4_symbol(-2, id)[)
+# define yyclearin (yychar = ]b4_symbol(empty, id)[)
 # undef YYFILL
 # define YYFILL(N) yyfill (yyvsp, &yylow, (N), yynormal)
 # undef YYBACKUP
@@ -893,21 +935,23 @@ yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* yyvsp,
  return yyerror (]b4_yyerror_args[YY_("syntax error: cannot back up")),     \
         yyerrok, yyerr

-  yylow = 1;
  if (yyrhslen == 0)
    *yyvalp = yyval_default;
  else
-    *yyvalp = yyvsp[YYFILL (1-yyrhslen)].yystate.yysemantics.yysval;]b4_locations_if([[
+    *yyvalp = yyvsp[YYFILL (1-yyrhslen)].yystate.yysemantics.yyval;]b4_locations_if([[
  /* Default location. */
  YYLLOC_DEFAULT ((*yylocp), (yyvsp - yyrhslen), yyrhslen);
-  yystackp->yyerror_range[1].yystate.yyloc = *yylocp;
-]])[]b4_glr_cc_if([[
+  yystackp->yyerror_range[1].yystate.yyloc = *yylocp;]])[
+  /* If yyk == -1, we are running a deferred action on a temporary
+     stack.  In that case, YY_REDUCE_PRINT must not play with YYFILL,
+     so pretend the stack is "normal". */
+  YY_REDUCE_PRINT ((yynormal || yyk == -1, yyvsp, yyk, yyrule]b4_user_args[));]b4_glr_cc_if([[
 #if YY_EXCEPTIONS
  typedef ]b4_namespace_ref[::]b4_parser_class[::syntax_error syntax_error;
  try
  {
 #endif // YY_EXCEPTIONS]])[
-  switch (yyn)
+  switch (yyrule)
    {
 ]b4_user_actions[
      default: break;
@@ -922,11 +966,13 @@ yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* yyvsp,
      YYERROR;
    }
 #endif // YY_EXCEPTIONS]])[
+  YY_SYMBOL_PRINT ("-> $$ =", yylhsNonterm (yyrule), yyvalp, yylocp);

  return yyok;
 # undef yyerrok
 # undef YYABORT
 # undef YYACCEPT
+# undef YYNOMEM
 # undef YYERROR
 # undef YYBACKUP
 # undef yyclearin
@@ -937,8 +983,8 @@ yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* yyvsp,
 static void
 yyuserMerge (int yyn, YYSTYPE* yy0, YYSTYPE* yy1)
 {
-  YYUSE (yy0);
-  YYUSE (yy1);
+  YY_USE (yy0);
+  YY_USE (yy1);

  switch (yyn)
    {
@@ -963,7 +1009,7 @@ yydestroyGLRState (char const *yymsg, yyGLRState *yys]b4_user_formals[)
 {
  if (yys->yyresolved)
    yydestruct (yymsg, yy_accessing_symbol (yys->yylrState),
-                &yys->yysemantics.yysval]b4_locuser_args([&yys->yyloc])[);
+                &yys->yysemantics.yyval]b4_locuser_args([&yys->yyloc])[);
  else
    {
 #if ]b4_api_PREFIX[DEBUG
@@ -990,13 +1036,6 @@ yydestroyGLRState (char const *yymsg, yyGLRState *yys]b4_user_formals[)
    }
 }

-/** Left-hand-side symbol for rule #YYRULE.  */
-static inline yysymbol_kind_t
-yylhsNonterm (yyRuleNum yyrule)
-{
-  return YY_CAST (yysymbol_kind_t, yyr1[yyrule]);
-}
-
 #define yypact_value_is_default(Yyn) \
  ]b4_table_value_equals([[pact]], [[Yyn]], [b4_pact_ninf], [YYPACT_NINF])[

@@ -1030,7 +1069,7 @@ static inline int
 yygetLRActions (yy_state_t yystate, yysymbol_kind_t yytoken, const short** yyconflicts)
 {
  int yyindex = yypact[yystate] + yytoken;
-  if (yytoken == ]b4_symbol(1, kind)[)
+  if (yytoken == ]b4_symbol(error, kind)[)
    {
      // This is the error token.
      *yyconflicts = yyconfl;
@@ -1117,7 +1156,7 @@ yyaddDeferredAction (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yyGLRState* yystate,
      yynewOption->yyloc = yylloc;])[
    }
  else
-    yynewOption->yyrawchar = ]b4_symbol(-2, id)[;
+    yynewOption->yyrawchar = ]b4_symbol(empty, id)[;
  yynewOption->yynext = yystate->yysemantics.yyfirstVal;
  yystate->yysemantics.yyfirstVal = yynewOption;

@@ -1338,7 +1377,7 @@ yyglrShift (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yy_state_t yylrState,
  yynewState->yyposn = yyposn;
  yynewState->yyresolved = yytrue;
  yynewState->yypred = yystackp->yytops.yystates[yyk];
-  yynewState->yysemantics.yysval = *yyvalp;]b4_locations_if([
+  yynewState->yysemantics.yyval = *yyvalp;]b4_locations_if([
  yynewState->yyloc = *yylocp;])[
  yystackp->yytops.yystates[yyk] = yynewState;

@@ -1366,14 +1405,7 @@ yyglrShiftDefer (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yy_state_t yylrState,
  yyaddDeferredAction (yystackp, yyk, yynewState, yyrhs, yyrule);
 }

-#if !]b4_api_PREFIX[DEBUG
-# define YY_REDUCE_PRINT(Args)
-#else
-# define YY_REDUCE_PRINT(Args)          \
-  do {                                  \
-    if (yydebug)                        \
-      yy_reduce_print Args;             \
-  } while (0)
+#if ]b4_api_PREFIX[DEBUG

 /*----------------------------------------------------------------------.
 | Report that stack #YYK of *YYSTACKP is going to be reduced by YYRULE. |
@@ -1396,7 +1428,7 @@ yy_reduce_print (yybool yynormal, yyGLRStackItem* yyvsp, YYPTRDIFF_T yyk,
      YY_FPRINTF ((stderr, "   $%d = ", yyi + 1));
      yy_symbol_print (stderr,
                       yy_accessing_symbol (yyvsp[yyi - yynrhs + 1].yystate.yylrState),
-                       &yyvsp[yyi - yynrhs + 1].yystate.yysemantics.yysval]b4_locations_if([,
+                       &yyvsp[yyi - yynrhs + 1].yystate.yysemantics.yyval]b4_locations_if([,
                       &]b4_rhs_location(yynrhs, yyi + 1))[]dnl
                       b4_user_args[);
      if (!yyvsp[yyi - yynrhs + 1].yystate.yyresolved)
@@ -1427,8 +1459,7 @@ yydoAction (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yyRuleNum yyrule,
      yystackp->yynextFree -= yynrhs;
      yystackp->yyspaceLeft += yynrhs;
      yystackp->yytops.yystates[0] = & yystackp->yynextFree[-1].yystate;
-      YY_REDUCE_PRINT ((yytrue, yyrhs, yyk, yyrule]b4_user_args[));
-      return yyuserAction (yyrule, yynrhs, yyrhs, yystackp,
+      return yyuserAction (yyrule, yynrhs, yyrhs, yystackp, yyk,
                           yyvalp]b4_locuser_args[);
    }
  else
@@ -1447,9 +1478,8 @@ yydoAction (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yyRuleNum yyrule,
        }
      yyupdateSplit (yystackp, yys);
      yystackp->yytops.yystates[yyk] = yys;
-      YY_REDUCE_PRINT ((yyfalse, yyrhsVals + YYMAXRHS + YYMAXLEFT - 1, yyk, yyrule]b4_user_args[));
      return yyuserAction (yyrule, yynrhs, yyrhsVals + YYMAXRHS + YYMAXLEFT - 1,
-                           yystackp, yyvalp]b4_locuser_args[);
+                           yystackp, yyk, yyvalp]b4_locuser_args[);
    }
 }

@@ -1472,21 +1502,20 @@ yyglrReduce (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yyRuleNum yyrule,

  if (yyforceEval || yystackp->yysplitPoint == YY_NULLPTR)
    {
-      YYSTYPE yysval;]b4_locations_if([[
+      YYSTYPE yyval;]b4_locations_if([[
      YYLTYPE yyloc;]])[

-      YYRESULTTAG yyflag = yydoAction (yystackp, yyk, yyrule, &yysval]b4_locuser_args([&yyloc])[);
+      YYRESULTTAG yyflag = yydoAction (yystackp, yyk, yyrule, &yyval]b4_locuser_args([&yyloc])[);
      if (yyflag == yyerr && yystackp->yysplitPoint != YY_NULLPTR)
        YY_DPRINTF ((stderr,
                     "Parse on stack %ld rejected by rule %d (line %d).\n",
-                     YY_CAST (long, yyk), yyrule - 1, yyrline[yyrule - 1]));
+                     YY_CAST (long, yyk), yyrule - 1, yyrline[yyrule]));
      if (yyflag != yyok)
        return yyflag;
-      YY_SYMBOL_PRINT ("-> $$ =", yylhsNonterm (yyrule), &yysval, &yyloc);
      yyglrShift (yystackp, yyk,
                  yyLRgotoState (yystackp->yytops.yystates[yyk]->yylrState,
                                 yylhsNonterm (yyrule)),
-                  yyposn, &yysval]b4_locations_if([, &yyloc])[);
+                  yyposn, &yyval]b4_locations_if([, &yyloc])[);
    }
  else
    {
@@ -1506,7 +1535,7 @@ yyglrReduce (yyGLRStack* yystackp, YYPTRDIFF_T yyk, yyRuleNum yyrule,
      YY_DPRINTF ((stderr,
                   "Reduced stack %ld by rule %d (line %d); action deferred.  "
                   "Now in state %d.\n",
-                   YY_CAST (long, yyk), yyrule - 1, yyrline[yyrule - 1],
+                   YY_CAST (long, yyk), yyrule - 1, yyrline[yyrule],
                   yynewLRState));
      for (yyi = 0; yyi < yystackp->yytops.yysize; yyi += 1)
        if (yyi != yyk && yystackp->yytops.yystates[yyi] != YY_NULLPTR)
@@ -1617,12 +1646,12 @@ yymergeOptionSets (yySemanticOption* yyy0, yySemanticOption* yyy1)
      else if (yys0->yyresolved)
        {
          yys1->yyresolved = yytrue;
-          yys1->yysemantics.yysval = yys0->yysemantics.yysval;
+          yys1->yysemantics.yyval = yys0->yysemantics.yyval;
        }
      else if (yys1->yyresolved)
        {
          yys0->yyresolved = yytrue;
-          yys0->yysemantics.yysval = yys1->yysemantics.yysval;
+          yys0->yysemantics.yyval = yys1->yysemantics.yyval;
        }
      else
        {
@@ -1676,8 +1705,8 @@ yypreference (yySemanticOption* y0, yySemanticOption* y1)
  return 0;
 }

-static YYRESULTTAG yyresolveValue (yyGLRState* yys,
-                                   yyGLRStack* yystackp]b4_user_formals[);
+static YYRESULTTAG
+yyresolveValue (yyGLRState* yys, yyGLRStack* yystackp]b4_user_formals[);


 /** Resolve the previous YYN states starting at and including state YYS
@@ -1733,7 +1762,7 @@ yyresolveAction (yySemanticOption* yyopt, yyGLRStack* yystackp,
    yylloc = yyopt->yyloc;])[
    yyflag = yyuserAction (yyopt->yyrule, yynrhs,
                           yyrhsVals + YYMAXRHS + YYMAXLEFT - 1,
-                           yystackp, yyvalp]b4_locuser_args[);
+                           yystackp, -1, yyvalp]b4_locuser_args[);
    yychar = yychar_current;
    yylval = yylval_current;]b4_locations_if([
    yylloc = yylloc_current;])[
@@ -1793,8 +1822,8 @@ static YYRESULTTAG
 yyreportAmbiguity (yySemanticOption* yyx0,
                   yySemanticOption* yyx1]b4_pure_formals[)
 {
-  YYUSE (yyx0);
-  YYUSE (yyx1);
+  YY_USE (yyx0);
+  YY_USE (yyx1);

 #if ]b4_api_PREFIX[DEBUG
  YY_FPRINTF ((stderr, "Ambiguity detected.\n"));
@@ -1868,7 +1897,7 @@ yyresolveValue (yyGLRState* yys, yyGLRStack* yystackp]b4_user_formals[)
  yySemanticOption* yybest = yyoptionList;
  yySemanticOption** yypp;
  yybool yymerge = yyfalse;
-  YYSTYPE yysval;
+  YYSTYPE yyval;
  YYRESULTTAG yyflag;]b4_locations_if([
  YYLTYPE *yylocp = &yys->yyloc;])[

@@ -1912,33 +1941,33 @@ yyresolveValue (yyGLRState* yys, yyGLRStack* yystackp]b4_user_formals[)
    {
      yySemanticOption* yyp;
      int yyprec = yydprec[yybest->yyrule];
-      yyflag = yyresolveAction (yybest, yystackp, &yysval]b4_locuser_args[);
+      yyflag = yyresolveAction (yybest, yystackp, &yyval]b4_locuser_args[);
      if (yyflag == yyok)
        for (yyp = yybest->yynext; yyp != YY_NULLPTR; yyp = yyp->yynext)
          {
            if (yyprec == yydprec[yyp->yyrule])
              {
-                YYSTYPE yysval_other;]b4_locations_if([
+                YYSTYPE yyval_other;]b4_locations_if([
                YYLTYPE yydummy;])[
-                yyflag = yyresolveAction (yyp, yystackp, &yysval_other]b4_locuser_args([&yydummy])[);
+                yyflag = yyresolveAction (yyp, yystackp, &yyval_other]b4_locuser_args([&yydummy])[);
                if (yyflag != yyok)
                  {
                    yydestruct ("Cleanup: discarding incompletely merged value for",
                                yy_accessing_symbol (yys->yylrState),
-                                &yysval]b4_locuser_args[);
+                                &yyval]b4_locuser_args[);
                    break;
                  }
-                yyuserMerge (yymerger[yyp->yyrule], &yysval, &yysval_other);
+                yyuserMerge (yymerger[yyp->yyrule], &yyval, &yyval_other);
              }
          }
    }
  else
-    yyflag = yyresolveAction (yybest, yystackp, &yysval]b4_locuser_args([yylocp])[);
+    yyflag = yyresolveAction (yybest, yystackp, &yyval]b4_locuser_args([yylocp])[);

  if (yyflag == yyok)
    {
      yys->yyresolved = yytrue;
-      yys->yysemantics.yysval = yysval;
+      yys->yysemantics.yyval = yyval;
    }
  else
    yys->yysemantics.yyfirstVal = YY_NULLPTR;
@@ -1963,18 +1992,24 @@ yyresolveStack (yyGLRStack* yystackp]b4_user_formals[)
  return yyok;
 }

+/** Called when returning to deterministic operation to clean up the extra
+ * stacks. */
 static void
 yycompressStack (yyGLRStack* yystackp)
 {
-  yyGLRState* yyp, *yyq, *yyr;
+  /* yyr is the state after the split point.  */
+  yyGLRState *yyr;

  if (yystackp->yytops.yysize != 1 || yystackp->yysplitPoint == YY_NULLPTR)
    return;

-  for (yyp = yystackp->yytops.yystates[0], yyq = yyp->yypred, yyr = YY_NULLPTR;
-       yyp != yystackp->yysplitPoint;
-       yyr = yyp, yyp = yyq, yyq = yyp->yypred)
-    yyp->yypred = yyr;
+  {
+    yyGLRState *yyp, *yyq;
+    for (yyp = yystackp->yytops.yystates[0], yyq = yyp->yypred, yyr = YY_NULLPTR;
+         yyp != yystackp->yysplitPoint;
+         yyr = yyp, yyp = yyq, yyq = yyp->yypred)
+      yyp->yypred = yyr;
+  }

  yystackp->yyspaceLeft += yystackp->yynextFree - yystackp->yyitems;
  yystackp->yynextFree = YY_REINTERPRET_CAST (yyGLRStackItem*, yystackp->yysplitPoint) + 1;
@@ -2108,7 +2143,7 @@ yypcontext_expected_tokens (const yyGLRStack* yystackp,
      int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
      int yyx;
      for (yyx = yyxbegin; yyx < yyxend; ++yyx)
-        if (yycheck[yyx + yyn] == yyx && yyx != ]b4_symbol(1, kind)[
+        if (yycheck[yyx + yyn] == yyx && yyx != ]b4_symbol(error, kind)[
            && !yytable_value_is_error (yytable[yyx + yyn]))
          {
            if (!yyarg)
@@ -2120,7 +2155,7 @@ yypcontext_expected_tokens (const yyGLRStack* yystackp,
          }
    }
  if (yyarg && yycount == 0 && 0 < yyargn)
-    yyarg[0] = ]b4_symbol(-2, kind)[;
+    yyarg[0] = ]b4_symbol(empty, kind)[;
  return yycount;
 }]])[

@@ -2138,19 +2173,19 @@ yypcontext_token (const yyGLRStack *yystackp) YY_ATTRIBUTE_UNUSED;
 static yysymbol_kind_t
 yypcontext_token (const yyGLRStack *yystackp)
 {
-  YYUSE (yystackp);
-  yysymbol_kind_t yytoken = yychar == ]b4_symbol(-2, id)[ ? ]b4_symbol(-2, kind)[ : YYTRANSLATE (yychar);
+  YY_USE (yystackp);
+  yysymbol_kind_t yytoken = yychar == ]b4_symbol(empty, id)[ ? ]b4_symbol(empty, kind)[ : YYTRANSLATE (yychar);
  return yytoken;
 }

 ]b4_locations_if([[/* The location of the lookahead of this context.  */
-static YYLTYPE *
+static const YYLTYPE *
 yypcontext_location (const yyGLRStack *yystackp) YY_ATTRIBUTE_UNUSED;

-static YYLTYPE *
+static const YYLTYPE *
 yypcontext_location (const yyGLRStack *yystackp)
 {
-  YYUSE (yystackp);
+  YY_USE (yystackp);
  return &yylloc;
 }]])],
         [detailed\|verbose],
@@ -2158,7 +2193,7 @@ yypcontext_location (const yyGLRStack *yystackp)
 yy_syntax_error_arguments (const yyGLRStack* yystackp,
                           yysymbol_kind_t yyarg[], int yyargn)
 {
-  yysymbol_kind_t yytoken = yychar == ]b4_symbol(-2, id)[ ? ]b4_symbol(-2, kind)[ : YYTRANSLATE (yychar);
+  yysymbol_kind_t yytoken = yychar == ]b4_symbol(empty, id)[ ? ]b4_symbol(empty, kind)[ : YYTRANSLATE (yychar);
  /* Actual size of YYARG. */
  int yycount = 0;
  /* There are many possibilities here to consider:
@@ -2174,12 +2209,7 @@ yy_syntax_error_arguments (const yyGLRStack* yystackp,
     - Don't assume there isn't a lookahead just because this state is a
       consistent state with a default action.  There might have been a
       previous inconsistent state, consistent state with a non-default
-       action, or user semantic action that manipulated yychar.]b4_lac_if([[
-       In the first two cases, it might appear that the current syntax
-       error should have been detected in the previous state when yy_lac
-       was invoked.  However, at that time, there might have been a
-       different syntax error that discarded a different initial context
-       during error recovery, leaving behind the current lookahead.]], [[
+       action, or user semantic action that manipulated yychar.
     - Of course, the expected token list depends on states to have
       correct lookahead information, and it depends on the parser not
       to perform extra reductions after fetching a lookahead from the
@@ -2187,9 +2217,9 @@ yy_syntax_error_arguments (const yyGLRStack* yystackp,
       (from LALR or IELR) and default reductions corrupt the expected
       token list.  However, the list is correct for canonical LR with
       one exception: it will still contain any token that will not be
-       accepted due to an error action in a later state.]])[
+       accepted due to an error action in a later state.
  */
-  if (yytoken != ]b4_symbol(-2, kind)[)
+  if (yytoken != ]b4_symbol(empty, kind)[)
    {
      int yyn;
      if (yyarg)
@@ -2316,9 +2346,9 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
      {
        yysymbol_kind_t yytoken;
        int yyj;
-        if (yychar == ]b4_symbol(0, [id])[)
+        if (yychar == ]b4_symbol(eof, [id])[)
          yyFail (yystackp][]b4_lpure_args[, YY_NULLPTR);
-        if (yychar != ]b4_symbol(-2, id)[)
+        if (yychar != ]b4_symbol(empty, id)[)
          {]b4_locations_if([[
            /* We throw away the lookahead, but the error range
               of the shifted error token must take it into account.  */
@@ -2330,7 +2360,7 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
            yytoken = YYTRANSLATE (yychar);
            yydestruct ("Error: discarding",
                        yytoken, &yylval]b4_locuser_args([&yylloc])[);
-            yychar = ]b4_symbol(-2, id)[;
+            yychar = ]b4_symbol(empty, id)[;
          }
        yytoken = ]b4_yygetToken_call[;
        yyj = yypact[yystackp->yytops.yystates[0]->yylrState];
@@ -2368,8 +2398,8 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
      int yyj = yypact[yys->yylrState];
      if (! yypact_value_is_default (yyj))
        {
-          yyj += ]b4_symbol(1, kind)[;
-          if (0 <= yyj && yyj <= YYLAST && yycheck[yyj] == ]b4_symbol(1, kind)[
+          yyj += ]b4_symbol(error, kind)[;
+          if (0 <= yyj && yyj <= YYLAST && yycheck[yyj] == ]b4_symbol(error, kind)[
              && yyisShiftAction (yytable[yyj]))
            {
              /* Shift the error token.  */
@@ -2397,20 +2427,16 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
    yyFail (yystackp][]b4_lpure_args[, YY_NULLPTR);
 }

-#define YYCHK1(YYE)                                                          \
-  do {                                                                       \
-    switch (YYE) {                                                           \
-    case yyok:                                                               \
-      break;                                                                 \
-    case yyabort:                                                            \
-      goto yyabortlab;                                                       \
-    case yyaccept:                                                           \
-      goto yyacceptlab;                                                      \
-    case yyerr:                                                              \
-      goto yyuser_error;                                                     \
-    default:                                                                 \
-      goto yybuglab;                                                         \
-    }                                                                        \
+#define YYCHK1(YYE)                             \
+  do {                                          \
+    switch (YYE) {                              \
+    case yyok:     break;                       \
+    case yyabort:  goto yyabortlab;             \
+    case yyaccept: goto yyacceptlab;            \
+    case yyerr:    goto yyuser_error;           \
+    case yynomem:  goto yyexhaustedlab;         \
+    default:       goto yybuglab;               \
+    }                                           \
  } while (0)

 /*----------.
@@ -2418,7 +2444,7 @@ yyrecoverSyntaxError (yyGLRStack* yystackp]b4_user_formals[)
 `----------*/

 int
-yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)
+]b4_glr_cc_if([yy_parse_impl], [yyparse])[ (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)
 {
  int yyresult;
  yyGLRStack yystack;
@@ -2427,7 +2453,7 @@ yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)

  YY_DPRINTF ((stderr, "Starting parse\n"));

-  yychar = ]b4_symbol(-2, id)[;
+  yychar = ]b4_symbol(empty, id)[;
  yylval = yyval_default;]b4_locations_if([
  yylloc = yyloc_default;])[
 ]m4_ifdef([b4_initial_action], [
@@ -2481,7 +2507,7 @@ b4_dollar_popdef])[]dnl
              if (yyisShiftAction (yyaction))
                {
                  YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
-                  yychar = ]b4_symbol(-2, id)[;
+                  yychar = ]b4_symbol(empty, id)[;
                  yyposn += 1;
                  yyglrShift (&yystack, 0, yyaction, yyposn, &yylval]b4_locations_if([, &yylloc])[);
                  if (0 < yystack.yyerrState)
@@ -2492,7 +2518,7 @@ b4_dollar_popdef])[]dnl
                  yystack.yyerror_range[1].yystate.yyloc = yylloc;]])[
                  /* Issue an error message unless the scanner already
                     did. */
-                  if (yychar != ]b4_symbol(1, id)[)
+                  if (yychar != ]b4_symbol(error, id)[)
                    yyreportSyntaxError (&yystack]b4_user_args[);
                  goto yyuser_error;
                }
@@ -2508,7 +2534,7 @@ b4_dollar_popdef])[]dnl
          YYPTRDIFF_T yys;

          for (yys = 0; yys < yystack.yytops.yysize; yys += 1)
-            yystackp->yytops.yylookaheadNeeds[yys] = yychar != ]b4_symbol(-2, id)[;
+            yystackp->yytops.yylookaheadNeeds[yys] = yychar != ]b4_symbol(empty, id)[;

          /* yyprocessOneStack returns one of three things:

@@ -2546,11 +2572,11 @@ b4_dollar_popdef])[]dnl

          /* If any yyglrShift call fails, it will fail after shifting.  Thus,
             a copy of yylval will already be on stack 0 in the event of a
-             failure in the following loop.  Thus, yychar is set to ]b4_symbol(-2, id)[
+             failure in the following loop.  Thus, yychar is set to ]b4_symbol(empty, id)[
             before the loop to make sure the user destructor for yylval isn't
             called twice.  */
          yytoken_to_shift = YYTRANSLATE (yychar);
-          yychar = ]b4_symbol(-2, id)[;
+          yychar = ]b4_symbol(empty, id)[;
          yyposn += 1;
          for (yys = 0; yys < yystack.yytops.yysize; yys += 1)
            {
@@ -2563,7 +2589,7 @@ b4_dollar_popdef])[]dnl
              YY_SYMBOL_PRINT ("shifting", yytoken_to_shift, &yylval, &yylloc);
              yyglrShift (&yystack, yys, yyaction, yyposn,
                          &yylval]b4_locations_if([, &yylloc])[);
-              YY_DPRINTF ((stderr, "Stack %ld now in state #%d\n",
+              YY_DPRINTF ((stderr, "Stack %ld now in state %d\n",
                           YY_CAST (long, yys),
                           yystack.yytops.yystates[yys]->yylrState));
            }
@@ -2584,7 +2610,7 @@ b4_dollar_popdef])[]dnl

 yyacceptlab:
  yyresult = 0;
-  goto yyreturn;
+  goto yyreturnlab;

 yybuglab:
  YY_ASSERT (yyfalse);
@@ -2592,15 +2618,15 @@ b4_dollar_popdef])[]dnl

 yyabortlab:
  yyresult = 1;
-  goto yyreturn;
+  goto yyreturnlab;

 yyexhaustedlab:
  yyerror (]b4_lyyerror_args[YY_("memory exhausted"));
  yyresult = 2;
-  goto yyreturn;
+  goto yyreturnlab;

- yyreturn:
-  if (yychar != ]b4_symbol(-2, id)[)
+ yyreturnlab:
+  if (yychar != ]b4_symbol(empty, id)[)
    yydestruct ("Cleanup: discarding lookahead",
                YYTRANSLATE (yychar), &yylval]b4_locuser_args([&yylloc])[);

@@ -2638,6 +2664,7 @@ b4_dollar_popdef])[]dnl

 /* DEBUGGING ONLY */
 #if ]b4_api_PREFIX[DEBUG
+/* Print *YYS and its predecessors. */
 static void
 yy_yypstack (yyGLRState* yys)
 {
@@ -2649,22 +2676,25 @@ yy_yypstack (yyGLRState* yys)
  YY_FPRINTF ((stderr, "%d@@%ld", yys->yylrState, YY_CAST (long, yys->yyposn)));
 }

+/* Print YYS (possibly NULL) and its predecessors. */
 static void
-yypstates (yyGLRState* yyst)
+yypstates (yyGLRState* yys)
 {
-  if (yyst == YY_NULLPTR)
+  if (yys == YY_NULLPTR)
    YY_FPRINTF ((stderr, "<null>"));
  else
-    yy_yypstack (yyst);
+    yy_yypstack (yys);
  YY_FPRINTF ((stderr, "\n"));
 }

+/* Print the stack #YYK.  */
 static void
 yypstack (yyGLRStack* yystackp, YYPTRDIFF_T yyk)
 {
  yypstates (yystackp->yytops.yystates[yyk]);
 }

+/* Print all the stacks.  */
 static void
 yypdumpstack (yyGLRStack* yystackp)
 {
@@ -2731,7 +2761,8 @@ m4_if(b4_prefix, [yy], [],
 #define yynerrs ]b4_prefix[nerrs]b4_locations_if([[
 #define yylloc  ]b4_prefix[lloc]])])[

-]m4_ifdef([b4_pre_epilogue], [b4_pre_epilogue])[]dnl This is a hack for glr.cc.  To remove when we have a better glr.cc.
-b4_percent_code_get([[epilogue]])[]dnl
+]b4_glr_cc_if([b4_glr_cc_pre_epilogue
+b4_glr_cc_cleanup])[
+]b4_percent_code_get([[epilogue]])[]dnl
 b4_epilogue[]dnl
 b4_output_end
@@ -1,6 +1,7 @@
 # C++ GLR skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,7 +14,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.


 # This skeleton produces a C++ class that encapsulates a C glr parser.
@@ -66,12 +67,6 @@ m4_defn([b4_parse_param]))],
           [[b4_namespace_ref::b4_parser_class[& yyparser], [[yyparser]]]])
 ])

-# b4_declare_symbol_enum
-# ----------------------
-m4_append([b4_declare_symbol_enum],
-[[typedef symbol_kind_type yysymbol_kind_t;
-]])
-

 # b4_yy_symbol_print_define
 # -------------------------
@@ -84,7 +79,7 @@ m4_define([b4_yy_symbol_print_define],

 static void
 yy_symbol_print (FILE *, ]b4_namespace_ref::b4_parser_class[::symbol_kind_type yytoken,
-                 const ]b4_namespace_ref::b4_parser_class[::semantic_type *yyvaluep]b4_locations_if([[,
+                 const ]b4_namespace_ref::b4_parser_class[::value_type *yyvaluep]b4_locations_if([[,
                 const ]b4_namespace_ref::b4_parser_class[::location_type *yylocationp]])[]b4_user_formals[)
 {
 ]b4_parse_param_use[]dnl
@@ -105,15 +100,9 @@ yyerror (]b4_locations_if([[const ]b4_namespace_ref::b4_parser_class[::location_
         ]])[]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param),
         ])[const char* msg);]])[

-]b4_percent_define_flag_if([[global_tokens_and_yystype]], [],
-[m4_define([b4_pre_epilogue],
-[[/* The user is using the C++ token kind, not the C one. */
-#undef ]b4_symbol(0, [id])
-])])[
-
-# Hijack the epilogue to define implementations (yyerror, parser member
+# Inserted before the epilogue to define implementations (yyerror, parser member
 # functions etc.).
-]m4_append([b4_epilogue],
+]m4_define([b4_glr_cc_pre_epilogue],
 [b4_syncline([@oline@], [@ofile@])dnl
 [
 /*------------------.
@@ -156,7 +145,7 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
  int
  ]b4_parser_class[::parse ()
  {
-    return ::yyparse (*this]b4_user_args[);
+    return ::yy_parse_impl (*this]b4_user_args[);
  }

 #if ]b4_api_PREFIX[DEBUG
@@ -166,25 +155,25 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl

  void
  ]b4_parser_class[::yy_symbol_value_print_ (symbol_kind_type yykind,
-                           const semantic_type* yyvaluep]b4_locations_if([[,
+                           const value_type* yyvaluep]b4_locations_if([[,
                           const location_type* yylocationp]])[) const
  {]b4_locations_if([[
-    YYUSE (yylocationp);]])[
-    YYUSE (yyvaluep);
+    YY_USE (yylocationp);]])[
+    YY_USE (yyvaluep);
    std::ostream& yyo = debug_stream ();
    std::ostream& yyoutput = yyo;
-    YYUSE (yyoutput);
+    YY_USE (yyoutput);
    ]b4_symbol_actions([printer])[
  }


  void
  ]b4_parser_class[::yy_symbol_print_ (symbol_kind_type yykind,
-                           const semantic_type* yyvaluep]b4_locations_if([[,
+                           const value_type* yyvaluep]b4_locations_if([[,
                           const location_type* yylocationp]])[) const
  {
    *yycdebug_ << (yykind < YYNTOKENS ? "token" : "nterm")
-               << ' ' << yytname[yykind] << " ("]b4_locations_if([[
+               << ' ' << yysymbol_name (yykind) << " ("]b4_locations_if([[
               << *yylocationp << ": "]])[;
    yy_symbol_value_print_ (yykind, yyvaluep]b4_locations_if([[, yylocationp]])[);
    *yycdebug_ << ')';
@@ -222,23 +211,18 @@ b4_namespace_close[]dnl
 ])


-# b4_shared_declarations(hh|cc)
-# -----------------------------
-# Declaration that might either go into the header (if --defines, $1 = hh)
-# or in the implementation file.
-m4_define([b4_shared_declarations],
-[m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
-b4_percent_code_get([[requires]])[
-#include <iostream>
-#include <stdexcept>
-#include <string>
+m4_define([b4_define_symbol_kind],
+[m4_format([#define %-15s %s],
+           b4_symbol($][1, kind_base),
+           b4_namespace_ref[::]b4_parser_class[::symbol_kind::]b4_symbol($1, kind_base))
+])

-]b4_cxx_portability[
-]m4_ifdef([b4_location_include],
-          [[# include ]b4_location_include])[
-]b4_variant_if([b4_variant_includes])[
-
-]b4_attribute_define[
+# b4_glr_cc_setup
+# ---------------
+# Setup redirections for glr.c: Map the names used in c.m4 to the ones used
+# in c++.m4.
+m4_define([b4_glr_cc_setup],
+[[]b4_attribute_define[
 ]b4_null_define[

 // This skeleton is based on C, yet compiles it as C++.
@@ -256,6 +240,62 @@ b4_percent_code_get([[requires]])[
 # pragma clang diagnostic ignored "-Wc++11-long-long"
 #endif

+#undef ]b4_symbol(empty, [id])[
+#define ]b4_symbol(empty, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(empty, [id])[
+#undef ]b4_symbol(eof, [id])[
+#define ]b4_symbol(eof, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(eof, [id])[
+#undef ]b4_symbol(error, [id])[
+#define ]b4_symbol(error, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(error, [id])[
+
+#ifndef ]b4_api_PREFIX[STYPE
+# define ]b4_api_PREFIX[STYPE ]b4_namespace_ref[::]b4_parser_class[::value_type
+#endif
+#ifndef ]b4_api_PREFIX[LTYPE
+# define ]b4_api_PREFIX[LTYPE ]b4_namespace_ref[::]b4_parser_class[::location_type
+#endif
+
+typedef ]b4_namespace_ref[::]b4_parser_class[::symbol_kind_type yysymbol_kind_t;
+
+// Expose C++ symbol kinds to C.
+]b4_define_symbol_kind(-2)dnl
+b4_symbol_foreach([b4_define_symbol_kind])])[
+]])
+
+
+m4_define([b4_undef_symbol_kind],
+[[#undef ]b4_symbol($1, kind_base)[
+]])
+
+
+# b4_glr_cc_cleanup
+# -----------------
+# Remove redirections for glr.c.
+m4_define([b4_glr_cc_cleanup],
+[[#undef ]b4_symbol(empty, [id])[
+#undef ]b4_symbol(eof, [id])[
+#undef ]b4_symbol(error, [id])[
+
+]b4_undef_symbol_kind(-2)dnl
+b4_symbol_foreach([b4_undef_symbol_kind])dnl
+])
+
+
+# b4_shared_declarations(hh|cc)
+# -----------------------------
+# Declaration that might either go into the header (if --header, $1 = hh)
+# or in the implementation file.
+m4_define([b4_shared_declarations],
+[m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
+b4_percent_code_get([[requires]])[
+#include <iostream>
+#include <stdexcept>
+#include <string>
+
+]b4_cxx_portability[
+]m4_ifdef([b4_location_include],
+          [[# include ]b4_location_include])[
+]b4_variant_if([b4_variant_includes])[
+
 // Whether we are compiled with exception support.
 #ifndef YY_EXCEPTIONS
 # if defined __GNUC__ && !defined __EXCEPTIONS
@@ -316,14 +356,14 @@ b4_percent_code_get([[requires]])[
    /// \param yyvaluep     Its semantic value.]b4_locations_if([[
    /// \param yylocationp  Its location.]])[
    virtual void yy_symbol_value_print_ (symbol_kind_type yykind,
-                                         const semantic_type* yyvaluep]b4_locations_if([[,
+                                         const value_type* yyvaluep]b4_locations_if([[,
                                         const location_type* yylocationp]])[) const;
    /// \brief Report a symbol on the debug stream.
    /// \param yykind       The symbol kind.
    /// \param yyvaluep     Its semantic value.]b4_locations_if([[
    /// \param yylocationp  Its location.]])[
    virtual void yy_symbol_print_ (symbol_kind_type yykind,
-                                   const semantic_type* yyvaluep]b4_locations_if([[,
+                                   const value_type* yyvaluep]b4_locations_if([[,
                                   const location_type* yylocationp]])[) const;
  private:
    /// Debug stream.
@@ -333,48 +373,22 @@ b4_percent_code_get([[requires]])[
 ]b4_parse_param_vars[
  };

-]dnl Redirections for glr.c.
-b4_percent_define_flag_if([[global_tokens_and_yystype]],
-[b4_token_defines
-])[
 ]b4_namespace_close[

-]dnl Map the name used in c.m4 to the one used in c++.m4.
-[#undef ]b4_symbol(-2, [id])[
-#define ]b4_symbol(-2, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(-2, [id])[
-#undef ]b4_symbol(0, [id])[
-#define ]b4_symbol(0, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(0, [id])[
-#undef ]b4_symbol(1, [id])[
-#define ]b4_symbol(1, [id])[ ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(1, [id])[
-
-#ifndef ]b4_api_PREFIX[STYPE
-# define ]b4_api_PREFIX[STYPE ]b4_namespace_ref[::]b4_parser_class[::semantic_type
-#endif
-#ifndef ]b4_api_PREFIX[LTYPE
-# define ]b4_api_PREFIX[LTYPE ]b4_namespace_ref[::]b4_parser_class[::location_type
-#endif
-
-]m4_define([b4_declare_symbol_enum],
-[[typedef ]b4_namespace_ref[::]b4_parser_class[::symbol_kind_type yysymbol_kind_t;
-#define ]b4_symbol_prefix[YYEMPTY  ]b4_namespace_ref[::]b4_parser_class[::symbol_kind::]b4_symbol_prefix[YYEMPTY
-#define ]b4_symbol_prefix[YYerror  ]b4_namespace_ref[::]b4_parser_class[::symbol_kind::]b4_symbol_prefix[YYerror
-#define ]b4_symbol_prefix[YYEOF    ]b4_namespace_ref[::]b4_parser_class[::symbol_kind::]b4_symbol_prefix[YYEOF
-#define ]b4_symbol_prefix[YYUNDEF  ]b4_namespace_ref[::]b4_parser_class[::symbol_kind::]b4_symbol_prefix[YYUNDEF
-]])[
 ]b4_percent_code_get([[provides]])[
 ]m4_popdef([b4_parse_param])dnl
-])
+])[

-b4_defines_if(
+]b4_header_if(
 [b4_output_begin([b4_spec_header_file])
 b4_copyright([Skeleton interface for Bison GLR parsers in C++],
-             [2002-2015, 2018-2020])[
+             [2002-2015, 2018-2022, 2025-2026])[
 // C++ GLR parser skeleton written by Akim Demaille.

 ]b4_disclaimer[
-]b4_cpp_guard_open([b4_spec_header_file])[
+]b4_cpp_guard_open([b4_spec_mapped_header_file])[
 ]b4_shared_declarations[
-]b4_cpp_guard_close([b4_spec_header_file])[
+]b4_cpp_guard_close([b4_spec_mapped_header_file])[
 ]b4_output_end])

 # Let glr.c (and b4_shared_declarations) believe that the user
@@ -2,8 +2,8 @@

 # Java skeleton dispatching for Bison.

-# Copyright (C) 2007, 2009-2015, 2018-2020 Free Software Foundation,
-# Inc.
+# Copyright (C) 2007, 2009-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -16,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 b4_glr_if(             [b4_complain([%%glr-parser not supported for Java])])
 b4_nondeterministic_if([b4_complain([%%nondeterministic-parser not supported for Java])])
@@ -2,7 +2,8 @@

 # Java language support for Bison

-# Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -15,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_include(b4_skeletonsdir/[c-like.m4])

@@ -71,12 +72,12 @@ m4_define([b4_lexer_if],
 # b4_identification
 # -----------------
 m4_define([b4_identification],
-[  /** Version number for the Bison executable that generated this parser.  */
-  public static final String bisonVersion = "b4_version";
+[[  /** Version number for the Bison executable that generated this parser.  */
+  public static final String bisonVersion = "]b4_version_string[";

  /** Name of the skeleton that generated this parser.  */
-  public static final String bisonSkeleton = b4_skeleton;
-])
+  public static final String bisonSkeleton = ]b4_skeleton[;
+]])


 ## ------------ ##
@@ -143,7 +144,7 @@ m4_define([b4_token_enum],
 ]],
               b4_symbol([$1], [tag]),
               b4_symbol([$1], [id]),
-               b4_symbol([$1], b4_api_token_raw_if([[number]], [[user_number]])))])])
+               b4_symbol([$1], b4_api_token_raw_if([[number]], [[code]])))])])


 # b4_token_enums
@@ -159,13 +160,20 @@ b4_symbol_foreach([b4_token_enum])])])
 ## Symbol kinds.  ##
 ## -------------- ##

+
+# b4_symbol_kind(NUM)
+# -------------------
+m4_define([b4_symbol_kind],
+[SymbolKind.b4_symbol_kind_base($@)])
+
+
 # b4_symbol_enum(SYMBOL-NUM)
 # --------------------------
 # Output the definition of this symbol as an enum.
 m4_define([b4_symbol_enum],
 [m4_format([    %-30s %s],
           m4_format([[%s(%s)%s]],
-                     b4_symbol([$1], [kind]),
+                     b4_symbol([$1], [kind_base]),
                     [$1],
                     m4_if([$1], b4_last_symbol, [[;]], [[,]])),
           [b4_symbol_tag_comment([$1])])])
@@ -255,11 +263,11 @@ m4_define([b4_declare_symbol_enum],



-# b4_case(ID, CODE)
-# -----------------
+# b4_case(ID, CODE, [COMMENTS])
+# -----------------------------
 # We need to fool Java's stupid unreachable code detection.
 m4_define([b4_case],
-[  case $1:
+[  case $1:m4_ifval([$3], [ b4_comment([$3])])
  if (yyn == $1)
    $2;
  break;
@@ -1,6 +1,7 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,15 +14,14 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_include(b4_skeletonsdir/[c++.m4])

 # api.value.type=variant is valid.
 m4_define([b4_value_type_setup_variant])

-# Check the value of %define parse.lac, where LAC stands for lookahead
-# correction.
+# parse.lac
 b4_percent_define_default([[parse.lac]], [[none]])
 b4_percent_define_check_values([[[[parse.lac]], [[full]], [[none]]]])
 b4_define_flag_if([lac])
@@ -59,6 +59,13 @@ m4_define([b4_integral_parser_table_define],
  };dnl
 ])

+
+# b4_symbol_kind(NUM)
+# -------------------
+m4_define([b4_symbol_kind],
+[symbol_kind::b4_symbol_kind_base($@)])
+
+
 # b4_symbol_value_template(VAL, SYMBOL-NUM, [TYPE])
 # -------------------------------------------------
 # Same as b4_symbol_value, but used in a template method.  It makes
@@ -139,21 +146,21 @@ b4_dollar_popdef[]dnl
 ])])


-# b4_lex
-# ------
+# b4_yylex
+# --------
 # Call yylex.
-m4_define([b4_lex],
+m4_define([b4_yylex],
 [b4_token_ctor_if(
 [b4_function_call([yylex],
                  [symbol_type], m4_ifdef([b4_lex_param], b4_lex_param))],
 [b4_function_call([yylex], [int],
-                  [b4_api_PREFIX[STYPE*], [&yyla.value]][]dnl
-b4_locations_if([, [[location*], [&yyla.location]]])dnl
+                  [[value_type *], [&yyla.value]][]dnl
+b4_locations_if([, [[location_type *], [&yyla.location]]])dnl
 m4_ifdef([b4_lex_param], [, ]b4_lex_param))])])


 m4_pushdef([b4_copyright_years],
-           [2002-2015, 2018-2020])
+           [2002-2015, 2018-2022, 2025-2026])

 m4_define([b4_parser_class],
          [b4_percent_define_get([[api.parser.class]])])
@@ -167,7 +174,7 @@ b4_variant_if([m4_include(b4_skeletonsdir/[variant.hh])])

 # b4_shared_declarations(hh|cc)
 # -----------------------------
-# Declaration that might either go into the header (if --defines, $1 = hh)
+# Declaration that might either go into the header (if --header, $1 = hh)
 # or in the implementation file.
 m4_define([b4_shared_declarations],
 [b4_percent_code_get([[requires]])[
@@ -264,9 +271,9 @@ m4_define([b4_shared_declarations],
    {
    public:
      context (const ]b4_parser_class[& yyparser, const symbol_type& yyla);
-      const symbol_type& lookahead () const { return yyla_; }
-      symbol_kind_type token () const { return yyla_.kind (); }]b4_locations_if([[
-      const location_type& location () const { return yyla_.location; }
+      const symbol_type& lookahead () const YY_NOEXCEPT { return yyla_; }
+      symbol_kind_type token () const YY_NOEXCEPT { return yyla_.kind (); }]b4_locations_if([[
+      const location_type& location () const YY_NOEXCEPT { return yyla_.location; }
 ]])[
      /// Put in YYARG at most YYARGN of the expected tokens, and return the
      /// number of tokens stored in YYARG.  If YYARG is null, return the
@@ -300,11 +307,11 @@ m4_define([b4_shared_declarations],
    /// Stored state numbers (used for stacks).
    typedef ]b4_int_type(0, m4_eval(b4_states_number - 1))[ state_type;
 ]b4_parse_error_bmatch(
-      [custom], [[
+[custom], [[
    /// Report a syntax error
    /// \param yyctx     the context in which the error occurred.
    void report_syntax_error (const context& yyctx) const;]],
-      [detailed\|verbose], [[
+[detailed\|verbose], [[
    /// The arguments of the error message.
    int yy_syntax_error_arguments_ (const context& yyctx,
                                    symbol_kind_type yyarg[], int yyargn) const;
@@ -319,19 +326,19 @@ m4_define([b4_shared_declarations],

    /// Whether the given \c yypact_ value indicates a defaulted state.
    /// \param yyvalue   the value to check
-    static bool yy_pact_value_is_default_ (int yyvalue);
+    static bool yy_pact_value_is_default_ (int yyvalue) YY_NOEXCEPT;

    /// Whether the given \c yytable_ value indicates a syntax error.
    /// \param yyvalue   the value to check
-    static bool yy_table_value_is_error_ (int yyvalue);
+    static bool yy_table_value_is_error_ (int yyvalue) YY_NOEXCEPT;

    static const ]b4_int_type(b4_pact_ninf, b4_pact_ninf)[ yypact_ninf_;
    static const ]b4_int_type(b4_table_ninf, b4_table_ninf)[ yytable_ninf_;

    /// Convert a scanner token kind \a t to a symbol kind.
    /// In theory \a t should be a token_kind_type, but character literals
-    /// are valid, yet not members of the token_type enum.
-    static symbol_kind_type yytranslate_ (int t);
+    /// are valid, yet not members of the token_kind_type enum.
+    static symbol_kind_type yytranslate_ (int t) YY_NOEXCEPT;

 ]b4_parse_error_bmatch(
 [simple],
@@ -401,7 +408,7 @@ m4_define([b4_shared_declarations],
      void move (by_state& that);

      /// The symbol kind (corresponding to \a state).
-      /// \a ]b4_symbol(-2, kind)[ when empty.
+      /// \a ]b4_symbol(empty, kind)[ when empty.
      symbol_kind_type kind () const YY_NOEXCEPT;

      /// The state number used to denote an empty symbol.
@@ -419,7 +426,7 @@ m4_define([b4_shared_declarations],
      /// Superclass.
      typedef basic_symbol<by_state> super_type;
      /// Construct an empty symbol.
-      stack_symbol_type ();
+      stack_symbol_type () YY_NOEXCEPT;
      /// Move or copy construction.
      stack_symbol_type (YY_RVREF (stack_symbol_type) that);
      /// Steal the contents from \a sym to build this.
@@ -468,7 +475,7 @@ m4_define([b4_shared_declarations],
    void yypush_ (const char* m, state_type s, YY_MOVE_REF (symbol_type) sym);

    /// Pop \a n symbols from the stack.
-    void yypop_ (int n = 1);
+    void yypop_ (int n = 1) YY_NOEXCEPT;

    /// Constants.
    enum
@@ -486,41 +493,42 @@ m4_define([b4_shared_declarations],
 ]b4_public_types_define([$1])])[
 ]b4_namespace_close[

-]b4_percent_define_flag_if([[global_tokens_and_yystype]],
-[b4_token_defines
-
-#ifndef ]b4_api_PREFIX[STYPE
- // Redirection for backward compatibility.
-# define ]b4_api_PREFIX[STYPE b4_namespace_ref::b4_parser_class::semantic_type
-#endif
-])[
 ]b4_percent_code_get([[provides]])[
-]])
+]])[
+

 ## -------------- ##
 ## Output files.  ##
 ## -------------- ##

-b4_defines_if(
-[b4_output_begin([b4_spec_header_file])
-b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++])
-[
+# ------------- #
+# Header file.  #
+# ------------- #
+
+]b4_header_if([[
+]b4_output_begin([b4_spec_header_file])[
+]b4_copyright([Skeleton interface for Bison LALR(1) parsers in C++])[
+
 /**
- ** \file ]b4_spec_header_file[
+ ** \file ]b4_spec_mapped_header_file[
 ** Define the ]b4_namespace_ref[::parser class.
 */

 // C++ LALR(1) parser skeleton written by Akim Demaille.

 ]b4_disclaimer[
-]b4_cpp_guard_open([b4_spec_header_file])[
+]b4_cpp_guard_open([b4_spec_mapped_header_file])[
 ]b4_shared_declarations(hh)[
-]b4_cpp_guard_close([b4_spec_header_file])[
+]b4_cpp_guard_close([b4_spec_mapped_header_file])[
 ]b4_output_end[
-]])
+]])[


-b4_output_begin([b4_parser_file_name])[
+# --------------------- #
+# Implementation file.  #
+# --------------------- #
+
+]b4_output_begin([b4_parser_file_name])[
 ]b4_copyright([Skeleton implementation for Bison LALR(1) parsers in C++])[
 ]b4_disclaimer[
 ]b4_percent_code_get([[top]])[]dnl
@@ -531,7 +539,7 @@ m4_if(b4_prefix, [yy], [],

 ]b4_user_pre_prologue[

-]b4_defines_if([[#include "@basename(]b4_spec_header_file[@)"]],
+]b4_header_if([[#include "@basename(]b4_spec_header_file[@)"]],
               [b4_shared_declarations([cc])])[

 ]b4_user_post_prologue[
@@ -598,7 +606,7 @@ m4_if(b4_prefix, [yy], [],
 #else // !]b4_api_PREFIX[DEBUG

 # define YYCDEBUG if (false) std::cerr
-# define YY_SYMBOL_PRINT(Title, Symbol)  YYUSE (Symbol)
+# define YY_SYMBOL_PRINT(Title, Symbol)  YY_USE (Symbol)
 # define YY_REDUCE_PRINT(Rule)           static_cast<void> (0)
 # define YY_STACK_PRINT()                static_cast<void> (0)

@@ -630,9 +638,9 @@ m4_if(b4_prefix, [yy], [],
  ]b4_parser_class[::syntax_error::~syntax_error () YY_NOEXCEPT YY_NOTHROW
  {}

-  /*---------------.
-  | symbol kinds.  |
-  `---------------*/
+  /*---------.
+  | symbol.  |
+  `---------*/

 ]b4_token_ctor_if([], [b4_public_types_define([cc])])[

@@ -666,12 +674,12 @@ m4_if(b4_prefix, [yy], [],
  ]b4_parser_class[::by_state::kind () const YY_NOEXCEPT
  {
    if (state == empty_state)
-      return symbol_kind::]b4_symbol(-2, kind)[;
+      return ]b4_symbol(empty, kind)[;
    else
      return YY_CAST (symbol_kind_type, yystos_[+state]);
  }

-  ]b4_parser_class[::stack_symbol_type::stack_symbol_type ()
+  ]b4_parser_class[::stack_symbol_type::stack_symbol_type () YY_NOEXCEPT
  {}

  ]b4_parser_class[::stack_symbol_type::stack_symbol_type (YY_RVREF (stack_symbol_type) that)
@@ -691,7 +699,7 @@ m4_if(b4_prefix, [yy], [],
    b4_symbol_variant([that.kind ()],
                      [value], [move], [YY_MOVE (that.value)])])[
    // that is emptied.
-    that.kind_ = symbol_kind::]b4_symbol(-2, kind)[;
+    that.kind_ = ]b4_symbol(empty, kind)[;
  }

 #if YY_CPLUSPLUS < 201103L
@@ -737,7 +745,7 @@ m4_if(b4_prefix, [yy], [],
  ]b4_parser_class[::yy_print_ (std::ostream& yyo, const basic_symbol<Base>& yysym) const
  {
    std::ostream& yyoutput = yyo;
-    YYUSE (yyoutput);
+    YY_USE (yyoutput);
    if (yysym.empty ())
      yyo << "empty symbol";
    else
@@ -772,7 +780,7 @@ m4_if(b4_prefix, [yy], [],
  }

  void
-  ]b4_parser_class[::yypop_ (int n)
+  ]b4_parser_class[::yypop_ (int n) YY_NOEXCEPT
  {
    yystack_.pop (n);
  }
@@ -815,13 +823,13 @@ m4_if(b4_prefix, [yy], [],
  }

  bool
-  ]b4_parser_class[::yy_pact_value_is_default_ (int yyvalue)
+  ]b4_parser_class[::yy_pact_value_is_default_ (int yyvalue) YY_NOEXCEPT
  {
    return yyvalue == yypact_ninf_;
  }

  bool
-  ]b4_parser_class[::yy_table_value_is_error_ (int yyvalue)
+  ]b4_parser_class[::yy_table_value_is_error_ (int yyvalue) YY_NOEXCEPT
  {
    return yyvalue == yytable_ninf_;
  }
@@ -835,12 +843,13 @@ m4_if(b4_prefix, [yy], [],
  int
  ]b4_parser_class[::parse ()
  {
+    YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
    int yyn;
    /// Length of the RHS of the rule being reduced.
    int yylen = 0;

    // Error handling.
-    int yynerrs_ = 0;
+    int yynerrs_ YY_ATTRIBUTE_UNUSED = 0;
    int yyerrstatus_ = 0;

    /// The lookahead symbol.
@@ -852,8 +861,8 @@ m4_if(b4_prefix, [yy], [],
    /// The return value of parse ().
    int yyresult;]b4_lac_if([[

-    /// Discard the LAC context in case there still is one left from a
-    /// previous invocation.
+    // Discard the LAC context in case there still is one left from a
+    // previous invocation.
    yy_lac_discard_ ("init");]])[

 #if YY_EXCEPTIONS
@@ -905,9 +914,9 @@ b4_dollar_popdef])[]dnl
        try
 #endif // YY_EXCEPTIONS
          {]b4_token_ctor_if([[
-            symbol_type yylookahead (]b4_lex[);
+            symbol_type yylookahead (]b4_yylex[);
            yyla.move (yylookahead);]], [[
-            yyla.kind_ = yytranslate_ (]b4_lex[);]])[
+            yyla.kind_ = yytranslate_ (]b4_yylex[);]])[
          }
 #if YY_EXCEPTIONS
        catch (const syntax_error& yyexc)
@@ -920,13 +929,13 @@ b4_dollar_popdef])[]dnl
      }
    YY_SYMBOL_PRINT ("Next token is", yyla);

-    if (yyla.kind () == ]symbol_kind::b4_symbol(1, kind)[)
+    if (yyla.kind () == ]b4_symbol(error, kind)[)
    {
      // The scanner already issued an error message, process directly
      // to error recovery.  But do not keep the error token as
      // lookahead, it is too special and may lead us to an endless
      // loop in error recovery. */
-      yyla.kind_ = ]symbol_kind::b4_symbol(2, kind)[;
+      yyla.kind_ = ]b4_symbol(undef, kind)[;
      goto yyerrlab1;
    }

@@ -936,7 +945,7 @@ b4_dollar_popdef])[]dnl
    if (yyn < 0 || yylast_ < yyn || yycheck_[yyn] != yyla.kind ())
      {]b4_lac_if([[
        if (!yy_lac_establish_ (yyla.kind ()))
-           goto yyerrlab;]])[
+          goto yyerrlab;]])[
        goto yydefault;
      }

@@ -947,7 +956,7 @@ b4_dollar_popdef])[]dnl
        if (yy_table_value_is_error_ (yyn))
          goto yyerrlab;]b4_lac_if([[
        if (!yy_lac_establish_ (yyla.kind ()))
-           goto yyerrlab;
+          goto yyerrlab;
 ]])[
        yyn = -yyn;
        goto yyreduce;
@@ -980,11 +989,11 @@ b4_dollar_popdef])[]dnl
    yylen = yyr2_[yyn];
    {
      stack_symbol_type yylhs;
-      yylhs.state = yy_lr_goto_state_ (yystack_[yylen].state, yyr1_[yyn]);]b4_variant_if([
+      yylhs.state = yy_lr_goto_state_ (yystack_[yylen].state, yyr1_[yyn]);]b4_variant_if([[
      /* Variants are always initialized to an empty instance of the
         correct type. The default '$$ = $1' action is NOT applied
         when using variants.  */
-      b4_symbol_variant([[yyr1_@{yyn@}]], [yylhs.value], [emplace])], [
+      ]b4_symbol_variant([[yyr1_@{yyn@}]], [yylhs.value], [emplace])], [[
      /* If YYLEN is nonzero, implement the default value of the
         action: '$$ = $1'.  Otherwise, use the top of the stack.

@@ -994,7 +1003,7 @@ b4_dollar_popdef])[]dnl
      if (yylen)
        yylhs.value = yystack_@{yylen - 1@}.value;
      else
-        yylhs.value = yystack_@{0@}.value;])[
+        yylhs.value = yystack_@{0@}.value;]])[
 ]b4_locations_if([dnl
 [
      // Default location.
@@ -1063,7 +1072,7 @@ b4_dollar_popdef])[]dnl
           error, discard it.  */

        // Return failure if at end of input.
-        if (yyla.kind () == symbol_kind::]b4_symbol_prefix[YYEOF)
+        if (yyla.kind () == ]b4_symbol(eof, kind)[)
          YYABORT;
        else if (!yyla.empty ())
          {
@@ -1104,9 +1113,9 @@ b4_dollar_popdef])[]dnl
        yyn = yypact_[+yystack_[0].state];
        if (!yy_pact_value_is_default_ (yyn))
          {
-            yyn += symbol_kind::]b4_symbol(1, kind)[;
+            yyn += ]b4_symbol(error, kind)[;
            if (0 <= yyn && yyn <= yylast_
-                && yycheck_[yyn] == symbol_kind::]b4_symbol(1, kind)[)
+                && yycheck_[yyn] == ]b4_symbol(error, kind)[)
              {
                yyn = yytable_[yyn];
                if (0 < yyn)
@@ -1171,6 +1180,7 @@ b4_dollar_popdef])[]dnl
      }

    return yyresult;
+    YY_IGNORE_MAYBE_UNINITIALIZED_END
  }
 #if YY_EXCEPTIONS
    catch (...)
@@ -1298,8 +1308,8 @@ b4_dollar_popdef])[]dnl
    for (int yyx = 0; yyx < YYNTOKENS; ++yyx)
      {
        symbol_kind_type yysym = YY_CAST (symbol_kind_type, yyx);
-        if (yysym != symbol_kind::]b4_symbol(1, kind)[
-            && yysym != symbol_kind::]b4_symbol_prefix[YYUNDEF
+        if (yysym != ]b4_symbol(error, kind)[
+            && yysym != ]b4_symbol(undef, kind)[
            && yyparser_.yy_lac_check_ (yysym))
          {
            if (!yyarg)
@@ -1310,18 +1320,18 @@ b4_dollar_popdef])[]dnl
              yyarg[yycount++] = yysym;
          }
      }]], [[
-    int yyn = yypact_[+yyparser_.yystack_[0].state];
+    const int yyn = yypact_[+yyparser_.yystack_[0].state];
    if (!yy_pact_value_is_default_ (yyn))
      {
        /* Start YYX at -YYN if negative to avoid negative indexes in
           YYCHECK.  In other words, skip the first -YYN actions for
           this state because they are default actions.  */
-        int yyxbegin = yyn < 0 ? -yyn : 0;
+        const int yyxbegin = yyn < 0 ? -yyn : 0;
        // Stay within bounds of both yycheck and yytname.
-        int yychecklim = yylast_ - yyn + 1;
-        int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
+        const int yychecklim = yylast_ - yyn + 1;
+        const int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
        for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
-          if (yycheck_[yyx + yyn] == yyx && yyx != symbol_kind::]b4_symbol(1, kind)[
+          if (yycheck_[yyx + yyn] == yyx && yyx != ]b4_symbol(error, kind)[
              && !yy_table_value_is_error_ (yytable_[yyx + yyn]))
            {
              if (!yyarg)
@@ -1334,11 +1344,13 @@ b4_dollar_popdef])[]dnl
      }
 ]])[
    if (yyarg && yycount == 0 && 0 < yyargn)
-      yyarg[0] = symbol_kind::]b4_symbol(-2, kind)[;
+      yyarg[0] = ]b4_symbol(empty, kind)[;
    return yycount;
  }

-]])b4_lac_if([[
+]])[
+
+]b4_lac_if([[
  bool
  ]b4_parser_class[::yy_lac_check_ (symbol_kind_type yytoken) const
  {
@@ -1411,7 +1423,7 @@ b4_dollar_popdef])[]dnl
                     : yylac_stack_.back ());
        // Push the resulting state of the reduction.
        state_type state = yy_lr_goto_state_ (top_state, yyr1_[yyrule]);
-        YYCDEBUG << " G" << state;
+        YYCDEBUG << " G" << int (state);
        yylac_stack_.push_back (state);
      }
  }
@@ -1443,7 +1455,9 @@ b4_dollar_popdef])[]dnl
       follows.  If no initial context is currently established for the
       current lookahead, then check if that lookahead can eventually be
       shifted if syntactic actions continue from the current context.  */
-    if (!yy_lac_established_)
+    if (yy_lac_established_)
+      return true;
+    else
      {
 #if ]b4_api_PREFIX[DEBUG
        YYCDEBUG << "LAC: initial context established for "
@@ -1452,12 +1466,11 @@ b4_dollar_popdef])[]dnl
        yy_lac_established_ = true;
        return yy_lac_check_ (yytoken);
      }
-    return true;
  }

  // Discard any previous initial lookahead context.
  void
-  ]b4_parser_class[::yy_lac_discard_ (const char* evt)
+  ]b4_parser_class[::yy_lac_discard_ (const char* event)
  {
   /* Discard any previous initial lookahead context because of Event,
      which may be a lookahead change or an invalidation of the currently
@@ -1473,11 +1486,12 @@ b4_dollar_popdef])[]dnl
    if (yy_lac_established_)
      {
        YYCDEBUG << "LAC: initial context discarded due to "
-                 << evt << '\n';
+                 << event << '\n';
        yy_lac_established_ = false;
      }
-  }]])b4_parse_error_bmatch([detailed\|verbose], [[
+  }]])[

+]b4_parse_error_bmatch([detailed\|verbose], [[
  int
  ]b4_parser_class[::yy_syntax_error_arguments_ (const context& yyctx,
                                                 symbol_kind_type yyarg[], int yyargn) const
@@ -1,6 +1,7 @@
-# Java skeleton for Bison                           -*- autoconf -*-
+# Java skeleton for Bison                           -*- java -*-

-# Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,11 +14,11 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_include(b4_skeletonsdir/[java.m4])

-b4_defines_if([b4_complain([%defines does not make sense in Java])])
+b4_header_if([b4_complain([%header/%defines does not make sense in Java])])

 m4_define([b4_symbol_no_destructor_assert],
 [b4_symbol_if([$1], [has_destructor],
@@ -25,7 +26,10 @@ m4_define([b4_symbol_no_destructor_assert],
                              [%destructor does not make sense in Java])])])
 b4_symbol_foreach([b4_symbol_no_destructor_assert])

-# Setup some macros for api.push-pull.
+## --------------- ##
+## api.push-pull.  ##
+## --------------- ##
+
 b4_percent_define_default([[api.push-pull]], [[pull]])
 b4_percent_define_check_values([[[[api.push-pull]],
                                 [[pull]], [[push]], [[both]]]])
@@ -52,9 +56,11 @@ b4_use_push_for_pull_if([
 # Define a macro to encapsulate the parse state variables.  This
 # allows them to be defined either in parse() when doing pull parsing,
 # or as class instance variable when doing push parsing.
-m4_define([b4_define_state],[[
-    /* Lookahead and lookahead in internal form.  */
+m4_define([b4_define_state],
+[[
+    /* Lookahead token kind.  */
    int yychar = YYEMPTY_;
+    /* Lookahead symbol kind.  */
    SymbolKind yytoken = null;

    /* State.  */
@@ -73,17 +79,31 @@ m4_define([b4_define_state],[[

    /* Semantic value of the lookahead.  */
    ]b4_yystype[ yylval = null;
-]])[
+]])

-]b4_output_begin([b4_parser_file_name])[
+# parse.lac
+b4_percent_define_default([[parse.lac]], [[none]])
+b4_percent_define_check_values([[[[parse.lac]], [[full]], [[none]]]])
+b4_define_flag_if([lac])
+m4_define([b4_lac_flag],
+          [m4_if(b4_percent_define_get([[parse.lac]]),
+                 [none], [[0]], [[1]])])
+
+
+## ------------- ##
+## Parser File.  ##
+## ------------- ##
+
+b4_output_begin([b4_parser_file_name])[
 ]b4_copyright([Skeleton implementation for Bison LALR(1) parsers in Java],
-              [2007-2015, 2018-2020])[
+              [2007-2015, 2018-2021])[
 ]b4_disclaimer[
-]b4_percent_define_ifdef([package], [package b4_percent_define_get([package]);[
+]b4_percent_define_ifdef([api.package], [package b4_percent_define_get([api.package]);[
 ]])[
 ]b4_user_pre_prologue[
 ]b4_user_post_prologue[
 import java.text.MessageFormat;
+import java.util.ArrayList;
 ]b4_percent_code_get([[imports]])[
 /**
 * A Bison parser, automatically generated from <tt>]m4_bpatsubst(b4_file_name, [^"\(.*\)"$], [\1])[</tt>.
@@ -156,11 +176,11 @@ import java.text.MessageFormat;
     * <code>]b4_position_type[</code> should override the <code>equals</code>
     * method.
     */
-    public String toString () {
+    public String toString() {
      if (begin.equals (end))
-        return begin.toString ();
+        return begin.toString();
      else
-        return begin.toString () + "-" + end.toString ();
+        return begin.toString() + "-" + end.toString();
    }
  }

@@ -180,8 +200,8 @@ import java.text.MessageFormat;
   */
  public interface Lexer {
 ]b4_token_enums[
-    /** Deprecated, use ]b4_symbol(0, id)[ instead.  */
-    public static final int EOF = ]b4_symbol(0, id)[;
+    /** Deprecated, use ]b4_symbol(eof, id)[ instead.  */
+    public static final int EOF = ]b4_symbol(eof, id)[;
 ]b4_pull_if([b4_locations_if([[
    /**
     * Method to retrieve the beginning position of the last scanned token.
@@ -225,7 +245,7 @@ import java.text.MessageFormat;
     *
     * @@param ctx  The context of the error.
     */
-     void reportSyntaxError (][Context ctx);
+     void reportSyntaxError(Context ctx);
 ]])[
  }

@@ -246,10 +266,12 @@ import java.text.MessageFormat;
  /**
   * Instantiates the Bison-generated parser.
   */
-  public ]b4_parser_class (b4_parse_param_decl([b4_lex_param_decl])[)]b4_maybe_throws([b4_init_throws])[
+  public ]b4_parser_class[(]b4_parse_param_decl([b4_lex_param_decl])[)]b4_maybe_throws([b4_init_throws])[
  {
-]b4_percent_code_get([[init]])[
-    this.yylexer = new YYLexer (]b4_lex_param_call[);
+]b4_percent_code_get([[init]])[]b4_lac_if([[
+    this.yylacStack = new ArrayList<Integer>();
+    this.yylacEstablished = false;]])[
+    this.yylexer = new YYLexer(]b4_lex_param_call[);
 ]b4_parse_param_cons[
  }
 ]])[
@@ -258,9 +280,11 @@ import java.text.MessageFormat;
   * Instantiates the Bison-generated parser.
   * @@param yylexer The scanner that will supply tokens to the parser.
   */
-  ]b4_lexer_if([[protected]], [[public]]) b4_parser_class[ (]b4_parse_param_decl([[Lexer yylexer]])[)]b4_maybe_throws([b4_init_throws])[
+  ]b4_lexer_if([[protected]], [[public]]) b4_parser_class[(]b4_parse_param_decl([[Lexer yylexer]])[)]b4_maybe_throws([b4_init_throws])[
  {
-]b4_percent_code_get([[init]])[
+]b4_percent_code_get([[init]])[]b4_lac_if([[
+    this.yylacStack = new ArrayList<Integer>();
+    this.yylacEstablished = false;]])[
    this.yylexer = yylexer;
 ]b4_parse_param_cons[
  }
@@ -271,13 +295,13 @@ import java.text.MessageFormat;
  /**
   * The <tt>PrintStream</tt> on which the debugging output is printed.
   */
-  public final java.io.PrintStream getDebugStream () { return yyDebugStream; }
+  public final java.io.PrintStream getDebugStream() { return yyDebugStream; }

  /**
   * Set the <tt>PrintStream</tt> on which the debug output is printed.
   * @@param s The stream that is used for debugging output.
   */
-  public final void setDebugStream (java.io.PrintStream s) { yyDebugStream = s; }
+  public final void setDebugStream(java.io.PrintStream s) { yyDebugStream = s; }

  private int yydebug = 0;

@@ -285,14 +309,14 @@ import java.text.MessageFormat;
   * Answer the verbosity of the debugging output; 0 means that all kinds of
   * output from the parser are suppressed.
   */
-  public final int getDebugLevel () { return yydebug; }
+  public final int getDebugLevel() { return yydebug; }

  /**
   * Set the verbosity of the debugging output; 0 means that all kinds of
   * output from the parser are suppressed.
   * @@param level The verbosity level for debugging output.
   */
-  public final void setDebugLevel (int level) { yydebug = level; }
+  public final void setDebugLevel(int level) { yydebug = level; }
 ]])[

  private int yynerrs = 0;
@@ -300,7 +324,7 @@ import java.text.MessageFormat;
  /**
   * The number of syntax errors so far.
   */
-  public final int getNumberOfErrors () { return yynerrs; }
+  public final int getNumberOfErrors() { return yynerrs; }

  /**
   * Print an error message via the lexer.
@@ -329,9 +353,14 @@ import java.text.MessageFormat;
      yylexer.yyerror(new ]b4_location_type[ (pos), msg);
  }]])[
 ]b4_parse_trace_if([[
-  protected final void yycdebug (String s) {
+  protected final void yycdebugNnl(String s) {
    if (0 < yydebug)
-      yyDebugStream.println (s);
+      yyDebugStream.print(s);
+  }
+
+  protected final void yycdebug(String s) {
+    if (0 < yydebug)
+      yyDebugStream.println(s);
  }]])[

  private final class YYStack {
@@ -342,65 +371,63 @@ import java.text.MessageFormat;
    public int size = 16;
    public int height = -1;

-    public final void push (int state, ]b4_yystype[ value]b4_locations_if([, ]b4_location_type[ loc])[) {
+    public final void push(int state, ]b4_yystype[ value]b4_locations_if([, ]b4_location_type[ loc])[) {
      height++;
-      if (size == height)
-        {
-          int[] newStateStack = new int[size * 2];
-          System.arraycopy (stateStack, 0, newStateStack, 0, height);
-          stateStack = newStateStack;]b4_locations_if([[
-          ]b4_location_type[[] newLocStack = new ]b4_location_type[[size * 2];
-          System.arraycopy (locStack, 0, newLocStack, 0, height);
-          locStack = newLocStack;]])
+      if (size == height) {
+        int[] newStateStack = new int[size * 2];
+        System.arraycopy(stateStack, 0, newStateStack, 0, height);
+        stateStack = newStateStack;]b4_locations_if([[
+        ]b4_location_type[[] newLocStack = new ]b4_location_type[[size * 2];
+        System.arraycopy(locStack, 0, newLocStack, 0, height);
+        locStack = newLocStack;]])

-          b4_yystype[[] newValueStack = new ]b4_yystype[[size * 2];
-          System.arraycopy (valueStack, 0, newValueStack, 0, height);
-          valueStack = newValueStack;
+        b4_yystype[[] newValueStack = new ]b4_yystype[[size * 2];
+        System.arraycopy(valueStack, 0, newValueStack, 0, height);
+        valueStack = newValueStack;

-          size *= 2;
-        }
+        size *= 2;
+      }

      stateStack[height] = state;]b4_locations_if([[
      locStack[height] = loc;]])[
      valueStack[height] = value;
    }

-    public final void pop () {
-      pop (1);
+    public final void pop() {
+      pop(1);
    }

-    public final void pop (int num) {
+    public final void pop(int num) {
      // Avoid memory leaks... garbage collection is a white lie!
      if (0 < num) {
-        java.util.Arrays.fill (valueStack, height - num + 1, height + 1, null);]b4_locations_if([[
-        java.util.Arrays.fill (locStack, height - num + 1, height + 1, null);]])[
+        java.util.Arrays.fill(valueStack, height - num + 1, height + 1, null);]b4_locations_if([[
+        java.util.Arrays.fill(locStack, height - num + 1, height + 1, null);]])[
      }
      height -= num;
    }

-    public final int stateAt (int i) {
+    public final int stateAt(int i) {
      return stateStack[height - i];
    }
 ]b4_locations_if([[

-    public final ]b4_location_type[ locationAt (int i) {
+    public final ]b4_location_type[ locationAt(int i) {
      return locStack[height - i];
    }
 ]])[
-    public final ]b4_yystype[ valueAt (int i) {
+    public final ]b4_yystype[ valueAt(int i) {
      return valueStack[height - i];
    }

    // Print the state stack on the debug stream.
-    public void print (java.io.PrintStream out) {
+    public void print(java.io.PrintStream out) {
      out.print ("Stack now");

-      for (int i = 0; i <= height; i++)
-        {
-          out.print (' ');
-          out.print (stateStack[i]);
-        }
-      out.println ();
+      for (int i = 0; i <= height; i++) {
+        out.print(' ');
+        out.print(stateStack[i]);
+      }
+      out.println();
    }
  }

@@ -457,8 +484,7 @@ import java.text.MessageFormat;
   * @@param yystate   the current state
   * @@param yysym     the nonterminal to push on the stack
   */
-  private int yyLRGotoState (int yystate, int yysym)
-  {
+  private int yyLRGotoState(int yystate, int yysym) {
    int yyr = yypgoto_[yysym - YYNTOKENS_] + yystate;
    if (0 <= yyr && yyr <= YYLAST_ && yycheck_[yyr] == yystate)
      return yytable_[yyr];
@@ -535,7 +561,12 @@ import java.text.MessageFormat;
    /* @@$.  */
    ]b4_location_type[ yyloc;]])[
 ]b4_push_if([],[[
-]b4_define_state[]b4_parse_trace_if([[
+]b4_define_state[
+]b4_lac_if([[
+    // Discard the LAC context in case there still is one left from a
+    // previous invocation.
+    yylacDiscard("init");]])[
+]b4_parse_trace_if([[
    yycdebug ("Starting parse");]])[
    yyerrstatus_ = 0;
    yynerrs = 0;
@@ -602,9 +633,9 @@ b4_dollar_popdef[]dnl
            push_token_consumed = false;]], [b4_parse_trace_if([[
            yycdebug ("Reading a token");]])[
            yychar = yylexer.yylex ();
-            yylval = yylexer.getLVal ();]b4_locations_if([
-            yylloc = new b4_location_type (yylexer.getStartPos (),
-                            yylexer.getEndPos ());])[
+            yylval = yylexer.getLVal();]b4_locations_if([[
+            yylloc = new ]b4_location_type[(yylexer.getStartPos(),
+                                          yylexer.getEndPos());]])[
 ]])[
          }

@@ -613,14 +644,14 @@ b4_dollar_popdef[]dnl
        yySymbolPrint("Next token is", yytoken,
                      yylval]b4_locations_if([, yylloc])[);]])[

-        if (yytoken == SymbolKind.]b4_symbol_prefix[YYerror)
+        if (yytoken == ]b4_symbol(error, kind)[)
          {
            // The scanner already issued an error message, process directly
            // to error recovery.  But do not keep the error token as
            // lookahead, it is too special and may lead us to an endless
            // loop in error recovery. */
-            yychar = Lexer.]b4_percent_define_get([api.token.prefix])[YYUNDEF;
-            yytoken = SymbolKind.]b4_symbol_prefix[YYUNDEF;]b4_locations_if([[
+            yychar = Lexer.]b4_symbol(undef, id)[;
+            yytoken = ]b4_symbol(undef, kind)[;]b4_locations_if([[
            yyerrloc = yylloc;]])[
            label = YYERRLAB1;
          }
@@ -628,20 +659,25 @@ b4_dollar_popdef[]dnl
          {
            /* If the proper action on seeing token YYTOKEN is to reduce or to
               detect an error, take that action.  */
-            yyn += yytoken.getCode ();
-            if (yyn < 0 || YYLAST_ < yyn || yycheck_[yyn] != yytoken.getCode ())
+            yyn += yytoken.getCode();
+            if (yyn < 0 || YYLAST_ < yyn || yycheck_[yyn] != yytoken.getCode()) {]b4_lac_if([[
+              if (!yylacEstablish(yystack, yytoken)) {
+                label = YYERRLAB;
+              } else]])[
              label = YYDEFAULT;
+            }

            /* <= 0 means reduce or error.  */
            else if ((yyn = yytable_[yyn]) <= 0)
              {
-                if (yyTableValueIsError (yyn))
+                if (yyTableValueIsError(yyn)) {
                  label = YYERRLAB;
-                else
-                  {
-                    yyn = -yyn;
-                    label = YYREDUCE;
-                  }
+                }]b4_lac_if([[ else if (!yylacEstablish(yystack, yytoken)) {
+                  label = YYERRLAB;
+                }]])[ else {
+                  yyn = -yyn;
+                  label = YYREDUCE;
+                }
              }

            else
@@ -659,7 +695,8 @@ b4_dollar_popdef[]dnl
                  --yyerrstatus_;

                yystate = yyn;
-                yystack.push (yystate, yylval]b4_locations_if([, yylloc])[);
+                yystack.push(yystate, yylval]b4_locations_if([, yylloc])[);]b4_lac_if([[
+                yylacDiscard("shift");]])[
                label = YYNEWSTATE;
              }
          }
@@ -682,7 +719,7 @@ b4_dollar_popdef[]dnl
      case YYREDUCE:
        yylen = yyr2_[yyn];
        label = yyaction(yyn, yystack, yylen);
-        yystate = yystack.stateAt (0);
+        yystate = yystack.stateAt(0);
        break;

      /*------------------------------------.
@@ -695,7 +732,7 @@ b4_dollar_popdef[]dnl
            ++yynerrs;
            if (yychar == YYEMPTY_)
              yytoken = null;
-            yyreportSyntaxError (new Context (yystack, yytoken]b4_locations_if([[, yylloc]])[));
+            yyreportSyntaxError(new Context(this, yystack, yytoken]b4_locations_if([[, yylloc]])[));
          }
 ]b4_locations_if([[
        yyerrloc = yylloc;]])[
@@ -704,10 +741,10 @@ b4_dollar_popdef[]dnl
            /* If just tried and failed to reuse lookahead token after an
               error, discard it.  */

-            if (yychar <= Lexer.]b4_symbol(0, id)[)
+            if (yychar <= Lexer.]b4_symbol(eof, id)[)
              {
                /* Return failure if at end of input.  */
-                if (yychar == Lexer.]b4_symbol(0, id)[)
+                if (yychar == Lexer.]b4_symbol(eof, id)[)
                  ]b4_push_if([{label = YYABORT; break;}], [return false;])[
              }
            else
@@ -728,7 +765,7 @@ b4_dollar_popdef[]dnl
           this YYERROR.  */
        yystack.pop (yylen);
        yylen = 0;
-        yystate = yystack.stateAt (0);
+        yystate = yystack.stateAt(0);
        label = YYERRLAB1;
        break;

@@ -744,9 +781,9 @@ b4_dollar_popdef[]dnl
            yyn = yypact_[yystate];
            if (!yyPactValueIsDefault (yyn))
              {
-                yyn += SymbolKind.]b4_symbol(1, kind)[.getCode ();
+                yyn += ]b4_symbol(error, kind)[.getCode();
                if (0 <= yyn && yyn <= YYLAST_
-                    && yycheck_[yyn] == SymbolKind.]b4_symbol(1, kind)[.getCode ())
+                    && yycheck_[yyn] == ]b4_symbol(error, kind)[.getCode())
                  {
                    yyn = yytable_[yyn];
                    if (0 < yyn)
@@ -762,7 +799,7 @@ b4_dollar_popdef[]dnl
 ]b4_locations_if([[
            yyerrloc = yystack.locationAt (0);]])[
            yystack.pop ();
-            yystate = yystack.stateAt (0);]b4_parse_trace_if([[
+            yystate = yystack.stateAt(0);]b4_parse_trace_if([[
            if (0 < yydebug)
              yystack.print (yyDebugStream);]])[
          }
@@ -778,8 +815,9 @@ b4_dollar_popdef[]dnl
        yyloc = yylloc (yystack, 2);
        yystack.pop (2);]])[

-        /* Shift the error token.  */]b4_parse_trace_if([[
-        yySymbolPrint("Shifting", SymbolKind.get (yystos_[yyn]),
+        /* Shift the error token.  */]b4_lac_if([[
+        yylacDiscard("error recovery");]])[]b4_parse_trace_if([[
+        yySymbolPrint("Shifting", SymbolKind.get(yystos_[yyn]),
                      yylval]b4_locations_if([, yyloc])[);]])[

        yystate = yyn;
@@ -814,7 +852,9 @@ b4_dollar_popdef[]dnl
    this.yyn = 0;
    this.yylen = 0;
    this.yystate = 0;
-    this.yystack = new YYStack ();
+    this.yystack = new YYStack();]b4_lac_if([[
+    this.yylacStack = new ArrayList<Integer>();
+    this.yylacEstablished = false;]])[
    this.label = YYNEWSTATE;

    /* Error handling.  */
@@ -874,23 +914,22 @@ b4_dollar_popdef[]dnl
   * Information needed to get the list of expected tokens and to forge
   * a syntax error diagnostic.
   */
-  public static final class Context
-  {
-    Context (YYStack stack, SymbolKind token]b4_locations_if([[, ]b4_location_type[ loc]])[)
-    {
+  public static final class Context {
+    Context(]b4_parser_class[ parser, YYStack stack, SymbolKind token]b4_locations_if([[, ]b4_location_type[ loc]])[) {
+      yyparser = parser;
      yystack = stack;
      yytoken = token;]b4_locations_if([[
      yylocation = loc;]])[
    }

+    private ]b4_parser_class[ yyparser;
    private YYStack yystack;


    /**
     * The symbol kind of the lookahead token.
     */
-    public final SymbolKind getToken ()
-    {
+    public final SymbolKind getToken() {
      return yytoken;
    }

@@ -899,8 +938,7 @@ b4_dollar_popdef[]dnl
    /**
     * The location of the lookahead.
     */
-    public final ]b4_location_type[ getLocation ()
-    {
+    public final ]b4_location_type[ getLocation() {
      return yylocation;
    }

@@ -913,16 +951,34 @@ b4_dollar_popdef[]dnl
     * YYARG is null, return the number of expected tokens (guaranteed to
     * be less than YYNTOKENS).
     */
-    int getExpectedTokens (SymbolKind yyarg[], int yyargn)
-    {
+    int getExpectedTokens(SymbolKind yyarg[], int yyargn) {
      return getExpectedTokens (yyarg, 0, yyargn);
    }

-    int getExpectedTokens (SymbolKind yyarg[], int yyoffset, int yyargn)
-    {
-      int yycount = yyoffset;
-      int yyn = yypact_[this.yystack.stateAt (0)];
-      if (!yyPactValueIsDefault (yyn))
+    int getExpectedTokens(SymbolKind yyarg[], int yyoffset, int yyargn) {
+      int yycount = yyoffset;]b4_lac_if([b4_parse_trace_if([[
+      // Execute LAC once. We don't care if it is successful, we
+      // only do it for the sake of debugging output.
+      if (!yyparser.yylacEstablished)
+        yyparser.yylacCheck(yystack, yytoken);
+]])[
+      for (int yyx = 0; yyx < YYNTOKENS_; ++yyx)
+        {
+          SymbolKind yysym = SymbolKind.get(yyx);
+          if (yysym != ]b4_symbol(error, kind)[
+              && yysym != ]b4_symbol(undef, kind)[
+              && yyparser.yylacCheck(yystack, yysym))
+            {
+              if (yyarg == null)
+                yycount += 1;
+              else if (yycount == yyargn)
+                return 0;
+              else
+                yyarg[yycount++] = yysym;
+            }
+        }]], [[
+      int yyn = yypact_[this.yystack.stateAt(0)];
+      if (!yyPactValueIsDefault(yyn))
        {
          /* Start YYX at -YYN if negative to avoid negative
             indexes in YYCHECK.  In other words, skip the first
@@ -933,27 +989,168 @@ b4_dollar_popdef[]dnl
          int yychecklim = YYLAST_ - yyn + 1;
          int yyxend = yychecklim < NTOKENS ? yychecklim : NTOKENS;
          for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
-            if (yycheck_[yyx + yyn] == yyx && yyx != SymbolKind.]b4_symbol(1, kind)[.getCode ()
-                && !yyTableValueIsError (yytable_[yyx + yyn]))
+            if (yycheck_[yyx + yyn] == yyx && yyx != ]b4_symbol(error, kind)[.getCode()
+                && !yyTableValueIsError(yytable_[yyx + yyn]))
              {
                if (yyarg == null)
                  yycount += 1;
                else if (yycount == yyargn)
                  return 0; // FIXME: this is incorrect.
                else
-                  yyarg[yycount++] = SymbolKind.get (yyx);
+                  yyarg[yycount++] = SymbolKind.get(yyx);
              }
-        }
+        }]])[
      if (yyarg != null && yycount == yyoffset && yyoffset < yyargn)
        yyarg[yycount] = null;
      return yycount - yyoffset;
    }
  }

+]b4_lac_if([[
+    /** Check the lookahead yytoken.
+     * \returns  true iff the token will be eventually shifted.
+     */
+    boolean yylacCheck(YYStack yystack, SymbolKind yytoken)
+    {
+      // Logically, the yylacStack's lifetime is confined to this function.
+      // Clear it, to get rid of potential left-overs from previous call.
+      yylacStack.clear();
+      // Reduce until we encounter a shift and thereby accept the token.
+      yycdebugNnl("LAC: checking lookahead " + yytoken.getName() + ":");
+      int lacTop = 0;
+      while (true)
+        {
+          int topState = (yylacStack.isEmpty()
+                          ? yystack.stateAt(lacTop)
+                          : yylacStack.get(yylacStack.size() - 1));
+          int yyrule = yypact_[topState];
+          if (yyPactValueIsDefault(yyrule)
+              || (yyrule += yytoken.getCode()) < 0 || YYLAST_ < yyrule
+              || yycheck_[yyrule] != yytoken.getCode())
+            {
+              // Use the default action.
+              yyrule = yydefact_[+topState];
+              if (yyrule == 0) {
+                yycdebug(" Err");
+                return false;
+              }
+            }
+          else
+            {
+              // Use the action from yytable.
+              yyrule = yytable_[yyrule];
+              if (yyTableValueIsError(yyrule)) {
+                yycdebug(" Err");
+                return false;
+              }
+              if (0 < yyrule) {
+                yycdebug(" S" + yyrule);
+                return true;
+              }
+              yyrule = -yyrule;
+            }
+          // By now we know we have to simulate a reduce.
+          yycdebugNnl(" R" + (yyrule - 1));
+          // Pop the corresponding number of values from the stack.
+          {
+            int yylen = yyr2_[yyrule];
+            // First pop from the LAC stack as many tokens as possible.
+            int lacSize = yylacStack.size();
+            if (yylen < lacSize) {
+              // yylacStack.setSize(lacSize - yylen);
+              for (/* Nothing */; 0 < yylen; yylen -= 1) {
+                yylacStack.remove(yylacStack.size() - 1);
+              }
+              yylen = 0;
+            } else if (lacSize != 0) {
+              yylacStack.clear();
+              yylen -= lacSize;
+            }
+            // Only afterwards look at the main stack.
+            // We simulate popping elements by incrementing lacTop.
+            lacTop += yylen;
+          }
+          // Keep topState in sync with the updated stack.
+          topState = (yylacStack.isEmpty()
+                      ? yystack.stateAt(lacTop)
+                      : yylacStack.get(yylacStack.size() - 1));
+          // Push the resulting state of the reduction.
+          int state = yyLRGotoState(topState, yyr1_[yyrule]);
+          yycdebugNnl(" G" + state);
+          yylacStack.add(state);
+        }
+    }
+
+    /** Establish the initial context if no initial context currently exists.
+     * \returns  true iff the token will be eventually shifted.
+     */
+    boolean yylacEstablish(YYStack yystack, SymbolKind yytoken) {
+      /* Establish the initial context for the current lookahead if no initial
+         context is currently established.
+
+         We define a context as a snapshot of the parser stacks.  We define
+         the initial context for a lookahead as the context in which the
+         parser initially examines that lookahead in order to select a
+         syntactic action.  Thus, if the lookahead eventually proves
+         syntactically unacceptable (possibly in a later context reached via a
+         series of reductions), the initial context can be used to determine
+         the exact set of tokens that would be syntactically acceptable in the
+         lookahead's place.  Moreover, it is the context after which any
+         further semantic actions would be erroneous because they would be
+         determined by a syntactically unacceptable token.
+
+         yylacEstablish should be invoked when a reduction is about to be
+         performed in an inconsistent state (which, for the purposes of LAC,
+         includes consistent states that don't know they're consistent because
+         their default reductions have been disabled).
+
+         For parse.lac=full, the implementation of yylacEstablish is as
+         follows.  If no initial context is currently established for the
+         current lookahead, then check if that lookahead can eventually be
+         shifted if syntactic actions continue from the current context.  */
+      if (yylacEstablished) {
+        return true;
+      } else {
+        yycdebug("LAC: initial context established for " + yytoken.getName());
+        yylacEstablished = true;
+        return yylacCheck(yystack, yytoken);
+      }
+    }
+
+    /** Discard any previous initial lookahead context because of event.
+     * \param event  the event which caused the lookahead to be discarded.
+     *               Only used for debbuging output.  */
+    void yylacDiscard(String event) {
+     /* Discard any previous initial lookahead context because of Event,
+        which may be a lookahead change or an invalidation of the currently
+        established initial context for the current lookahead.
+
+        The most common example of a lookahead change is a shift.  An example
+        of both cases is syntax error recovery.  That is, a syntax error
+        occurs when the lookahead is syntactically erroneous for the
+        currently established initial context, so error recovery manipulates
+        the parser stacks to try to find a new initial context in which the
+        current lookahead is syntactically acceptable.  If it fails to find
+        such a context, it discards the lookahead.  */
+      if (yylacEstablished) {
+        yycdebug("LAC: initial context discarded due to " + event);
+        yylacEstablished = false;
+      }
+    }
+
+    /** The stack for LAC.
+     * Logically, the yylacStack's lifetime is confined to the function
+     * yylacCheck. We just store it as a member of this class to hold
+     * on to the memory and to avoid frequent reallocations.
+     */
+    ArrayList<Integer> yylacStack;
+    /**  Whether an initial LAC context was established. */
+    boolean yylacEstablished;
+]])[
+
 ]b4_parse_error_bmatch(
 [detailed\|verbose], [[
-  private int yysyntaxErrorArguments (Context yyctx, SymbolKind[] yyarg, int yyargn)
-  {
+  private int yysyntaxErrorArguments(Context yyctx, SymbolKind[] yyarg, int yyargn) {
    /* There are many possibilities here to consider:
       - If this state is a consistent state with a default action,
         then the only way this function was invoked is if the
@@ -981,12 +1178,12 @@ b4_dollar_popdef[]dnl
         to an error action in a later state.
    */
    int yycount = 0;
-    if (yyctx.getToken () != null)
+    if (yyctx.getToken() != null)
      {
        if (yyarg != null)
-          yyarg[yycount] = yyctx.getToken ();
+          yyarg[yycount] = yyctx.getToken();
        yycount += 1;
-        yycount += yyctx.getExpectedTokens (yyarg, 1, yyargn);
+        yycount += yyctx.getExpectedTokens(yyarg, 1, yyargn);
      }
    return yycount;
  }
@@ -1031,8 +1228,7 @@ b4_dollar_popdef[]dnl
   * Whether the given <code>yypact_</code> value indicates a defaulted state.
   * @@param yyvalue   the value to check
   */
-  private static boolean yyPactValueIsDefault (int yyvalue)
-  {
+  private static boolean yyPactValueIsDefault(int yyvalue) {
    return yyvalue == yypact_ninf_;
  }

@@ -1041,8 +1237,7 @@ b4_dollar_popdef[]dnl
   * value indicates a syntax error.
   * @@param yyvalue the value to check
   */
-  private static boolean yyTableValueIsError (int yyvalue)
-  {
+  private static boolean yyTableValueIsError(int yyvalue) {
    return yyvalue == yytable_ninf_;
  }

@@ -1071,27 +1266,28 @@ b4_dollar_popdef[]dnl
    /* The symbols being reduced.  */
    for (int yyi = 0; yyi < yynrhs; yyi++)
      yySymbolPrint("   $" + (yyi + 1) + " =",
-                    SymbolKind.get (yystos_[yystack.stateAt (yynrhs - (yyi + 1))]),
+                    SymbolKind.get(yystos_[yystack.stateAt(yynrhs - (yyi + 1))]),
                    ]b4_rhs_data(yynrhs, yyi + 1)b4_locations_if([,
                    b4_rhs_location(yynrhs, yyi + 1)])[);
  }]])[

  /* YYTRANSLATE_(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
     as returned by yylex, with out-of-bounds checking.  */
-  private static final SymbolKind yytranslate_ (int t)
+  private static final SymbolKind yytranslate_(int t)
 ]b4_api_token_raw_if(dnl
 [[  {
-    return SymbolKind.get (t);
+    return SymbolKind.get(t);
  }
 ]],
 [[  {
-    int user_token_number_max_ = ]b4_user_token_number_max[;
+    // Last valid token kind.
+    int code_max = ]b4_code_max[;
    if (t <= 0)
-      return SymbolKind.]b4_symbol_prefix[YYEOF;
-    else if (t <= user_token_number_max_)
-      return SymbolKind.get (yytranslate_table_[t]);
+      return ]b4_symbol(eof, kind)[;
+    else if (t <= code_max)
+      return SymbolKind.get(yytranslate_table_[t]);
    else
-      return SymbolKind.]b4_symbol_prefix[YYUNDEF;
+      return ]b4_symbol(undef, kind)[;
  }
  ]b4_integral_parser_table_define([translate_table], [b4_translate])[
 ]])[
@@ -1,6 +1,7 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,17 +14,10 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_pushdef([b4_copyright_years],
-           [2002-2015, 2018-2020])
-
-
-# b4_position_file
-# ----------------
-# Name of the file containing the position class, if we want this file.
-b4_defines_if([b4_required_version_if([302], [],
-                                      [m4_define([b4_position_file], [position.hh])])])])
+           [2002-2015, 2018-2022, 2025-2026])


 # b4_location_file
@@ -32,7 +26,7 @@ b4_defines_if([b4_required_version_if([302], [],
 # if we want this file.
 b4_percent_define_check_file([b4_location_file],
                             [[api.location.file]],
-                             b4_defines_if([[location.hh]]))
+                             b4_header_if([[location.hh]]))

 # b4_location_include
 # -------------------
@@ -48,12 +42,22 @@ m4_ifdef([b4_location_file],
                                  ["b4_location_file"])])
 m4_define([b4_location_path],
           b4_percent_define_get([[api.location.include]],
-                                 ["b4_dir_prefix[]b4_location_file"]))
+                                 ["b4_mapped_dir_prefix[]b4_location_file"]))
 m4_define([b4_location_path],
           m4_substr(m4_defn([b4_location_path]), 1, m4_eval(m4_len(m4_defn([b4_location_path])) - 2)))
 ])


+# b4_position_file
+# ----------------
+# Name of the file containing the position class, if we want this file.
+b4_header_if(
+  [b4_required_version_if(
+    [30200], [],
+    [m4_ifdef([b4_location_file],
+              [m4_define([b4_position_file], [position.hh])])])])
+
+

 # b4_location_define
 # ------------------
@@ -63,11 +67,13 @@ m4_define([b4_location_define],
  class position
  {
  public:
+    /// Type for file name.
+    typedef ]b4_percent_define_get([[api.filename.type]])[ filename_type;
    /// Type for line and column numbers.
    typedef int counter_type;
 ]m4_ifdef([b4_location_constructors], [[
    /// Construct a position.
-    explicit position (]b4_percent_define_get([[filename_type]])[* f = YY_NULLPTR,
+    explicit position (filename_type* f = YY_NULLPTR,
                       counter_type l = ]b4_location_initial_line[,
                       counter_type c = ]b4_location_initial_column[)
      : filename (f)
@@ -77,7 +83,7 @@ m4_define([b4_location_define],

 ]])[
    /// Initialization.
-    void initialize (]b4_percent_define_get([[filename_type]])[* fn = YY_NULLPTR,
+    void initialize (filename_type* fn = YY_NULLPTR,
                     counter_type l = ]b4_location_initial_line[,
                     counter_type c = ]b4_location_initial_column[)
    {
@@ -106,7 +112,7 @@ m4_define([b4_location_define],
    /** \} */

    /// File name to which this position refers.
-    ]b4_percent_define_get([[filename_type]])[* filename;
+    filename_type* filename;
    /// Current line number.
    counter_type line;
    /// Current column number.
@@ -184,6 +190,8 @@ m4_define([b4_location_define],
  class location
  {
  public:
+    /// Type for file name.
+    typedef position::filename_type filename_type;
    /// Type for line and column numbers.
    typedef position::counter_type counter_type;
 ]m4_ifdef([b4_location_constructors], [
@@ -200,7 +208,7 @@ m4_define([b4_location_define],
    {}

    /// Construct a 0-width location in \a f, \a l, \a c.
-    explicit location (]b4_percent_define_get([[filename_type]])[* f,
+    explicit location (filename_type* f,
                       counter_type l = ]b4_location_initial_line[,
                       counter_type c = ]b4_location_initial_column[)
      : begin (f, l, c)
@@ -209,7 +217,7 @@ m4_define([b4_location_define],

 ])[
    /// Initialization.
-    void initialize (]b4_percent_define_get([[filename_type]])[* f = YY_NULLPTR,
+    void initialize (filename_type* f = YY_NULLPTR,
                     counter_type l = ]b4_location_initial_line[,
                     counter_type c = ]b4_location_initial_column[)
    {
@@ -1,6 +1,7 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,14 +14,14 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.


 # b4_stack_file
 # -------------
 # Name of the file containing the stack class, if we want this file.
-b4_defines_if([b4_required_version_if([302], [],
-                                      [m4_define([b4_stack_file], [stack.hh])])])
+b4_header_if([b4_required_version_if([30200], [],
+                                     [m4_define([b4_stack_file], [stack.hh])])])


 # b4_stack_define
@@ -37,7 +38,7 @@ m4_define([b4_stack_define],
      typedef typename S::size_type size_type;
      typedef typename std::ptrdiff_t index_type;

-      stack (size_type n = 200)
+      stack (size_type n = 200) YY_NOEXCEPT
        : seq_ (n)
      {}

@@ -116,7 +117,7 @@ m4_define([b4_stack_define],
      class slice
      {
      public:
-        slice (const stack& stack, index_type range)
+        slice (const stack& stack, index_type range) YY_NOEXCEPT
          : stack_ (stack)
          , range_ (range)
        {}
@@ -0,0 +1,2 @@
+dnl GNU M4 treats -dV in a position-independent manner.
+m4_debugmode(V)m4_traceon()dnl
@@ -1,6 +1,7 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,13 +14,20 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.


 ## --------- ##
 ## variant.  ##
 ## --------- ##

+# b4_assert
+# ---------
+# The name of YY_ASSERT.
+m4_define([b4_assert],
+          [b4_api_PREFIX[]_ASSERT])
+
+
 # b4_symbol_variant(YYTYPE, YYVAL, ACTION, [ARGS])
 # ------------------------------------------------
 # Run some ACTION ("build", or "destroy") on YYVAL of symbol type
@@ -71,12 +79,12 @@ m4_map([      b4_symbol_tag_comment], [$@])dnl
 # -------------------
 # The needed includes for variants support.
 m4_define([b4_variant_includes],
-[b4_parse_assert_if([[#include <typeinfo>]])[
-#ifndef YY_ASSERT
+[b4_parse_assert_if([[#include <typeinfo>
+#ifndef ]b4_assert[
 # include <cassert>
-# define YY_ASSERT assert
+# define ]b4_assert[ assert
 #endif
-]])
+]])])



@@ -87,45 +95,45 @@ m4_define([b4_variant_includes],

 # b4_value_type_declare
 # ---------------------
-# Define semantic_type.
+# Define value_type.
 m4_define([b4_value_type_declare],
 [[  /// A buffer to store and retrieve objects.
  ///
  /// Sort of a variant, but does not keep track of the nature
  /// of the stored data, since that knowledge is available
  /// via the current parser state.
-  class semantic_type
+  class value_type
  {
  public:
    /// Type of *this.
-    typedef semantic_type self_type;
+    typedef value_type self_type;

    /// Empty construction.
-    semantic_type () YY_NOEXCEPT
-      : yybuffer_ ()]b4_parse_assert_if([
+    value_type () YY_NOEXCEPT
+      : yyraw_ ()]b4_parse_assert_if([
      , yytypeid_ (YY_NULLPTR)])[
    {}

    /// Construct and fill.
    template <typename T>
-    semantic_type (YY_RVREF (T) t)]b4_parse_assert_if([
+    value_type (YY_RVREF (T) t)]b4_parse_assert_if([
      : yytypeid_ (&typeid (T))])[
-    {
-      YY_ASSERT (sizeof (T) <= size);
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (sizeof (T) <= size);]])[
      new (yyas_<T> ()) T (YY_MOVE (t));
    }

 #if 201103L <= YY_CPLUSPLUS
    /// Non copyable.
-    semantic_type (const self_type&) = delete;
+    value_type (const self_type&) = delete;
    /// Non copyable.
    self_type& operator= (const self_type&) = delete;
 #endif

    /// Destruction, allowed only if empty.
-    ~semantic_type () YY_NOEXCEPT
+    ~value_type () YY_NOEXCEPT
    {]b4_parse_assert_if([
-      YY_ASSERT (!yytypeid_);
+      ]b4_assert[ (!yytypeid_);
    ])[}

 # if 201103L <= YY_CPLUSPLUS
@@ -133,10 +141,10 @@ m4_define([b4_value_type_declare],
    template <typename T, typename... U>
    T&
    emplace (U&&... u)
-    {]b4_parse_assert_if([
-      YY_ASSERT (!yytypeid_);
-      YY_ASSERT (sizeof (T) <= size);
-      yytypeid_ = & typeid (T);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (!yytypeid_);
+      ]b4_assert[ (sizeof (T) <= size);
+      yytypeid_ = & typeid (T);]])[
      return *new (yyas_<T> ()) T (std::forward <U>(u)...);
    }
 # else
@@ -144,10 +152,10 @@ m4_define([b4_value_type_declare],
    template <typename T>
    T&
    emplace ()
-    {]b4_parse_assert_if([
-      YY_ASSERT (!yytypeid_);
-      YY_ASSERT (sizeof (T) <= size);
-      yytypeid_ = & typeid (T);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (!yytypeid_);
+      ]b4_assert[ (sizeof (T) <= size);
+      yytypeid_ = & typeid (T);]])[
      return *new (yyas_<T> ()) T ();
    }

@@ -155,10 +163,10 @@ m4_define([b4_value_type_declare],
    template <typename T>
    T&
    emplace (const T& t)
-    {]b4_parse_assert_if([
-      YY_ASSERT (!yytypeid_);
-      YY_ASSERT (sizeof (T) <= size);
-      yytypeid_ = & typeid (T);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (!yytypeid_);
+      ]b4_assert[ (sizeof (T) <= size);
+      yytypeid_ = & typeid (T);]])[
      return *new (yyas_<T> ()) T (t);
    }
 # endif
@@ -185,10 +193,10 @@ m4_define([b4_value_type_declare],
    template <typename T>
    T&
    as () YY_NOEXCEPT
-    {]b4_parse_assert_if([
-      YY_ASSERT (yytypeid_);
-      YY_ASSERT (*yytypeid_ == typeid (T));
-      YY_ASSERT (sizeof (T) <= size);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (yytypeid_);
+      ]b4_assert[ (*yytypeid_ == typeid (T));
+      ]b4_assert[ (sizeof (T) <= size);]])[
      return *yyas_<T> ();
    }

@@ -196,10 +204,10 @@ m4_define([b4_value_type_declare],
    template <typename T>
    const T&
    as () const YY_NOEXCEPT
-    {]b4_parse_assert_if([
-      YY_ASSERT (yytypeid_);
-      YY_ASSERT (*yytypeid_ == typeid (T));
-      YY_ASSERT (sizeof (T) <= size);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (yytypeid_);
+      ]b4_assert[ (*yytypeid_ == typeid (T));
+      ]b4_assert[ (sizeof (T) <= size);]])[
      return *yyas_<T> ();
    }

@@ -214,9 +222,9 @@ m4_define([b4_value_type_declare],
    template <typename T>
    void
    swap (self_type& that) YY_NOEXCEPT
-    {]b4_parse_assert_if([
-      YY_ASSERT (yytypeid_);
-      YY_ASSERT (*yytypeid_ == *that.yytypeid_);])[
+    {]b4_parse_assert_if([[
+      ]b4_assert[ (yytypeid_);
+      ]b4_assert[ (*yytypeid_ == *that.yytypeid_);]])[
      std::swap (as<T> (), that.as<T> ());
    }

@@ -267,7 +275,7 @@ m4_define([b4_value_type_declare],
  private:
 #if YY_CPLUSPLUS < 201103L
    /// Non copyable.
-    semantic_type (const self_type&);
+    value_type (const self_type&);
    /// Non copyable.
    self_type& operator= (const self_type&);
 #endif
@@ -277,7 +285,7 @@ m4_define([b4_value_type_declare],
    T*
    yyas_ () YY_NOEXCEPT
    {
-      void *yyp = yybuffer_.yyraw;
+      void *yyp = yyraw_;
      return static_cast<T*> (yyp);
     }

@@ -286,7 +294,7 @@ m4_define([b4_value_type_declare],
    const T*
    yyas_ () const YY_NOEXCEPT
    {
-      const void *yyp = yybuffer_.yyraw;
+      const void *yyp = yyraw_;
      return static_cast<const T*> (yyp);
     }

@@ -301,10 +309,10 @@ m4_define([b4_value_type_declare],
    union
    {
      /// Strongest alignment constraints.
-      long double yyalign_me;
+      long double yyalign_me_;
      /// A buffer large enough to store any of the semantic values.
-      char yyraw[size];
-    } yybuffer_;]b4_parse_assert_if([
+      char yyraw_[size];
+    };]b4_parse_assert_if([

    /// Whether the content is built: if defined, the name of the stored type.
    const std::type_info *yytypeid_;])[
@@ -388,18 +396,74 @@ m4_define([_b4_token_maker_define],
 ])])


-m4_define([_b4_type_clause],
-[b4_symbol_if([$1], [is_token],
-              [b4_symbol_if([$1], [has_id],
-                            [tok == token::b4_symbol([$1], [id])],
-                            [tok == b4_symbol([$1], [user_number])])])])
+# b4_token_kind(SYMBOL-NUM)
+# -------------------------
+# Some tokens don't have an ID.
+m4_define([b4_token_kind],
+[b4_symbol_if([$1], [has_id],
+              [token::b4_symbol([$1], [id])],
+              [b4_symbol([$1], [code])])])


-# _b4_token_constructor_define(SYMBOL-NUM...)
-# -------------------------------------------
-# Define a unique make_symbol for all the SYMBOL-NUM (they
+# _b4_tok_in(SYMBOL-NUM, ...)
+# ---------------------------
+# See b4_tok_in below.  The SYMBOL-NUMs... are tokens only.
+#
+# We iterate over the tokens to group them by "range" of token numbers (not
+# symbols numbers!).
+#
+# b4_fst is the start of that range.
+# b4_prev is the previous value.
+# b4_val is the current value.
+# If b4_val is the successor of b4_prev in token numbers, update the latter,
+#   otherwise emit the code for range b4_fst .. b4_prev.
+# $1 is also used as a terminator in the foreach, but it will not be printed.
+#
+m4_define([_b4_tok_in],
+[m4_pushdef([b4_prev], [$1])dnl
+m4_pushdef([b4_fst], [$1])dnl
+m4_pushdef([b4_sep], [])dnl
+m4_foreach([b4_val], m4_dquote(m4_shift($@, $1)),
+           [m4_if(b4_symbol(b4_val, [code]), m4_eval(b4_symbol(b4_prev, [code]) + 1), [],
+                  [b4_sep[]m4_if(b4_fst, b4_prev,
+                         [tok == b4_token_kind(b4_fst)],
+                         [(b4_token_kind(b4_fst) <= tok && tok <= b4_token_kind(b4_prev))])[]dnl
+m4_define([b4_fst], b4_val)dnl
+m4_define([b4_sep], [
+                   || ])])dnl
+m4_define([b4_prev], b4_val)])dnl
+m4_popdef([b4_sep])dnl
+m4_popdef([b4_fst])dnl
+m4_popdef([b4_prev])dnl
+])
+
+
+# _b4_filter_tokens(SYMBOL-NUM, ...)
+# ----------------------------------
+# Expand as the list of tokens amongst SYMBOL-NUM.
+m4_define([_b4_filter_tokens],
+[m4_pushdef([b4_sep])dnl
+m4_foreach([b4_val], [$@],
+           [b4_symbol_if(b4_val, [is_token], [b4_sep[]b4_val[]m4_define([b4_sep], [,])])])dnl
+m4_popdef([b4_sep])dnl
+])
+
+
+# b4_tok_in(SYMBOL-NUM, ...)
+# ---------------------------
+# A C++ conditional that checks that `tok` is a member of this list of symbol
+# numbers.
+m4_define([b4_tok_in],
+          [_$0(_b4_filter_tokens($@))])
+
+
+
+
+# _b4_symbol_constructor_define(SYMBOL-NUM...)
+# --------------------------------------------
+# Define a symbol_type constructor common to all the SYMBOL-NUM (they
 # have the same type).  Use at class-level.
-m4_define([_b4_token_constructor_define],
+m4_define([_b4_symbol_constructor_define],
 [m4_ifval(_b4_includes_tokens($@),
 [[#if 201103L <= YY_CPLUSPLUS
      symbol_type (]b4_join(
@@ -407,25 +471,24 @@ m4_define([_b4_token_constructor_define],
          b4_symbol_if([$1], [has_type],
                       [b4_symbol([$1], [type]) v]),
          b4_locations_if([location_type l]))[)
-        : super_type(]b4_join([token_type (tok)],
-                              b4_symbol_if([$1], [has_type], [std::move (v)]),
-                              b4_locations_if([std::move (l)]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], [$@]))[);
-      }
+        : super_type (]b4_join([token_kind_type (tok)],
+                               b4_symbol_if([$1], [has_type], [std::move (v)]),
+                               b4_locations_if([std::move (l)]))[)
 #else
      symbol_type (]b4_join(
          [int tok],
          b4_symbol_if([$1], [has_type],
                       [const b4_symbol([$1], [type])& v]),
          b4_locations_if([const location_type& l]))[)
-        : super_type(]b4_join([token_type (tok)],
-                              b4_symbol_if([$1], [has_type], [v]),
-                              b4_locations_if([l]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], [$@]))[);
-      }
+        : super_type (]b4_join([token_kind_type (tok)],
+                               b4_symbol_if([$1], [has_type], [v]),
+                               b4_locations_if([l]))[)
 #endif
+      {]b4_parse_assert_if([[
+#if !defined _MSC_VER || defined __clang__
+        ]b4_assert[ (]b4_tok_in($@)[);
+#endif
+      ]])[}
 ]])])


@@ -457,7 +520,7 @@ m4_define([b4_basic_symbol_constructor_define],

 # b4_token_constructor_define
 # ---------------------------
-# Define the overloaded versions of make_symbol for all the value types.
+# Define the overloaded versions of make_FOO for all the token kinds.
 m4_define([b4_token_constructor_define],
-[    // Implementation of make_symbol for each symbol type.
+[    // Implementation of make_symbol for each token kind.
 b4_symbol_foreach([_b4_token_maker_define])])
@@ -1,11 +1,11 @@
 #                                                            -*- C -*-
 # Yacc compatible skeleton for Bison

-# Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2020 Free Software
-# Foundation, Inc.
+# Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2022, 2025-2026 Free
+# Software Foundation, Inc.

 m4_pushdef([b4_copyright_years],
-           [1984, 1989-1990, 2000-2015, 2018-2020])
+           [1984, 1989-1990, 2000-2015, 2018-2022, 2025-2026])

 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -18,10 +18,11 @@ m4_pushdef([b4_copyright_years],
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 m4_include(b4_skeletonsdir/[c.m4])

+
 ## ---------- ##
 ## api.pure.  ##
 ## ---------- ##
@@ -48,6 +49,10 @@ m4_define([b4_pure_if],
 ## api.push-pull.  ##
 ## --------------- ##

+# b4_pull_if, b4_push_if
+# ----------------------
+# Whether the pull/push APIs are needed.  Both can be enabled.
+
 b4_percent_define_default([[api.push-pull]], [[pull]])
 b4_percent_define_check_values([[[[api.push-pull]],
                                 [[pull]], [[push]], [[both]]]])
@@ -97,6 +102,16 @@ m4_define([b4_yyerror_arg_loc_if],
                          [1], [m4_ifset([b4_parse_param], [$1])],
                          [2], [$1])])])

+# b4_yyerror_formals
+# ------------------
+m4_define([b4_yyerror_formals],
+[b4_pure_if([b4_locations_if([, [[const ]b4_api_PREFIX[LTYPE *yyllocp], [&yylloc]]])[]dnl
+m4_ifdef([b4_parse_param], [, b4_parse_param])[]dnl
+,])dnl
+[[const char *msg], [msg]]])
+
+
+
 # b4_yyerror_args
 # ---------------
 # Arguments passed to yyerror: user args plus yylloc.
@@ -111,6 +126,16 @@ m4_ifset([b4_parse_param], [b4_args(b4_parse_param), ])])
 ## ----------------- ##


+# b4_accept([SYMBOL-NUM])
+# -----------------------
+# Used in actions of the rules of accept, the initial symbol, to call
+# YYACCEPT.  If SYMBOL-NUM is specified, run "yyvalue->SLOT = $2;"
+# before, using the slot of SYMBOL-NUM.
+m4_define([b4_accept],
+[m4_ifval([$1],
+          [b4_symbol_value(yyimpl->yyvalue, [$1]) = b4_rhs_value(2, 1, [$1]); ]) YYACCEPT])
+
+
 # b4_lhs_value(SYMBOL-NUM, [TYPE])
 # --------------------------------
 # See README.
@@ -150,14 +175,61 @@ m4_define([b4_rhs_location],
 ## Declarations.  ##
 ## -------------- ##

+# _b4_declare_sub_yyparse(START-SYMBOL-NUM, SWITCHING-TOKEN-SYMBOL-NUM)
+# ---------------------------------------------------------------------
+# Define the return type of the parsing function for SYMBOL-NUM, and
+# declare its parsing function.
+m4_define([_b4_declare_sub_yyparse],
+[[
+// Return type when parsing one ]_b4_symbol($1, tag)[.
+typedef struct
+{]b4_symbol_if([$1], [has_type], [[
+  ]_b4_symbol($1, type)[ yyvalue;]])[
+  int yystatus;
+  int yynerrs;
+} ]b4_prefix[parse_]_b4_symbol($1, id)[_t;
+
+// Parse one ]_b4_symbol($1, tag)[.
+]b4_prefix[parse_]_b4_symbol($1, id)[_t ]b4_prefix[parse_]_b4_symbol($1, id)[ (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[);
+]])
+
+
+# _b4_first_switching_token
+# -------------------------
+m4_define([b4_first], [$1])
+m4_define([b4_second], [$2])
+m4_define([_b4_first_switching_token],
+[b4_second(b4_first(b4_start_symbols))])
+
+
+# _b4_define_sub_yyparse(START-SYMBOL-NUM, SWITCHING-TOKEN-SYMBOL-NUM)
+# --------------------------------------------------------------------
+# Define the parsing function for START-SYMBOL-NUM.
+m4_define([_b4_define_sub_yyparse],
+[[
+]b4_prefix[parse_]_b4_symbol($1, id)[_t
+]b4_prefix[parse_]_b4_symbol($1, id)[ (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)
+{
+  ]b4_prefix[parse_]_b4_symbol($1, id)[_t yyres;
+  yy_parse_impl_t yyimpl;
+  yyres.yystatus = yy_parse_impl (]b4_symbol($2, id)[, &yyimpl]m4_ifset([b4_parse_param],
+                           [[, ]b4_args(b4_parse_param)])[);]b4_symbol_if([$1], [has_type], [[
+  yyres.yyvalue = yyimpl.yyvalue.]b4_symbol($1, slot)[;]])[
+  yyres.yynerrs = yyimpl.yynerrs;
+  return yyres;
+}
+]])
+
+
 # b4_declare_scanner_communication_variables
 # ------------------------------------------
 # Declare the variables that are global, or local to YYPARSE if
 # pure-parser.
 m4_define([b4_declare_scanner_communication_variables], [[
-/* The lookahead symbol.  */
+]m4_ifdef([b4_start_symbols], [],
+[[/* Lookahead token kind.  */
 int yychar;
-
+]])[
 ]b4_pure_if([[
 /* The semantic value of the lookahead symbol.  */
 /* Default value used for initialization, for pacifying older GCCs
@@ -176,68 +248,47 @@ YYLTYPE yylloc]b4_yyloc_default[;]])[
 int yynerrs;]])])


-# b4_declare_parser_state_variables
-# ---------------------------------
+# b4_declare_parser_state_variables([INIT])
+# -----------------------------------------
 # Declare all the variables that are needed to maintain the parser state
 # between calls to yypush_parse.
+# If INIT is non-null, initialize these variables.
 m4_define([b4_declare_parser_state_variables],
 [b4_pure_if([[
    /* Number of syntax errors so far.  */
-    int yynerrs;
+    int yynerrs YY_ATTRIBUTE_UNUSED]m4_ifval([$1], [ = 0])[;
 ]])[
-    yy_state_fast_t yystate;
+    yy_state_fast_t yystate]m4_ifval([$1], [ = 0])[;
    /* Number of tokens to shift before error messages enabled.  */
-    int yyerrstatus;
+    int yyerrstatus]m4_ifval([$1], [ = 0])[;

-    /* The stacks and their tools:
-       'yyss': related to states.
-       'yyvs': related to semantic values.]b4_locations_if([[
-       'yyls': related to locations.]])[
-
-       Refer to the stacks through separate pointers, to allow yyoverflow
+    /* Refer to the stacks through separate pointers, to allow yyoverflow
       to reallocate them elsewhere.  */

    /* Their size.  */
-    YYPTRDIFF_T yystacksize;
+    YYPTRDIFF_T yystacksize]m4_ifval([$1], [ = YYINITDEPTH])[;

-    /* The state stack.  */
+    /* The state stack: array, bottom, top.  */
    yy_state_t yyssa[YYINITDEPTH];
-    yy_state_t *yyss;
-    yy_state_t *yyssp;
+    yy_state_t *yyss]m4_ifval([$1], [ = yyssa])[;
+    yy_state_t *yyssp]m4_ifval([$1], [ = yyss])[;

-    /* The semantic value stack.  */
+    /* The semantic value stack: array, bottom, top.  */
    YYSTYPE yyvsa[YYINITDEPTH];
-    YYSTYPE *yyvs;
-    YYSTYPE *yyvsp;]b4_locations_if([[
+    YYSTYPE *yyvs]m4_ifval([$1], [ = yyvsa])[;
+    YYSTYPE *yyvsp]m4_ifval([$1], [ = yyvs])[;]b4_locations_if([[

-    /* The location stack.  */
+    /* The location stack: array, bottom, top.  */
    YYLTYPE yylsa[YYINITDEPTH];
-    YYLTYPE *yyls;
-    YYLTYPE *yylsp;]])[]b4_lac_if([[
+    YYLTYPE *yyls]m4_ifval([$1], [ = yylsa])[;
+    YYLTYPE *yylsp]m4_ifval([$1], [ = yyls])[;]])[]b4_lac_if([[

    yy_state_t yyesa@{]b4_percent_define_get([[parse.lac.es-capacity-initial]])[@};
-    yy_state_t *yyes;
-    YYPTRDIFF_T yyes_capacity;]])])
-
-
-# b4_initialize_parser_state_variables
-# ------------------------------------
-# Initialize these variables.
-m4_define([b4_initialize_parser_state_variables],
-[[  yynerrs = 0;
-  yystate = 0;
-  yyerrstatus = 0;
-
-  yystacksize = YYINITDEPTH;
-  yyssp = yyss = yyssa;
-  yyvsp = yyvs = yyvsa;]b4_locations_if([[
-  yylsp = yyls = yylsa;]])[]b4_lac_if([[
-
-  yyes = yyesa;
-  yyes_capacity = ]b4_percent_define_get([[parse.lac.es-capacity-initial]])[;
-  if (YYMAXDEPTH < yyes_capacity)
-    yyes_capacity = YYMAXDEPTH;]])[
-]])
+    yy_state_t *yyes]m4_ifval([$1], [ = yyesa])[;
+    YYPTRDIFF_T yyes_capacity][]m4_ifval([$1],
+            [m4_do([ = b4_percent_define_get([[parse.lac.es-capacity-initial]]) < YYMAXDEPTH],
+                   [ ? b4_percent_define_get([[parse.lac.es-capacity-initial]])],
+                   [ : YYMAXDEPTH])])[;]])])


 m4_define([b4_macro_define],
@@ -293,11 +344,14 @@ int ]b4_prefix[push_parse (]b4_prefix[pstate *ps]b4_pure_if([[,
 void ]b4_prefix[pstate_delete (]b4_prefix[pstate *ps);
 ]])

+
 # _b4_declare_yyparse
 # -------------------
 # When not the push parser.
 m4_define([_b4_declare_yyparse],
-[[int ]b4_prefix[parse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[);]])
+[[int ]b4_prefix[parse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[);
+]m4_ifdef([b4_start_symbols],
+          [m4_map([_b4_declare_sub_yyparse], m4_defn([b4_start_symbols]))])])


 # b4_declare_yyparse
@@ -308,19 +362,35 @@ m4_define([b4_declare_yyparse],
 ])


+# b4_declare_yyerror_and_yylex
+# ----------------------------
+# Comply with POSIX Yacc.
+# <https://austingroupbugs.net/view.php?id=1388#c5220>
+m4_define([b4_declare_yyerror_and_yylex],
+[b4_posix_if([[#if !defined ]b4_prefix[error && !defined ]b4_api_PREFIX[ERROR_IS_DECLARED
+]b4_function_declare([b4_prefix[error]], void, b4_yyerror_formals)[
+#endif
+#if !defined ]b4_prefix[lex && !defined ]b4_api_PREFIX[LEX_IS_DECLARED
+]b4_function_declare([b4_prefix[lex]], int, b4_yylex_formals)[
+#endif
+]])dnl
+])
+
+
 # b4_shared_declarations
 # ----------------------
-# Declaration that might either go into the header (if --defines)
-# or open coded in the parser body.
+# Declarations that might either go into the header (if --header)
+# or into the implementation file.
 m4_define([b4_shared_declarations],
-[b4_cpp_guard_open([b4_spec_header_file])[
+[b4_cpp_guard_open([b4_spec_mapped_header_file])[
 ]b4_declare_yydebug[
 ]b4_percent_code_get([[requires]])[
 ]b4_token_enums_defines[
 ]b4_declare_yylstype[
+]b4_declare_yyerror_and_yylex[
 ]b4_declare_yyparse[
 ]b4_percent_code_get([[provides]])[
-]b4_cpp_guard_close([b4_spec_header_file])[]dnl
+]b4_cpp_guard_close([b4_spec_mapped_header_file])[]dnl
 ])


@@ -335,7 +405,7 @@ m4_define([b4_header_include_if],
                                   [$2])],
          [$2])])

-m4_if(b4_spec_header_file, [[y.tab.h]],
+m4_if(b4_spec_header_file, [y.tab.h], [],
      [b4_percent_define_default([[api.header.include]],
                                 [["@basename(]b4_spec_header_file[@)"]])])

@@ -347,13 +417,13 @@ m4_if(b4_spec_header_file, [[y.tab.h]],
 ## -------------- ##


-b4_defines_if([[
+b4_header_if([[
 ]b4_output_begin([b4_spec_header_file])[
 ]b4_copyright([Bison interface for Yacc-like parsers in C])[
 ]b4_disclaimer[
 ]b4_shared_declarations[
 ]b4_output_end[
-]])# b4_defines_if
+]])# b4_header_if

 b4_output_begin([b4_parser_file_name])[
 ]b4_copyright([Bison implementation for Yacc-like parsers in C])[
@@ -511,10 +581,27 @@ void free (void *); /* INFRINGES ON USER NAME SPACE */
 # define YYCOPY_NEEDED 1]])[
 #endif /* ]b4_lac_if([[1]], [b4_parse_error_case([simple], [[!defined yyoverflow]], [[1]])])[ */

-#if (! defined yyoverflow \
-     && (! defined __cplusplus \
-         || (]b4_locations_if([[defined ]b4_api_PREFIX[LTYPE_IS_TRIVIAL && ]b4_api_PREFIX[LTYPE_IS_TRIVIAL \
-             && ]])[defined ]b4_api_PREFIX[STYPE_IS_TRIVIAL && ]b4_api_PREFIX[STYPE_IS_TRIVIAL)))
+#ifndef yyoverflow
+/* In C++, ]b4_api_PREFIX[STYPE must be trivially copyable.
+   If ]b4_api_PREFIX[STYPE_IS_TRIVIAL, this is already known.
+   Otherwise check this if easy, as in newer C++ compilers.]b4_locations_if([[
+   Likewise for ]b4_api_PREFIX[LTYPE.]])[  */
+# if (! (]b4_locations_if([[defined ]b4_api_PREFIX[LTYPE_IS_TRIVIAL && ]b4_api_PREFIX[LTYPE_IS_TRIVIAL \
+         && ]])[defined ]b4_api_PREFIX[STYPE_IS_TRIVIAL && ]b4_api_PREFIX[STYPE_IS_TRIVIAL) \
+      && defined __cplusplus && 201103 <= __cplusplus \
+      && !(defined _GLIBCXX_RELEASE \
+           ? _GLIBCXX_RELEASE < 5 \
+           : defined __GLIBCXX__) \
+      && defined __has_include)
+#  if __has_include (<type_traits>)
+#   include <type_traits>
+]b4_locations_if(
+[[static_assert (std::is_trivially_copyable<]b4_api_PREFIX[LTYPE>::value,
+               "Bison error: api.location.type is not trivially copyable");
+]])[static_assert (std::is_trivially_copyable<]b4_api_PREFIX[STYPE>::value,
+               "Bison error: api.value.type is not trivially copyable");
+#  endif
+# endif

 /* A type that is properly aligned for any stack member.  */
 union yyalloc
@@ -592,7 +679,8 @@ union yyalloc
 /* YYNSTATES -- Number of states.  */
 #define YYNSTATES  ]b4_states_number[

-#define YYMAXUTOK   ]b4_user_token_number_max[
+/* YYMAXUTOK -- Last valid token kind.  */
+#define YYMAXUTOK   ]b4_code_max[


 /* YYTRANSLATE(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
@@ -657,15 +745,6 @@ yysymbol_name (yysymbol_kind_t yysymbol)
 }]])[
 #endif

-#ifdef YYPRINT
-/* YYTOKNUM[NUM] -- (External) token number corresponding to the
-   (internal) symbol number NUM (which must be that of a token).  */
-static const ]b4_int_type_for([b4_toknum])[ yytoknum[] =
-{
-  ]b4_toknum[
-};
-#endif
-
 #define YYPACT_NINF (]b4_pact_ninf[)

 #define yypact_value_is_default(Yyn) \
@@ -681,18 +760,19 @@ static const ]b4_int_type_for([b4_toknum])[ yytoknum[] =
 enum { YYENOMEM = -2 };

 #define yyerrok         (yyerrstatus = 0)
-#define yyclearin       (yychar = ]b4_symbol(-2, id)[)
+#define yyclearin       (yychar = ]b4_symbol(empty, id)[)

 #define YYACCEPT        goto yyacceptlab
 #define YYABORT         goto yyabortlab
 #define YYERROR         goto yyerrorlab
+#define YYNOMEM         goto yyexhaustedlab


 #define YYRECOVERING()  (!!yyerrstatus)

 #define YYBACKUP(Token, Value)                                    \
  do                                                              \
-    if (yychar == ]b4_symbol(-2, id)[)                                        \
+    if (yychar == ]b4_symbol(empty, id)[)                                        \
      {                                                           \
        yychar = (Token);                                         \
        yylval = (Value);                                         \
@@ -709,8 +789,8 @@ enum { YYENOMEM = -2 };
  while (0)

 /* Backward compatibility with an undocumented macro.
-   Use ]b4_symbol(1, id)[ or ]b4_symbol(2, id)[. */
-#define YYERRCODE ]b4_symbol(2, id)[
+   Use ]b4_symbol(error, id)[ or ]b4_symbol(undef, id)[. */
+#define YYERRCODE ]b4_symbol(undef, id)[
 ]b4_locations_if([[
 ]b4_yylloc_default_define[
 #define YYRHSLOC(Rhs, K) ((Rhs)[K])
@@ -730,7 +810,7 @@ do {                                            \
    YYFPRINTF Args;                             \
 } while (0)

-]b4_yy_location_print_define[
+]b4_yylocation_print_define[

 # define YY_SYMBOL_PRINT(Title, Kind, Value, Location)                    \
 do {                                                                      \
@@ -829,7 +909,8 @@ int yydebug;
 /* Parser data structure.  */
 struct yypstate
  {]b4_declare_parser_state_variables[
-    /* Whether this instance has not started parsing yet.  */
+    /* Whether this instance has not started parsing yet.
+     * If 2, it corresponds to a finished parsing.  */
    int yynew;
  };]b4_pure_if([], [[

@@ -940,7 +1021,7 @@ do {                                                                    \
      switch (yy_lac (yyesa, &yyes, &yyes_capacity, yyssp, yytoken))    \
        {                                                               \
        case YYENOMEM:                                                  \
-          goto yyexhaustedlab;                                          \
+          YYNOMEM;                                                      \
        case 1:                                                         \
          goto yyerrlab;                                                \
        }                                                               \
@@ -1118,7 +1199,7 @@ yypcontext_expected_tokens (const yypcontext_t *yyctx,
  for (yyx = 0; yyx < YYNTOKENS; ++yyx)
    {
      yysymbol_kind_t yysym = YY_CAST (yysymbol_kind_t, yyx);
-      if (yysym != ]b4_symbol(1, kind)[ && yysym != ]b4_symbol_prefix[YYUNDEF)
+      if (yysym != ]b4_symbol(error, kind)[ && yysym != ]b4_symbol_prefix[YYUNDEF)
        switch (yy_lac (]b4_push_if([[yyps->yyesa, &yyps->yyes, &yyps->yyes_capacity, yyps->yyssp, yysym]],
                                    [[yyctx->yyesa, yyctx->yyes, yyctx->yyes_capacity, yyctx->yyssp, yysym]])[))
          {
@@ -1147,7 +1228,7 @@ yypcontext_expected_tokens (const yypcontext_t *yyctx,
      int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
      int yyx;
      for (yyx = yyxbegin; yyx < yyxend; ++yyx)
-        if (yycheck[yyx + yyn] == yyx && yyx != ]b4_symbol(1, kind)[
+        if (yycheck[yyx + yyn] == yyx && yyx != ]b4_symbol(error, kind)[
            && !yytable_value_is_error (yytable[yyx + yyn]))
          {
            if (!yyarg)
@@ -1159,7 +1240,7 @@ yypcontext_expected_tokens (const yypcontext_t *yyctx,
          }
    }]])[
  if (yyarg && yycount == 0 && 0 < yyargn)
-    yyarg[0] = ]b4_symbol(-2, kind)[;
+    yyarg[0] = ]b4_symbol(empty, kind)[;
  return yycount;
 }

@@ -1322,7 +1403,7 @@ yy_syntax_error_arguments (const yypcontext_t *yyctx,
       one exception: it will still contain any token that will not be
       accepted due to an error action in a later state.]])[
  */
-  if (yyctx->yytoken != ]b4_symbol(-2, kind)[)
+  if (yyctx->yytoken != ]b4_symbol(empty, kind)[)
    {
      int yyn;]b4_lac_if([[
      YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
@@ -1444,49 +1525,56 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
 int
 yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)
 {
-  return yypull_parse (YY_NULLPTR]b4_user_args[);
+  yypstate *yyps = yypstate_new ();
+  if (!yyps)
+    {]b4_pure_if([b4_locations_if([[
+      static YYLTYPE yyloc_default][]b4_yyloc_default[;
+      YYLTYPE yylloc = yyloc_default;]])[
+      yyerror (]b4_yyerror_args[YY_("memory exhausted"));]], [[
+      if (!yypstate_allocated)
+        yyerror (]b4_yyerror_args[YY_("memory exhausted"));]])[
+      return 2;
+    }
+  int yystatus = yypull_parse (yyps]b4_user_args[);
+  yypstate_delete (yyps);
+  return yystatus;
 }

 int
 yypull_parse (yypstate *yyps]b4_user_formals[)
-{]b4_pure_if([b4_locations_if([[
+{
+  YY_ASSERT (yyps);]b4_pure_if([b4_locations_if([[
  static YYLTYPE yyloc_default][]b4_yyloc_default[;
  YYLTYPE yylloc = yyloc_default;]])])[
-  yypstate *yyps_local;
-  if (yyps)
-    yyps_local = yyps;
-  else
-    {
-      yyps_local = yypstate_new ();
-      if (!yyps_local)
-        {]b4_pure_if([[
-          yyerror (]b4_yyerror_args[YY_("memory exhausted"));]], [[
-          if (!yypstate_allocated)
-            yyerror (]b4_yyerror_args[YY_("memory exhausted"));]])[
-          return 2;
-        }
-    }
  int yystatus;
  do {
-]b4_pure_if([[    YYSTYPE yylval;
-    int ]])[yychar = ]b4_lex[;
-    yystatus = yypush_parse (yyps_local]b4_pure_if([[, yychar, &yylval]b4_locations_if([[, &yylloc]])])m4_ifset([b4_parse_param], [, b4_args(b4_parse_param)])[);
+]b4_pure_if([[    YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
+    YYSTYPE yylval;
+    int ]])[yychar = ]b4_yylex[;
+    yystatus = yypush_parse (yyps]b4_pure_if([[, yychar, &yylval]b4_locations_if([[, &yylloc]])])m4_ifset([b4_parse_param], [, b4_args(b4_parse_param)])[);]b4_pure_if([[
+    YY_IGNORE_MAYBE_UNINITIALIZED_END]])[
  } while (yystatus == YYPUSH_MORE);
-  if (!yyps)
-    yypstate_delete (yyps_local);
  return yystatus;
 }]])[

 ]b4_parse_state_variable_macros([b4_pstate_macro_define])[

 /* Initialize the parser data structure.  */
-void
+static void
 yypstate_clear (yypstate *yyps)
 {
-]b4_initialize_parser_state_variables[
+  yynerrs = 0;
+  yystate = 0;
+  yyerrstatus = 0;
+
+  yyssp = yyss;
+  yyvsp = yyvs;]b4_locations_if([[
+  yylsp = yyls;]])[
+
  /* Initialize the state stack, in case yypcontext_expected_tokens is
     called before the first call to yyparse. */
  *yyssp = 0;
+  yyps->yynew = 1;
 }

 /* Initialize the parser data structure.  */
@@ -1496,11 +1584,18 @@ yypstate_new (void)
  yypstate *yyps;]b4_pure_if([], [[
  if (yypstate_allocated)
    return YY_NULLPTR;]])[
-  yyps = YY_CAST (yypstate *, malloc (sizeof *yyps));
+  yyps = YY_CAST (yypstate *, YYMALLOC (sizeof *yyps));
  if (!yyps)
-    return YY_NULLPTR;
-  yyps->yynew = 1;]b4_pure_if([], [[
+    return YY_NULLPTR;]b4_pure_if([], [[
  yypstate_allocated = 1;]])[
+  yystacksize = YYINITDEPTH;
+  yyss = yyssa;
+  yyvs = yyvsa;]b4_locations_if([[
+  yyls = yylsa;]])[]b4_lac_if([[
+  yyes = yyesa;
+  yyes_capacity = ]b4_percent_define_get([[parse.lac.es-capacity-initial]])[;
+  if (YYMAXDEPTH < yyes_capacity)
+    yyes_capacity = YYMAXDEPTH;]])[
  yypstate_clear (yyps);
  return yyps;
 }
@@ -1513,12 +1608,12 @@ yypstate_delete (yypstate *yyps)
 #ifndef yyoverflow
      /* If the stack was reallocated but the parse did not complete, then the
         stack still needs to be freed.  */
-      if (!yyps->yynew && yyss != yyssa)
+      if (yyss != yyssa)
        YYSTACK_FREE (yyss);
 #endif]b4_lac_if([[
-      if (!yyps->yynew && yyes != yyesa)
+      if (yyes != yyesa)
        YYSTACK_FREE (yyes);]])[
-      free (yyps);]b4_pure_if([], [[
+      YYFREE (yyps);]b4_pure_if([], [[
      yypstate_allocated = 0;]])[
    }
 }
@@ -1537,23 +1632,46 @@ yypush_parse (yypstate *yyps]b4_pure_if([[,
 | yyparse.  |
 `----------*/

+]m4_ifdef([b4_start_symbols],
+[[// Extract data from the parser.
+typedef struct
+{
+  YYSTYPE yyvalue;
+  int yynerrs;
+} yy_parse_impl_t;
+
+// Run a full parse, using YYCHAR as switching token.
+static int
+yy_parse_impl (int yychar, yy_parse_impl_t *yyimpl]m4_ifset([b4_parse_param], [, b4_formals(b4_parse_param)])[);
+
+]m4_map([_b4_define_sub_yyparse], m4_defn([b4_start_symbols]))[
+
 int
-yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)]])[
+yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)
+{
+  return yy_parse_impl (]b4_symbol(_b4_first_switching_token, id)[, YY_NULLPTR]m4_ifset([b4_parse_param],
+                                                    [[, ]b4_args(b4_parse_param)])[);
+}
+
+static int
+yy_parse_impl (int yychar, yy_parse_impl_t *yyimpl]m4_ifset([b4_parse_param], [, b4_formals(b4_parse_param)])[)]],
+[[int
+yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)]])])[
 {]b4_pure_if([b4_declare_scanner_communication_variables
 ])b4_push_if([b4_pure_if([], [[
  int yypushed_char = yychar;
  YYSTYPE yypushed_val = yylval;]b4_locations_if([[
  YYLTYPE yypushed_loc = yylloc;]])
 ])],
-  [b4_declare_parser_state_variables
+  [b4_declare_parser_state_variables([init])
 ])b4_lac_if([[
  /* Whether LAC context is established.  A Boolean.  */
  int yy_lac_established = 0;]])[
  int yyn;
  /* The return value of yyparse.  */
  int yyresult;
-  /* Lookahead token as an internal (translated) token number.  */
-  yysymbol_kind_t yytoken = ]b4_symbol(-2, kind)[;
+  /* Lookahead symbol kind.  */
+  yysymbol_kind_t yytoken = ]b4_symbol(empty, kind)[;
  /* The variables used to return semantic value and location from the
     action routines.  */
  YYSTYPE yyval;]b4_locations_if([[
@@ -1572,18 +1690,27 @@ yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)]])[

  /* The number of symbols on the RHS of the reduced rule.
     Keep to zero when no symbol should be popped.  */
-  int yylen = 0;
-]b4_push_if([[
-  if (!yyps->yynew)
+  int yylen = 0;]b4_push_if([[
+
+  switch (yyps->yynew)
    {
+    case 0:
      yyn = yypact[yystate];
      goto yyread_pushed_token;
-    }]], [
-b4_initialize_parser_state_variables])[
+
+    case 2:
+      yypstate_clear (yyps);
+      break;
+
+    default:
+      break;
+    }]])[

  YYDPRINTF ((stderr, "Starting parse\n"));

-  yychar = ]b4_symbol(-2, id)[; /* Cause a token to be read.  */
+]m4_ifdef([b4_start_symbols], [],
+[[  yychar = ]b4_symbol(empty, id)[; /* Cause a token to be read.  */
+]])[
 ]m4_ifdef([b4_initial_action], [
 b4_dollar_pushdef([m4_define([b4_dollar_dollar_used])yylval], [], [],
                  [b4_push_if([b4_pure_if([*])yypushed_loc], [yylloc])])dnl
@@ -1618,7 +1745,7 @@ yysetstate:

  if (yyss + yystacksize - 1 <= yyssp)
 #if !defined yyoverflow && !defined YYSTACK_RELOCATE
-    goto yyexhaustedlab;
+    YYNOMEM;
 #else
    {
      /* Get the current used size of the three stacks, in elements.  */
@@ -1649,7 +1776,7 @@ yysetstate:
 # else /* defined YYSTACK_RELOCATE */
      /* Extend the stack our own way.  */
      if (YYMAXDEPTH <= yystacksize)
-        goto yyexhaustedlab;
+        YYNOMEM;
      yystacksize *= 2;
      if (YYMAXDEPTH < yystacksize)
        yystacksize = YYMAXDEPTH;
@@ -1660,7 +1787,7 @@ yysetstate:
          YY_CAST (union yyalloc *,
                   YYSTACK_ALLOC (YY_CAST (YYSIZE_T, YYSTACK_BYTES (yystacksize))));
        if (! yyptr)
-          goto yyexhaustedlab;
+          YYNOMEM;
        YYSTACK_RELOCATE (yyss_alloc, yyss);
        YYSTACK_RELOCATE (yyvs_alloc, yyvs);]b4_locations_if([
        YYSTACK_RELOCATE (yyls_alloc, yyls);])[
@@ -1684,8 +1811,9 @@ yysetstate:
    }
 #endif /* !defined yyoverflow && !defined YYSTACK_RELOCATE */

+]m4_ifdef([b4_start_symbols], [], [[
  if (yystate == YYFINAL)
-    YYACCEPT;
+    YYACCEPT;]])[

  goto yybackup;

@@ -1705,7 +1833,7 @@ yybackup:
  /* Not known => get a lookahead token if don't already have one.  */

  /* YYCHAR is either empty, or end-of-input, or a valid lookahead.  */
-  if (yychar == ]b4_symbol(-2, id)[)
+  if (yychar == ]b4_symbol(empty, id)[)
    {]b4_push_if([[
      if (!yyps->yynew)
        {]b4_use_push_for_pull_if([], [[
@@ -1727,23 +1855,23 @@ yyread_pushed_token:]])[
        yylval = *yypushed_val;]b4_locations_if([[
      if (yypushed_loc)
        yylloc = *yypushed_loc;]])])], [[
-      yychar = ]b4_lex[;]])[
+      yychar = ]b4_yylex[;]])[
    }

-  if (yychar <= ]b4_symbol(0, [id])[)
+  if (yychar <= ]b4_symbol(eof, [id])[)
    {
-      yychar = ]b4_symbol(0, [id])[;
-      yytoken = ]b4_symbol(0, [kind])[;
+      yychar = ]b4_symbol(eof, [id])[;
+      yytoken = ]b4_symbol(eof, [kind])[;
      YYDPRINTF ((stderr, "Now at end of input.\n"));
    }
-  else if (yychar == ]b4_symbol(1, [id])[)
+  else if (yychar == ]b4_symbol(error, [id])[)
    {
      /* The scanner already issued an error message, process directly
         to error recovery.  But do not keep the error token as
         lookahead, it is too special and may lead us to an endless
         loop in error recovery. */
-      yychar = ]b4_symbol(2, [id])[;
-      yytoken = ]b4_symbol(1, [kind])[;]b4_locations_if([[
+      yychar = ]b4_symbol(undef, [id])[;
+      yytoken = ]b4_symbol(error, [kind])[;]b4_locations_if([[
      yyerror_range[1] = yylloc;]])[
      goto yyerrlab1;
    }
@@ -1766,9 +1894,9 @@ yyread_pushed_token:]])[
  if (yyn <= 0)
    {
      if (yytable_value_is_error (yyn))
-        goto yyerrlab;]b4_lac_if([[
+        goto yyerrlab;
+      yyn = -yyn;]b4_lac_if([[
      YY_LAC_ESTABLISH;]])[
-      yyn = -yyn;
      goto yyreduce;
    }

@@ -1786,7 +1914,7 @@ yyread_pushed_token:]])[
  *++yylsp = yylloc;])[

  /* Discard the shifted token.  */
-  yychar = ]b4_symbol(-2, id)[;]b4_lac_if([[
+  yychar = ]b4_symbol(empty, id)[;]b4_lac_if([[
  YY_LAC_DISCARD ("shift");]])[
  goto yynewstate;

@@ -1877,7 +2005,7 @@ yyreduce:
 yyerrlab:
  /* Make sure we have latest lookahead translation.  See comments at
     user semantic actions for why this is necessary.  */
-  yytoken = yychar == ]b4_symbol(-2, id)[ ? ]b4_symbol(-2, kind)[ : YYTRANSLATE (yychar);
+  yytoken = yychar == ]b4_symbol(empty, id)[ ? ]b4_symbol(empty, kind)[ : YYTRANSLATE (yychar);
  /* If not already recovering from an error, report this error.  */
  if (!yyerrstatus)
    {
@@ -1887,11 +2015,11 @@ yyerrlab:
 [[      {
        yypcontext_t yyctx
          = {]b4_push_if([[yyps]], [[yyssp]b4_lac_if([[, yyesa, &yyes, &yyes_capacity]])])[, yytoken]b4_locations_if([[, &yylloc]])[};]b4_lac_if([[
-        if (yychar != ]b4_symbol(-2, id)[)
+        if (yychar != ]b4_symbol(empty, id)[)
          YY_LAC_ESTABLISH;]])[
        if (yyreport_syntax_error (&yyctx]m4_ifset([b4_parse_param],
-                                  [[, ]b4_args(b4_parse_param)])[) == 2)
-          goto yyexhaustedlab;
+                                   [[, ]b4_args(b4_parse_param)])[) == 2)
+          YYNOMEM;
      }]],
         [simple],
 [[      yyerror (]b4_yyerror_args[YY_("syntax error"));]],
@@ -1900,7 +2028,7 @@ yyerrlab:
          = {]b4_push_if([[yyps]], [[yyssp]b4_lac_if([[, yyesa, &yyes, &yyes_capacity]])])[, yytoken]b4_locations_if([[, &yylloc]])[};
        char const *yymsgp = YY_("syntax error");
        int yysyntax_error_status;]b4_lac_if([[
-        if (yychar != ]b4_symbol(-2, id)[)
+        if (yychar != ]b4_symbol(empty, id)[)
          YY_LAC_ESTABLISH;]])[
        yysyntax_error_status = yysyntax_error (&yymsg_alloc, &yymsg, &yyctx);
        if (yysyntax_error_status == 0)
@@ -1926,7 +2054,7 @@ yyerrlab:
          }
        yyerror (]b4_yyerror_args[yymsgp);
        if (yysyntax_error_status == YYENOMEM)
-          goto yyexhaustedlab;
+          YYNOMEM;
      }]])[
    }
 ]b4_locations_if([[
@@ -1936,17 +2064,17 @@ yyerrlab:
      /* If just tried and failed to reuse lookahead token after an
         error, discard it.  */

-      if (yychar <= ]b4_symbol(0, [id])[)
+      if (yychar <= ]b4_symbol(eof, [id])[)
        {
          /* Return failure if at end of input.  */
-          if (yychar == ]b4_symbol(0, [id])[)
+          if (yychar == ]b4_symbol(eof, [id])[)
            YYABORT;
        }
      else
        {
          yydestruct ("Error: discarding",
                      yytoken, &yylval]b4_locations_if([, &yylloc])[]b4_user_args[);
-          yychar = ]b4_symbol(-2, id)[;
+          yychar = ]b4_symbol(empty, id)[;
        }
    }

@@ -1963,6 +2091,7 @@ yyerrorlab:
     label yyerrorlab therefore never appears in user code.  */
  if (0)
    YYERROR;
+  ++yynerrs;

  /* Do not reclaim the symbols of the rule whose action triggered
     this YYERROR.  */
@@ -1985,8 +2114,8 @@ yyerrlab1:
      yyn = yypact[yystate];
      if (!yypact_value_is_default (yyn))
        {
-          yyn += ]b4_symbol(1, kind)[;
-          if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == ]b4_symbol(1, kind)[)
+          yyn += ]b4_symbol(error, kind)[;
+          if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == ]b4_symbol(error, kind)[)
            {
              yyn = yytable[yyn];
              if (0 < yyn)
@@ -2030,7 +2159,7 @@ yyerrlab1:
 `-------------------------------------*/
 yyacceptlab:
  yyresult = 0;
-  goto yyreturn;
+  goto yyreturnlab;


 /*-----------------------------------.
@@ -2038,25 +2167,23 @@ yyacceptlab:
 `-----------------------------------*/
 yyabortlab:
  yyresult = 1;
-  goto yyreturn;
+  goto yyreturnlab;


-#if ]b4_lac_if([[1]], [b4_parse_error_case([simple], [[!defined yyoverflow]], [[1]])])[
-/*-------------------------------------------------.
-| yyexhaustedlab -- memory exhaustion comes here.  |
-`-------------------------------------------------*/
+/*-----------------------------------------------------------.
+| yyexhaustedlab -- YYNOMEM (memory exhaustion) comes here.  |
+`-----------------------------------------------------------*/
 yyexhaustedlab:
  yyerror (]b4_yyerror_args[YY_("memory exhausted"));
  yyresult = 2;
-  /* Fall through.  */
-#endif
+  goto yyreturnlab;


-/*-----------------------------------------------------.
-| yyreturn -- parsing is finished, return the result.  |
-`-----------------------------------------------------*/
-yyreturn:
-  if (yychar != ]b4_symbol(-2, id)[)
+/*----------------------------------------------------------.
+| yyreturnlab -- parsing is finished, clean up and return.  |
+`----------------------------------------------------------*/
+yyreturnlab:
+  if (yychar != ]b4_symbol(empty, id)[)
    {
      /* Make sure we have latest lookahead translation.  See comments at
         user semantic actions for why this is necessary.  */
@@ -2073,24 +2200,26 @@ yyreturn:
      yydestruct ("Cleanup: popping",
                  YY_ACCESSING_SYMBOL (+*yyssp), yyvsp]b4_locations_if([, yylsp])[]b4_user_args[);
      YYPOPSTACK (1);
-    }
+    }]b4_push_if([[
+  yyps->yynew = 2;
+  goto yypushreturn;
+
+
+/*-------------------------.
+| yypushreturn -- return.  |
+`-------------------------*/
+yypushreturn:]], [[
 #ifndef yyoverflow
  if (yyss != yyssa)
    YYSTACK_FREE (yyss);
 #endif]b4_lac_if([[
  if (yyes != yyesa)
-    YYSTACK_FREE (yyes);]])b4_push_if([[
-  yypstate_clear (yyps);
-  yyps->yynew = 1;
-
-
-/*-----------------------------------------.
-| yypushreturn -- ask for the next token.  |
-`-----------------------------------------*/
-yypushreturn:]])[
+    YYSTACK_FREE (yyes);]])])[
 ]b4_parse_error_bmatch([detailed\|verbose],
 [[  if (yymsg != yymsgbuf)
-    YYSTACK_FREE (yymsg);]])[
+    YYSTACK_FREE (yymsg);]])[]m4_ifdef([b4_start_symbols], [[
+  if (yyimpl)
+    yyimpl->yynerrs = yynerrs;]])[
  return yyresult;
 }
 ]b4_push_if([b4_parse_state_variable_macros([b4_macro_undef])])[
@@ -3,7 +3,8 @@
 <!--
    bison.xsl - common templates for Bison XSLT.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+    Foundation, Inc.

    This file is part of Bison, the GNU Compiler Compiler.

@@ -18,12 +19,12 @@
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
  -->

 <xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  xmlns:bison="http://www.gnu.org/software/bison/">
+  xmlns:bison="https://www.gnu.org/software/bison/">

 <xsl:key
  name="bison:symbolByName"
@@ -3,7 +3,8 @@
 <!--
    xml2dot.xsl - transform Bison XML Report into DOT.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+    Foundation, Inc.

    This file is part of Bison, the GNU Compiler Compiler.

@@ -18,14 +19,14 @@
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.

    Written by Wojciech Polak <polak@gnu.org>.
  -->

 <xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  xmlns:bison="http://www.gnu.org/software/bison/">
+  xmlns:bison="https://www.gnu.org/software/bison/">

 <xsl:import href="bison.xsl"/>
 <xsl:output method="text" encoding="UTF-8" indent="no"/>
@@ -159,7 +160,7 @@
  <xsl:param name="prev-rule-number"
    select="preceding-sibling::item[1]/@rule-number"/>
  <xsl:apply-templates select="key('bison:ruleByNumber', @rule-number)">
-    <xsl:with-param name="point" select="@point"/>
+    <xsl:with-param name="dot" select="@dot"/>
    <xsl:with-param name="num" select="@rule-number"/>
    <xsl:with-param name="prev-lhs"
      select="key('bison:ruleByNumber', $prev-rule-number)/lhs[text()]"
@@ -169,7 +170,7 @@
 </xsl:template>

 <xsl:template match="rule">
-  <xsl:param name="point"/>
+  <xsl:param name="dot"/>
  <xsl:param name="num"/>
  <xsl:param name="prev-lhs"/>
  <xsl:text>&#10;</xsl:text>
@@ -198,14 +199,14 @@
      <xsl:text>:</xsl:text>
    </xsl:otherwise>
  </xsl:choose>
-  <xsl:if test="$point = 0">
+  <xsl:if test="$dot = 0">
    <xsl:text> .</xsl:text>
  </xsl:if>

  <!-- RHS -->
  <xsl:for-each select="rhs/symbol|rhs/empty">
    <xsl:apply-templates select="."/>
-    <xsl:if test="$point = position()">
+    <xsl:if test="$dot = position()">
      <xsl:text> .</xsl:text>
    </xsl:if>
  </xsl:for-each>
@@ -3,7 +3,8 @@
 <!--
    xml2text.xsl - transform Bison XML Report into plain text.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+    Foundation, Inc.

    This file is part of Bison, the GNU Compiler Compiler.

@@ -18,14 +19,14 @@
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.

    Written by Wojciech Polak <polak@gnu.org>.
  -->

 <xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  xmlns:bison="http://www.gnu.org/software/bison/">
+  xmlns:bison="https://www.gnu.org/software/bison/">

 <xsl:import href="bison.xsl"/>
 <xsl:output method="text" encoding="UTF-8" indent="no"/>
@@ -52,7 +53,7 @@
  <xsl:if test="nonterminal[@usefulness='useless-in-grammar']">
    <xsl:text>Nonterminals useless in grammar&#10;&#10;</xsl:text>
    <xsl:for-each select="nonterminal[@usefulness='useless-in-grammar']">
-      <xsl:text>   </xsl:text>
+      <xsl:text>    </xsl:text>
      <xsl:value-of select="@name"/>
      <xsl:text>&#10;</xsl:text>
    </xsl:for-each>
@@ -65,7 +66,7 @@
    <xsl:text>Terminals unused in grammar&#10;&#10;</xsl:text>
    <xsl:for-each select="terminal[@usefulness='unused-in-grammar']">
      <xsl:sort select="@symbol-number" data-type="number"/>
-      <xsl:text>   </xsl:text>
+      <xsl:text>    </xsl:text>
      <xsl:value-of select="@name"/>
      <xsl:text>&#10;</xsl:text>
    </xsl:for-each>
@@ -136,6 +137,7 @@
 </xsl:template>

 <xsl:template match="terminal">
+  <xsl:text>    </xsl:text>
  <xsl:value-of select="@name"/>
  <xsl:call-template name="line-wrap">
    <xsl:with-param name="first-line-length">
@@ -148,6 +150,9 @@
    </xsl:with-param>
    <xsl:with-param name="line-length" select="66" />
    <xsl:with-param name="text">
+      <xsl:if test="string-length(@type) != 0">
+        <xsl:value-of select="concat(' &lt;', @type, '&gt;')"/>
+      </xsl:if>
      <xsl:value-of select="concat(' (', @token-number, ')')"/>
      <xsl:for-each select="key('bison:ruleByRhs', @name)">
        <xsl:value-of select="concat(' ', @number)"/>
@@ -157,14 +162,18 @@
 </xsl:template>

 <xsl:template match="nonterminal">
+  <xsl:text>    </xsl:text>
  <xsl:value-of select="@name"/>
+  <xsl:if test="string-length(@type) != 0">
+    <xsl:value-of select="concat(' &lt;', @type, '&gt;')"/>
+  </xsl:if>
  <xsl:value-of select="concat(' (', @symbol-number, ')')"/>
  <xsl:text>&#10;</xsl:text>
  <xsl:variable name="output">
    <xsl:call-template name="line-wrap">
      <xsl:with-param name="line-length" select="66" />
      <xsl:with-param name="text">
-        <xsl:text>    </xsl:text>
+        <xsl:text>        </xsl:text>
        <xsl:if test="key('bison:ruleByLhs', @name)">
          <xsl:text>on@left:</xsl:text>
          <xsl:for-each select="key('bison:ruleByLhs', @name)">
@@ -173,7 +182,7 @@
        </xsl:if>
        <xsl:if test="key('bison:ruleByRhs', @name)">
          <xsl:if test="key('bison:ruleByLhs', @name)">
-            <xsl:text>, </xsl:text>
+            <xsl:text>&#10;        </xsl:text>
          </xsl:if>
          <xsl:text>on@right:</xsl:text>
          <xsl:for-each select="key('bison:ruleByRhs', @name)">
@@ -300,7 +309,7 @@
      name="prev-lhs"
      select="key('bison:ruleByNumber', $prev-rule-number)/lhs[text()]"
   />
-    <xsl:with-param name="point" select="@point"/>
+    <xsl:with-param name="dot" select="@dot"/>
    <xsl:with-param name="lookaheads">
      <xsl:apply-templates select="lookaheads"/>
    </xsl:with-param>
@@ -311,7 +320,7 @@
  <xsl:param name="itemset"/>
  <xsl:param name="pad"/>
  <xsl:param name="prev-lhs"/>
-  <xsl:param name="point"/>
+  <xsl:param name="dot"/>
  <xsl:param name="lookaheads"/>

  <xsl:if test="$itemset != 'true' and not($prev-lhs = lhs[text()])">
@@ -347,12 +356,12 @@

  <!-- RHS -->
  <xsl:for-each select="rhs/*">
-    <xsl:if test="position() = $point + 1">
-      <xsl:text> .</xsl:text>
+    <xsl:if test="position() = $dot + 1">
+      <xsl:text> •</xsl:text>
    </xsl:if>
    <xsl:apply-templates select="."/>
-    <xsl:if test="position() = last() and position() = $point">
-      <xsl:text> .</xsl:text>
+    <xsl:if test="position() = last() and position() = $dot">
+      <xsl:text> •</xsl:text>
    </xsl:if>
  </xsl:for-each>
  <xsl:if test="$lookaheads">
@@ -3,7 +3,8 @@
 <!--
    xml2html.xsl - transform Bison XML Report into XHTML.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2022, 2025-2026 Free Software
+    Foundation, Inc.

    This file is part of Bison, the GNU Compiler Compiler.

@@ -18,7 +19,7 @@
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.

    Written by Wojciech Polak <polak@gnu.org>.
  -->
@@ -26,7 +27,7 @@
 <xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns="http://www.w3.org/1999/xhtml"
-  xmlns:bison="http://www.gnu.org/software/bison/">
+  xmlns:bison="https://www.gnu.org/software/bison/">

 <xsl:import href="bison.xsl"/>

@@ -75,7 +76,7 @@
      ol.lower-alpha {
        list-style-type: lower-alpha;
      }
-      .point {
+      .dot {
        color: #cc0000;
      }
      #footer {
@@ -88,7 +89,7 @@
      <xsl:apply-templates select="bison-xml-report"/>
      <xsl:text>&#10;&#10;</xsl:text>
      <div id="footer"><hr />This document was generated using
-      <a href="http://www.gnu.org/software/bison/" title="GNU Bison">
+      <a href="https://www.gnu.org/software/bison/" title="GNU Bison">
      GNU Bison <xsl:value-of select="/bison-xml-report/@version"/></a>
      XML Automaton Report.<br />
      <!-- default copying notice -->
@@ -227,6 +228,7 @@
  <xsl:text>&#10;</xsl:text>
  <p class="pre">
    <xsl:call-template name="style-rule-set">
+      <xsl:with-param name="anchor" select="'true'" />
      <xsl:with-param
        name="rule-set" select="rules/rule[@usefulness!='useless-in-grammar']"
      />
@@ -238,9 +240,11 @@
 </xsl:template>

 <xsl:template name="style-rule-set">
+  <xsl:param name="anchor"/>
  <xsl:param name="rule-set"/>
  <xsl:for-each select="$rule-set">
    <xsl:apply-templates select=".">
+      <xsl:with-param name="anchor" select="$anchor"/>
      <xsl:with-param name="pad" select="'3'"/>
      <xsl:with-param name="prev-lhs">
        <xsl:if test="position()>1">
@@ -306,9 +310,10 @@
    <xsl:text> Terminals, with rules where they appear</xsl:text>
  </h3>
  <xsl:text>&#10;&#10;</xsl:text>
-  <p class="pre">
+  <ul>
+    <xsl:text>&#10;</xsl:text>
    <xsl:apply-templates select="terminal"/>
-  </p>
+  </ul>
  <xsl:text>&#10;&#10;</xsl:text>
 </xsl:template>

@@ -318,41 +323,64 @@
    <xsl:text> Nonterminals, with rules where they appear</xsl:text>
  </h3>
  <xsl:text>&#10;&#10;</xsl:text>
-  <p class="pre">
+  <ul>
+    <xsl:text>&#10;</xsl:text>
    <xsl:apply-templates
      select="nonterminal[@usefulness!='useless-in-grammar']"
    />
-  </p>
+  </ul>
 </xsl:template>

 <xsl:template match="terminal">
-  <b><xsl:value-of select="@name"/></b>
-  <xsl:value-of select="concat(' (', @token-number, ')')"/>
-  <xsl:for-each select="key('bison:ruleByRhs', @name)">
-    <xsl:apply-templates select="." mode="number-link"/>
-  </xsl:for-each>
+  <xsl:text>  </xsl:text>
+  <li>
+    <b><xsl:value-of select="@name"/></b>
+    <xsl:if test="string-length(@type) != 0">
+      <xsl:value-of select="concat(' &lt;', @type, '&gt;')"/>
+    </xsl:if>
+    <xsl:value-of select="concat(' (', @token-number, ')')"/>
+    <xsl:for-each select="key('bison:ruleByRhs', @name)">
+      <xsl:apply-templates select="." mode="number-link"/>
+    </xsl:for-each>
+  </li>
  <xsl:text>&#10;</xsl:text>
 </xsl:template>

 <xsl:template match="nonterminal">
-  <b><xsl:value-of select="@name"/></b>
-  <xsl:value-of select="concat(' (', @symbol-number, ')')"/>
-  <xsl:text>&#10;    </xsl:text>
-  <xsl:if test="key('bison:ruleByLhs', @name)">
-    <xsl:text>on left:</xsl:text>
-    <xsl:for-each select="key('bison:ruleByLhs', @name)">
-      <xsl:apply-templates select="." mode="number-link"/>
-    </xsl:for-each>
-  </xsl:if>
-  <xsl:if test="key('bison:ruleByRhs', @name)">
-    <xsl:if test="key('bison:ruleByLhs', @name)">
-      <xsl:text>&#10;    </xsl:text>
+  <xsl:text>  </xsl:text>
+  <li>
+    <b><xsl:value-of select="@name"/></b>
+    <xsl:if test="string-length(@type) != 0">
+      <xsl:value-of select="concat(' &lt;', @type, '&gt;')"/>
    </xsl:if>
-    <xsl:text>on right:</xsl:text>
-    <xsl:for-each select="key('bison:ruleByRhs', @name)">
-      <xsl:apply-templates select="." mode="number-link"/>
-    </xsl:for-each>
-  </xsl:if>
+    <xsl:value-of select="concat(' (', @symbol-number, ')')"/>
+    <xsl:text>&#10;    </xsl:text>
+    <ul>
+      <xsl:text>&#10;</xsl:text>
+      <xsl:if test="key('bison:ruleByLhs', @name)">
+        <xsl:text>      </xsl:text>
+        <li>
+          <xsl:text>on left:</xsl:text>
+          <xsl:for-each select="key('bison:ruleByLhs', @name)">
+            <xsl:apply-templates select="." mode="number-link"/>
+          </xsl:for-each>
+        </li>
+        <xsl:text>&#10;</xsl:text>
+      </xsl:if>
+      <xsl:if test="key('bison:ruleByRhs', @name)">
+        <xsl:text>      </xsl:text>
+        <li>
+          <xsl:text>on right:</xsl:text>
+          <xsl:for-each select="key('bison:ruleByRhs', @name)">
+            <xsl:apply-templates select="." mode="number-link"/>
+          </xsl:for-each>
+        </li>
+        <xsl:text>&#10;</xsl:text>
+      </xsl:if>
+    <xsl:text>    </xsl:text>
+    </ul>
+    <xsl:text>&#10;  </xsl:text>
+  </li>
  <xsl:text>&#10;</xsl:text>
 </xsl:template>

@@ -385,7 +413,7 @@
        <xsl:value-of select="concat('state_', @number)"/>
      </xsl:attribute>
    </a>
-    <xsl:text>state </xsl:text>
+    <xsl:text>State </xsl:text>
    <xsl:value-of select="@number"/>
  </h3>
  <xsl:text>&#10;&#10;</xsl:text>
@@ -457,35 +485,44 @@
    <xsl:with-param name="prev-lhs"
      select="key('bison:ruleByNumber', $prev-rule-number)/lhs[text()]"
   />
-    <xsl:with-param name="point" select="@point"/>
+    <xsl:with-param name="dot" select="@dot"/>
    <xsl:with-param name="lookaheads">
      <xsl:apply-templates select="lookaheads"/>
    </xsl:with-param>
  </xsl:apply-templates>
 </xsl:template>

+<!--
+anchor = 'true': define as an <a> anchor.
+itemset = 'true': show the items.
+ -->
 <xsl:template match="rule">
+  <xsl:param name="anchor"/>
  <xsl:param name="itemset"/>
  <xsl:param name="pad"/>
  <xsl:param name="prev-lhs"/>
-  <xsl:param name="point"/>
+  <xsl:param name="dot"/>
  <xsl:param name="lookaheads"/>

  <xsl:if test="$itemset != 'true' and not($prev-lhs = lhs[text()])">
    <xsl:text>&#10;</xsl:text>
  </xsl:if>

-  <xsl:if test="$itemset != 'true'">
-    <a>
-      <xsl:attribute name="name">
-        <xsl:value-of select="concat('rule_', @number)"/>
-      </xsl:attribute>
-    </a>
-  </xsl:if>
  <xsl:text>  </xsl:text>

  <xsl:choose>
-    <xsl:when test="$itemset = 'true'">
+    <xsl:when test="$anchor = 'true'">
+      <a>
+        <xsl:attribute name="name">
+          <xsl:value-of select="concat('rule_', @number)"/>
+        </xsl:attribute>
+        <xsl:call-template name="lpad">
+          <xsl:with-param name="str" select="string(@number)"/>
+          <xsl:with-param name="pad" select="number($pad)"/>
+        </xsl:call-template>
+      </a>
+    </xsl:when>
+    <xsl:otherwise>
      <a>
        <xsl:attribute name="href">
          <xsl:value-of select="concat('#rule_', @number)"/>
@@ -495,25 +532,13 @@
          <xsl:with-param name="pad" select="number($pad)"/>
        </xsl:call-template>
      </a>
-    </xsl:when>
-    <xsl:otherwise>
-      <xsl:call-template name="lpad">
-        <xsl:with-param name="str" select="string(@number)"/>
-        <xsl:with-param name="pad" select="number($pad)"/>
-      </xsl:call-template>
    </xsl:otherwise>
  </xsl:choose>
  <xsl:text> </xsl:text>

  <!-- LHS -->
  <xsl:choose>
-    <xsl:when test="$itemset != 'true' and $prev-lhs = lhs[text()]">
-      <xsl:call-template name="lpad">
-        <xsl:with-param name="str" select="'|'"/>
-        <xsl:with-param name="pad" select="number(string-length(lhs[text()])) + 2"/>
-      </xsl:call-template>
-    </xsl:when>
-    <xsl:when test="$itemset = 'true' and $prev-lhs = lhs[text()]">
+    <xsl:when test="$prev-lhs = lhs[text()]">
      <xsl:call-template name="lpad">
        <xsl:with-param name="str" select="'|'"/>
        <xsl:with-param name="pad" select="number(string-length(lhs[text()])) + 2"/>
@@ -529,14 +554,14 @@

  <!-- RHS -->
  <xsl:for-each select="rhs/*">
-    <xsl:if test="position() = $point + 1">
+    <xsl:if test="position() = $dot + 1">
      <xsl:text> </xsl:text>
-      <span class="point">.</span>
+      <span class="dot">&#x2022;</span>
    </xsl:if>
    <xsl:apply-templates select="."/>
-    <xsl:if test="position() = last() and position() = $point">
+    <xsl:if test="position() = last() and position() = $dot">
      <xsl:text> </xsl:text>
-      <span class="point">.</span>
+      <span class="dot">&#x2022;</span>
    </xsl:if>
  </xsl:for-each>
  <xsl:if test="$lookaheads">
@@ -8,29 +8,19 @@
 #/bison.cp
 #/bison.cps
 #/bison.toc
-
-/*~
-/.dirstamp
+*.dvi
+*.ps
 /bison.1
-/bison.dvi
 /bison.help
 /bison.html
 /bison.info
-/bison.info.bak
-/bison.log
-/bison.pdf
-/bison.ps
 /cross-options.texi
-/fdl.texi
+/figs/*.eps
+/figs/*.svg
 /gendocs_template
 /gendocs_template_min
 /gpl-3.0.texi
-/refcard.dvi
-/refcard.log
-/refcard.ps
+/relocatable.texi
 /stamp-vti
 /version.texi
 /yacc.1
-/relocatable.texi
-/figs/*.eps
-/figs/*.svg
@@ -1,4 +1,4 @@
-# Doxyfile 1.8.17
+# Doxyfile 1.9.1

 # This file describes the settings to be used by the documentation system
 # doxygen (www.doxygen.org) for a project.
@@ -32,13 +32,13 @@ DOXYFILE_ENCODING      = UTF-8
 # title of most generated pages and in a few other places.
 # The default value is: My Project.

-PROJECT_NAME           = "@PACKAGE_NAME@"
+PROJECT_NAME           = @PACKAGE_NAME@

 # The PROJECT_NUMBER tag can be used to enter a project or revision number. This
 # could be handy for archiving the generated documentation or if some version
 # control system is used.

-PROJECT_NUMBER         = "@PACKAGE_VERSION@"
+PROJECT_NUMBER         = @PACKAGE_VERSION@

 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
@@ -217,6 +217,14 @@ QT_AUTOBRIEF           = NO

 MULTILINE_CPP_IS_BRIEF = NO

+# By default Python docstrings are displayed as preformatted text and doxygen's
+# special commands cannot be used. By setting PYTHON_DOCSTRING to NO the
+# doxygen's special commands can be used and the contents of the docstring
+# documentation blocks is shown as doxygen documentation.
+# The default value is: YES.
+
+PYTHON_DOCSTRING       = YES
+
 # If the INHERIT_DOCS tag is set to YES then an undocumented member inherits the
 # documentation from any documented member that it re-implements.
 # The default value is: YES.
@@ -253,12 +261,6 @@ TAB_SIZE               = 8

 ALIASES                =

-# This tag can be used to specify a number of word-keyword mappings (TCL only).
-# A mapping has the form "name=value". For example adding "class=itcl::class"
-# will allow you to use the command class in the itcl::class meaning.
-
-TCL_SUBST              =
-
 # Set the OPTIMIZE_OUTPUT_FOR_C tag to YES if your project consists of C sources
 # only. Doxygen will then generate output that is more tailored for C. For
 # instance, some of the names that are used will be different. The list of all
@@ -300,18 +302,21 @@ OPTIMIZE_OUTPUT_SLICE  = NO
 # extension. Doxygen has a built-in mapping, but you can override or extend it
 # using this tag. The format is ext=language, where ext is a file extension, and
 # language is one of the parsers supported by doxygen: IDL, Java, JavaScript,
-# Csharp (C#), C, C++, D, PHP, md (Markdown), Objective-C, Python, Slice,
+# Csharp (C#), C, C++, D, PHP, md (Markdown), Objective-C, Python, Slice, VHDL,
 # Fortran (fixed format Fortran: FortranFixed, free formatted Fortran:
 # FortranFree, unknown formatted Fortran: Fortran. In the later case the parser
 # tries to guess whether the code is fixed or free formatted code, this is the
-# default for Fortran type files), VHDL, tcl. For instance to make doxygen treat
-# .inc files as Fortran files (default is PHP), and .f files as C (default is
-# Fortran), use: inc=Fortran f=C.
+# default for Fortran type files). For instance to make doxygen treat .inc files
+# as Fortran files (default is PHP), and .f files as C (default is Fortran),
+# use: inc=Fortran f=C.
 #
 # Note: For files without extension you can use no_extension as a placeholder.
 #
 # Note that for custom extensions you also need to set FILE_PATTERNS otherwise
-# the files are not read by doxygen.
+# the files are not read by doxygen. When specifying no_extension you should add
+# * to the FILE_PATTERNS.
+#
+# Note see also the list of default file extension mappings.

 EXTENSION_MAPPING      =

@@ -445,6 +450,19 @@ TYPEDEF_HIDES_STRUCT   = NO

 LOOKUP_CACHE_SIZE      = 0

+# The NUM_PROC_THREADS specifies the number threads doxygen is allowed to use
+# during processing. When set to 0 doxygen will based this on the number of
+# cores available in the system. You can set it explicitly to a value larger
+# than 0 to get more control over the balance between CPU load and processing
+# speed. At this moment only the input processing can be done using multiple
+# threads. Since this is still an experimental feature the default is set to 1,
+# which efficively disables parallel processing. Please report any issues you
+# encounter. Generating dot graphs in parallel is controlled by the
+# DOT_NUM_THREADS setting.
+# Minimum value: 0, maximum value: 32, default value: 1.
+
+NUM_PROC_THREADS       = 1
+
 #---------------------------------------------------------------------------
 # Build related configuration options
 #---------------------------------------------------------------------------
@@ -508,6 +526,13 @@ EXTRACT_LOCAL_METHODS  = NO

 EXTRACT_ANON_NSPACES   = NO

+# If this flag is set to YES, the name of an unnamed parameter in a declaration
+# will be determined by the corresponding definition. By default unnamed
+# parameters remain unnamed in the output.
+# The default value is: YES.
+
+RESOLVE_UNNAMED_PARAMS = YES
+
 # If the HIDE_UNDOC_MEMBERS tag is set to YES, doxygen will hide all
 # undocumented members inside documented classes or files. If set to NO these
 # members will be included in the various overviews, but no documentation
@@ -545,11 +570,18 @@ HIDE_IN_BODY_DOCS      = NO

 INTERNAL_DOCS          = NO

-# If the CASE_SENSE_NAMES tag is set to NO then doxygen will only generate file
-# names in lower-case letters. If set to YES, upper-case letters are also
-# allowed. This is useful if you have classes or files whose names only differ
-# in case and if your file system supports case sensitive file names. Windows
-# (including Cygwin) ands Mac users are advised to set this option to NO.
+# With the correct setting of option CASE_SENSE_NAMES doxygen will better be
+# able to match the capabilities of the underlying filesystem. In case the
+# filesystem is case sensitive (i.e. it supports files in the same directory
+# whose names only differ in casing), the option must be set to YES to properly
+# deal with such files in case they appear in the input. For filesystems that
+# are not case sensitive the option should be be set to NO to properly deal with
+# output files written for symbols that only differ in casing, such as for two
+# classes, one named CLASS and the other named Class, and to also support
+# references to files without having to specify the exact matching casing. On
+# Windows (including Cygwin) and MacOS, users should typically set this option
+# to NO, whereas on Linux or other Unix flavors it should typically be set to
+# YES.
 # The default value is: system dependent.

 CASE_SENSE_NAMES       = YES
@@ -788,7 +820,10 @@ WARN_IF_DOC_ERROR      = YES
 WARN_NO_PARAMDOC       = NO

 # If the WARN_AS_ERROR tag is set to YES then doxygen will immediately stop when
-# a warning is encountered.
+# a warning is encountered. If the WARN_AS_ERROR tag is set to FAIL_ON_WARNINGS
+# then doxygen will continue running as if WARN_AS_ERROR tag is set to NO, but
+# at the end of the doxygen process doxygen will return with a non-zero status.
+# Possible values are: NO, YES and FAIL_ON_WARNINGS.
 # The default value is: NO.

 WARN_AS_ERROR          = NO
@@ -825,8 +860,8 @@ INPUT                  = @top_srcdir@/src \
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
 # libiconv (or the iconv built into libc) for the transcoding. See the libiconv
-# documentation (see: https://www.gnu.org/software/libiconv/) for the list of
-# possible encodings.
+# documentation (see:
+# https://www.gnu.org/software/libiconv/) for the list of possible encodings.
 # The default value is: UTF-8.

 INPUT_ENCODING         = UTF-8
@@ -839,13 +874,15 @@ INPUT_ENCODING         = UTF-8
 # need to set EXTENSION_MAPPING for the extension otherwise the files are not
 # read by doxygen.
 #
+# Note the list of default checked file patterns might differ from the list of
+# default file extension mappings.
+#
 # If left blank the following patterns are tested:*.c, *.cc, *.cxx, *.cpp,
 # *.c++, *.java, *.ii, *.ixx, *.ipp, *.i++, *.inl, *.idl, *.ddl, *.odl, *.h,
 # *.hh, *.hxx, *.hpp, *.h++, *.cs, *.d, *.php, *.php4, *.php5, *.phtml, *.inc,
 # *.m, *.markdown, *.md, *.mm, *.dox (to be provided as doxygen C comment),
-# *.doc (to be provided as doxygen C comment), *.txt (to be provided as doxygen
-# C comment), *.py, *.pyw, *.f90, *.f95, *.f03, *.f08, *.f, *.for, *.tcl, *.vhd,
-# *.vhdl, *.ucf, *.qsf and *.ice.
+# *.py, *.pyw, *.f90, *.f95, *.f03, *.f08, *.f18, *.f, *.for, *.vhd, *.vhdl,
+# *.ucf, *.qsf and *.ice.

 FILE_PATTERNS          = *.c \
                         *.h \
@@ -1075,13 +1112,6 @@ VERBATIM_HEADERS       = YES

 ALPHABETICAL_INDEX     = YES

-# The COLS_IN_ALPHA_INDEX tag can be used to specify the number of columns in
-# which the alphabetical index list will be split.
-# Minimum value: 1, maximum value: 20, default value: 5.
-# This tag requires that the tag ALPHABETICAL_INDEX is set to YES.
-
-COLS_IN_ALPHA_INDEX    = 5
-
 # In case all classes in a project start with a common prefix, all classes will
 # be put under the same header in the alphabetical index. The IGNORE_PREFIX tag
 # can be used to specify a prefix (or a list of prefixes) that should be ignored
@@ -1252,10 +1282,11 @@ HTML_INDEX_NUM_ENTRIES = 100

 # If the GENERATE_DOCSET tag is set to YES, additional index files will be
 # generated that can be used as input for Apple's Xcode 3 integrated development
-# environment (see: https://developer.apple.com/xcode/), introduced with OSX
-# 10.5 (Leopard). To create a documentation set, doxygen will generate a
-# Makefile in the HTML output directory. Running make will produce the docset in
-# that directory and running make install will install the docset in
+# environment (see:
+# https://developer.apple.com/xcode/), introduced with OSX 10.5 (Leopard). To
+# create a documentation set, doxygen will generate a Makefile in the HTML
+# output directory. Running make will produce the docset in that directory and
+# running make install will install the docset in
 # ~/Library/Developer/Shared/Documentation/DocSets so that Xcode will find it at
 # startup. See https://developer.apple.com/library/archive/featuredarticles/Doxy
 # genXcode/_index.html for more information.
@@ -1297,8 +1328,8 @@ DOCSET_PUBLISHER_NAME  = Publisher
 # If the GENERATE_HTMLHELP tag is set to YES then doxygen generates three
 # additional HTML index files: index.hhp, index.hhc, and index.hhk. The
 # index.hhp is a project file that can be read by Microsoft's HTML Help Workshop
-# (see: https://www.microsoft.com/en-us/download/details.aspx?id=21138) on
-# Windows.
+# (see:
+# https://www.microsoft.com/en-us/download/details.aspx?id=21138) on Windows.
 #
 # The HTML Help Workshop contains a compiler that can convert all HTML output
 # generated by doxygen into a single compiled HTML file (.chm). Compiled HTML
@@ -1328,7 +1359,7 @@ CHM_FILE               =
 HHC_LOCATION           =

 # The GENERATE_CHI flag controls if a separate .chi index file is generated
-# (YES) or that it should be included in the master .chm file (NO).
+# (YES) or that it should be included in the main .chm file (NO).
 # The default value is: NO.
 # This tag requires that the tag GENERATE_HTMLHELP is set to YES.

@@ -1373,7 +1404,8 @@ QCH_FILE               =

 # The QHP_NAMESPACE tag specifies the namespace to use when generating Qt Help
 # Project output. For more information please see Qt Help Project / Namespace
-# (see: https://doc.qt.io/archives/qt-4.8/qthelpproject.html#namespace).
+# (see:
+# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#namespace).
 # The default value is: org.doxygen.Project.
 # This tag requires that the tag GENERATE_QHP is set to YES.

@@ -1381,8 +1413,8 @@ QHP_NAMESPACE          = org.doxygen.Project

 # The QHP_VIRTUAL_FOLDER tag specifies the namespace to use when generating Qt
 # Help Project output. For more information please see Qt Help Project / Virtual
-# Folders (see: https://doc.qt.io/archives/qt-4.8/qthelpproject.html#virtual-
-# folders).
+# Folders (see:
+# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#virtual-folders).
 # The default value is: doc.
 # This tag requires that the tag GENERATE_QHP is set to YES.

@@ -1390,16 +1422,16 @@ QHP_VIRTUAL_FOLDER     = doc

 # If the QHP_CUST_FILTER_NAME tag is set, it specifies the name of a custom
 # filter to add. For more information please see Qt Help Project / Custom
-# Filters (see: https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-
-# filters).
+# Filters (see:
+# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-filters).
 # This tag requires that the tag GENERATE_QHP is set to YES.

 QHP_CUST_FILTER_NAME   =

 # The QHP_CUST_FILTER_ATTRS tag specifies the list of the attributes of the
 # custom filter to add. For more information please see Qt Help Project / Custom
-# Filters (see: https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-
-# filters).
+# Filters (see:
+# https://doc.qt.io/archives/qt-4.8/qthelpproject.html#custom-filters).
 # This tag requires that the tag GENERATE_QHP is set to YES.

 QHP_CUST_FILTER_ATTRS  =
@@ -1411,9 +1443,9 @@ QHP_CUST_FILTER_ATTRS  =

 QHP_SECT_FILTER_ATTRS  =

-# The QHG_LOCATION tag can be used to specify the location of Qt's
-# qhelpgenerator. If non-empty doxygen will try to run qhelpgenerator on the
-# generated .qhp file.
+# The QHG_LOCATION tag can be used to specify the location (absolute path
+# including file name) of Qt's qhelpgenerator. If non-empty doxygen will try to
+# run qhelpgenerator on the generated .qhp file.
 # This tag requires that the tag GENERATE_QHP is set to YES.

 QHG_LOCATION           =
@@ -1490,6 +1522,17 @@ TREEVIEW_WIDTH         = 250

 EXT_LINKS_IN_WINDOW    = NO

+# If the HTML_FORMULA_FORMAT option is set to svg, doxygen will use the pdf2svg
+# tool (see https://github.com/dawbarton/pdf2svg) or inkscape (see
+# https://inkscape.org) to generate formulas as SVG images instead of PNGs for
+# the HTML output. These images will generally look nicer at scaled resolutions.
+# Possible values are: png (the default) and svg (looks nicer but requires the
+# pdf2svg or inkscape tool).
+# The default value is: png.
+# This tag requires that the tag GENERATE_HTML is set to YES.
+
+HTML_FORMULA_FORMAT    = png
+
 # Use this tag to change the font size of LaTeX formulas included as images in
 # the HTML documentation. When you change the font size after a successful
 # doxygen run you need to manually remove any form_*.png images from the HTML
@@ -1529,7 +1572,7 @@ USE_MATHJAX            = NO

 # When MathJax is enabled you can set the default output format to be used for
 # the MathJax output. See the MathJax site (see:
-# http://docs.mathjax.org/en/latest/output.html) for more details.
+# http://docs.mathjax.org/en/v2.7-latest/output.html) for more details.
 # Possible values are: HTML-CSS (which is slower, but has the best
 # compatibility), NativeMML (i.e. MathML) and SVG.
 # The default value is: HTML-CSS.
@@ -1545,7 +1588,7 @@ MATHJAX_FORMAT         = HTML-CSS
 # Content Delivery Network so you can quickly see the result without installing
 # MathJax. However, it is strongly recommended to install a local copy of
 # MathJax from https://www.mathjax.org before deployment.
-# The default value is: https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/.
+# The default value is: https://cdn.jsdelivr.net/npm/mathjax@2.
 # This tag requires that the tag USE_MATHJAX is set to YES.

 MATHJAX_RELPATH        = http://cdn.mathjax.org/mathjax/latest
@@ -1559,7 +1602,8 @@ MATHJAX_EXTENSIONS     =

 # The MATHJAX_CODEFILE tag can be used to specify a file with javascript pieces
 # of code that will be used on startup of the MathJax code. See the MathJax site
-# (see: http://docs.mathjax.org/en/latest/output.html) for more details. For an
+# (see:
+# http://docs.mathjax.org/en/v2.7-latest/output.html) for more details. For an
 # example see the documentation.
 # This tag requires that the tag USE_MATHJAX is set to YES.

@@ -1606,7 +1650,8 @@ SERVER_BASED_SEARCH    = NO
 #
 # Doxygen ships with an example indexer (doxyindexer) and search engine
 # (doxysearch.cgi) which are based on the open source search engine library
-# Xapian (see: https://xapian.org/).
+# Xapian (see:
+# https://xapian.org/).
 #
 # See the section "External Indexing and Searching" for details.
 # The default value is: NO.
@@ -1619,8 +1664,9 @@ EXTERNAL_SEARCH        = NO
 #
 # Doxygen ships with an example indexer (doxyindexer) and search engine
 # (doxysearch.cgi) which are based on the open source search engine library
-# Xapian (see: https://xapian.org/). See the section "External Indexing and
-# Searching" for details.
+# Xapian (see:
+# https://xapian.org/). See the section "External Indexing and Searching" for
+# details.
 # This tag requires that the tag SEARCHENGINE is set to YES.

 SEARCHENGINE_URL       =
@@ -1715,7 +1761,7 @@ COMPACT_LATEX          = NO
 # The default value is: a4.
 # This tag requires that the tag GENERATE_LATEX is set to YES.

-PAPER_TYPE             = a4wide
+PAPER_TYPE             = a4

 # The EXTRA_PACKAGES tag can be used to specify one or more LaTeX package names
 # that should be included in the LaTeX output. The package can be specified just
@@ -1784,9 +1830,11 @@ LATEX_EXTRA_FILES      =

 PDF_HYPERLINKS         = YES

-# If the USE_PDFLATEX tag is set to YES, doxygen will use pdflatex to generate
-# the PDF file directly from the LaTeX files. Set this option to YES, to get a
-# higher quality PDF documentation.
+# If the USE_PDFLATEX tag is set to YES, doxygen will use the engine as
+# specified with LATEX_CMD_NAME to generate the PDF file directly from the LaTeX
+# files. Set this option to YES, to get a higher quality PDF documentation.
+#
+# See also section LATEX_CMD_NAME for selecting the engine.
 # The default value is: YES.
 # This tag requires that the tag GENERATE_LATEX is set to YES.

@@ -2299,10 +2347,32 @@ UML_LOOK               = NO
 # but if the number exceeds 15, the total amount of fields shown is limited to
 # 10.
 # Minimum value: 0, maximum value: 100, default value: 10.
-# This tag requires that the tag HAVE_DOT is set to YES.
+# This tag requires that the tag UML_LOOK is set to YES.

 UML_LIMIT_NUM_FIELDS   = 10

+# If the DOT_UML_DETAILS tag is set to NO, doxygen will show attributes and
+# methods without types and arguments in the UML graphs. If the DOT_UML_DETAILS
+# tag is set to YES, doxygen will add type and arguments for attributes and
+# methods in the UML graphs. If the DOT_UML_DETAILS tag is set to NONE, doxygen
+# will not generate fields with class member information in the UML graphs. The
+# class diagrams will look similar to the default class diagrams but using UML
+# notation for the relationships.
+# Possible values are: NO, YES and NONE.
+# The default value is: NO.
+# This tag requires that the tag UML_LOOK is set to YES.
+
+DOT_UML_DETAILS        = NO
+
+# The DOT_WRAP_THRESHOLD tag can be used to set the maximum number of characters
+# to display on a single line. If the actual line length exceeds this threshold
+# significantly it will wrapped across multiple lines. Some heuristics are apply
+# to avoid ugly line breaks.
+# Minimum value: 0, maximum value: 1000, default value: 17.
+# This tag requires that the tag HAVE_DOT is set to YES.
+
+DOT_WRAP_THRESHOLD     = 17
+
 # If the TEMPLATE_RELATIONS tag is set to YES then the inheritance and
 # collaboration graphs will show the relations between templates and their
 # instances.
@@ -2492,9 +2562,11 @@ DOT_MULTI_TARGETS      = NO

 GENERATE_LEGEND        = YES

-# If the DOT_CLEANUP tag is set to YES, doxygen will remove the intermediate dot
+# If the DOT_CLEANUP tag is set to YES, doxygen will remove the intermediate
 # files that are used to generate the various graphs.
+#
+# Note: This setting is not only used for dot files but also for msc and
+# plantuml temporary files.
 # The default value is: YES.
-# This tag requires that the tag HAVE_DOT is set to YES.

 DOT_CLEANUP            = YES
@@ -2,48 +2,49 @@
 bison \- GNU Project parser generator (yacc replacement)

 [description]
-.I Bison
-is a parser generator in the style of
-.IR yacc (1).
-It should be upwardly compatible with input files designed
-for
-.IR yacc .
+The
+.B bison
+parser generator inputs grammars in the style of
+.BR yacc (1)
+and outputs parsers for those grammers.
 .PP
 Input files should follow the
-.I yacc
+.B yacc
 convention of ending in
-.BR .y .
+.IR .y .
 Unlike
-.IR yacc ,
+.BR yacc ,
 the generated files do not have fixed names, but instead use the prefix
 of the input file.
-Moreover, if you need to put
-.I C++
-code in the input file, you can end his name by a C++-like extension
-(.ypp or .y++), then bison will follow your extension to name the
-output file (.cpp or .c++).
+Moreover, if you need to put C++
+code in the input file, you can end its name by a C++-like extension
+.RI ( .ypp
+or
+.IR .y++ ),
+and then
+.B bison
+will follow your extension to name the
+output file
+.RI ( .cpp
+or
+.IR .c++ ).
 For instance, a grammar description file named
-.B parse.yxx
+.I parse.yxx
 would produce the generated parser in a file named
-.BR parse.tab.cxx ,
+.IR parse.tab.cxx ,
 instead of
-.IR yacc 's
-.B y.tab.c
-or old
-.I Bison
-version's
-.BR parse.tab.c .
+.BR yacc 's
+.IR y.tab.c .
 .PP
 This description of the options that can be given to
-.I bison
+.B bison
 is adapted from the node
 .B Invocation
-in the
-.B bison.texi
-manual, which should be taken as authoritative.
+in the Bison manual, which should be taken as authoritative.
 .PP
-.I Bison
-supports both traditional single-letter options and mnemonic long
+The
+.B bison
+command supports both traditional single-letter options and mnemonic long
 option names.  Long option names are indicated with
 .B \-\-
 instead of
@@ -0,0 +1,23 @@
+%union
+{
+  int ival;
+  const char *sval;
+}
+
+%token <ival> NUM
+%nterm <ival> exp
+%token <sval> STR
+%nterm <sval> useless
+
+%left '+' '-'
+%left '*'
+
+%%
+exp:
+  exp '+' exp
+| exp '-' exp
+| exp '*' exp
+| exp '/' exp
+| NUM
+;
+useless: STR;
@@ -0,0 +1,13 @@
+%%
+stmt:
+  expr
+| if_stmt
+;
+
+if_stmt:
+  "if" expr "then" stmt
+| "if" expr "then" stmt "else" stmt
+;
+
+expr:
+  "identifier"
@@ -0,0 +1,505 @@
+@c The GNU Free Documentation License.
+@center Version 1.3, 3 November 2008
+
+@c This file is intended to be included within another document,
+@c hence no sectioning command or @node.
+
+@display
+Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+@uref{https://fsf.org/}
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+@end display
+
+@enumerate 0
+@item
+PREAMBLE
+
+The purpose of this License is to make a manual, textbook, or other
+functional and useful document @dfn{free} in the sense of freedom: to
+assure everyone the effective freedom to copy and redistribute it,
+with or without modifying it, either commercially or noncommercially.
+Secondarily, this License preserves for the author and publisher a way
+to get credit for their work, while not being considered responsible
+for modifications made by others.
+
+This License is a kind of ``copyleft'', which means that derivative
+works of the document must themselves be free in the same sense.  It
+complements the GNU General Public License, which is a copyleft
+license designed for free software.
+
+We have designed this License in order to use it for manuals for free
+software, because free software needs free documentation: a free
+program should come with manuals providing the same freedoms that the
+software does.  But this License is not limited to software manuals;
+it can be used for any textual work, regardless of subject matter or
+whether it is published as a printed book.  We recommend this License
+principally for works whose purpose is instruction or reference.
+
+@item
+APPLICABILITY AND DEFINITIONS
+
+This License applies to any manual or other work, in any medium, that
+contains a notice placed by the copyright holder saying it can be
+distributed under the terms of this License.  Such a notice grants a
+world-wide, royalty-free license, unlimited in duration, to use that
+work under the conditions stated herein.  The ``Document'', below,
+refers to any such manual or work.  Any member of the public is a
+licensee, and is addressed as ``you''.  You accept the license if you
+copy, modify or distribute the work in a way requiring permission
+under copyright law.
+
+A ``Modified Version'' of the Document means any work containing the
+Document or a portion of it, either copied verbatim, or with
+modifications and/or translated into another language.
+
+A ``Secondary Section'' is a named appendix or a front-matter section
+of the Document that deals exclusively with the relationship of the
+publishers or authors of the Document to the Document's overall
+subject (or to related matters) and contains nothing that could fall
+directly within that overall subject.  (Thus, if the Document is in
+part a textbook of mathematics, a Secondary Section may not explain
+any mathematics.)  The relationship could be a matter of historical
+connection with the subject or with related matters, or of legal,
+commercial, philosophical, ethical or political position regarding
+them.
+
+The ``Invariant Sections'' are certain Secondary Sections whose titles
+are designated, as being those of Invariant Sections, in the notice
+that says that the Document is released under this License.  If a
+section does not fit the above definition of Secondary then it is not
+allowed to be designated as Invariant.  The Document may contain zero
+Invariant Sections.  If the Document does not identify any Invariant
+Sections then there are none.
+
+The ``Cover Texts'' are certain short passages of text that are listed,
+as Front-Cover Texts or Back-Cover Texts, in the notice that says that
+the Document is released under this License.  A Front-Cover Text may
+be at most 5 words, and a Back-Cover Text may be at most 25 words.
+
+A ``Transparent'' copy of the Document means a machine-readable copy,
+represented in a format whose specification is available to the
+general public, that is suitable for revising the document
+straightforwardly with generic text editors or (for images composed of
+pixels) generic paint programs or (for drawings) some widely available
+drawing editor, and that is suitable for input to text formatters or
+for automatic translation to a variety of formats suitable for input
+to text formatters.  A copy made in an otherwise Transparent file
+format whose markup, or absence of markup, has been arranged to thwart
+or discourage subsequent modification by readers is not Transparent.
+An image format is not Transparent if used for any substantial amount
+of text.  A copy that is not ``Transparent'' is called ``Opaque''.
+
+Examples of suitable formats for Transparent copies include plain
+ASCII without markup, Texinfo input format, La@TeX{} input
+format, SGML or XML using a publicly available
+DTD, and standard-conforming simple HTML,
+PostScript or PDF designed for human modification.  Examples
+of transparent image formats include PNG, XCF and
+JPG@.  Opaque formats include proprietary formats that can be
+read and edited only by proprietary word processors, SGML or
+XML for which the DTD and/or processing tools are
+not generally available, and the machine-generated HTML,
+PostScript or PDF produced by some word processors for
+output purposes only.
+
+The ``Title Page'' means, for a printed book, the title page itself,
+plus such following pages as are needed to hold, legibly, the material
+this License requires to appear in the title page.  For works in
+formats which do not have any title page as such, ``Title Page'' means
+the text near the most prominent appearance of the work's title,
+preceding the beginning of the body of the text.
+
+The ``publisher'' means any person or entity that distributes copies
+of the Document to the public.
+
+A section ``Entitled XYZ'' means a named subunit of the Document whose
+title either is precisely XYZ or contains XYZ in parentheses following
+text that translates XYZ in another language.  (Here XYZ stands for a
+specific section name mentioned below, such as ``Acknowledgements'',
+``Dedications'', ``Endorsements'', or ``History''.)  To ``Preserve the Title''
+of such a section when you modify the Document means that it remains a
+section ``Entitled XYZ'' according to this definition.
+
+The Document may include Warranty Disclaimers next to the notice which
+states that this License applies to the Document.  These Warranty
+Disclaimers are considered to be included by reference in this
+License, but only as regards disclaiming warranties: any other
+implication that these Warranty Disclaimers may have is void and has
+no effect on the meaning of this License.
+
+@item
+VERBATIM COPYING
+
+You may copy and distribute the Document in any medium, either
+commercially or noncommercially, provided that this License, the
+copyright notices, and the license notice saying this License applies
+to the Document are reproduced in all copies, and that you add no other
+conditions whatsoever to those of this License.  You may not use
+technical measures to obstruct or control the reading or further
+copying of the copies you make or distribute.  However, you may accept
+compensation in exchange for copies.  If you distribute a large enough
+number of copies you must also follow the conditions in section 3.
+
+You may also lend copies, under the same conditions stated above, and
+you may publicly display copies.
+
+@item
+COPYING IN QUANTITY
+
+If you publish printed copies (or copies in media that commonly have
+printed covers) of the Document, numbering more than 100, and the
+Document's license notice requires Cover Texts, you must enclose the
+copies in covers that carry, clearly and legibly, all these Cover
+Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
+the back cover.  Both covers must also clearly and legibly identify
+you as the publisher of these copies.  The front cover must present
+the full title with all words of the title equally prominent and
+visible.  You may add other material on the covers in addition.
+Copying with changes limited to the covers, as long as they preserve
+the title of the Document and satisfy these conditions, can be treated
+as verbatim copying in other respects.
+
+If the required texts for either cover are too voluminous to fit
+legibly, you should put the first ones listed (as many as fit
+reasonably) on the actual cover, and continue the rest onto adjacent
+pages.
+
+If you publish or distribute Opaque copies of the Document numbering
+more than 100, you must either include a machine-readable Transparent
+copy along with each Opaque copy, or state in or with each Opaque copy
+a computer-network location from which the general network-using
+public has access to download using public-standard network protocols
+a complete Transparent copy of the Document, free of added material.
+If you use the latter option, you must take reasonably prudent steps,
+when you begin distribution of Opaque copies in quantity, to ensure
+that this Transparent copy will remain thus accessible at the stated
+location until at least one year after the last time you distribute an
+Opaque copy (directly or through your agents or retailers) of that
+edition to the public.
+
+It is requested, but not required, that you contact the authors of the
+Document well before redistributing any large number of copies, to give
+them a chance to provide you with an updated version of the Document.
+
+@item
+MODIFICATIONS
+
+You may copy and distribute a Modified Version of the Document under
+the conditions of sections 2 and 3 above, provided that you release
+the Modified Version under precisely this License, with the Modified
+Version filling the role of the Document, thus licensing distribution
+and modification of the Modified Version to whoever possesses a copy
+of it.  In addition, you must do these things in the Modified Version:
+
+@enumerate A
+@item
+Use in the Title Page (and on the covers, if any) a title distinct
+from that of the Document, and from those of previous versions
+(which should, if there were any, be listed in the History section
+of the Document).  You may use the same title as a previous version
+if the original publisher of that version gives permission.
+
+@item
+List on the Title Page, as authors, one or more persons or entities
+responsible for authorship of the modifications in the Modified
+Version, together with at least five of the principal authors of the
+Document (all of its principal authors, if it has fewer than five),
+unless they release you from this requirement.
+
+@item
+State on the Title page the name of the publisher of the
+Modified Version, as the publisher.
+
+@item
+Preserve all the copyright notices of the Document.
+
+@item
+Add an appropriate copyright notice for your modifications
+adjacent to the other copyright notices.
+
+@item
+Include, immediately after the copyright notices, a license notice
+giving the public permission to use the Modified Version under the
+terms of this License, in the form shown in the Addendum below.
+
+@item
+Preserve in that license notice the full lists of Invariant Sections
+and required Cover Texts given in the Document's license notice.
+
+@item
+Include an unaltered copy of this License.
+
+@item
+Preserve the section Entitled ``History'', Preserve its Title, and add
+to it an item stating at least the title, year, new authors, and
+publisher of the Modified Version as given on the Title Page.  If
+there is no section Entitled ``History'' in the Document, create one
+stating the title, year, authors, and publisher of the Document as
+given on its Title Page, then add an item describing the Modified
+Version as stated in the previous sentence.
+
+@item
+Preserve the network location, if any, given in the Document for
+public access to a Transparent copy of the Document, and likewise
+the network locations given in the Document for previous versions
+it was based on.  These may be placed in the ``History'' section.
+You may omit a network location for a work that was published at
+least four years before the Document itself, or if the original
+publisher of the version it refers to gives permission.
+
+@item
+For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
+the Title of the section, and preserve in the section all the
+substance and tone of each of the contributor acknowledgements and/or
+dedications given therein.
+
+@item
+Preserve all the Invariant Sections of the Document,
+unaltered in their text and in their titles.  Section numbers
+or the equivalent are not considered part of the section titles.
+
+@item
+Delete any section Entitled ``Endorsements''.  Such a section
+may not be included in the Modified Version.
+
+@item
+Do not retitle any existing section to be Entitled ``Endorsements'' or
+to conflict in title with any Invariant Section.
+
+@item
+Preserve any Warranty Disclaimers.
+@end enumerate
+
+If the Modified Version includes new front-matter sections or
+appendices that qualify as Secondary Sections and contain no material
+copied from the Document, you may at your option designate some or all
+of these sections as invariant.  To do this, add their titles to the
+list of Invariant Sections in the Modified Version's license notice.
+These titles must be distinct from any other section titles.
+
+You may add a section Entitled ``Endorsements'', provided it contains
+nothing but endorsements of your Modified Version by various
+parties---for example, statements of peer review or that the text has
+been approved by an organization as the authoritative definition of a
+standard.
+
+You may add a passage of up to five words as a Front-Cover Text, and a
+passage of up to 25 words as a Back-Cover Text, to the end of the list
+of Cover Texts in the Modified Version.  Only one passage of
+Front-Cover Text and one of Back-Cover Text may be added by (or
+through arrangements made by) any one entity.  If the Document already
+includes a cover text for the same cover, previously added by you or
+by arrangement made by the same entity you are acting on behalf of,
+you may not add another; but you may replace the old one, on explicit
+permission from the previous publisher that added the old one.
+
+The author(s) and publisher(s) of the Document do not by this License
+give permission to use their names for publicity for or to assert or
+imply endorsement of any Modified Version.
+
+@item
+COMBINING DOCUMENTS
+
+You may combine the Document with other documents released under this
+License, under the terms defined in section 4 above for modified
+versions, provided that you include in the combination all of the
+Invariant Sections of all of the original documents, unmodified, and
+list them all as Invariant Sections of your combined work in its
+license notice, and that you preserve all their Warranty Disclaimers.
+
+The combined work need only contain one copy of this License, and
+multiple identical Invariant Sections may be replaced with a single
+copy.  If there are multiple Invariant Sections with the same name but
+different contents, make the title of each such section unique by
+adding at the end of it, in parentheses, the name of the original
+author or publisher of that section if known, or else a unique number.
+Make the same adjustment to the section titles in the list of
+Invariant Sections in the license notice of the combined work.
+
+In the combination, you must combine any sections Entitled ``History''
+in the various original documents, forming one section Entitled
+``History''; likewise combine any sections Entitled ``Acknowledgements'',
+and any sections Entitled ``Dedications''.  You must delete all
+sections Entitled ``Endorsements.''
+
+@item
+COLLECTIONS OF DOCUMENTS
+
+You may make a collection consisting of the Document and other documents
+released under this License, and replace the individual copies of this
+License in the various documents with a single copy that is included in
+the collection, provided that you follow the rules of this License for
+verbatim copying of each of the documents in all other respects.
+
+You may extract a single document from such a collection, and distribute
+it individually under this License, provided you insert a copy of this
+License into the extracted document, and follow this License in all
+other respects regarding verbatim copying of that document.
+
+@item
+AGGREGATION WITH INDEPENDENT WORKS
+
+A compilation of the Document or its derivatives with other separate
+and independent documents or works, in or on a volume of a storage or
+distribution medium, is called an ``aggregate'' if the copyright
+resulting from the compilation is not used to limit the legal rights
+of the compilation's users beyond what the individual works permit.
+When the Document is included in an aggregate, this License does not
+apply to the other works in the aggregate which are not themselves
+derivative works of the Document.
+
+If the Cover Text requirement of section 3 is applicable to these
+copies of the Document, then if the Document is less than one half of
+the entire aggregate, the Document's Cover Texts may be placed on
+covers that bracket the Document within the aggregate, or the
+electronic equivalent of covers if the Document is in electronic form.
+Otherwise they must appear on printed covers that bracket the whole
+aggregate.
+
+@item
+TRANSLATION
+
+Translation is considered a kind of modification, so you may
+distribute translations of the Document under the terms of section 4.
+Replacing Invariant Sections with translations requires special
+permission from their copyright holders, but you may include
+translations of some or all Invariant Sections in addition to the
+original versions of these Invariant Sections.  You may include a
+translation of this License, and all the license notices in the
+Document, and any Warranty Disclaimers, provided that you also include
+the original English version of this License and the original versions
+of those notices and disclaimers.  In case of a disagreement between
+the translation and the original version of this License or a notice
+or disclaimer, the original version will prevail.
+
+If a section in the Document is Entitled ``Acknowledgements'',
+``Dedications'', or ``History'', the requirement (section 4) to Preserve
+its Title (section 1) will typically require changing the actual
+title.
+
+@item
+TERMINATION
+
+You may not copy, modify, sublicense, or distribute the Document
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense, or distribute it is void, and
+will automatically terminate your rights under this License.
+
+However, if you cease all violation of this License, then your license
+from a particular copyright holder is reinstated (a) provisionally,
+unless and until the copyright holder explicitly and finally
+terminates your license, and (b) permanently, if the copyright holder
+fails to notify you of the violation by some reasonable means prior to
+60 days after the cessation.
+
+Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License.  If your rights have been terminated and not permanently
+reinstated, receipt of a copy of some or all of the same material does
+not give you any rights to use it.
+
+@item
+FUTURE REVISIONS OF THIS LICENSE
+
+The Free Software Foundation may publish new, revised versions
+of the GNU Free Documentation License from time to time.  Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.  See
+@uref{https://www.gnu.org/licenses/}.
+
+Each version of the License is given a distinguishing version number.
+If the Document specifies that a particular numbered version of this
+License ``or any later version'' applies to it, you have the option of
+following the terms and conditions either of that specified version or
+of any later version that has been published (not as a draft) by the
+Free Software Foundation.  If the Document does not specify a version
+number of this License, you may choose any version ever published (not
+as a draft) by the Free Software Foundation.  If the Document
+specifies that a proxy can decide which future versions of this
+License can be used, that proxy's public statement of acceptance of a
+version permanently authorizes you to choose that version for the
+Document.
+
+@item
+RELICENSING
+
+``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
+World Wide Web server that publishes copyrightable works and also
+provides prominent facilities for anybody to edit those works.  A
+public wiki that anybody can edit is an example of such a server.  A
+``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
+site means any set of copyrightable works thus published on the MMC
+site.
+
+``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
+license published by Creative Commons Corporation, a not-for-profit
+corporation with a principal place of business in San Francisco,
+California, as well as future copyleft versions of that license
+published by that same organization.
+
+``Incorporate'' means to publish or republish a Document, in whole or
+in part, as part of another Document.
+
+An MMC is ``eligible for relicensing'' if it is licensed under this
+License, and if all works that were first published under this License
+somewhere other than this MMC, and subsequently incorporated in whole
+or in part into the MMC, (1) had no cover texts or invariant sections,
+and (2) were thus incorporated prior to November 1, 2008.
+
+The operator of an MMC Site may republish an MMC contained in the site
+under CC-BY-SA on the same site at any time before August 1, 2009,
+provided the MMC is eligible for relicensing.
+
+@end enumerate
+
+@page
+@heading ADDENDUM: How to use this License for your documents
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+
+@smallexample
+@group
+  Copyright (C)  @var{year}  @var{your name}.
+  Permission is granted to copy, distribute and/or modify this document
+  under the terms of the GNU Free Documentation License, Version 1.3
+  or any later version published by the Free Software Foundation;
+  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+  Texts.  A copy of the license is included in the section entitled ``GNU
+  Free Documentation License''.
+@end group
+@end smallexample
+
+If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the ``with@dots{}Texts.''@: line with this:
+
+@smallexample
+@group
+    with the Invariant Sections being @var{list their titles}, with
+    the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
+    being @var{list}.
+@end group
+@end smallexample
+
+If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
+
+@c Local Variables:
+@c ispell-local-pdict: "ispell-dict"
+@c End:
@@ -3,7 +3,7 @@ digraph "reduce.y"
  node [fontname=courier shape=box]
  edge [fontname=courier]

-  1 [label="State 1\n  3 a: \"0\" .  [\".\"]\l  4 b: \"0\" .  [\";\"]\l"]
+  1 [label="State 1\n  3 a: \"0\" •  [\".\"]\l  4 b: \"0\" •  [\";\"]\l"]
  1 -> "1R3" [label="" style=solid]
 "1R3" [style=filled shape=diamond fillcolor=yellowgreen label="R3"]
  1 -> "1R4" [label="[\";\"]" style=solid]
@@ -1,7 +1,7 @@
       .------------------.
       |     State 1      |
-       | 3 a: "0" . [";"] |
-       | 4 b: "0" . ["."] |
+       | 3 a: "0" • [";"] |
+       | 4 b: "0" • ["."] |
       `------------------'
             /     \
            /       \ ["."]
@@ -3,7 +3,7 @@ digraph "shift.y"
  node [fontname=courier shape=box]
  edge [fontname=courier]

-  3 [label="State 3\n  1 exp: a . \".\"\l"]
+  3 [label="State 3\n  1 exp: a • \".\"\l"]
  3 -> 6 [style=solid label="\".\""]
-  6 [label="State 6\n  1 exp: a \".\" .\l"]
+  6 [label="State 6\n  1 exp: a \".\" •\l"]
 }
@@ -1,6 +1,6 @@
 .----------------.
 |    State 3     |
-| 1 exp: a . ";" |
+| 1 exp: a • ";" |
 `----------------'
        |
        | ";"
@@ -8,5 +8,5 @@
        v
 .----------------.
 |    State 6     |
-| 1 exp: a ";" . |
+| 1 exp: a ";" • |
 `----------------'
@@ -1,35 +1,35 @@
 // Generated by GNU Bison 2.6.90.
 // Report bugs to <[email protected]>.
-// Home page: <http://www.gnu.org/software/bison/>.
+// Home page: <https://www.gnu.org/software/bison/>.

-digraph "/tmp/fo.y"
+digraph "example.y"
 {
  node [fontname = courier, shape = box, colorscheme = paired6]
  edge [fontname = courier]

-  0 [label="State 0\n\l  0 $accept: . exp $end\l  1 exp: . a \";\"\l  2    | . b \".\"\l  3 a: . \"0\"\l  4 b: . \"0\"\l"]
+  0 [label="State 0\n\l  0 $accept: • exp $end\l  1 exp: • a \";\"\l  2    | • b \".\"\l  3 a: • \"0\"\l  4 b: • \"0\"\l"]
  0 -> 1 [style=solid label="\"0\""]
  0 -> 2 [style=dashed label="exp"]
  0 -> 3 [style=dashed label="a"]
  0 -> 4 [style=dashed label="b"]
-  1 [label="State 1\n\l  3 a: \"0\" .  [\";\"]\l  4 b: \"0\" .  [\".\"]\l"]
+  1 [label="State 1\n\l  3 a: \"0\" •  [\";\"]\l  4 b: \"0\" •  [\".\"]\l"]
  1 -> "1R3" [style=solid]
 "1R3" [label="R3", fillcolor=3, shape=diamond, style=filled]
  1 -> "1R4" [label="[\".\"]", style=solid]
 "1R4" [label="R4", fillcolor=3, shape=diamond, style=filled]
-  2 [label="State 2\n\l  0 $accept: exp . $end\l"]
+  2 [label="State 2\n\l  0 $accept: exp • $end\l"]
  2 -> 5 [style=solid label="$end"]
-  3 [label="State 3\n\l  1 exp: a . \";\"\l"]
+  3 [label="State 3\n\l  1 exp: a • \";\"\l"]
  3 -> 6 [style=solid label="\";\""]
-  4 [label="State 4\n\l  2 exp: b . \".\"\l"]
+  4 [label="State 4\n\l  2 exp: b • \".\"\l"]
  4 -> 7 [style=solid label="\".\""]
-  5 [label="State 5\n\l  0 $accept: exp $end .\l"]
+  5 [label="State 5\n\l  0 $accept: exp $end •\l"]
  5 -> "5R0" [style=solid]
 "5R0" [label="Acc", fillcolor=1, shape=diamond, style=filled]
-  6 [label="State 6\n\l  1 exp: a \";\" .\l"]
+  6 [label="State 6\n\l  1 exp: a \";\" •\l"]
  6 -> "6R1" [style=solid]
 "6R1" [label="R1", fillcolor=3, shape=diamond, style=filled]
-  7 [label="State 7\n\l  2 exp: b \".\" .\l"]
+  7 [label="State 7\n\l  2 exp: b \".\" •\l"]
  7 -> "7R2" [style=solid]
 "7R2" [label="R2", fillcolor=3, shape=diamond, style=filled]
 }
@@ -0,0 +1,5 @@
+%token ID
+%%
+s: a ID
+a: expr
+expr: %empty | expr ID ','
@@ -1,5 +1,5 @@
-## Copyright (C) 2001-2003, 2005-2015, 2018-2020 Free Software
-## Foundation, Inc.
+## Copyright (C) 2001-2003, 2005-2015, 2018-2022, 2025-2026 Free
+## Software Foundation, Inc.

 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -12,7 +12,7 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 AM_MAKEINFOFLAGS =                                              \
  --no-split                                                    \
@@ -56,8 +56,8 @@ MAINTAINERCLEANFILES = $(CROSS_OPTIONS_TEXI)


 # Fix Info's @code in @deftype
-# https://lists.gnu.org/archive/html/help-texinfo/2019-11/msg00004.html
-all: $(srcdir)/$(%C%_bison).info.bak
+# https://lists.gnu.org/r/help-texinfo/2019-11/msg00004.html
+all-local: $(srcdir)/$(%C%_bison).info.bak
 $(srcdir)/$(%C%_bison).info.bak: $(srcdir)/$(%C%_bison).info
 	$(AM_V_GEN) $(PERL) -pi.bak -0777	\
 	  -e 's{(^ --.*\n(?: {10}.*\n)*)}'	\
@@ -114,7 +114,7 @@ $(top_srcdir)/%D%/bison.help: src/bison$(EXEEXT)
 	$(AM_V_at) LC_ALL=C tests/bison --version >%D%/bison.help.tmp
 	$(AM_V_at) LC_ALL=C tests/bison --help | \
 ## Avoid depending on the path to Bison.
-	  sed -e 's,^Usage: .*/bison \[OPTION\],Usage: bison [OPTION],g' \
+	  sed -e 's,^Usage: .*/bison \[OPTION],Usage: bison [OPTION],g' \
 ## Avoid variations in the output depending on whether we are
 ## on a glibc system.
 	      -e '/translation bugs/d'  >>%D%/bison.help.tmp
@@ -19,8 +19,8 @@
 \def\finalout{\overfullrule=0pt}
 %\finalout

-% Copyright (c) 1998, 2001, 2009--2015, 2018--2020 Free Software
-% Foundation, Inc.
+% Copyright (c) 1998, 2001, 2009--2015, 2018--2022, 2025--2026 Free
+% Software Foundation, Inc.
 %
 % This file is part of Bison.
 %
@@ -35,7 +35,7 @@
 % GNU General Public License for more details.
 %
 % You should have received a copy of the GNU General Public License
-% along with this program.  If not, see <http://www.gnu.org/licenses/>.
+% along with this program.  If not, see <https://www.gnu.org/licenses/>.
 %
 % This file is intended to be processed by plain TeX (TeX82).
 %
@@ -0,0 +1,10 @@
+%%
+sequence:
+  %empty
+| maybeword
+| sequence "word"
+;
+maybeword:
+  %empty
+| "word"
+;
@@ -5,14 +5,15 @@ yacc \- GNU Project parser generator
 .B yacc
 [\fIOPTION\fR]... \fIFILE\fR
 .SH DESCRIPTION
-.I Yacc
+The program
+.B yacc
 (Yet Another Compiler Compiler) is a parser generator.  This
 version is a simple wrapper around
-.IR bison (1).
+.BR bison (1).
 It passes option
 \fB\-y\fR, \fB\-\-yacc\fR
 to activate the upward compatibility mode.  See
-.IR bison (1)
+.BR bison (1)
 for more information.
 .SH AUTHOR
 Written by Paul Eggert.
@@ -1,38 +0,0 @@
-* bench.pl
-A primitive Perl script to run benches.  Currently its only bench is
-the usual calculator: it has a lightweight processing part (but not
-null), so it is really emphasizing the cost of the whole parsing
-(including scanning and I/O).
-
-Set the envvars BISON and CC to the programs and flags you want to
-use.  They default to bison and gcc.  To run a non-installed bison
-from a tarball built in _build, I suggest the following.
-
-     BISON=_build/tests/bison CC='gcc -O2' ./bench.pl
-
-(The _build/tests/bison wrapper makes sure that _build/src/bison will
-use the tarballs' skeletons, not those already installed as a
-straightforward use of _build/src/bison would.)
-
--
-
-Copyright (C) 2006, 2009-2015, 2018-2020 Free Software Foundation, Inc.
-
-This file is part of Bison, the GNU Compiler Compiler.
-
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-Local Variables:
-mode: outline
-End:
@@ -0,0 +1,37 @@
+# bench.pl
+A primitive Perl script to run benches.  Currently its only bench is the
+usual calculator: it has a lightweight processing part (but not null), so it
+is really emphasizing the cost of the whole parsing (including scanning and
+I/O).
+
+Set the envvars `BISON` and `CC` to the programs and flags you want to use.
+They default to `bison` and `gcc`.  To run a non-installed bison from a
+tarball built in _build, I suggest the following.
+
+    BISON=_build/tests/bison CC='gcc -O2' ./bench.pl
+
+(The `_build/tests/bison` wrapper makes sure that `_build/src/bison` will
+use the tarballs' skeletons, not those already installed as a
+straightforward use of `_build/src/bison` would.)
+
+<!--
+
+Local Variables:
+mode: markdown
+fill-column: 76
+ispell-dictionary: "american"
+End:
+
+Copyright (C) 2006, 2009-2015, 2018-2022, 2025-2026 Free Software
+Foundation, Inc.
+
+This file is part of Bison, the GNU Compiler Compiler.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the "GNU Free
+Documentation License" file as part of this distribution.
+
+-->
@@ -1,7 +1,7 @@
 #! /usr/bin/perl -w

-# Copyright (C) 2006, 2008-2015, 2018-2020 Free Software Foundation,
-# Inc.
+# Copyright (C) 2006, 2008-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.
 #
 # This file is part of Bison, the GNU Compiler Compiler.
 #
@@ -16,7 +16,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 =head1 NAME

@@ -185,13 +185,13 @@ my $verbose = 1;

 =over 4

-=item C<verbose($level, $message)>
+=item C<verbose ($level, $message)>

 Report the C<$message> is C<$level> E<lt>= C<$verbose>.

 =cut

-sub verbose($$)
+sub verbose ($$)
 {
  my ($level, $message) = @_;
  print STDERR $message
@@ -201,13 +201,13 @@ sub verbose($$)

 ######################################################################

-=item C<directives($bench, @directive)>
+=item C<directives ($bench, @directive)>

 Format the list of directives for Bison for bench named C<$bench>.

 =cut

-sub directives($@)
+sub directives ($@)
 {
  my ($bench, @directive) = @_;
  my $res = "/* Directives for bench '$bench'. */\n";
@@ -218,6 +218,27 @@ sub directives($@)

 ######################################################################

+=item C<is_pure (@directive)>
+
+Whether api.pure is set.
+
+=cut
+
+sub is_pure (@)
+{
+  my (@directive) = @_;
+  for my $dir (@directive)
+    {
+      if ($dir =~ /\A%define api.pure/)
+        {
+          return 1;
+        }
+    }
+  return 0;
+}
+
+######################################################################
+
 =item C<generate_grammar_triangular ($base, $max, @directive)>

 Create a large triangular grammar which looks like :
@@ -389,18 +410,14 @@ sub generate_grammar_calc ($$@)
 %define api.value.type union
 $directives

-%{
+%code provides {
 static int power (int base, int exponent);
 /* yyerror receives the location if:
   - %location & %pure & %glr
   - %location & %pure & %yacc & %parse-param. */
 static void yyerror (const char *s);
-#if YYPURE
-static int yylex (YYSTYPE* yylvalp);
-#else
-static int yylex (void);
-#endif
-%}
+static int yylex (@{[is_pure (@directive) ? "YYSTYPE *yylvalp" : "void"]});
+}

 /* Bison Declarations */
 %token
@@ -467,12 +484,7 @@ yyerror (const char *s)
 }

 static int
-#if YYPURE
-# define yylval (*yylvalp)
-yylex (YYSTYPE* yylvalp)
-#else
-yylex (void)
-#endif
+yylex (@{[is_pure (@directive) ? "YYSTYPE *yylvalp" : "void"]})
 {
  int c;

@@ -498,14 +510,15 @@ yylex (void)
    case '5': case '6': case '7': case '8': case '9':
      {
        int nchars = 0;
-        sscanf (input - 1, "%d%n", &yylval.NUM, &nchars);
+        int n = sscanf (input - 1, "%d%n", &@{[is_pure (@directive) ? "yylvalp->" : "yylval."]}NUM, &nchars);
+        assert (n == 1);
        input += nchars - 1;
        return NUM;
      }

    default:
      yyerror ("error: invalid character");
-      return yylex ();
+      return yylex (@{[is_pure (@directive) ? "yylvalp" : ""]});
    }
 }
 EOF
@@ -568,7 +581,7 @@ sub generate_grammar_list ($$@)
    or die;
  print $out <<EOF;
 %language "C++"
-%defines
+%header
 %locations
 $directives

@@ -591,10 +604,10 @@ $directives
  // Prototype of the yylex function providing subsequent tokens.
  static
 #if USE_TOKEN_CTOR
-  yy::parser::symbol_type yylex();
+  yy::parser::symbol_type yylex ();
 #else
-  yy::parser::token_type yylex(yy::parser::semantic_type* yylvalp,
-                               yy::parser::location_type* yyllocp);
+  yy::parser::token_type yylex (yy::parser::semantic_type *yylvalp,
+                                yy::parser::location_type *yyllocp);
 #endif

  // Conversion to string.
@@ -617,8 +630,8 @@ EOF
      print $out <<'EOF';
 %token <std::string> TEXT
 %token <int> NUMBER
-%printer { std::cerr << "Number: " << $$; } <int>
-%printer { std::cerr << "Text: " << $$; } <std::string>
+%printer { yyo << "Number: " << $$; } <int>
+%printer { yyo << "Text: " << $$; } <std::string>
 %type <std::string> text result

 %%
@@ -640,8 +653,8 @@ EOF
 %union {int ival; std::string* sval;}
 %token <sval> TEXT
 %token <ival> NUMBER
-%printer { std::cerr << "Number: " << $$; } <ival>
-%printer { std::cerr << "Text: " << *$$; } <sval>
+%printer { yyo << "Number: " << $$; } <ival>
+%printer { yyo << "Text: " << *$$; } <sval>
 %type <sval> text result

 %%
@@ -663,10 +676,10 @@ EOF

 static
 #if USE_TOKEN_CTOR
-yy::parser::symbol_type yylex()
+yy::parser::symbol_type yylex ()
 #else
-yy::parser::token_type yylex(yy::parser::semantic_type* yylvalp,
-                             yy::parser::location_type* yyllocp)
+yy::parser::token_type yylex (yy::parser::semantic_type *yylvalp,
+                              yy::parser::location_type *yyllocp)
 #endif
 {
  typedef yy::parser::location_type location_type;
@@ -775,7 +788,31 @@ sub run ($)

 ##################################################################

-=item C<compile ($base)>
+=item C<language ($base)>
+
+The language to use depending on the %language specification in
+C<$base.y>: C<c> or C<c++>.
+
+=cut
+
+sub language ($)
+{
+  my ($base) = @_;
+  if ($gbench)
+    {
+      "c++";
+    }
+  else
+    {
+      my $language = `sed -ne '/%language "\\(.*\\)"/{s//\\1/;p;q;}' $base.y`;
+      chomp $language;
+      $language eq 'C++' ? "c++" : "c";
+    }
+}
+
+##################################################################
+
+=item C<compiler ($base)>

 The compiler to use depending on the %language specification in
 C<$base.y>.
@@ -785,16 +822,12 @@ C<$base.y>.
 sub compiler ($)
 {
  my ($base) = @_;
-  if ($gbench)
-    {
-      $cxx;
-    }
-  else
-    {
-      my $language = `sed -ne '/%language "\\(.*\\)"/{s//\\1/;p;q;}' $base.y`;
-      chomp $language;
-      $language eq 'C++' ? $cxx : $cc;
-    }
+  my %compiler =
+    (
+      'c++' => $cxx,
+      'c'   => $cc,
+    );
+  $compiler{language ($base)};
 }

 ##################################################################
@@ -805,21 +838,38 @@ Compile C<$base.y> to an executable.

 =cut

-sub compile ($)
+sub compile ($$)
 {
-  my ($base) = @_;
+  my ($makefile, $base) = @_;
  my $compiler = compiler ($base);

  my $my_bison = `sed -ne '/[/][/] %bison "\\(.*\\)"/{s//\\1/;p;q;}' $base.y`;
  chop $my_bison;
-  run ((length $my_bison ? $my_bison : $bison) . " $base.y -o $base.c");
+  my %ext =
+    (
+      'c++' => 'cc',
+      'c'   => 'c',
+    );
+  my $ext = $ext{language ($base)};
  if ($gbench)
    {
-      run "$compiler -c -o $base.o $cflags $base.c";
+      print $makefile <<EOF;
+$base.$ext: $base.y
+\t@{[length $my_bison ? $my_bison : $bison]} $base.y -o $base.$ext
+
+$base.o: $base.$ext
+\t$compiler -c -o $base.o $cflags $base.$ext
+EOF
    }
  else
    {
-      run "$compiler -o $base $cflags $base.c";
+      print $makefile <<EOF;
+$base.$ext: $base.y
+\t@{[length $my_bison ? $my_bison : $bison]} $base.y -o $base.$ext
+
+$base: $base.$ext
+\t$compiler -o $base $cflags $base.$ext
+EOF
    }
 }

@@ -849,11 +899,13 @@ sub bench_with_timethese ($@)
  # For each bench, capture the size.
  my %size;

+  my $makefile = new IO::File ">Makefile";
  while (my ($name, $directives) = each %bench)
    {
      generate_grammar ($grammar, $name, $directives);
      # Compile the executable.
-      compile ($name);
+      compile ($makefile, $name);
+      run "make $name";
      $bench{$name} = "system ('./$name');";
      chop($size{$name} = `wc -c <$name`);
    }
@@ -906,6 +958,20 @@ sub bench_with_gbenchmark ($@)
  my $readme = new IO::File ">README.md";
  print $readme <<EOF;
 compiler: $compiler $cflags
+EOF
+
+  my $makefile = new IO::File ">Makefile";
+  print $makefile <<EOF;
+.PHONY: bench
+bench: main
+\t./main \$(BENCHFLAGS) | tee -a README.md
+
+# Link the bench cases in a different order to run the bench case in a
+# different order.
+.PHONY: rand
+rand:
+\t-rm main
+\tmake bench OBJECTS="\$\$(shuf -e \$(OBJECTS) | xargs)"
 EOF

  my @obj = ();
@@ -916,19 +982,24 @@ EOF
      print $m;
      print $readme $m;
      generate_grammar ($grammar, $base, $directive[$i]);
-      compile ($base);
+      compile ($makefile, $base);
      push @obj, "$base.o";
    }

-  my $out = new IO::File ">main.c";
+  my $out = new IO::File ">main.cc";
  print $out <<EOF;
 #include <benchmark/benchmark.h>

 BENCHMARK_MAIN();
 EOF

-  run "$compiler -o main $cflags main.c @obj -lbenchmark";
-  run "./main | tee -a README.md";
+  print $makefile <<EOF;
+OBJECTS = @{obj}
+main: \$(OBJECTS)
+\t$compiler -o main $cflags main.cc \$(OBJECTS) -lbenchmark
+EOF
+
+  run "make";
 }

 ######################################################################
@@ -1001,7 +1072,7 @@ sub help ($)
 {
  my ($verbose) = @_;
  use Pod::Usage;
-  # See <URL:http://perldoc.perl.org/pod2man.html#NOTES>.
+  # See <URL:https://perldoc.perl.org/pod2man.html#NOTES>.
  pod2usage( { -message => "Bench Bison parsers",
               -exitval => 0,
               -verbose => $verbose,
@@ -1,5 +1,5 @@
-## Copyright (C) 2006, 2008-2015, 2018-2020 Free Software Foundation,
-## Inc.
+## Copyright (C) 2006, 2008-2015, 2018-2022, 2025-2026 Free Software
+## Foundation, Inc.

 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -12,6 +12,7 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

-nodist_noinst_SCRIPTS = etc/bench.pl
+dist_noinst_DATA = %D%/README.md
+nodist_noinst_SCRIPTS = %D%/bench.pl
@@ -0,0 +1,13 @@
+*.c
+*.cc
+*.class
+*.h
+*.hh
+!/c++/glr/ast.hh
+*.java
+*.ll
+/c/bistromathic/bistromathic
+/c/calc/calc
+/c/glr/c++-types
+/c/lexcalc/lexcalc
+/c/pushcalc/calc
@@ -17,7 +17,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -1 +1,5 @@
+/glr/c++-types
+/simple
 /simple.yy
+/variant
+/variant-11
@@ -11,8 +11,8 @@ variant-11: CXXFLAGS = -std=c++11

 all: $(PROGS)

-%.cc %.hh: %.yy
-	$(BISON) $(BISONFLAGS) -o $*.cc $<
+%.cc %.hh %.html %.gv: %.yy
+	$(BISON) $(BISONFLAGS) --html --graph -o $*.cc $<

 %: %.cc
 	$(CXX) $(CXXFLAGS) -o$@ $<
@@ -39,6 +39,15 @@ examples.
 Extracted from the documentation: [A Complete C++
 Example](https://www.gnu.org/software/bison/manual/html_node/A-Complete-C_002b_002b-Example.html).

+## glr
+
+This example demonstrates the use of GLR parsers to handle (local)
+ambiguities in the C++ language.  See the node "Merging GLR Parses" in
+Bison's documentation.
+
+It uses (Bison) variants to store objects as semantic values.  It also
+demonstrates custom error messages in C++.
+
 <!---

 Local Variables:
@@ -46,7 +55,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -1,19 +1,2 @@
-/*.o
-/*.tmp
-/.deps
 /calc++
-/calc++.cc
-/calc++.exe
-/calc.stamp
-/driver.cc
-/driver.hh
-/location.hh
-/parser.cc
-/parser.hh
-/parser.output
-/parser.stamp
 /parser.yy
-/position.hh
-/scanner.cc
-/scanner.ll
-/stack.hh
@@ -5,12 +5,11 @@ BASE = calc++
 BISON = bison
 CXX = g++
 FLEX = flex
-XSLTPROC = xsltproc

 all: $(BASE)

-%.cc %.hh %.xml %.gv: %.yy
-	$(BISON) $(BISONFLAGS) --xml --graph=$*.gv -o $*.cc $<
+%.cc %.hh %.html %.gv: %.yy
+	$(BISON) $(BISONFLAGS) --html --graph -o $*.cc $<

 %.cc: %.ll
 	$(FLEX) $(FLEXFLAGS) -o$@ $<
@@ -29,10 +28,6 @@ run: $(BASE)
 	@echo "Type arithmetic expressions.  Quit with ctrl-d."
 	./$< -

-html: parser.html
-%.html: %.xml
-	$(XSLTPROC) $(XSLTPROCFLAGS) -o $@ $$($(BISON) --print-datadir)/xslt/xml2xhtml.xsl $<
-
 CLEANFILES =										\
  $(BASE) *.o										\
  parser.hh parser.cc parser.output parser.xml parser.html parser.gv location.hh	\
@@ -36,7 +36,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -1,6 +1,7 @@
 #! /bin/sh

-# Copyright (C) 2005-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2005-2015, 2018-2022, 2025-2026 Free Software
+# Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,7 +14,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 cat >input <<EOF
 toto := 1
@@ -50,6 +51,21 @@ EOF
 run 1 'err: -:2.1: syntax error, unexpected end of file, expecting ( or identifier or number'


+# Check handling of tabs.
+cat >input <<EOF
+        *1
+EOF
+run 1 'err: -:1.9: syntax error, unexpected *, expecting ( or identifier or number'
+cat >input <<EOF
+	*2
+EOF
+run 1 'err: -:1.9: syntax error, unexpected *, expecting ( or identifier or number'
+cat >input <<EOF
+       	*3
+EOF
+run 1 'err: -:1.9: syntax error, unexpected *, expecting ( or identifier or number'
+
+
 # LAC finds many more tokens.
 cat >input <<EOF
 a := 1
@@ -1,5 +1,5 @@
-## Copyright (C) 2005-2006, 2008-2015, 2018-2020 Free Software
-## Foundation, Inc.
+## Copyright (C) 2005-2006, 2008-2015, 2018-2022, 2025-2026 Free
+## Software Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -12,13 +12,12 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 ## ------------------- ##
 ## Parser generation.  ##
 ## ------------------- ##

-%D%/parser.stamp: $(dependencies)
 SUFFIXES += .yy .stamp
 .yy.stamp:
 	$(AM_V_YACC)rm -f $@
@@ -26,12 +25,13 @@ SUFFIXES += .yy .stamp
 	$(AM_V_at)$(YACCCOMPILE) -o $*.cc $<
 	$(AM_V_at)mv -f $@.tmp $@

+%D%/parser.stamp: $(dependencies)
 $(calcxx_sources_generated): %D%/parser.stamp
 	@test -f $@ || rm -f %D%/parser.stamp
 	@test -f $@ || $(MAKE) $(AM_MAKEFLAGS) %D%/parser.stamp
 CLEANFILES +=					\
  $(calcxx_sources_generated)			\
-  %D%/parser.dot				\
+  %D%/parser.gv					\
  %D%/parser.output				\
  %D%/parser.stamp				\
  %D%/scanner.cc
@@ -0,0 +1,23 @@
+# This Makefile is designed to be simple and readable.  It does not
+# aim at portability.  It requires GNU Make.
+
+BASE = c++-types
+BISON = bison
+
+all: $(BASE)
+
+%.c %.h %.html %.gv: %.y
+	$(BISON) $(BISONFLAGS) --header --html --graph -o $*.c $<
+
+$(BASE): $(BASE).o
+	$(CC) $(CFLAGS) -o $@ $^
+
+run: $(BASE)
+	@echo "Type C++ declarations or expressions.  Quit with ctrl-d."
+	./$<
+
+CLEANFILES =									\
+  $(BASE) *.o $(BASE).[ch] $(BASE).output $(BASE).xml $(BASE).html $(BASE).gv
+
+clean:
+	rm -f $(CLEANFILES)
@@ -0,0 +1,27 @@
+# glr
+
+This example demonstrates the use of GLR parsers to handle (local)
+ambiguities in the C++ language.  See the node "Merging GLR Parses" in
+Bison's documentation.
+
+It uses (Bison) variants to store objects as semantic values.  It also
+demonstrates custom error messages in C++.
+
+<!---
+Local Variables:
+fill-column: 76
+ispell-dictionary: "american"
+End:
+
+Copyright (C) 2020-2022, 2025-2026 Free Software Foundation, Inc.
+
+This file is part of Bison, the GNU Compiler Compiler.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.  A copy of the license is included in the "GNU Free
+Documentation License" file as part of this distribution.
+
+--->
@@ -0,0 +1,173 @@
+/*
+  Copyright (C) 2020-2022, 2025-2026 Free Software Foundation, Inc.
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include <cstddef> // nullptr_t
+#include <iostream>
+#include <memory>
+
+// Type erasure 101 <https://stackoverflow.com/a/26199467/1353549>.
+class NodeInterface;
+
+class Node
+{
+public:
+  Node (const Node& node) = default;
+  Node (Node&& node) = default;
+  Node () = default;
+  ~Node () = default;
+
+  template <typename T,
+            // SFINAE block using this ctor as a copy/move ctor:
+            std::enable_if_t<!std::is_same<Node, std::decay_t<T>>::value, int>* = nullptr>
+  Node (T&& t);
+
+  Node& operator= (const Node& node) = default;
+  Node& operator= (Node&& node) = default;
+
+  explicit operator bool () const
+  {
+    return impl_ != nullptr;
+  }
+
+  std::ostream& print (std::ostream& o) const;
+
+  std::shared_ptr<NodeInterface> impl_;
+};
+
+static std::ostream&
+operator<< (std::ostream& o, const Node &node)
+{
+  return node.print (o);
+}
+
+class NodeInterface
+{
+public:
+  virtual ~NodeInterface () = default;
+  virtual std::ostream& print (std::ostream& o) const = 0;
+};
+
+
+std::ostream& Node::print (std::ostream& o) const
+{
+  if (impl_)
+    impl_->print (o);
+  return o;
+}
+
+
+template <typename T,
+          std::enable_if_t<!std::is_same<std::nullptr_t, std::decay_t<T>>::value, int>* = nullptr>
+struct NodeImpl : public NodeInterface
+{
+  template <typename U>
+  explicit NodeImpl (U&& u)
+    : t{std::forward<U> (u)}
+  {}
+  virtual ~NodeImpl () = default;
+  virtual std::ostream& print (std::ostream& o) const
+  {
+    return o << t;
+  }
+
+  T t;
+};
+
+
+template <typename T,
+          std::enable_if_t<!std::is_same<Node, std::decay_t<T>>::value, int>*>
+Node::Node (T&& t)
+  : impl_ (new NodeImpl<std::decay_t<T>>{std::forward<T> (t)})
+{}
+
+class Nterm
+{
+public:
+  Nterm (std::string form,
+         Node child0 = Node (), Node child1 = Node (), Node child2 = Node ())
+    : form_ (std::move (form))
+  {
+    children_[0] = child0;
+    children_[1] = child1;
+    children_[2] = child2;
+  }
+
+  friend std::ostream& operator<< (std::ostream& o, const Nterm& t)
+  {
+    o << t.form_;
+    if (t.children_[0])
+      {
+        o << '(' << t.children_[0];
+        if (t.children_[1])
+          o << ", " << t.children_[1];
+        if (t.children_[2])
+          o << ", " << t.children_[2];
+        o << ')';
+      }
+    return o;
+  }
+
+private:
+  std::string form_;
+  Node children_[3];
+};
+
+
+
+class Term
+{
+public:
+  Term (std::string text)
+    : text_ (std::move (text))
+  {}
+
+  friend std::ostream& operator<< (std::ostream& o, const Term& t)
+  {
+    return o << t.text_;
+  }
+
+private:
+  std::string text_;
+};
+
+#ifdef TEST
+int main ()
+{
+  Node n0;
+  std::cout << n0 << '\n';
+
+  Node n;
+  n = n0;
+  std::cout << n0 << '\n';
+
+  Term t1 = Term ("T");
+  std::cout << t1 << '\n';
+
+  n = t1;
+  std::cout << n << '\n';
+  std::cout << Nterm ("+", t1, t1) << '\n';
+
+  auto n1
+    = Nterm ("<OR>",
+             Nterm ("<declare>", Term ("T"), Term ("x")),
+             Nterm ("<cast>", Term ("x"), Term ("T")));
+  std::cout << n1 << '\n';
+
+  n = n1;
+  std::cout << n1 << '\n';
+}
+#endif
@@ -0,0 +1,50 @@
+#! /bin/sh
+
+# Copyright (C) 2020-2022, 2025-2026 Free Software Foundation, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+cat >input <<EOF
+z + q;
+
+T x;
+
+T x = y;
+
+x = y;
+EOF
+run 0 "\
+1.0-5: +(z, q)
+3.0-3: <declare>(T, x)
+5.0-7: <init-declare>(T, x, y)
+7.0-5: =(x, y)"
+
+cat >input <<EOF
+T (x) + y;
+
+T (x);
+
+T (y) = z + q;
+
+T (y y) = z + q;
+
+z + q;
+EOF
+run 0 "\
+1.0-9: +(<cast>(x, T), y)
+3.0-5: <OR>(<declare>(T, x), <cast>(x, T))
+5.0-13: <OR>(<init-declare>(T, y, +(z, q)), =(<cast>(y, T), +(z, q)))
+7.0-15: <error>
+9.0-5: +(z, q)
+err: 7.5: syntax error on token identifier (expected = or + or ))"
@@ -0,0 +1,257 @@
+/*                                                       -*- C++ -*-
+  Copyright (C) 2020-2022, 2025-2026 Free Software Foundation, Inc.
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+/* Simplified C++ Type and Expression Grammar.
+   Written by Paul Hilfinger for Bison's test suite.  */
+
+%require "3.8"
+%glr-parser
+%skeleton "glr2.cc"
+%define parse.assert
+%define api.token.constructor
+%header
+%locations
+%debug
+
+// Custom error messages.
+%define parse.error custom
+
+%code requires
+{
+  #include "ast.hh"
+}
+
+%define api.value.type variant
+
+%code
+{
+  #include <cassert>
+  #include <cctype>
+  #include <fstream>
+  #include <cstring>
+
+  // Merge two semantic values.
+  static Node
+  stmt_merge (const Node& x0, const Node& x1);
+
+  // Fetch a token.
+  static yy::parser::symbol_type
+  yylex ();
+}
+
+%expect-rr 1
+
+%type <Node> TYPENAME ID stmt expr decl declarator
+%printer { yyo << $$; } <Node>
+
+%token
+  TYPENAME  "typename"
+  ID        "identifier"
+  SEMICOLON ";"
+  EQUAL     "="
+  PLUS      "+"
+  LPAREN    "("
+  RPAREN    ")"
+
+%right "="
+%left "+"
+
+%%
+
+prog : %empty
+     | prog stmt   { std::cout << @2 << ": " << $2 << '\n'; }
+     ;
+
+stmt : expr ";"  %merge <stmt_merge>   { $$ = $1; }
+     | decl      %merge <stmt_merge>
+     | error ";"                       { $$ = Nterm ("<error>"); }
+     ;
+
+expr : ID
+     | TYPENAME "(" expr ")"  { $$ = Nterm ("<cast>", $3, $1); }
+     | expr "+" expr          { $$ = Nterm ("+", $1, $3); }
+     | expr "=" expr          { $$ = Nterm ("=", $1, $3); }
+     ;
+
+decl : TYPENAME declarator ";"
+                        { $$ = Nterm ("<declare>", $1, $2); }
+     | TYPENAME declarator "=" expr ";"
+                        { $$ = Nterm ("<init-declare>", $1, $2, $4); }
+     ;
+
+declarator
+     : ID
+     | "(" declarator ")" { $$ = $2; }
+     ;
+
+%%
+std::istream* input = nullptr;
+yy::parser::location_type loc;
+
+
+/*---------.
+| Parser.  |
+`---------*/
+
+// Generate a custom error message.
+void
+yy::parser::report_syntax_error (const context& ctx) const
+{
+  std::cerr << ctx.location () << ": syntax error";
+  if (!ctx.lookahead ().empty ())
+    std::cerr << " on token " << ctx.lookahead ().name ();
+  {
+    enum { TOKENMAX = 10 };
+    symbol_kind_type expected[TOKENMAX];
+    int n = ctx.expected_tokens (expected, TOKENMAX);
+    if (0 < n)
+      {
+        for (int i = 0; i < n; ++i)
+          std::cerr << (i == 0 ? " (expected " : " or ")
+                    << symbol_name (expected[i]);
+        std::cerr << ')';
+      }
+  }
+  std::cerr << '\n';
+}
+
+// Report the error to the user.
+void
+yy::parser::error (const location_type& l, const std::string& m)
+{
+  std::cerr << l << ": " << m << '\n';
+}
+
+// Fetch the next token.
+static yy::parser::symbol_type
+yylex ()
+{
+  while (true)
+    {
+      loc.step ();
+      loc += 1;
+      assert (!input->eof ());
+      switch (int c = input->get ())
+        {
+        case EOF:
+          return yy::parser::make_YYEOF (loc);
+        case '\t':
+          loc.end.column = (loc.end.column + 7) & ~7;
+          loc.step ();
+          break;
+        case ' ': case '\f':
+          loc.step ();
+          break;
+        case '\n':
+          loc.lines (1);
+          loc.end.column = 0;
+          loc.step ();
+          break;
+        case '+':
+          return yy::parser::make_PLUS (loc);
+        case '=':
+          return yy::parser::make_EQUAL (loc);
+        case '(':
+          return yy::parser::make_LPAREN (loc);
+        case ')':
+          return yy::parser::make_RPAREN (loc);
+        case ';':
+          return yy::parser::make_SEMICOLON (loc);
+        default:
+          if (isalpha (c))
+            {
+              std::string form;
+              do
+                {
+                  form += static_cast<char> (c);
+                  loc += 1;
+                  c = input->get ();
+                }
+              while (isalnum (c) || c == '_');
+              input->unget ();
+              loc -= 1;
+              if (isupper (static_cast <unsigned char> (form[0])))
+                return yy::parser::make_TYPENAME (Term (form), loc);
+              else
+                return yy::parser::make_ID (Term (form), loc);
+            }
+          else
+            {
+              auto msg = "invalid character: " + std::string(1, static_cast<char> (c));
+              throw yy::parser::syntax_error (loc, msg);
+            }
+        }
+    }
+}
+
+// Merge two semantic values as an AST including both alternatives.
+static Node
+stmt_merge (const Node& x0, const Node& x1)
+{
+  return Nterm ("<OR>", x0, x1);
+}
+
+
+/*-------.
+| Main.  |
+`-------*/
+
+// Parse `file` using parser `parse`.
+int
+process (yy::parser& parse, const std::string& file)
+{
+  bool is_stdin = file == "-" || file.empty ();
+  if (is_stdin)
+    input = &std::cin;
+  else
+    input = new std::ifstream (file.c_str ());
+  loc.initialize (nullptr, 1, 0);
+  int status = parse ();
+  if (!is_stdin)
+    delete input;
+  return status;
+}
+
+int
+main (int argc, char **argv)
+{
+  yy::parser parse;
+
+  if (getenv ("YYDEBUG"))
+    parse.set_debug_level (1);
+
+  bool ran = false;
+  for (int i = 1; i < argc; ++i)
+    // Enable parse traces on option -p.
+    if (strcmp (argv[i], "-p") == 0)
+      parse.set_debug_level (1);
+    else
+      {
+        int status = process (parse, argv[i]);
+        ran = true;
+        if (!status)
+          return status;
+      }
+
+  if (!ran)
+    {
+      int status = process (parse, "");
+      if (!status)
+        return status;
+    }
+  return 0;
+}
@@ -0,0 +1,52 @@
+## Copyright (C) 2020-2022, 2025-2026 Free Software Foundation, Inc.
+##
+## This program is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+glrxxdir = $(docdir)/%D%
+
+## ----------- ##
+## c++-types.  ##
+## ----------- ##
+
+%D%/c++-types.stamp: $(dependencies)
+$(nodist_%C%_c___types_SOURCES): %D%/c++-types.stamp
+	@test -f $@ || rm -f %D%/c++-types.stamp
+	@test -f $@ || $(MAKE) $(AM_MAKEFLAGS) %D%/c++-types.stamp
+CLEANFILES +=					\
+  $(nodist_%C%_c___types_SOURCES)		\
+  %D%/c++-types.stamp				\
+  %D%/c++-types.output				\
+  %D%/location.hh
+CLEANDIRS += %D%/*.dSYM
+
+## -------------------- ##
+## Building & testing.  ##
+## -------------------- ##
+
+# Avoid using BUILT_SOURCES which is too global.
+$(%C%_c___types_OBJECTS): $(cxx_types_sources_generated)
+
+if ENABLE_CXX14
+  check_PROGRAMS += %D%/c++-types
+  dist_%C%_c___types_SOURCES =			\
+    %D%/ast.hh
+  nodist_%C%_c___types_SOURCES =		\
+    %D%/c++-types.cc				\
+    %D%/c++-types.hh
+  # Don't use gnulib's system headers.
+  %C%_c___types_CPPFLAGS = -I$(top_srcdir)/%D% -I$(top_builddir)/%D%
+  %C%_c___types_CXXFLAGS = $(CXX14_CXXFLAGS) $(WARN_CXXFLAGS_TEST)
+  TESTS += %D%/c++-types.test
+endif ENABLE_CXX14
+EXTRA_DIST += %D%/c++-types.yy %D%/c++-types.test
@@ -1,4 +1,4 @@
-## Copyright (C) 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
 ## it under the terms of the GNU General Public License as published by
@@ -11,10 +11,11 @@
 ## GNU General Public License for more details.
 ##
 ## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+## along with this program.  If not, see <https://www.gnu.org/licenses/>.

 cxxdir = $(docdir)/%D%
 include %D%/calc++/local.mk
+include %D%/glr/local.mk

 ## -------- ##
 ## Simple.  ##
@@ -29,7 +30,7 @@ simple_extracted = %D%/simple.yy
 simple_sources = $(simple_extracted)
 extracted += $(simple_extracted)

-if ENABLE_CXX14
+if ENABLE_CXX11
  check_PROGRAMS += %D%/simple
  nodist_%C%_simple_SOURCES = $(simple_sources)

@@ -1,6 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2022, 2025-2026 Free Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -13,7 +13,7 @@
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.

 : >input
 run 0 "{I have numbers for you., 1, 2, 3, And that's all!}" 4
--- a/Show More
+++ b/Show More
@@ -1 +1 @@
 .6.1
 .8.2