version 3.7.5

* NEWS: Record release date.
tables: fix handling for useless tokens
2026-08-09 02:35:15 +00:00 · 2021-01-24 08:30:41 +01:00 · 2021-01-24 08:28:45 +01:00 · 2021-01-24 08:24:56 +01:00 · 2021-01-23 15:08:48 +01:00 · 2021-01-23 15:02:49 +01:00
251 changed files with 5548 additions and 1870 deletions
@@ -1 +1 @@
-3.6.4
+3.7.4
@@ -50,6 +50,7 @@ jobs:
        - 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
@@ -119,6 +120,8 @@ jobs:
        - CXX='clang++-10 -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
@@ -127,7 +130,7 @@ 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:
@@ -24,7 +24,7 @@ and nasty bugs.

 -----

-Copyright (C) 1998-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 1998-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -26733,7 +26733,7 @@

 	-----

-	Copyright (C) 1987-1988, 1991-2015, 2018-2020 Free Software
+	Copyright (C) 1987-1988, 1991-2015, 2018-2021 Free Software
 	Foundation, Inc.

 	Copying and distribution of this file, with or without
@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.

-# Copyright (C) 2001-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2001-2015, 2018-2021 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
@@ -133,9 +133,10 @@ gen-ChangeLog:
 	$(CC) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -o $@ -E $<

 .PHONY: codespell
+CODESPELL = codespell
 codespell:
 	$(AM_V_GEN) cd $(srcdir) \
-	&& codespell \
+	&& $(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)
@@ -1,6 +1,108 @@
 GNU Bison NEWS

-* Noteworthy changes in release 3.6.90 (2020-07-04) [beta]
+* Noteworthy changes in release 3.7.5 (2021-01-24) [stable]
+
+** Bug fixes
+
+*** Counterexample Generation
+
+  In some cases counterexample generation could crash.  This is fixed.
+
+*** Fix Table Generation
+
+  In some very rare conditions, when there are many useless tokens, it was
+  possible to generate incorrect parsers.
+
+*** GLR parsers now support %merge together with api.value.type=union.
+
+*** C++ parsers use noexcept in more places.
+
+*** Generated parsers avoid some warnings about signedness issues.
+
+*** C-language parsers now avoid warnings from pedantic clang.
+
+*** C-language parsers now work around quirks of HP-UX 11.23 (2003).
+
+
+* Noteworthy changes in release 3.7.4 (2020-11-14) [stable]
+
+** Bug fixes
+
+*** Bug fixes in yacc.c
+
+  In Yacc mode, all the tokens are defined twice: once as an enum, and then
+  as a macro.  YYEMPTY was missing its macro.
+
+*** Bug fixes in lalr1.cc
+
+  The lalr1.cc skeleton used to emit internal assertions (using YY_ASSERT)
+  even when the `parse.assert` %define variable is not enabled.  It no
+  longer does.
+
+  The private internal macro YY_ASSERT now obeys the `api.prefix` %define
+  variable.
+
+  When there is a very large number of tokens, some assertions could be long
+  enough to hit arbitrary limits in Visual C++.  They have been rewritten to
+  work around this limitation.
+
+** Changes
+
+  The YYBISON macro in generated "regular C parsers" (from the "yacc.c"
+  skeleton) used to be defined to 1.  It is now defined to the version of
+  Bison as an integer (e.g., 30704 for version 3.7.4).
+
+* Noteworthy changes in release 3.7.3 (2020-10-13) [stable]
+
+** Bug fixes
+
+  Fix concurrent build issues.
+
+  The bison executable is no longer linked uselessly against libreadline.
+
+  Fix incorrect use of yytname in glr.cc.
+
+* Noteworthy changes in release 3.7.2 (2020-09-05) [stable]
+
+  This release of Bison fixes all known bugs reported for Bison in MITRE's
+  Common Vulnerabilities and Exposures (CVE) system.  These vulnerabilities
+  are only about bison-the-program itself, not the generated code.
+
+  Although these bugs are typically irrelevant to how Bison is used, they
+  are worth fixing if only to give users peace of mind.
+
+  There is no known vulnerability in the generated parsers.
+
+** Bug fixes
+
+  Fix concurrent build issues (introduced in Bison 3.5).
+
+  Push parsers always use YYMALLOC/YYFREE (no direct calls to malloc/free).
+
+  Fix portability issues of the test suite, and of bison itself.
+
+  Some unlikely crashes found by fuzzing have been fixed.  This is only
+  about bison itself, not the generated parsers.
+
+
+* Noteworthy changes in release 3.7.1 (2020-08-02) [stable]
+
+** Bug fixes
+
+  Crash when a token alias contains a NUL byte.
+
+  Portability issues with libtextstyle.
+
+  Portability issues of Bison itself with MSVC.
+
+** Changes
+
+  Improvements and fixes in the documentation.
+
+  More precise location about symbol type redefinitions.
+
+
+* Noteworthy changes in release 3.7 (2020-07-23) [stable]

 ** Deprecated features

@@ -18,28 +120,115 @@ GNU Bison NEWS

  Contributed by Vincent Imbimbo.

-  When given `--report=counterexamples` or `-Wcounterexamples`, bison will
-  now output counterexamples for conflicts in the grammar.  These are
-  strings in the grammar which can be parsed in two ways due to the
-  conflict.  For example:
+  When given `-Wcounterexamples`/`-Wcex`, bison will now output
+  counterexamples for conflicts.

-    Example              exp '+' exp • '/' exp
-    First derivation     exp ::=[ exp ::=[ exp '+' exp • ] '/' exp ]
-    Second derivation    exp ::=[ exp '+' exp ::=[ exp • '/' exp ] ]
+**** Unifying Counterexamples

-  This is a shift/reduce conflict caused by none of the operators having
-  precedence, so the example can be parsed in the two ways shown.   When
-  bison cannot find an example that can be derived in two ways, it instead
-  generates two examples that are the same up until the dot:
+  Unifying counterexamples are strings which can be parsed in two ways due
+  to the conflict.  For example on a grammar that contains the usual
+  "dangling else" ambiguity:

-    First example        expr • ID $end
-    First derivation     $accept ::=[ s ::=[ a ::=[ expr • ] ID ] $end ]
-    Second example       expr • ID ',' ID $end
-    Second derivation    $accept ::=[ s ::=[ a ::=[ expr ::=[ expr • ID ',' ] ] ID ] $end ]
+    $ bison else.y
+    else.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
+    else.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
+
+    $ bison else.y -Wcex
+    else.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
+    else.y: warning: shift/reduce conflict on token "else" [-Wcounterexamples]
+      Example: "if" exp "then" "if" exp "then" exp • "else" exp
+      Shift derivation
+        exp
+        ↳ "if" exp "then" exp
+                          ↳ "if" exp "then" exp • "else" exp
+      Example: "if" exp "then" "if" exp "then" exp • "else" exp
+      Reduce derivation
+        exp
+        ↳ "if" exp "then" exp                     "else" exp
+                          ↳ "if" exp "then" exp •
+
+  When text styling is enabled, colors are used in the examples and the
+  derivations to highlight the structure of both analyses.  In this case,
+
+    "if" exp "then" [ "if" exp "then" exp • ] "else" exp
+
+  vs.
+
+    "if" exp "then" [ "if" exp "then" exp • "else" exp ]
+
+
+  The counterexamples are "focused", in two different ways.  First, they do
+  not clutter the output with all the derivations from the start symbol,
+  rather they start on the "conflicted nonterminal". They go straight to the
+  point.  Second, they don't "expand" nonterminal symbols uselessly.
+
+**** Nonunifying Counterexamples
+
+  In the case of the dangling else, Bison found an example that can be
+  parsed in two ways (therefore proving that the grammar is ambiguous).
+  When it cannot find such an example, it instead generates two examples
+  that are the same up until the dot:
+
+    $ bison foo.y
+    foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
+    foo.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
+    foo.y:4.4-7: warning: rule useless in parser due to conflicts [-Wother]
+        4 | a: expr
+          |    ^~~~
+
+    $ bison -Wcex foo.y
+    foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
+    foo.y: warning: shift/reduce conflict on token ID [-Wcounterexamples]
+      First example: expr • ID ',' ID $end
+      Shift derivation
+        $accept
+        ↳ s                      $end
+          ↳ a                 ID
+            ↳ expr
+              ↳ expr • ID ','
+      Second example: expr • ID $end
+      Reduce derivation
+        $accept
+        ↳ s             $end
+          ↳ a        ID
+            ↳ expr •
+    foo.y:4.4-7: warning: rule useless in parser due to conflicts [-Wother]
+        4 | a: expr
+          |    ^~~~

  In these cases, the parser usually doesn't have enough lookahead to
  differentiate the two given examples.

+**** Reports
+
+  Counterexamples are also included in the report when given
+  `--report=counterexamples`/`-rcex` (or `--report=all`), with more
+  technical details:
+
+    State 7
+
+      1 exp: "if" exp "then" exp •  [$end, "then", "else"]
+      2    | "if" exp "then" exp • "else" exp
+
+      "else"  shift, and go to state 8
+
+      "else"    [reduce using rule 1 (exp)]
+      $default  reduce using rule 1 (exp)
+
+      shift/reduce conflict on token "else":
+          1 exp: "if" exp "then" exp •
+          2 exp: "if" exp "then" exp • "else" exp
+        Example: "if" exp "then" "if" exp "then" exp • "else" exp
+        Shift derivation
+          exp
+          ↳ "if" exp "then" exp
+                            ↳ "if" exp "then" exp • "else" exp
+        Example: "if" exp "then" "if" exp "then" exp • "else" exp
+        Reduce derivation
+          exp
+          ↳ "if" exp "then" exp                     "else" exp
+                            ↳ "if" exp "then" exp •
+
 *** File prefix mapping

  Contributed by Joshua Watt.
@@ -52,6 +241,11 @@ GNU Bison NEWS

 ** Changes

+*** Diagnostics
+
+  When text styling is enabled and the terminal supports it, the warnings
+  now include hyperlinks to the documentation.
+
 *** Relocatable installation

  When installed to be relocatable (via `configure --enable-relocatable`),
@@ -92,6 +286,18 @@ GNU Bison NEWS
  Now the parser state can be examined when parsing is finished.  The parser
  state is reset when starting a new parse.

+** Documentation
+
+*** Examples
+
+  The bistromathic demonstrates %param and how to quote sources in the error
+  messages:
+
+    > 123 456
+    1.5-7: syntax error: expected end of file or + or - or * or / or ^ before number
+        1 | 123 456
+          |     ^~~
+
 ** Bug fixes

 *** Include the generated header (yacc.c)
@@ -433,7 +639,8 @@ GNU Bison NEWS
  \005) with incorrect styling.  Fixes for similar issues with unexpectedly
  short lines (e.g., the file was changed between parsing and diagnosing).

-  Several unlikely crashes found by fuzzing have been fixed.
+  Some unlikely crashes found by fuzzing have been fixed.  This is only
+  about bison itself, not the generated parsers.


 * Noteworthy changes in release 3.5.2 (2020-02-13) [stable]
@@ -4357,7 +4564,7 @@ LocalWords:  yysymbol yytnamerr yyreport ctx ARGMAX yysyntax stderr LPAREN
 LocalWords:  symrec yypcontext TOKENMAX yyexpected YYEMPTY yypstate YYEOF
 LocalWords:  autocompletion bistromathic submessages Cayuela lexcalc hoc
 LocalWords:  yytoken YYUNDEF YYerror basename Automake's UTF ifdef ffile
-LocalWords:  gotos readline Imbimbo Wcounterexamples
+LocalWords:  gotos readline Imbimbo Wcounterexamples Wcex Nonunifying rcex

 Local Variables:
 ispell-dictionary: "american"
@@ -4365,7 +4572,7 @@ mode: outline
 fill-column: 76
 End:

-Copyright (C) 1995-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 1995-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -36,7 +36,7 @@ to the bison package.

 -----

-Copyright (C) 2002, 2005, 2009-2015, 2018-2020 Free Software Foundation,
+Copyright (C) 2002, 2005, 2009-2015, 2018-2021 Free Software Foundation,
 Inc.

 This file is part of Bison, the GNU Compiler Compiler.
@@ -27,7 +27,7 @@ Bison from the git repo.  Roughly, run:
 then proceed with the usual `configure && make` steps.

 ## Build from tarball
-See the [INSTALL file](INSTALL] for generic compilation and installation
+See the [INSTALL file](INSTALL) for generic compilation and installation
 instructions.

 Bison requires GNU m4 1.4.6 or later.  See
@@ -42,9 +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.
@@ -61,6 +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.

@@ -111,7 +120,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018-2020 Free
+Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018-2021 Free
 Software Foundation, Inc.

 This file is part of GNU bison, the GNU Compiler Compiler.
@@ -12,7 +12,7 @@ the problems you encounter.

 -----

-Copyright (C) 2002, 2004, 2009-2015, 2018-2020 Free Software Foundation,
+Copyright (C) 2002, 2004, 2009-2015, 2018-2021 Free Software Foundation,
 Inc.

 This file is part of GNU Bison.
@@ -211,6 +211,8 @@ 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",
@@ -442,7 +444,7 @@ 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

@@ -567,7 +569,7 @@ bootstrapped.

 <!--

-Copyright (C) 2002-2005, 2007-2015, 2018-2020 Free Software Foundation,
+Copyright (C) 2002-2005, 2007-2015, 2018-2021 Free Software Foundation,
 Inc.

 This file is part of GNU Bison.
@@ -45,6 +45,7 @@ Csaba Raduly              [email protected]
 Dagobert Michelsen        [email protected]
 Daniel Frużyński          [email protected]
 Daniel Galloway           [email protected]
+Daniela Becker            [email protected]
 Daniel Hagerty            [email protected]
 David Barto               [email protected]
 David J. MacKenzie        [email protected]
@@ -105,9 +106,11 @@ 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]
@@ -184,6 +187,7 @@ 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]
@@ -233,7 +237,7 @@ End:

 -----

-Copyright (C) 2000-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2000-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -1,4 +1,12 @@
-* Bison 3.7
+* Soon
+** gnulib
+Bruno notes:
+
+> I haven't looked deeply, but it strikes me that gnulib/lib/bitset/array.c
+> does not make use of the 'ffsl' function, nor or the 'integer_length_l'
+> function. Maybe because in Bison, all bitsets are so dense that it does
+> not give a performance advantage?
+
 ** Cex
 *** Improve gnulib
 Don't do this (counterexample.c):
@@ -36,8 +44,6 @@ Unless we play it dumb (little structure).
 - How about not evaluating incomplete lines when the text is not finished
  (as shells do).

- Caret diagnostics
-
 ** Questions
 *** Java
 - Should i18n be part of the Lexer?  Currently it's a static method of
@@ -50,13 +56,6 @@ Unless we play it dumb (little structure).

 - 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

@@ -69,7 +68,7 @@ Stop hard-coding "Calc".  Adjust local.at (look for FIXME).

 ** 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.
+Autoconf does.  It would have caught over-quotation issues.

 ** doc
 I feel it's ugly to use the GNU style to declare functions in the doc.  It
@@ -90,7 +89,7 @@ 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:

@@ -204,18 +203,282 @@ 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.

+* 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.
+
+** Rename the D example
+Move the current content of examples/d into examples/d/simple.
+
+** Create a second example
+Duplicate examples/d/simple into examples/d/calc.
+
+** Add location tracking to d/calc
+Look at the examples in the other languages to see how to do that.
+
+** yysymbol_name
+The SymbolKind is an enum.  For a given SymbolKind we want to get its string
+representation.  Currently it's a separate table in the parser that does
+that:
+
+  /* Symbol kinds.  */
+  public enum SymbolKind
+  {
+    S_YYEMPTY = -2,  /* No symbol.  */
+    S_YYEOF = 0,                   /* "end of file"  */
+    S_YYerror = 1,                 /* error  */
+    S_YYUNDEF = 2,                 /* "invalid token"  */
+    S_EQ = 3,                      /* "="  */
+    ...
+    S_input = 14,                  /* input  */
+    S_line = 15,                   /* line  */
+    S_exp = 16,                    /* exp  */
+  };
+
+  ...
+
+  /* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
+     First, the terminals, then, starting at \a yyntokens_, nonterminals.  */
+  private static immutable string[] yytname_ =
+  [
+  "\"end of file\"", "error", "\"invalid token\"", "\"=\"", "\"+\"",
+  "\"-\"", "\"*\"", "\"/\"", "\"(\"", "\")\"", "\"end of line\"",
+  "\"number\"", "UNARY", "$accept", "input", "line", "exp", null
+  ];
+
+  ...
+
+So to get a symbol kind, one runs `yytname_[yykind]`.
+
+Is there a way to attach this conversion to string to SymbolKind?  In Java
+for instance, we have:
+
+  public enum SymbolKind
+  {
+    S_YYEOF(0),                    /* "end of file"  */
+    S_YYerror(1),                  /* error  */
+    S_YYUNDEF(2),                  /* "invalid token"  */
+    ...
+    S_input(16),                   /* input  */
+    S_line(17),                    /* line  */
+    S_exp(18);                     /* exp  */
+
+    private final int yycode_;
+
+    SymbolKind (int n) {
+      this.yycode_ = n;
+    }
+    ...
+    /* YYNAMES_[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
+       First, the terminals, then, starting at \a YYNTOKENS_, nonterminals.  */
+    private static final String[] yynames_ = yynames_init();
+    private static final String[] yynames_init()
+    {
+      return new String[]
+      {
+        i18n("end of file"), i18n("error"), i18n("invalid token"), "!", "+", "-", "*",
+        "/", "^", "(", ")", "=", i18n("end of line"), i18n("number"), "NEG",
+        "$accept", "input", "line", "exp", null
+      };
+    }
+
+    /* The user-facing name of this symbol.  */
+    public final String getName() {
+      return yynames_[yycode_];
+    }
+  };
+
+which allows to write more naturally `yykind.getName()` rather than
+`yytname_[yykind]`.  Is there something comparable in (idiomatic) D?
+
+** Change the return value of yylex
+Historically people were allowed to return any int from the scanner (which
+is convenient and allows `return '+'` from the scanner).  Akim tends to see
+this as an error, we should restrict the return values to TokenKind (not to
+be confused with SymbolKind).
+
+In the case of D, without the history, we have the choice to support or not
+`int`.  If we want to _keep_ `int`, is there a way, say via introspection,
+to support both signatures of yylex?  If we don't keep `int`, just move to
+TokenKind.
+
+** Documentation
+Write documentation about D support in doc/bison.texi.  Imitate the Java
+documentation.  You should be more succinct IMHO.
+
+** Complete Symbols
+The current interface from the scanner to the parser is somewhat clumsy: the
+token kind is returned by yylex, but the value and location are stored in
+the scanner.  This reflects the fact that the implementation of the parser
+uses three variables to deal with each parsed symbol: its kind, its value,
+its location.
+
+So today the scanner of examples/d/calc.d (no locations) looks like:
+
+    if (input.front.isNumber)
+      {
+        import std.conv : parse;
+        semanticVal_.ival = input.parse!int;
+        return TokenKind.NUM;
+      }
+
+and the generated parser:
+
+    /* Read a lookahead token.  */
+    if (yychar == TokenKind.YYEMPTY)
+    {
+      yychar = yylex ();
+      yylval = yylexer.semanticVal;
+    }
+
+The parser class should feature a `Symbol` type which binds together kind,
+value and location, and the scanner should be able to return an instance of
+that type.  Something like
+
+    if (input.front.isNumber)
+      {
+        import std.conv : parse;
+        return parser.Symbol (TokenKind.NUM, input.parse!int);
+      }
+
+** Token Constructors
+In the previous example it is possible to mix incorrectly kinds and values,
+and for instance:
+
+        return parser.Symbol (TokenKind.NUM, "Hello, World!\n");
+
+attaches a string value to NUM kind (wrong, of course).  When
+api.token.constructor is set, in C++, Bison generated "token constructors":
+parser.make_NUM. parser.make_PLUS, parser.make_STRING, etc.  The previous
+example becomes
+
+        return parser.make_NUM ("Hello, World!\n");
+
+which would easily be caught by the type checker.
+
+** Lookahead Correction
+Add support for LAC to the D skeleton.  It should not be too hard: look how
+this is done in lalr1.cc, and mock it.
+
+** Push Parser
+Add support for push parser.  Do not start a nice skeleton, just enhance the
+current one to support push parsers.  This is going to be a tougher nut to
+crack.
+
+First, you need to understand well how the push parser is expected to work.
+To this end:
+- read the doc
+- look at examples/c/pushcalc
+- create an example of a Java push parser.
+- have a look at the generated parser in Java, which has the advantage of
+  being already based on a parser object, instead of just a function.
+
+The C case is harder to read, but it may help too.  Keep in mind that
+because there's no object to maintain state, the C push parser uses some
+struct (yypstate) to preserve this state.  We don't need this in D, the
+parser object will suffice.
+
+I think working directly on the skeleton to add push-parser support is not
+the simplest path.  I suggest that you (1) transform a generated parser into
+a push parser by hand, and then (2) transform lalr1.d to generate such a
+parser.
+
+Use `git commit` frequently to make sure you keep track of your progress.
+
+*** (1.a) Prepare pull parser by hand
+Copy again one of the D examples into say examples/d/pushcalc.  Also
+check-in the generated parser to facilitate experimentation.
+
+- find local variables of yyparse should become members of the parser object
+  (so that we preserve state from one call to the next).
+
+- do it in your generated D parser.  We don't need an equivalent for
+  yypstate, because we already have it: that the parser object itself.
+
+- have your *pull*-parser (i.e., the good old yy::parser::parse()) work
+  properly this way.  Write and run tests.  That's one of the reasons I
+  suggest using examples/d/calc as a starting point: it already has tests,
+  you can/should add more.
+
+At this point you have a pull-parser which you prepared to turn into a
+push-parser.
+
+*** (1.b) Turn pull parser into push parser by hand
+
+- look again at how push parsers are implemented in Java/C to see what needs
+  to change in yyparse so that the control is inverted: parse() will
+  be *given* the tokens, instead of having to call yylex itself.  When I say
+  "look at C", I think your best option are (i) yacc.c (look for b4_push_if)
+  and (ii) examples/c/pushcalc.
+
+- rename parse() as push_parse(Symbol yyla) (or push_parse(TokenKind, Value,
+  Location)) that takes the symbol as argument.  That's the push parser we
+  are looking for.
+
+- define a new parse() function which has the same signature as the usual
+  pull-parser, that repeatedly calls the push_parse function.  Something
+  like this:
+
+int parse ()
+{
+ int status = 0;
+ do {
+  status = this->push_parse (yylex());
+ } while (status == YYPUSH_MORE);
+ return status;
+}
+
+- show me that parser, so that we can validate the approach.
+
+*** (2) Port that into the skeleton
+- once we agree on the API of the push parser, implement it into lalr1.d.
+  You will probaby need help on this regard, but imitation, again, should
+  help.
+
+- have example/d/pushcalc work properly and pass tests
+
+- add tests in the "real" test suite.  Do that in tests/calc.at.  I can
+  help.
+
+- document
+
+** 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
@@ -233,7 +496,7 @@ 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)
@@ -303,7 +566,7 @@ 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?
@@ -581,15 +844,40 @@ 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 semanticVal ival yychar yylval yylexer Tolmer hoc
+# LocalWords:  Sobisch YYPTRDIFF ptrdiff Autotest YYPRINT 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
+Copyright (C) 2001-2004, 2006, 2008-2015, 2018-2021 Free Software
 Foundation, Inc.

 This file is part of Bison, the GNU Compiler Compiler.
@@ -1,6 +1,6 @@
 # Bootstrap configuration.

-# Copyright (C) 2006-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2006-2015, 2018-2021 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
@@ -44,7 +44,9 @@ gnulib_modules='
  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
  unicodeio unistd unistd-safer unlink unlocked-io
  update-copyright unsetenv verify
@@ -1,4 +1,4 @@
-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2021 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 +1,4 @@
-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2021 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
@@ -2,7 +2,7 @@

 # Generate a release announcement message.

-# Copyright (C) 2007-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2021 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 +1,4 @@
-## Copyright (C) 2000-2015, 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2000-2015, 2018-2021 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
@@ -3,7 +3,7 @@
 # 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, 2018-2021 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
@@ -2,7 +2,7 @@

 # 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, 2018-2021 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
@@ -2,7 +2,7 @@

 # Update expectations in an Autotest test suite.

-# Copyright (C) 2019-2020 Free Software Foundation, Inc.
+# Copyright (C) 2019-2021 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 +1,5 @@
 ## Customize maint.mk                           -*- makefile -*-
-## Copyright (C) 2008-2015, 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2008-2015, 2018-2021 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
@@ -126,7 +126,7 @@ _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]$$' > /dev/null; then	\
@@ -156,6 +156,8 @@ exclude = \
 $(call exclude,                                                                 \
  bindtextdomain=^lib/main.c$$                                                  \
  cast_of_argument_to_free=^src/muscle-tab.c$$                                  \
+  copyright_check=gnulib/lib/version-etc.c$$                                    \
+  error_message_uppercase=etc/bench.pl.in$$                                     \
  po_check=^tests|(^po/POTFILES.in|.md)$$                                       \
  preprocessor_indentation=^data/|^lib/|^src/parse-gram.[ch]$$                  \
  program_name=^lib/main.c$$                                                    \
@@ -1,6 +1,6 @@
 # Configure template for GNU Bison.                   -*-Autoconf-*-
 #
-# Copyright (C) 2001-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2001-2015, 2018-2021 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
@@ -29,7 +29,7 @@ AC_INIT([GNU Bison],
        [[email protected]],
        [],
        [https://www.gnu.org/software/bison/])
-AC_SUBST([PACKAGE_COPYRIGHT_YEAR], [2020])
+AC_SUBST([PACKAGE_COPYRIGHT_YEAR], [2021])
 AC_DEFINE_UNQUOTED([PACKAGE_COPYRIGHT_YEAR], [$PACKAGE_COPYRIGHT_YEAR],
                   [The copyright year for this package])

@@ -60,6 +60,9 @@ AC_PROG_CXX
 # Gnulib (early checks).
 gl_EARLY

+# We want ostream_printf and hyperlink support.
+gl_LIBTEXTSTYLE_OPTIONAL([0.20.5])
+
 # Gnulib uses '#pragma GCC diagnostic push' to silence some
 # warnings, but older gcc doesn't support this.
 AC_CACHE_CHECK([whether pragma GCC diagnostic push works],
@@ -86,7 +86,7 @@ The macro `b4_symbol(NUM, FIELD)` gives access to the following FIELDS:
 - `has_id`: 0 or 1
  Whether the symbol has an `id`.

- `id`: string
+- `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
@@ -105,9 +105,9 @@ The macro `b4_symbol(NUM, FIELD)` gives access to the following FIELDS:
 - `is_token`: 0 or 1
  Whether this is a terminal symbol.

- `kind_base`: string
+- `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 mapping to its `number`.
+  nonterminal) which is mapped to its `number`.

 - `kind`: string
  Same as `kind_base`, but possibly with a prefix in some languages.  E.g.,
@@ -142,11 +142,17 @@ 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
@@ -187,7 +193,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2002, 2008-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2002, 2008-2015, 2018-2021 Free Software Foundation, Inc.

 This file is part of GNU Bison.

@@ -1,5 +1,5 @@
 /* Default styling rules for Bison when doing terminal output.
-   Copyright (C) 2019-2020 Free Software Foundation, Inc.
+   Copyright (C) 2019-2021 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
@@ -49,6 +49,10 @@
 .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; }
@@ -1,4 +1,4 @@
-## Copyright (C) 2002, 2005-2015, 2018-2020 Free Software Foundation,
+## Copyright (C) 2002, 2005-2015, 2018-2021 Free Software Foundation,
 ## Inc.

 ## This program is free software: you can redistribute it and/or modify
@@ -2,7 +2,7 @@

 # Language-independent M4 Macros for Bison.

-# Copyright (C) 2002, 2004-2015, 2018-2020 Free Software Foundation,
+# Copyright (C) 2002, 2004-2015, 2018-2021 Free Software Foundation,
 # Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -49,7 +49,7 @@ m4_define([m4_shift4], [m4_shift(m4_shift(m4_shift(m4_shift($@))))])
 # 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])
@@ -465,6 +465,19 @@ m4_case([$1],
 # 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.
@@ -475,6 +488,7 @@ m4_define([b4_symbol],
         [id],        [b4_symbol_token_kind([$1])],
         [kind_base], [b4_symbol_kind_base([$1])],
         [kind],      [b4_symbol_kind([$1])],
+         [slot],      [b4_symbol_slot([$1])],
         [_b4_symbol($@)])])


@@ -537,7 +551,7 @@ m4_defn([b4_actions_])[]dnl
        break;
    }dnl
 ],
-[YYUSE (m4_default([$2], [yykind]));])dnl
+[YY_USE (m4_default([$2], [yykind]));])dnl
 m4_popdef([b4_actions_])dnl
 ])

@@ -633,11 +647,11 @@ 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]))])



@@ -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, 2018-2021 Free Software
 # Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -2,7 +2,7 @@

 # C++ skeleton for Bison

-# Copyright (C) 2002-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2021 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
@@ -321,8 +321,9 @@ 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])[);
@@ -339,7 +340,7 @@ m4_define([b4_symbol_type_define],
      }

      /// Destroy contents, and record that is empty.
-      void clear ()
+      void clear () YY_NOEXCEPT
      {]b4_variant_if([[
        // User destructor.
        symbol_kind_type yykind = this->kind ();
@@ -423,7 +424,7 @@ m4_define([b4_symbol_type_define],
      by_kind (kind_type t);

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

      /// Steal the symbol kind from \a that.
      void move (by_kind& that);
@@ -543,7 +544,7 @@ m4_define([b4_public_types_define],
  {}

  ]b4_inline([$1])[void
-  ]b4_parser_class[::by_kind::clear ()
+  ]b4_parser_class[::by_kind::clear () YY_NOEXCEPT
  {
    kind_ = ]b4_symbol(-2, kind)[;
  }
@@ -594,11 +595,12 @@ m4_define([b4_yytranslate_define],
    {
  ]b4_translate[
    };
-    const int code_max_ = ]b4_code_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 <= code_max_)
+    else if (t <= code_max)
      return YY_CAST (symbol_kind_type, translate_table[t]);
    else
      return symbol_kind::]b4_symbol_prefix[YYUNDEF;]])[
@@ -2,7 +2,7 @@

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

-# Copyright (C) 2012-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2012-2015, 2018-2021 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
@@ -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, 2018-2021 Free Software
 # Foundation, Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -2,7 +2,7 @@

 # C M4 Macros for Bison.

-# Copyright (C) 2002, 2004-2015, 2018-2020 Free Software Foundation,
+# Copyright (C) 2002, 2004-2015, 2018-2021 Free Software Foundation,
 # Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -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], [[
@@ -160,11 +160,11 @@ m4_popdef([$1])dnl

 # 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], [  YY_USE ([$1]);])dnl
+b4_locations_if([m4_ifvaln([$2], [  YY_USE ([$2]);])])dnl
+b4_parse_param_for([Decl], [Formal], [  YY_USE (Formal);
 ])dnl
 ])

@@ -242,6 +242,18 @@ 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 \
@@ -366,14 +378,16 @@ dnl use C' _Noreturn in C++, to avoid -Wc11-extensions warnings.
      && ((201103 <= __cplusplus && !(__GNUC__ == 4 && __GNUC_MINOR__ == 7)) \
          || (defined _MSC_VER && 1900 <= _MSC_VER)))
 #  define _Noreturn [[noreturn]]
-# elif (!defined __cplusplus                     \
-        && (201112 <= (defined __STDC_VERSION__ ? __STDC_VERSION__ : 0)  \
-            || 4 < __GNUC__ + (7 <= __GNUC_MINOR__) \
-            || (defined __apple_build_version__ \
-                ? 6000000 <= __apple_build_version__ \
-                : 3 < __clang_major__ + (5 <= __clang_minor__))))
+# elif ((!defined __cplusplus || defined __clang__) \
+        && (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)
@@ -384,9 +398,9 @@ dnl use C' _Noreturn in C++, to avoid -Wc11-extensions warnings.

 ]])[/* 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__
@@ -509,10 +523,11 @@ 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([-2], [id])[ -2
+]m4_join([
 ], b4_symbol_map([b4_token_define]))
-])])
+])


 # b4_token_enum(TOKEN-NUM)
@@ -2,7 +2,7 @@

 # D skeleton dispatching for Bison.

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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
@@ -2,7 +2,7 @@

 # D language support for Bison

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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
@@ -103,12 +103,12 @@ 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[;
+]])


 ## ------------ ##
@@ -1,8 +1,8 @@
-                                                                    -*- C -*-
+#                                                             -*- C -*-

 # GLR skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -145,6 +145,15 @@ 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.  ##
 ## -------------- ##
@@ -188,7 +197,7 @@ b4_glr_cc_if([],
 [b4_defines_if(
 [b4_output_begin([b4_spec_header_file])
 b4_copyright([Skeleton interface for Bison GLR parsers in C],
-             [2002-2015, 2018-2020])[
+             [2002-2015, 2018-2021])[
 ]b4_cpp_guard_open([b4_spec_mapped_header_file])[
 ]b4_shared_declarations[
 ]b4_cpp_guard_close([b4_spec_mapped_header_file])[
@@ -202,7 +211,7 @@ 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, 2018-2021])[
 /* C GLR parser skeleton written by Paul Hilfinger.  */

 ]b4_disclaimer[
@@ -215,7 +224,7 @@ 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([], [[
@@ -333,7 +342,7 @@ 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).  */
+/* YYMAXUTOK -- Last valid token kind.  */
 #define YYMAXUTOK   ]b4_code_max[

 /* YYTRANSLATE(TOKEN-NUM) -- Symbol number corresponding to TOKEN-NUM
@@ -875,7 +884,7 @@ yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* yyvsp,
  yybool yynormal YY_ATTRIBUTE_UNUSED = yystackp->yysplitPoint == YY_NULLPTR;
  int yylow;
 ]b4_parse_param_use([yyvalp], [yylocp])dnl
-[  YYUSE (yyrhslen);
+[  YY_USE (yyrhslen);
 # undef yyerrok
 # define yyerrok (yystackp->yyerrState = 0)
 # undef YYACCEPT
@@ -939,8 +948,8 @@ 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)
    {
@@ -1795,8 +1804,8 @@ 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"));
@@ -2140,7 +2149,7 @@ yypcontext_token (const yyGLRStack *yystackp) YY_ATTRIBUTE_UNUSED;
 static yysymbol_kind_t
 yypcontext_token (const yyGLRStack *yystackp)
 {
-  YYUSE (yystackp);
+  YY_USE (yystackp);
  yysymbol_kind_t yytoken = yychar == ]b4_symbol(-2, id)[ ? ]b4_symbol(-2, kind)[ : YYTRANSLATE (yychar);
  return yytoken;
 }
@@ -2152,7 +2161,7 @@ yypcontext_location (const yyGLRStack *yystackp) YY_ATTRIBUTE_UNUSED;
 static YYLTYPE *
 yypcontext_location (const yyGLRStack *yystackp)
 {
-  YYUSE (yystackp);
+  YY_USE (yystackp);
  return &yylloc;
 }]])],
         [detailed\|verbose],
@@ -2420,7 +2429,7 @@ 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;
@@ -1,6 +1,6 @@
 # C++ GLR skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -144,7 +144,7 @@ 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
@@ -157,11 +157,11 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
                           const semantic_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])[
  }

@@ -172,7 +172,7 @@ m4_pushdef([b4_parse_param], m4_defn([b4_parse_param_orig]))dnl
                           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_ << ')';
@@ -381,7 +381,7 @@ b4_percent_code_get([[requires]])[
 ]b4_defines_if(
 [b4_output_begin([b4_spec_header_file])
 b4_copyright([Skeleton interface for Bison GLR parsers in C++],
-             [2002-2015, 2018-2020])[
+             [2002-2015, 2018-2021])[
 // C++ GLR parser skeleton written by Akim Demaille.

 ]b4_disclaimer[
@@ -2,7 +2,7 @@

 # Java skeleton dispatching for Bison.

-# Copyright (C) 2007, 2009-2015, 2018-2020 Free Software Foundation,
+# Copyright (C) 2007, 2009-2015, 2018-2021 Free Software Foundation,
 # Inc.

 # This program is free software: you can redistribute it and/or modify
@@ -2,7 +2,7 @@

 # Java language support for Bison

-# Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2015, 2018-2021 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
@@ -71,12 +71,12 @@ 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[;
+]])


 ## ------------ ##
@@ -1,6 +1,6 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -160,7 +160,7 @@ m4_ifdef([b4_lex_param], [, ]b4_lex_param))])])


 m4_pushdef([b4_copyright_years],
-           [2002-2015, 2018-2020])
+           [2002-2015, 2018-2021])

 m4_define([b4_parser_class],
          [b4_percent_define_get([[api.parser.class]])])
@@ -271,9 +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
@@ -597,7 +597,7 @@ 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)

@@ -736,7 +736,7 @@ 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
@@ -1,6 +1,6 @@
 # D skeleton for Bison -*- autoconf -*-

-# Copyright (C) 2007-2012, 2019-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2012, 2019-2021 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
@@ -20,7 +20,7 @@ m4_include(b4_skeletonsdir/[d.m4])

 b4_output_begin([b4_parser_file_name])
 b4_copyright([Skeleton implementation for Bison LALR(1) parsers in D],
-             [2007-2012, 2019-2020])[
+             [2007-2012, 2019-2021])[
 ]b4_disclaimer[
 ]b4_percent_define_ifdef([package], [module b4_percent_define_get([package]);
 ])[
@@ -428,8 +428,9 @@ b4_locations_if([, ref ]b4_location_type[ yylocationp])[)
   */
  public bool parse ()
  {
-    /// Lookahead and lookahead in internal form.
+    // Lookahead token kind.
    int yychar = TokenKind.YYEMPTY;
+    // Lookahead symbol kind.
    SymbolKind yytoken = ]b4_symbol(-2, kind)[;

    /* State.  */
@@ -841,11 +842,12 @@ m4_popdef([b4_at_dollar])])dnl
  ]b4_translate[
    @};

-    immutable int code_max_ = ]b4_code_max[;
+    // Last valid token kind.
+    immutable int code_max = ]b4_code_max[;

    if (t <= 0)
      return ]b4_symbol(0, kind)[;
-    else if (t <= code_max_)
+    else if (t <= code_max)
      {
        import std.conv : to;
        return to!SymbolKind (translate_table[t]);
@@ -1,6 +1,6 @@
 # Java skeleton for Bison                           -*- autoconf -*-

-# Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2007-2015, 2018-2021 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
@@ -53,8 +53,9 @@ b4_use_push_for_pull_if([
 # 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.  */
+    /* Lookahead token kind.  */
    int yychar = YYEMPTY_;
+    /* Lookahead symbol kind.  */
    SymbolKind yytoken = null;

    /* State.  */
@@ -77,7 +78,7 @@ m4_define([b4_define_state],[[

 ]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([api.package], [package b4_percent_define_get([api.package]);[
 ]])[
@@ -1078,17 +1079,18 @@ b4_dollar_popdef[]dnl

  /* 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);
  }
 ]],
 [[  {
-    int code_max_ = ]b4_code_max[;
+    // Last valid token kind.
+    int code_max = ]b4_code_max[;
    if (t <= 0)
      return ]b4_symbol(0, kind)[;
-    else if (t <= code_max_)
+    else if (t <= code_max)
      return SymbolKind.get(yytranslate_table_[t]);
    else
      return ]b4_symbol(2, kind)[;
@@ -1,6 +1,6 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -16,13 +16,13 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.

 m4_pushdef([b4_copyright_years],
-           [2002-2015, 2018-2020])
+           [2002-2015, 2018-2021])


 # b4_position_file
 # ----------------
 # Name of the file containing the position class, if we want this file.
-b4_defines_if([b4_required_version_if([302], [],
+b4_defines_if([b4_required_version_if([30200], [],
                                      [m4_define([b4_position_file], [position.hh])])])])


@@ -1,6 +1,6 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -19,7 +19,7 @@
 # b4_stack_file
 # -------------
 # Name of the file containing the stack class, if we want this file.
-b4_defines_if([b4_required_version_if([302], [],
+b4_defines_if([b4_required_version_if([30200], [],
                                      [m4_define([b4_stack_file], [stack.hh])])])


@@ -1,6 +1,6 @@
 # C++ skeleton for Bison

-# Copyright (C) 2002-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2002-2015, 2018-2021 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
@@ -20,6 +20,13 @@
 ## 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 +78,12 @@ 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
-]])
+]])])



@@ -110,8 +117,8 @@ m4_define([b4_value_type_declare],
    template <typename T>
    semantic_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));
    }

@@ -125,7 +132,7 @@ m4_define([b4_value_type_declare],
    /// Destruction, allowed only if empty.
    ~semantic_type () YY_NOEXCEPT
    {]b4_parse_assert_if([
-      YY_ASSERT (!yytypeid_);
+      ]b4_assert[ (!yytypeid_);
    ])[}

 # if 201103L <= YY_CPLUSPLUS
@@ -133,10 +140,10 @@ 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 +151,10 @@ 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 +162,10 @@ 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 +192,10 @@ 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 +203,10 @@ 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 +221,9 @@ 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> ());
    }

@@ -388,11 +395,67 @@ 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], [code])])])])
+# 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_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_token_constructor_define(SYMBOL-NUM...)
@@ -410,9 +473,6 @@ m4_define([_b4_token_constructor_define],
        : super_type(]b4_join([token_type (tok)],
                              b4_symbol_if([$1], [has_type], [std::move (v)]),
                              b4_locations_if([std::move (l)]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], [$@]))[);
-      }
 #else
      symbol_type (]b4_join(
          [int tok],
@@ -422,10 +482,10 @@ m4_define([_b4_token_constructor_define],
        : super_type(]b4_join([token_type (tok)],
                              b4_symbol_if([$1], [has_type], [v]),
                              b4_locations_if([l]))[)
-      {
-        YY_ASSERT (]m4_join([ || ], m4_map_sep([_b4_type_clause], [, ], [$@]))[);
-      }
 #endif
+      {]b4_parse_assert_if([[
+        ]b4_assert[ (]b4_tok_in($@)[);
+      ]])[}
 ]])])


@@ -1,11 +1,11 @@
 #                                                            -*- C -*-
 # Yacc compatible skeleton for Bison

-# Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2020 Free Software
+# Copyright (C) 1984, 1989-1990, 2000-2015, 2018-2021 Free Software
 # Foundation, Inc.

 m4_pushdef([b4_copyright_years],
-           [1984, 1989-1990, 2000-2015, 2018-2020])
+           [1984, 1989-1990, 2000-2015, 2018-2021])

 # 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
@@ -48,6 +48,10 @@ 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]]]])
@@ -155,7 +159,7 @@ m4_define([b4_rhs_location],
 # Declare the variables that are global, or local to YYPARSE if
 # pure-parser.
 m4_define([b4_declare_scanner_communication_variables], [[
-/* The lookahead symbol.  */
+/* Lookahead token kind.  */
 int yychar;

 ]b4_pure_if([[
@@ -571,6 +575,7 @@ union yyalloc
 /* YYNSTATES -- Number of states.  */
 #define YYNSTATES  ]b4_states_number[

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


@@ -1481,7 +1486,7 @@ 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;]b4_pure_if([], [[
  yypstate_allocated = 1;]])[
@@ -1510,7 +1515,7 @@ yypstate_delete (yypstate *yyps)
 #endif]b4_lac_if([[
      if (yyes != yyesa)
        YYSTACK_FREE (yyes);]])[
-      free (yyps);]b4_pure_if([], [[
+      YYFREE (yyps);]b4_pure_if([], [[
      yypstate_allocated = 0;]])[
    }
 }
@@ -1544,7 +1549,7 @@ yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)]])[
  int yyn;
  /* The return value of yyparse.  */
  int yyresult;
-  /* Lookahead token as an internal (translated) token number.  */
+  /* Lookahead symbol kind.  */
  yysymbol_kind_t yytoken = ]b4_symbol(-2, kind)[;
  /* The variables used to return semantic value and location from the
     action routines.  */
@@ -3,7 +3,7 @@
 <!--
    bison.xsl - common templates for Bison XSLT.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -3,7 +3,7 @@
 <!--
    xml2dot.xsl - transform Bison XML Report into DOT.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -3,7 +3,7 @@
 <!--
    xml2text.xsl - transform Bison XML Report into plain text.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -52,7 +52,7 @@
  <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 +65,7 @@
    <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 +136,7 @@
 </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 +149,9 @@
    </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 +161,18 @@
 </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 +181,7 @@
        </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)">
@@ -348,11 +356,11 @@
  <!-- RHS -->
  <xsl:for-each select="rhs/*">
    <xsl:if test="position() = $dot + 1">
-      <xsl:text> .</xsl:text>
+      <xsl:text> •</xsl:text>
    </xsl:if>
    <xsl:apply-templates select="."/>
    <xsl:if test="position() = last() and position() = $dot">
-      <xsl:text> .</xsl:text>
+      <xsl:text> •</xsl:text>
    </xsl:if>
  </xsl:for-each>
  <xsl:if test="$lookaheads">
@@ -3,7 +3,7 @@
 <!--
    xml2html.xsl - transform Bison XML Report into XHTML.

-    Copyright (C) 2007-2015, 2018-2020 Free Software Foundation, Inc.
+    Copyright (C) 2007-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -227,6 +227,7 @@
  <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 +239,11 @@
 </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 +309,10 @@
    <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 +322,64 @@
    <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 +412,7 @@
        <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>
@@ -464,7 +491,12 @@
  </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"/>
@@ -475,17 +507,21 @@
    <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($pad)"/>
+        </xsl:call-template>
+      </a>
+    </xsl:when>
+    <xsl:otherwise>
      <a>
        <xsl:attribute name="href">
          <xsl:value-of select="concat('#rule_', @number)"/>
@@ -495,25 +531,13 @@
          <xsl:with-param name="pad" select="number($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"/>
@@ -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 +1,5 @@
+%token ID
+%%
+s: a ID
+a: expr
+expr: %empty | expr ID ','
@@ -0,0 +1,13 @@
+%%
+stmt:
+  expr
+| if_stmt
+;
+
+if_stmt:
+  "if" expr "then" stmt
+| "if" expr "then" stmt "else" stmt
+;
+
+expr:
+  "identifier"
@@ -1,4 +1,4 @@
-## Copyright (C) 2001-2003, 2005-2015, 2018-2020 Free Software
+## Copyright (C) 2001-2003, 2005-2015, 2018-2021 Free Software
 ## Foundation, Inc.

 ## This program is free software: you can redistribute it and/or modify
@@ -57,7 +57,7 @@ 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
+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)*)}'	\
@@ -19,7 +19,7 @@
 \def\finalout{\overfullrule=0pt}
 %\finalout

-% Copyright (c) 1998, 2001, 2009--2015, 2018--2020 Free Software
+% Copyright (c) 1998, 2001, 2009--2015, 2018--2021 Free Software
 % Foundation, Inc.
 %
 % This file is part of Bison.
@@ -0,0 +1,10 @@
+%%
+sequence:
+  %empty
+| maybeword
+| sequence "word"
+;
+maybeword:
+  %empty
+| "word"
+;
@@ -22,7 +22,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2006, 2009-2015, 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2006, 2009-2015, 2018-2021 Free Software Foundation, Inc.

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

@@ -1,6 +1,6 @@
 #! /usr/bin/perl -w

-# Copyright (C) 2006, 2008-2015, 2018-2020 Free Software Foundation,
+# Copyright (C) 2006, 2008-2015, 2018-2021 Free Software Foundation,
 # Inc.
 #
 # This file is part of Bison, the GNU Compiler Compiler.
@@ -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;

@@ -498,7 +510,7 @@ yylex (void)
    case '5': case '6': case '7': case '8': case '9':
      {
        int nchars = 0;
-        int n = 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;
@@ -506,7 +518,7 @@ yylex (void)

    default:
      yyerror ("error: invalid character");
-      return yylex ();
+      return yylex (@{[is_pure (@directive) ? "yylvalp" : ""]});
    }
 }
 EOF
@@ -592,10 +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.
@@ -618,8 +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

 %%
@@ -641,8 +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

 %%
@@ -664,10 +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;
@@ -1,4 +1,4 @@
-## Copyright (C) 2006, 2008-2015, 2018-2020 Free Software Foundation,
+## Copyright (C) 2006, 2008-2015, 2018-2021 Free Software Foundation,
 ## Inc.

 ## This program is free software: you can redistribute it and/or modify
@@ -17,7 +17,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 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
@@ -46,7 +46,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 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
@@ -36,7 +36,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 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 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2005-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2005-2015, 2018-2021 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 +1,4 @@
-## Copyright (C) 2005-2006, 2008-2015, 2018-2020 Free Software
+## Copyright (C) 2005-2006, 2008-2015, 2018-2021 Free Software
 ## Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
@@ -1,4 +1,4 @@
-## Copyright (C) 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2018-2021 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
@@ -1,6 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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 +1,5 @@
 /*
-  Copyright (C) 2008-2015, 2018-2020 Free Software Foundation, Inc.
+  Copyright (C) 2008-2015, 2018-2021 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
@@ -1,6 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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 +1,5 @@
 /*
-  Copyright (C) 2008-2015, 2018-2020 Free Software Foundation, Inc.
+  Copyright (C) 2008-2015, 2018-2021 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
@@ -53,7 +53,9 @@ push-parser model.
 This example demonstrates best practices when using Bison.
 - Its hand-written scanner tracks locations.
 - Its interface is pure.
- It uses the `error` token to get error recovery.
+- It uses %params to pass user information to the parser and scanner.
+- Its scanner uses the `error` token to signal lexical errors and enter
+  error recovery.
 - Its interface is "incremental", well suited for interaction: it uses the
  push-parser API to feed the parser with the incoming tokens.
 - It features an interactive command line with completion based on the
@@ -62,6 +64,13 @@ This example demonstrates best practices when using Bison.
  messages.
 - It uses a custom syntax error with location, lookahead correction and
  token internationalization.
+- Error messages quote the source with squiggles that underline the error:
+```
+> 123 456
+1.5-7: syntax error: expected end of file or + or - or * or / or ^ before number
+    1 | 123 456
+      |     ^~~
+```
 - It supports debug traces with semantic values.
 - It uses named references instead of the traditional $1, $2, etc.

@@ -72,7 +81,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 Free Software Foundation, Inc.

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

@@ -2,7 +2,9 @@
 This example demonstrates best practices when using Bison.
 - Its hand-written scanner tracks locations.
 - Its interface is pure.
- It uses the `error` token to get error recovery.
+- It uses %params to pass user information to the parser and scanner.
+- Its scanner uses the `error` token to signal lexical errors and enter
+  error recovery.
 - Its interface is "incremental", well suited for interaction: it uses the
  push-parser API to feed the parser with the incoming tokens.
 - It features an interactive command line with completion based on the
@@ -11,6 +13,13 @@ This example demonstrates best practices when using Bison.
  messages.
 - It uses a custom syntax error with location, lookahead correction and
  token internationalization.
+- Error messages quote the source with squiggles that underline the error:
+```
+> 123 456
+1.5-7: syntax error: expected end of file or + or - or * or / or ^ before number
+    1 | 123 456
+      |     ^~~
+```
 - It supports debug traces with semantic values.
 - It uses named references instead of the traditional $1, $2, etc.

@@ -23,7 +32,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2020 Free Software Foundation, Inc.
+Copyright (C) 2020-2021 Free Software Foundation, Inc.

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

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

-# Copyright (C) 2020 Free Software Foundation, Inc.
+# Copyright (C) 2020-2021 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
@@ -101,14 +101,28 @@ cat >input <<EOF
 EOF
 run 0 '> *
 > ''
-err: 1.1: syntax error: expected end of file or - or ( or exit or number or function etc., before *'
+err: 1.1: syntax error: expected end of file or - or ( or exit or number or function etc., before *
+err:     1 | *
+err:       | ^'
+
+# Underline long errors.
+cat >input <<EOF
+123 123456
+EOF
+run 0 '> 123 123456
+> ''
+err: 1.5-10: syntax error: expected end of file or + or - or * or / or ^ before number
+err:     1 | 123 123456
+err:       |     ^~~~~~'

 cat >input <<EOF
 1 + 2 * * 3
 EOF
 run 0 '> 1 + 2 * * 3
 > ''
-err: 1.9: syntax error: expected - or ( or number or function or variable before *'
+err: 1.9: syntax error: expected - or ( or number or function or variable before *
+err:     1 | 1 + 2 * * 3
+err:       |         ^'

 cat >input <<EOF
 1 / 0
@@ -132,8 +146,14 @@ run 0 '> ((1 ++ 2) ** 3)
 1332
 > ''
 err: 1.6: syntax error: expected - or ( or number or function or variable before +
+err:     1 | ((1 ++ 2) ** 3)
+err:       |      ^
 err: 2.5: syntax error: expected - or ( or number or function or variable before +
-err: 2.16: syntax error: expected - or ( or number or function or variable before *'
+err:     2 | (1 ++ 2) + (3 ** 4)
+err:       |     ^
+err: 2.16: syntax error: expected - or ( or number or function or variable before *
+err:     2 | (1 ++ 2) + (3 ** 4)
+err:       |                ^'

 # The rule "( error )" should work even if there are no tokens between "(" and ")".
 cat >input <<EOF
@@ -142,7 +162,9 @@ EOF
 run 0 '> ()
 666
 > ''
-err: 1.2: syntax error: expected - or ( or number or function or variable before )'
+err: 1.2: syntax error: expected - or ( or number or function or variable before )
+err:     1 | ()
+err:       |  ^'


 cat >input <<EOF
@@ -189,6 +211,8 @@ err: LAC: checking lookahead function: S5
 err: LAC: checking lookahead variable: S6
 err: LAC: checking lookahead NEG: Err
 err: 1.2: syntax error: expected - or ( or number or function or variable before +
+err:     1 | (+_)
+err:       |  ^
 err: LAC: initial context discarded due to error recovery
 err: Shifting token error (1.2: )
 err: Entering state 10
@@ -227,29 +251,29 @@ err: Next token is token ) (1.4: )
 err: Shifting token ) (1.4: )
 err: Entering state 20
 err: Stack now 0 2 10 20
-err: Reducing stack by rule 15 (line 151):
+err: Reducing stack by rule XX (line XXX):
 err:    $1 = token ( (1.1: )
 err:    $2 = token error (1.2-3: )
 err:    $3 = token ) (1.4: )
 err: -> $$ = nterm exp (1.1-4: 666)
-err: Entering state 7
-err: Stack now 0 7
+err: Entering state 8
+err: Stack now 0 8
 err: Return for a new token:
 err: Reading a token
 err: Now at end of input.
 err: LAC: initial context established for end of file
-err: LAC: checking lookahead end of file: R2 G8 S19
-err: Reducing stack by rule 2 (line 126):
+err: LAC: checking lookahead end of file: R2 G7 S14
+err: Reducing stack by rule XX (line XXX):
 err:    $1 = nterm exp (1.1-4: 666)
 err: -> $$ = nterm input (1.1-4: )
-err: Entering state 8
-err: Stack now 0 8
+err: Entering state 7
+err: Stack now 0 7
 err: Now at end of input.
 err: Shifting token end of file (1.5: )
 err: LAC: initial context discarded due to shift
-err: Entering state 19
-err: Stack now 0 8 19
-err: Stack now 0 8 19
+err: Entering state 14
+err: Stack now 0 7 14
+err: Stack now 0 7 14
 err: Cleanup: popping token end of file (1.5: )
 err: Cleanup: popping nterm input (1.1-4: )' -p

@@ -286,7 +310,9 @@ run 0 '> (1+
 (       -       atan    cos     exp     ln      number  sin     sqrt
 > (1+
 > ''
-err: 1.4: syntax error: expected - or ( or number or function or variable before end of file'
+err: 1.4: syntax error: expected - or ( or number or function or variable before end of file
+err:     1 | (1+
+err:       |    ^'

 # Check the completion of a word.
 sed -e 's/\\t/	/g' >input <<EOF
@@ -294,7 +320,9 @@ sed -e 's/\\t/	/g' >input <<EOF
 EOF
 run 0 '> (atan ( ''
 > ''
-err: 1.9: syntax error: expected - or ( or number or function or variable before end of file'
+err: 1.9: syntax error: expected - or ( or number or function or variable before end of file
+err:     1 | (atan ( ''
+err:       |         ^'

 # Check the completion at the very beginning.
 sed -e 's/\\t/	/g' >input <<EOF
@@ -313,8 +341,9 @@ sed -e 's/\\t/	/g' >input <<EOF
 EOF
 run -n 0 '> 1++ ''
 > ''
-err: 1.1: syntax error: expected - or ( or number or function or variable before +
 err: 1.3: syntax error: expected - or ( or number or function or variable before +
+err:     1 | 1++ ''
+err:       |   ^
 '

 # And even when the error was recovered from.
@@ -323,8 +352,10 @@ sed -e 's/\\t/	/g' >input <<EOF
 EOF
 run -n 0 '> (1++2) + 3 +  ''
 > ''
-err: 1.1: syntax error: expected - or ( or number or function or variable before +
-err: 1.1: syntax error: expected - or ( or number or function or variable before +
 err: 1.4: syntax error: expected - or ( or number or function or variable before +
+err:     1 | (1++2) + 3 +  ''
+err:       |    ^
 err: 1.15: syntax error: expected - or ( or number or function or variable before end of file
+err:     1 | (1++2) + 3 +  ''
+err:       |               ^
 '
@@ -1,4 +1,4 @@
-## Copyright (C) 2020 Free Software Foundation, Inc.
+## Copyright (C) 2020-2021 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 +1,25 @@
-%require "3.6"
+/* Parser and scanner for bistromathic.   -*- C -*-

+   Copyright (C) 2019-2021 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/>.  */
+
+%require "3.7"
+
+// Emitted on top of the implementation file.
 %code top {
  #include <ctype.h>  // isdigit
  #include <locale.h> // LC_ALL
@@ -24,6 +44,7 @@
  #endif
 }

+// Emitted in the header file, before the definition of YYSTYPE.
 %code requires {
  // Function type.
  typedef double (func_t) (double);
@@ -44,19 +65,34 @@

  symrec *putsym (char const *name, int sym_type);
  symrec *getsym (char const *name);
+
+  // Exchanging information with the parser.
+  typedef struct
+  {
+    // Whether to not emit error messages.
+    int silent;
+    // The current input line.
+    const char *line;
+  } user_context;
 }

+// Emitted in the header file, after the definition of YYSTYPE.
 %code provides {
 # ifndef __attribute__
 #  ifndef __GNUC__
 #   define __attribute__(Spec) /* empty */
 #  endif
 # endif
-  int yylex (const char **line, YYSTYPE *yylval, YYLTYPE *yylloc);
-  void yyerror (YYLTYPE *loc, char const *format, ...)
-    __attribute__ ((__format__ (__printf__, 2, 3)));
+
+  yytoken_kind_t
+  yylex (const char **line, YYSTYPE *yylval, YYLTYPE *yylloc,
+         const user_context *uctx);
+  void yyerror (YYLTYPE *loc, const user_context *uctx,
+                char const *format, ...)
+    __attribute__ ((__format__ (__printf__, 3, 4)));
 }

+// Emitted in the implementation file.
 %code {
  #if defined ENABLE_NLS && ENABLE_NLS
  # define _(Msgid)  gettext (Msgid)
@@ -68,6 +104,9 @@
  int done = 0;
 }

+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
 // Don't share global variables between the scanner and the parser.
 %define api.pure full

@@ -90,6 +129,9 @@
 // Generate the parser description file (calc.output).
 %verbose

+// User information exchanged with the parser and scanner.
+%param {const user_context *uctx}
+
 // Generate YYSTYPE from the types assigned to symbols.
 %define api.value.type union
 %token
@@ -145,7 +187,7 @@ exp:
  {
    if ($r == 0)
      {
-        yyerror (&@$, "error: division by zero");
+        yyerror (&@$, uctx, "error: division by zero");
        YYERROR;
      }
    else
@@ -231,8 +273,9 @@ symbol_count (void)
 | Scanner.  |
 `----------*/

-int
-yylex (const char **line, YYSTYPE *yylval, YYLTYPE *yylloc)
+yytoken_kind_t
+yylex (const char **line, YYSTYPE *yylval, YYLTYPE *yylloc,
+       const user_context *uctx)
 {
  int c;

@@ -302,7 +345,7 @@ yylex (const char **line, YYSTYPE *yylval, YYLTYPE *yylloc)

      // Stray characters.
    default:
-      yyerror (yylloc, "syntax error: invalid character: %c", c);
+      yyerror (yylloc, uctx, "syntax error: invalid character: %c", c);
      return TOK_YYerror;
    }
 }
@@ -340,8 +383,11 @@ error_format_string (int argc)


 int
-yyreport_syntax_error (const yypcontext_t *ctx)
+yyreport_syntax_error (const yypcontext_t *ctx, const user_context *uctx)
 {
+  if (uctx->silent)
+    return 0;
+
  enum { ARGS_MAX = 6 };
  yysymbol_kind_t arg[ARGS_MAX];
  int argsize = yypcontext_expected_tokens (ctx, arg, ARGS_MAX);
@@ -352,11 +398,12 @@ yyreport_syntax_error (const yypcontext_t *ctx)
    argsize = ARGS_MAX;
  const char *format = error_format_string (1 + argsize + too_many_expected_tokens);

+  const YYLTYPE *loc = yypcontext_location (ctx);
  while (*format)
    // %@: location.
    if (format[0] == '%' && format[1] == '@')
      {
-        YY_LOCATION_PRINT (stderr, *yypcontext_location (ctx));
+        YY_LOCATION_PRINT (stderr, *loc);
        format += 2;
      }
    // %u: unexpected token.
@@ -381,13 +428,25 @@ yyreport_syntax_error (const yypcontext_t *ctx)
        ++format;
      }
  fputc ('\n', stderr);
+
+  // Quote the source line.
+  {
+    fprintf (stderr, "%5d | %s\n", loc->first_line, uctx->line);
+    fprintf (stderr, "%5s | %*s", "", loc->first_column, "^");
+    for (int i = loc->last_column - loc->first_column - 1; 0 < i; --i)
+      putc ('~', stderr);
+    putc ('\n', stderr);
+  }
  return 0;
 }


 // Called by yyparse on error.
-void yyerror (YYLTYPE *loc, char const *format, ...)
+void yyerror (YYLTYPE *loc, const user_context *uctx, char const *format, ...)
 {
+  if (uctx->silent)
+    return;
+
  YY_LOCATION_PRINT (stderr, *loc);
  fputs (": ", stderr);
  va_list args;
@@ -423,11 +482,13 @@ xstrndup (const char *string, size_t n)
 static int
 process_line (YYLTYPE *lloc, const char *line)
 {
+  user_context uctx = {0, line};
  yypstate *ps = yypstate_new ();
  int status = 0;
  do {
    YYSTYPE lval;
-    status = yypush_parse (ps, yylex (&line, &lval, lloc), &lval, lloc);
+    yytoken_kind_t token = yylex (&line, &lval, lloc, &uctx);
+    status = yypush_parse (ps, token, &lval, lloc, &uctx);
  } while (status == YYPUSH_MORE);
  yypstate_delete (ps);
  lloc->last_line++;
@@ -442,18 +503,19 @@ expected_tokens (const char *input,
                 int *tokens, int ntokens)
 {
  YYDPRINTF ((stderr, "expected_tokens (\"%s\")", input));
+  user_context uctx = {1, input};

  // Parse the current state of the line.
  yypstate *ps = yypstate_new ();
  int status = 0;
+  YYLTYPE lloc = { 1, 1, 1, 1 };
  do {
-    YYLTYPE lloc = { 1, 1, 1, 1 };
    YYSTYPE lval;
-    int token = yylex (&input, &lval, &lloc);
+    yytoken_kind_t token = yylex (&input, &lval, &lloc, &uctx);
    // Don't let the parse know when we reach the end of input.
-    if (!token)
+    if (token == TOK_YYEOF)
      break;
-    status = yypush_parse (ps, token, &lval, &lloc);
+    status = yypush_parse (ps, token, &lval, &lloc, &uctx);
  } while (status == YYPUSH_MORE);

  int res = 0;
@@ -9,7 +9,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2019-2020 Free Software Foundation, Inc.
+Copyright (C) 2019-2021 Free Software Foundation, Inc.

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

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

-# Copyright (C) 2019-2020 Free Software Foundation, Inc.
+# Copyright (C) 2019-2021 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 +1,4 @@
-## Copyright (C) 2019-2020 Free Software Foundation, Inc.
+## Copyright (C) 2019-2021 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 +11,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 Free Software Foundation, Inc.

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

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

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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 +1,4 @@
-## Copyright (C) 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2018-2021 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
@@ -31,6 +31,13 @@ endif FLEX_WORKS

 %D%/parse.c: $(dependencies)

+# Tell Make scan.o depends on parse.h, except that Make sees only
+# parse.c, not parse.h.  We can't use BUILT_SOURCES to this end, since
+# we use the built bison.
+%D%/lexcalc$(DASH)scan.o: %D%/parse.c
+# Likewise, but for Automake before 1.16.
+%D%/examples_c_lexcalc_lexcalc$(DASH)scan.o: %D%/parse.c
+
 EXTRA_DIST += %D%/lexcalc.test
 dist_lexcalc_DATA = %D%/parse.y %D%/scan.l %D%/Makefile %D%/README.md
 CLEANFILES += %D%/parse.[ch] %D%/scan.c %D%/parse.output
@@ -1,3 +1,22 @@
+/* Parser for lexcalc.   -*- C -*-
+
+   Copyright (C) 2018-2021 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/>.  */
+
 // Prologue (directives).
 %expect 0

@@ -19,6 +38,9 @@
 #include <stdlib.h> // getenv.
 }

+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
 // Don't share global variables between the scanner and the parser.
 %define api.pure full

@@ -1,4 +1,23 @@
-/* Prologue (directives).   -*- C -*- */
+/* Scanner for lexcalc.   -*- C -*-
+
+   Copyright (C) 2018-2021 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/>.  */
+
+/* Prologue (directives). */

 /* Disable Flex features we don't need, to avoid warnings. */
 %option nodefault noinput nounput noyywrap
@@ -1,4 +1,4 @@
-## Copyright (C) 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2018-2021 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 +1,4 @@
-## Copyright (C) 2005-2006, 2008-2015, 2018-2020 Free Software
+## Copyright (C) 2005-2006, 2008-2015, 2018-2021 Free Software
 ## Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
@@ -1,6 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2005-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2005-2015, 2018-2021 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
@@ -20,7 +20,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2020 Free Software Foundation, Inc.
+Copyright (C) 2020-2021 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 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2020 Free Software Foundation, Inc.
+# Copyright (C) 2020-2021 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
@@ -1,3 +1,22 @@
+/* Parser and scanner for pushcalc.   -*- C -*-
+
+   Copyright (C) 2020-2021 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/>.  */
+
 %code top {
  #include <ctype.h>  /* isdigit. */
  #include <stdio.h>  /* printf. */
@@ -1,4 +1,4 @@
-## Copyright (C) 2020 Free Software Foundation, Inc.
+## Copyright (C) 2020-2021 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
@@ -26,7 +26,7 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 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
@@ -1,4 +1,4 @@
-## Copyright (C) 2019-2020 Free Software Foundation, Inc.
+## Copyright (C) 2019-2021 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
@@ -1,3 +1,22 @@
+/* Parser for reccalc.   -*- C -*-
+
+   Copyright (C) 2019-2021 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/>.  */
+
 // Prologue (directives).
 %expect 0

@@ -46,14 +65,29 @@
  result parse (void);
 }

+// Include the header in the implementation rather than duplicating it.
+%define api.header.include {"parse.h"}
+
+// Don't share global variables between the scanner and the parser.
 %define api.pure full
+
+// To avoid name clashes (e.g., with C's EOF) prefix token definitions
+// with TOK_ (e.g., TOK_EOF).
 %define api.token.prefix {TOK_}
+
+// Generate YYSTYPE from the types assigned to symbols.
 %define api.value.type union
-%define parse.error verbose
+
+// Error messages with "unexpected XXX, expected XXX...".
+%define parse.error detailed
+
+// Enable run-time traces (yydebug).
 %define parse.trace
+
+// Generate the parser description file (parse.output).
 %verbose

- // Scanner and error count are exchanged between main, yyparse and yylex.
+// Scanner and error count are exchanged between main, yyparse and yylex.
 %param {yyscan_t scanner}{result *res}

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

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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
@@ -1,3 +1,22 @@
+/* Scanner for reccalc.   -*- C -*-
+
+   Copyright (C) 2019-2021 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/>.  */
+
 /* Prologue (directives).   -*- C -*- */

 /* Disable Flex features we don't need, to avoid warnings. */
@@ -1,4 +1,4 @@
-## Copyright (C) 2005-2006, 2008-2015, 2018-2020 Free Software
+## Copyright (C) 2005-2006, 2008-2015, 2018-2021 Free Software
 ## Foundation, Inc.
 ##
 ## This program is free software: you can redistribute it and/or modify
@@ -1,6 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2005-2015, 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2005-2015, 2018-2021 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 @@ fill-column: 76
 ispell-dictionary: "american"
 End:

-Copyright (C) 2018-2020 Free Software Foundation, Inc.
+Copyright (C) 2018-2021 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 +1,6 @@
 #! /bin/sh

-# Copyright (C) 2018-2020 Free Software Foundation, Inc.
+# Copyright (C) 2018-2021 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
@@ -1,3 +1,22 @@
+/* Parser and scanner for calc in D.   -*- D -*-
+
+   Copyright (C) 2018-2021 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/>.  */
+
 %language "D"

 %define api.parser.class {Calc}
@@ -1,4 +1,4 @@
-## Copyright (C) 2018-2020 Free Software Foundation, Inc.
+## Copyright (C) 2018-2021 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
@@ -27,7 +27,7 @@ EXTRA_DIST += %D%/calc.test

 %D%/calc.d: %D%/calc.y $(dependencies)
 	$(AM_V_GEN)$(MKDIR_P) %D%
-	$(AM_V_at)$(BISON) $(srcdir)/%D%/calc.y -o $@
+	$(AM_V_at)$(BISON) -o $@ $(srcdir)/%D%/calc.y

 %D%/calc: %D%/calc.d
 	$(AM_V_GEN) $(DC) $(DCFLAGS) -of$@ %D%/calc.d
@@ -3,7 +3,7 @@

 # This file is part of GNU Bison

-# Copyright (C) 1992, 2000-2001, 2005-2006, 2009-2015, 2018-2020 Free
+# Copyright (C) 1992, 2000-2001, 2005-2006, 2009-2015, 2018-2021 Free
 # Software Foundation, Inc.
 #
 # This program is free software: you can redistribute it and/or modify
--- a/Show More
+++ b/Show More
@@ -1 +1 @@
 .6.4
 .7.4