package: make bison a relocatable package

Suggested by David Barto
https://lists.gnu.org/archive/html/help-bison/2015-02/msg00004.html
and Victor Zverovich.
https://lists.gnu.org/archive/html/bison-patches/2018-10/msg00121.html

This is very easy to do, thanks to work by Bruno Haible in gnulib.
See "Supporting Relocation" in gnulib's documentation.

* bootstrap.conf: We need relocatable-prog and relocatable-script (for yacc).

* src/yacc.in: New.
* configure.ac, src/local.mk: Instantiate it.
* src/main.c, src/output.c (main, pkgdatadir): Use relocatable2.

* doc/bison.texi (FAQ): Document it.

src/local.mk

@@ -13,10 +13,17 @@
 ## You should have received a copy of the GNU General Public License
 ## along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+CLEANDIRS += %D%/*.dSYM
+
 bin_PROGRAMS = src/bison
 # Prettify Automake-computed names of compiled objects.
 src_bison_SHORTNAME = bison
 
+src_bison_CPPFLAGS = $(AM_CPPFLAGS) -DINSTALLDIR=\"$(bindir)\"
+if RELOCATABLE_VIA_LD
+  src_bison_LDFLAGS = `$(RELOCATABLE_LDFLAGS) $(bindir)`
+endif
+
 src_bison_CFLAGS = $(AM_CFLAGS) $(WERROR_CFLAGS)
 src_bison_SOURCES =                             \
   src/AnnotationList.c                          \
@@ -127,16 +134,7 @@ src_bison_LDADD =                               \
 ## ------ ##
 
 if ENABLE_YACC
-  bin_SCRIPTS = src/yacc
+  nodist_bin_SCRIPTS = src/yacc
 endif
 EXTRA_SCRIPTS = src/yacc
 MOSTLYCLEANFILES += src/yacc
-CLEANDIRS += %D%/*.dSYM
-
-src/yacc:
-	$(AM_V_GEN)rm -f $@ $@.tmp
-	$(AM_V_at)$(MKDIR_P) src
-	$(AM_V_at)echo '#! /bin/sh' >$@.tmp
-	$(AM_V_at)echo "exec '$(bindir)/bison' -y "'"$$@"' >>$@.tmp
-	$(AM_V_at)chmod a+x $@.tmp
-	$(AM_V_at)mv $@.tmp $@

src/main.c

@@ -26,6 +26,7 @@
 #include <configmake.h>
 #include <progname.h>
 #include <quotearg.h>
+#include <relocatable.h> /* relocate2 */
 #include <timevar.h>
 
 #include "LR0.h"
@@ -58,10 +59,16 @@
 int
 main (int argc, char *argv[])
 {
+#define DEPENDS_ON_LIBINTL 1
   set_program_name (argv[0]);
   setlocale (LC_ALL, "");
-  (void) bindtextdomain (PACKAGE, LOCALEDIR);
-  (void) bindtextdomain ("bison-runtime", LOCALEDIR);
+  {
+    char *cp = NULL;
+    char const *localedir = relocate2 (LOCALEDIR, &cp);
+    (void) bindtextdomain (PACKAGE, localedir);
+    (void) bindtextdomain ("bison-runtime", localedir);
+    free (cp);
+  }
   (void) textdomain (PACKAGE);
 
   {

src/output.c

@@ -26,6 +26,7 @@
 #include <get-errno.h>
 #include <path-join.h>
 #include <quotearg.h>
+#include <relocatable.h> /* relocate2 */
 #include <spawn-pipe.h>
 #include <timevar.h>
 #include <wait-process.h>
@@ -44,6 +45,9 @@
 
 static struct obstack format_obstack;
 
+/* Memory allocated by relocate2, to free.  */
+static char *relocate_buffer = NULL;
+
 
 /*-------------------------------------------------------------------.
 | Create a function NAME which associates to the muscle NAME the     |
@@ -718,11 +722,17 @@ output (void)
     unlink_generated_sources ();
 
   obstack_free (&format_obstack, NULL);
+  free (relocate_buffer);
 }
 
 char const *
 pkgdatadir (void)
 {
-  char const *cp = getenv ("BISON_PKGDATADIR");
-  return cp ? cp : PKGDATADIR;
+  if (relocate_buffer)
+    return relocate_buffer;
+  else
+    {
+      char const *cp = getenv ("BISON_PKGDATADIR");
+      return cp ? cp : relocate2 (PKGDATADIR, &relocate_buffer);
+    }
 }

src/yacc.in

@@ -0,0 +1,22 @@
+#! /bin/sh
+
+@relocatable_sh@
+if test "@RELOCATABLE@" = yes; then
+  exec_prefix="@exec_prefix@"
+  bindir="@bindir@"
+  orig_installdir="$bindir" # see Makefile.am's *_SCRIPTS variables
+  func_find_curr_installdir # determine curr_installdir
+  func_find_prefixes
+  relocate () {
+    echo "$1/" \
+    | sed -e "s%^${orig_installprefix}/%${curr_installprefix}/%" \
+    | sed -e 's,/$,,'
+  }
+else
+  relocate () {
+    echo "$1"
+  }
+fi
+
+bindir=`relocate "@bindir@"`
+exec "$bindir/bison" -y "$@"