intl: Unbreak intl build with bison 3 when no regeneration is needed [PR92008]

As Iain reported, my change broke the case when one has bison >= 3,
but make decides there is no reason to regenerate plural.c, unfortunately
that seems to be a scenario I haven't tested.  The problem is that
the pregenerated plural.c has been generated with bison 1.35, but when
config.h says HAVE_BISON3, the code assumes it is the bison3 variant.
What used to work fine is when one has bison >= 3 and plural.c has been
regenerated (e.g. do touch intl/plural.y and it will work), or when
one doesn't have any bison (then nothing is regenerated, but HAVE_BISON3
isn't defined either), or when one has bison < 3 and doesn't need to
regenerate, or when one has bison < 3 and it is regenerated.

The following patch fixes this, by killing the HAVE_BISON3 macro from
config.h, and instead remembering the fact whether plural.c has been created
with bison < 3 or bison >= 3 in a separate new plural-config.h header.
The way this works:
- user doesn't have bison
- user has bison >= 3, but intl/{plural-config.h,plural.c} aren't older than intl/plural.y
- user has bison < 3, but intl/{plural-config.h,plural.c} aren't older than intl/plural.y
	pregenerated !USE_BISON3 plural.c and plural-config.h from source
	dir is used, nothing in the objdir
- user has bison >= 3 and intl/plural.y is newer
	Makefile generates plural.c and USE_BISON3 plural-config.h in the
	objdir, which is then used in preference to srcdir copies
- user has bison < 3 and intl/plural.y is newer
	Makefile generates plural.c and !USE_BISON3 plural-config.h in the
	objdir, which is then used in preference to srcdir copies
I have tested all these cases and make all-yes worked in all the cases.
If one uses the unsupported ./configure where srcdir == objdir, I guess
(though haven't tested) that it should still work, just it would be nice
if such people didn't try to check in the plural{.c,-config.h} they have
regenerated.
What doesn't work, but didn't work before either (just tested gcc-9 branch
too) is when one doesn't have bison and plural.y is newer than plural.c.
Don't do that ;)

intl/ChangeLog
2020-04-16  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/92008
	* configure.ac: Remove HAVE_BISON3 AC_DEFINE.
	* Makefile.in (HEADERS): Add plural-config.h.
	(.y.c): Also create plural-config.h.
	(dcigettext.o loadmsgcat.o plural.o plural-exp.o): Also depend
	on plural-config.h.
	(plural-config.h): Depend on plural.c.
	* plural-exp.h: Include plural-config.h.  Use USE_BISON3 instead
	of HAVE_BISON3.
	* plural.y: Use USE_BISON3 instead of HAVE_BISON3.
	* configure: Regenerated.
	* plural.c: Regenerated.
	* config.h.in: Regenerated.
	* plural-config.h: Generated.

1 files changed, 6 insertions, 1 deletions

diff --git a/intl/Makefile.in b/intl/Makefile.in
index bdb74ebb78c..356c8ab9b65 100644
--- a/intl/Makefile.in
+++ b/intl/Makefile.in
@@ -57,6 +57,7 @@ HEADERS = \
   gettextP.h \
   hash-string.h \
   loadinfo.h \
+  plural-config.h \
   plural-exp.h \
   eval-plural.h \
   localcharset.h \
@@ -133,10 +134,12 @@ libintl.h: $(srcdir)/libgnuintl.h
 	$(COMPILE) $<
 
 .y.c:
+@BISON3_YES@	echo '#define USE_BISON3' > $(patsubst %.c,%-config.h,$@)
 @BISON3_YES@	sed 's,%pure_parser,,;s,^/\* BISON3 \(.*\) \*/$$,\1,' $< > $@.y
 @BISON3_YES@	$(YACC) $(YFLAGS) --output $@.c $@.y
 @BISON3_YES@	sed 's/\.c\.y"/.y"/' $@.c > $@
 @BISON3_YES@	rm -f $@.c $@.y $@.h
+@BISON3_NO@	echo '/* #define USE_BISON3 */' > $(patsubst %.c,%-config.h,$@)
 @BISON3_NO@	$(YACC) $(YFLAGS) --output $@ $<
 	rm -f $*.h
 
@@ -165,7 +168,7 @@ dngettext.o finddomain.o gettext.o intl-compat.o loadmsgcat.o \
 localealias.o ngettext.o textdomain.o: gettextP.h gmo.h loadinfo.h
 dcigettext.o loadmsgcat.o: hash-string.h
 explodename.o l10nflist.o: loadinfo.h
-dcigettext.o loadmsgcat.o plural.o plural-exp.o: plural-exp.h
+dcigettext.o loadmsgcat.o plural.o plural-exp.o: plural-exp.h plural-config.h
 dcigettext.o: eval-plural.h
 localcharset.o: localcharset.h
 localealias.o localcharset.o relocatable.o: relocatable.h
@@ -242,6 +245,8 @@ $(srcdir)/aclocal.m4: @MAINT@ $(aclocal_deps)
 config.h: stamp-h1
 	test -f config.h || (rm -f stamp-h1 && $(MAKE) stamp-h1)
 
+plural-config.h: plural.c
+
 stamp-h1: $(srcdir)/config.h.in config.status
 	-rm -f stamp-h1
 	$(SHELL) ./config.status config.h