[PATCH] automake rules fail to make y.tab.h if y.tab.c exists

[Bernd Jendrissek]

BTW I *did* make the patch apply cleanly to 1.6.1 - 1.5's notwithstanding.

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I'm not happy with the make rules stock automake emits.

Whether it's considered a feature, bug, or limitation, I don't know, but
having yacc-generated headers in a project is a little fragile.

Stock automake spots the use of "AM_YFLAGS = -d" in Makefile.am, and
emits a rule that y.tab.h (placeholder name) depends on y.tab.c; this is
not formally correct.  When y.tab.h is missing but y.tab.c is present
(or y.tab.c is touched for some reason), make thinks it can rebuild
y.tab.h from y.tab.c - a false assumption since there is no rule.

I have a patch the Works For Me (tm) by unconditionally using the
MORE_THAN_ONE rule - i.e. the build *always* uses ylwrap to generate files.
This allows me to rebuild the header when the C parser is already
up-to-date.  Unfortunately, that does mean that y.tab.c and y.tab.h are
generated separately, and always incur shell script overhead, but I don't
know if that really matters (most projects I've seen use at most a handful
of yacc parsers).

Is this useful?  Anyway, I'm sure someone else can do it a little better,
a little cleaner.

Bernd Jendrissek

P.S.  My employer doesn't really "get" Free Software *or* Open Source; I
hope this patch is simple enough not to need any paperwork.

P.S.2  I had to patch *all* the yacc tests to use $AUTOMAKE -a so that
ylwrap would be copied in.

diff -Nur automake-1.5/automake.in automake-1.5-bernd/automake.in
--- automake-1.5/automake.in    2001-08-23 07:26:53
+++ automake-1.5-bernd/automake.in      2002-01-10 11:04:28
@@ -5470,7 +5470,6 @@
        # Add a dependency for the generated header file, and arrange
        # for that file to be included in the distribution.
        # FIXME: this fails for `nodist_*_SOURCES'.
-       $output_rules .= "${header}: $output\n";
        &push_dist_common ($header);
        # If the files are built in the build directory, then we want
        # to remove them with `make clean'.  If they are in srcdir
@@ -5512,10 +5511,7 @@
                 "`YACCFLAGS' obsolete; use `YFLAGS' instead")
       if variable_defined ('YACCFLAGS');
 
-    if (count_files_for_language ('yacc') > 1)
-    {
-       &yacc_lex_finish_helper;
+    &yacc_lex_finish_helper;
-    }
 }
 
 
# A similar hunk to force use of ylwrap instead f?lex.
#@@ -5115,10 +5111,7 @@
#       &am_error ("lex source seen but `AC_DECL_YYTEXT' not in 
`$configure_ac'");
#     }
# 
#-    if (count_files_for_language ('lex') > 1)
#-    {
#-      &yacc_lex_finish_helper;
#-    }
#+    &yacc_lex_finish_helper;
# }
# 
# 
diff -Nur automake-1.5/lib/am/yacc.am automake-1.5-bernd/lib/am/yacc.am
--- automake-1.5/lib/am/yacc.am 2001-08-23 07:29:16
+++ automake-1.5-bernd/lib/am/yacc.am   2002-01-10 11:59:28
@@ -18,34 +18,10 @@

 ?GENERIC?%EXT%%DERIVED-EXT%:
 ?!GENERIC?%OBJ%: %SOURCE%
-if %?MORE-THAN-ONE%
-       $(SHELL) $(YLWRAP) `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE% 
y.tab.c %OBJ% y.tab.h %BASE%.h y.output %BASE%.output -- %COMPILE%
+       $(SHELL) $(YLWRAP) `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE% 
y.tab.c %OBJ% -- %COMPILE%
-else !%?MORE-THAN-ONE%
-       %COMPILE% `test -f '%SOURCE%' || echo '$(srcdir)/'`%SOURCE%
-## Edit out `#line' or `#' directives.
-       sed '/^#/ s|y\.tab\.c|%OBJ%|' y.tab.c >%OBJ%
-       rm -f y.tab.c
-## Edit out Bison multiple inclusion guards.  It may be BISON_Y_TAB_H,
-## or Y_TAB_H depending upon the version, that's why the regexp is
-## so loose.
-       if test -f y.tab.h; then \
-         to=`echo "%BASE%_H" | sed \
-                -e 'y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/' \
-                -e 's/[^ABCDEFGHIJKLMNOPQRSTUVWXYZ]/_/g'`; \
-         sed "/^#/ s/Y_TAB_H/$$to/g" y.tab.h >%BASE%.ht; \
-         rm -f y.tab.h; \
-         if cmp -s %BASE%.ht %BASE%.h; then \
-           rm -f %BASE%.ht ;\
-         else \
-           mv %BASE%.ht %BASE%.h; \
-         fi; \
-       fi
-       if test -f y.output; then \
-         mv y.output %BASE%.output; \
-       fi
-endif !%?MORE-THAN-ONE%
 
+## Try to fix the yaccity automake problem
+?GENERIC?%EXT%.h:
+?!GENERIC?%BASE%.h: %SOURCE%
+       $(SHELL) $(YLWRAP) %SOURCE% y.tab.h %BASE%.h -- %COMPILE%
+
-## Also generate a dependency for the .h file.
-if !%?GENERIC%
-%BASE%.h: %OBJ%
-endif !%?GENERIC%

# The test cases need to run automake with -a so ylwrap is copied.

diff -Nur automake-1.5/tests/yacc.test automake-1.5-bernd/tests/yacc.test
--- automake-1.5/tests/yacc.test
+++ automake-1.5-bernd/tests/yacc.test
@@ -16,6 +16,6 @@
 END
 
 $ACLOCAL || exit 1
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 grep 'zardoz.c' Makefile.in
diff -Nur automake-1.5/tests/yacc2.test automake-1.5-bernd/tests/yacc2.test
--- automake-1.5/tests/yacc2.test
+++ automake-1.5-bernd/tests/yacc2.test
@@ -22,7 +22,7 @@
 
 
 $ACLOCAL || exit 1
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 # If zardoz.h IS mentioned, fail
 grep 'zardoz.h' Makefile.in > /dev/null && exit 1
@@ -32,7 +32,7 @@
 cp Makefile.src Makefile.am
 echo 'AM_YFLAGS = -d' >> Makefile.am
 
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 # If zardoz.h is NOT mentioned, fail
 grep 'zardoz.h' Makefile.in > /dev/null || exit 1
@@ -42,7 +42,7 @@
 cp Makefile.src Makefile.am
 echo 'AM_YFLAGS = ' >> Makefile.am
 
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 # If zardoz.h IS mentioned, fail
 grep 'zardoz.h' Makefile.in > /dev/null && exit 1
@@ -52,7 +52,7 @@
 cp Makefile.src Makefile.am
 echo 'YFLAGS = -d' >> Makefile.am
 
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 # If zardoz.h is NOT mentioned, fail
 grep 'zardoz.h' Makefile.in > /dev/null || exit 1
@@ -62,7 +62,7 @@
 cp Makefile.src Makefile.am
 echo 'YFLAGS = ' >> Makefile.am
 
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 # If zardoz.h IS mentioned, fail
 grep 'zardoz.h' Makefile.in > /dev/null && exit 1
diff -Nur automake-1.5/tests/yacc3.test automake-1.5-bernd/tests/yacc3.test
--- automake-1.5/tests/yacc3.test
+++ automake-1.5-bernd/tests/yacc3.test
@@ -19,7 +19,7 @@
 END
 
 $ACLOCAL || exit 1
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 fgrep -v @SET_MAKE@ Makefile.in > Makefile.sed
 # It should not be disted here
@@ -32,6 +32,6 @@
    cp Save Makefile.am
    echo "$flag = -d" >> Makefile.am
 
-   $AUTOMAKE || exit 1
+   $AUTOMAKE -a || exit 1
    grep 'zardoz.h' Makefile.in || exit 1
 done
diff -Nur automake-1.5/tests/yacc7.test automake-1.5-bernd/tests/yacc7.test
--- automake-1.5/tests/yacc7.test
+++ automake-1.5-bernd/tests/yacc7.test
@@ -1,6 +1,7 @@
 #! /bin/sh
 
 # Test to make sure dependencies are generated correctly for .h files.
+# Changed by Bernd Jendrissek to check independent regeneration of files.
 # Report from Richard Boulton.
 
 . $srcdir/defs || exit 1
@@ -32,8 +33,29 @@
 $AUTOCONF || exit 1
 ./configure || exit 1
 
-$MAKE foo.h || exit 1
-
-test -f foo.h || exit 1
+# Test sequences:
+# .h  .c    .h  .c
+# no  no    no  no
+# no  yes   yes no
+# yes yes   yes yes
+# TODO: could also check that "other" file isn't unexpectedly regenerated.
+$MAKE foo.h || exit 1
+# *only* foo.h must exist
+test -e foo.h || exit 1
+test -e foo.c && exit 1
+$MAKE foo.c || exit 1
+# *both* foo.h and foo.c must exist
+test -e foo.h || exit 1
+test -e foo.c || exit 1
+rm -f foo.c foo.h
+
+$MAKE foo.c || exit 1
+# *only* foo.c must exist
+test -e foo.c || exit 1
+test -e foo.h && exit 1
+$MAKE foo.h || exit 1
+# *both* foo.h and foo.c must exist
+test -e foo.h || exit 1
+test -e foo.c || exit 1
 
 exit 0
diff -Nur automake-1.5/tests/yaccpp.test automake-1.5-bernd/tests/yaccpp.test
--- automake-1.5/tests/yaccpp.test
+++ automake-1.5-bernd/tests/yaccpp.test
@@ -15,6 +15,6 @@
 END
 
 $ACLOCAL || exit 1
-$AUTOMAKE || exit 1
+$AUTOMAKE -a || exit 1
 
 grep zardoz.cc Makefile.in
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