build: use yacc pattern rule with "y" as stem.

Thanks to a recent discussion in the GNU Make mailing list
about some issue related to grouped patterns, I hit upon the
realization that the rule y.tab.h y.tab.c: parser.y has
a common stem, y, which can be exploited to write a pattern
rule. This is only active in maintainer mode; in user mode,
the y.tab.h and y.tab.c are separately produced from .shipped
files.

* Makefile (y.tab.h): Eliminate rule which detects a removed
y.tab.h.
(y.tab.c): Delete rule, replacing with new rule.
(%.tab.c %.tab.h): New pattern rule, which groups the targets
together.

1 files changed, 1 insertions, 9 deletions

diff --git a/Makefile b/Makefile
index f0426802..37eb677d 100644
--- a/Makefile
+++ b/Makefile
@@ -274,15 +274,7 @@ lex.yy.c: $(top_srcdir)parser.l
 	  fi)
 	$(call SH,chmod a-w $@)
 
-y.tab.h: y.tab.c
-	$(call SH,                                              \
-	  if ! [ -e y.tab.h ] ; then                            \
-	    echo "Someone removed y.tab.h but left y.tab.c" ;   \
-	    echo "Remove y.tab.c and re-run make" ;             \
-	    exit 1 ;                                            \
-	  fi)
-
-y.tab.c: $(top_srcdir)parser.y
+%.tab.c %.tab.h: $(top_srcdir)parser.%
 	$(call ABBREV,YACC)
 	$(call SH,                                              \
 	  if [ -e y.tab.h ]; then mv y.tab.h y.tab.h.old ; fi)