From aff53b27f0942cf9a0dcc5b10dca528e88b0cabf Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Fri, 16 Nov 2001 16:32:33 +0000
Subject: Make the yacc rules safe for parallel make.  See discussion on
 pgsql-patches and comment in src/backend/parser/Makefile for the technical
 details.

---
 src/backend/parser/Makefile | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

(limited to 'src/backend/parser')

diff --git a/src/backend/parser/Makefile b/src/backend/parser/Makefile
index 62ff3098ed2..ed910f09a45 100644
--- a/src/backend/parser/Makefile
+++ b/src/backend/parser/Makefile
@@ -2,7 +2,7 @@
 #
 # Makefile for parser
 #
-# $Header: /cvsroot/pgsql/src/backend/parser/Makefile,v 1.34 2001/08/09 18:13:23 petere Exp $
+# $Header: /cvsroot/pgsql/src/backend/parser/Makefile,v 1.35 2001/11/16 16:32:33 petere Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -20,15 +20,26 @@ all: SUBSYS.o
 SUBSYS.o: $(OBJS)
 	$(LD) $(LDREL) $(LDOUT) $@ $^
 
-$(srcdir)/gram.c $(srcdir)/parse.h: gram.y
+
+# There is no correct way to write a rule that generates two files.
+# Rules with two targets don't have that meaning, they are merely
+# shorthand for two otherwise separate rules.  To be safe for parallel
+# make, we must chain the dependencies like this.  The semicolon is
+# important, otherwise make will choose the built-in rule for
+# gram.y=>gram.c.
+
+$(srcdir)/gram.c: $(srcdir)/parse.h ;
+
+$(srcdir)/parse.h: gram.y
 ifdef YACC
 	$(YACC) -d $(YFLAGS) $<
-	mv y.tab.c $(srcdir)/gram.c
-	mv y.tab.h $(srcdir)/parse.h
+	mv -f y.tab.c $(srcdir)/gram.c
+	mv -f y.tab.h $(srcdir)/parse.h
 else
 	@$(missing) bison $< $@
 endif
 
+
 $(srcdir)/scan.c: scan.l
 ifdef FLEX
 	$(FLEX) $(FLEXFLAGS) -Pbase_yy -o'$@' $<
-- 
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