From 0becf7375e1b0d6976c9637aca52c3985bb61b41 Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Mon, 20 Jun 2011 21:35:13 -0400
Subject: [PATCH] Don't touch unchanged flex/bison headers.

This prevents some spurious rebuilds.
---
 Makefile.am | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 6921dbb..6ea246a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -20,7 +20,8 @@ src/parse.$(OBJEXT): src/scan.h
 src/scan.$(OBJEXT): src/parse.h
 src/libcdecl.$(OBJEXT): src/scan.h src/parse.h
 
-# These are required to prevent the builtin lex/yacc rules from triggering...
+# These are required to prevent the builtin lex/yacc rules from
+# superseding ours...
 src/scan.c src/scan.h: src/scan.stamp
 src/parse.c src/parse.h: src/parse.stamp
 
@@ -39,12 +40,22 @@ FLEX_V_0 = @echo "  FLEX  " $<;
 
 .y.stamp:
 	$(AM_V_at) touch $@.tmp
-	$(BISON_V) $(BISON) -o $*.c --defines=$*.h $(BISONFLAGS) $<
+	$(BISON_V) $(BISON) -o $*.c --defines=$*.h.tmp $(BISONFLAGS) $<
+	$(AM_V_at) if cmp $*.h.tmp $*.h >/dev/null 2>&1; then \
+		rm -f $*.h.tmp; \
+	else \
+		mv -f $*.h.tmp $*.h; \
+	fi
 	$(AM_V_at) mv -f $@.tmp $@
 
 .l.stamp:
 	$(AM_V_at) touch $@.tmp
-	$(FLEX_V) $(FLEX) -o $*.c --header-file=$*.h $(FLEXFLAGS) $<
+	$(FLEX_V) $(FLEX) -o $*.c --header-file=$*.h.tmp $(FLEXFLAGS) $<
+	$(AM_V_at) if cmp $*.h.tmp $*.h >/dev/null 2>&1; then \
+		rm -f $*.h.tmp; \
+	else \
+		mv -f $*.h.tmp $*.h; \
+	fi
 	$(AM_V_at) mv -f $@.tmp $@
 
 .stamp.c:
-- 
2.43.2