[Qemu-devel] [PATCH 2/4] Makefile: clean timestamp generation rule

["Michael S. Tsirkin" <mst@redhat.com>]

create timestamp by rule without sideeffects.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 trace/Makefile.objs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index 27fe26b..dde9d57 100644
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -4,24 +4,24 @@
 # Auto-generated header for tracing routines
 
 $(obj)/generated-tracers.h: $(obj)/generated-tracers.h-timestamp
+	@cmp -s $< $@ || cp $< $@
 $(obj)/generated-tracers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=h \
 		--backend=$(TRACE_BACKEND) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 ######################################################################
 # Auto-generated tracing routines (non-DTrace)
 
 ifneq ($(TRACE_BACKEND),dtrace)
 $(obj)/generated-tracers.c: $(obj)/generated-tracers.c-timestamp
+	@cmp -s $< $@ || cp $< $@
 $(obj)/generated-tracers.c-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=c \
 		--backend=$(TRACE_BACKEND) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-tracers.o: $(obj)/generated-tracers.c $(obj)/generated-tracers.h
 endif
-- 
MST