[Qemu-devel] [PATCH 1/2] trace: fix make foo-timestamp rules

[Stefan Hajnoczi <stefanha@redhat.com>]

The Makefile uses intermediate timestamp files to avoid rebuilding if
tracetool output is unchanged.

Timestamps are implemented incorrectly.  This was fixed for rules.mak in
commit 4b25966ab976f3a7fd9008193b2defcc82f8f04d ("rules.mak: cleanup
config generation rules") but never fixed in trace/Makefile.objs.

The problem with the old timestamp implementation was that make doesn't
notice the updated file modification time until the next time it is run.
It was necessary to run make twice in a row to achieve a full rebuild.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 trace/Makefile.objs | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/trace/Makefile.objs b/trace/Makefile.objs
index 32f7a32..73bec38 100644
--- a/trace/Makefile.objs
+++ b/trace/Makefile.objs
@@ -5,20 +5,20 @@
 
 ifeq ($(findstring ust,$(TRACE_BACKENDS)),ust)
 $(obj)/generated-ust-provider.h: $(obj)/generated-ust-provider.h-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-ust-provider.h-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=ust-events-h \
 		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-ust.c: $(obj)/generated-ust.c-timestamp $(BUILD_DIR)/config-host.mak
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-ust.c-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=ust-events-c \
 		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-events.h: $(obj)/generated-ust-provider.h
 $(obj)/generated-events.c: $(obj)/generated-ust.c
@@ -28,20 +28,20 @@ endif
 # Auto-generated event descriptions
 
 $(obj)/generated-events.h: $(obj)/generated-events.h-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-events.h-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=events-h \
 		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-events.c: $(obj)/generated-events.c-timestamp $(BUILD_DIR)/config-host.mak
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-events.c-timestamp: $(SRC_PATH)/trace-events
 	$(call quiet-command,$(TRACETOOL) \
 		--format=events-c \
 		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 util-obj-y += generated-events.o
 
@@ -81,12 +81,12 @@ $(obj)/generated-tracers.o: $(obj)/generated-tracers.c $(obj)/generated-tracers.
 # rule file. So we use '.dtrace' instead
 ifeq ($(findstring dtrace,$(TRACE_BACKENDS)),dtrace)
 $(obj)/generated-tracers-dtrace.dtrace: $(obj)/generated-tracers-dtrace.dtrace-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-tracers-dtrace.dtrace-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=d \
 		--backends=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-tracers-dtrace.h: $(obj)/generated-tracers-dtrace.dtrace
 	$(call quiet-command,dtrace -o $@ -h -s $<, "  GEN   $@")
@@ -100,28 +100,28 @@ endif
 # Translation level
 
 $(obj)/generated-helpers-wrappers.h: $(obj)/generated-helpers-wrappers.h-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-helpers-wrappers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=tcg-helper-wrapper-h \
 		--backend=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-helpers.h: $(obj)/generated-helpers.h-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-helpers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=tcg-helper-h \
 		--backend=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-helpers.c: $(obj)/generated-helpers.c-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-helpers.c-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=tcg-helper-c \
 		--backend=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 $(obj)/generated-helpers.o: $(obj)/generated-helpers.c
 
@@ -129,12 +129,12 @@ target-obj-y += generated-helpers.o
 
 
 $(obj)/generated-tcg-tracers.h: $(obj)/generated-tcg-tracers.h-timestamp
+	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 $(obj)/generated-tcg-tracers.h-timestamp: $(SRC_PATH)/trace-events $(BUILD_DIR)/config-host.mak
 	$(call quiet-command,$(TRACETOOL) \
 		--format=tcg-h \
 		--backend=$(TRACE_BACKENDS) \
 		< $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
-	@cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst %-timestamp,%,$@)
 
 
 ######################################################################
-- 
2.4.3