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trace: avoid unnecessary recompilation if nothing changed

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Add logic to detect changes in generated files. If the old
and new files are identical, don't touch the generated file.
This avoids a lot of churn since many files depend on trace.h.

Based on suggestion by Paolo Bonzini.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Blue Swirl 2010-10-02 14:28:12 +00:00
parent 904fe1fbd1
commit a82cdd58fd
1 changed files with 8 additions and 4 deletions
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12
Makefile
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@ -106,11 +106,15 @@ ui/vnc.o: QEMU_CFLAGS += $(VNC_TLS_CFLAGS)
bt-host.o: QEMU_CFLAGS += $(BLUEZ_CFLAGS)
trace.h: $(SRC_PATH)/trace-events config-host.mak
$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -h < $< > $@," GEN $@")
trace.h: trace.h-timestamp
trace.h-timestamp: $(SRC_PATH)/trace-events config-host.mak
$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -h < $< > $@," GEN trace.h")
@cmp -s $@ trace.h || cp $@ trace.h
trace.c: $(SRC_PATH)/trace-events config-host.mak
$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -c < $< > $@," GEN $@")
trace.c: trace.c-timestamp
trace.c-timestamp: $(SRC_PATH)/trace-events config-host.mak
$(call quiet-command,sh $(SRC_PATH)/tracetool --$(TRACE_BACKEND) -c < $< > $@," GEN trace.c")
@cmp -s $@ trace.c || cp $@ trace.c
trace.o: trace.c $(GENERATED_HEADERS)