Re: [Qemu-devel] [PATCH v4 3/5] Adapt Makefiles to the new LTTng ust interface.

[Stefan Hajnoczi]

On Fri, Oct 18, 2013 at 02:39:51AM -0400, Mohamad Gebai wrote:
>  ######################################################################
> +# Auto-generated event descriptions for LTTng ust code
> +
> +ifeq ($(TRACE_BACKEND),ust)
> +$(obj)/generated-ust-provider.h: $(obj)/generated-ust-provider.h-timestamp
> +$(obj)/generated-ust-provider.h-timestamp: $(SRC_PATH)/trace-events
> +     $(call quiet-command,$(TRACETOOL) \
> +             --format=ust-events-h \
> +             --backend=events \
> +             < $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
> +     @cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst 
> %-timestamp,%,$@)
> +
> +$(obj)/generated-ust.c: $(obj)/generated-ust.c-timestamp 
> $(BUILD_DIR)/config-host.mak
> +$(obj)/generated-ust.c-timestamp: $(SRC_PATH)/trace-events
> +     $(call quiet-command,$(TRACETOOL) \
> +             --format=ust-events-c \
> +             --backend=events \
> +             < $< > $@,"  GEN   $(patsubst %-timestamp,%,$@)")
> +     @cmp -s $@ $(patsubst %-timestamp,%,$@) || cp $@ $(patsubst 
> %-timestamp,%,$@)
> +
> +ust_provider=$(obj)/generated-ust-provider.h
> +ust=$(obj)/generated-ust.c

I think you can avoid the variables by defining single dependencies
upfront:

$(obj)/generated-events.h: $(obj)/generated-ust-provider.h
$(obj)/generated-events.c: $(obj)/generated-ust.c