On Tue, Oct 18, 2022 at 01:01:14PM +0200, Ulrich Drepper via Gcc-patches wrote:
> This is of course not a new problem in general. GNU make has for a long
> time support for order-only prerequisites. With those one can exactly
> express what is needed:
>
> ifeq ($(ENABLE_MAINTAINER_RULES), true)
> FOO.h: FOO.gperf
> else
> FOO.h: | FOO.gperf
> endif
> gperf ...
>
> ifeq ($(ENABLE_MAINTAINER_RULES), true)
> FOO.gperf: CSV
> else
> FOO.gperf: | CSV
> endif
> python ...
>
> The question here is whether there is a reason not to depend on GNU make
> features (and whatever other make implemented this extension).
GCC requires GNU make and we already use order-only prerequisities in
gcc/Makefile.in :
# In order for parallel make to really start compiling the expensive
# objects from $(OBJS) as early as possible, build all their
# prerequisites strictly before all objects.
$(ALL_HOST_OBJS) : | $(generated_files)
Jakub
