Re: [RFC] xen/arm: build: add missed dependency for head.S

[Ian Jackson <Ian.Jackson@eu.citrix.com>]

Julien Grall writes ("Re: [RFC] xen/arm: build: add missed dependency for head.S"):
> On 03/06/16 11:07, Wei Chen wrote:
> > When we update the header files that had been included in head.S.
> > The build system would not re-compile the head.S. Because in the
> > build rules, the dependencies are setting to .*.d (eg. DEPS = .*.d)
> > files in the same folder as Makefile.
> >
> > But head.S is very special, it was used by the Makefile in the parent
> > folder: "ALL_OBJS := $(TARGET_SUBARCH)/head.o".
> >
> > In this case, the build system could not find the dependency in DEPS.
> > When we update the header files, the build system is unware of this
> > update. If we re-build the Xen without doing make clean or touching
> > the head.S, the build system will not recompile the head.S.
> >
> > Signed-off-by: Wei Chen <Wei.Chen@linaro.org>

Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

This should be in 4.7 and is a backport candidate.

> > In my mind, the better way to fix this bug is converting the DEPS from
> > ALL_OBJS. But I am afraid of the impact. I am not sure whether there
> > are some dependencies are not generated from obj files.

I do like this idea but I have the same worry.  It might be possible
to dump ALL_OBJS out somehow and check this, but it might be
arch-dependent.

Wei Chen's patch is IMO a straightforward fix.

Thanks,
Ian.

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