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

[Julien Grall <julien.grall@xxxxxxx>]

Hi Ian,

On 07/06/16 11:03, Ian Jackson wrote:
> 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@xxxxxxxxxx>
> Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>
> This should be in 4.7 and is a backport candidate.
Sounds good to me.

> > > 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.
FWIW, Wei sent a new version today [1] which implement his suggestion. 
Although it might be too risky for Xen 4.7.
Regards,

[1] 
http://lists.xenproject.org/archives/html/xen-devel/2016-06/msg00781.html
--
Julien Grall

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