Re: [PATCH v2 2/2] perf jevents: Enable warnings through HOSTCFLAGS

[John Garry]

On 25/10/2021 17:20, Arnaldo Carvalho de Melo wrote:
> Em Mon, Oct 25, 2021 at 01:40:44PM +0200, Jiri Olsa escreveu:
> > On Fri, Oct 22, 2021 at 10:42:11AM +0100, John Garry wrote:
> > > On 21/10/2021 13:48, Jiri Olsa wrote:
> > > > > +HOSTCFLAGS += -Wall
> > > > > +HOSTCFLAGS += -Wextra
> > > > > +
> > > > >    # Enforce a non-executable stack, as we may regress (again) in the future by
> > > > >    # adding assembler files missing the .GNU-stack linker note.
> > > > >    LDFLAGS += -Wl,-z,noexecstack
> > > > > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > > > > index 7df13e74450c..118bcdc70bb4 100644
> > > > > --- a/tools/perf/Makefile.perf
> > > > > +++ b/tools/perf/Makefile.perf
> > > > > @@ -226,7 +226,7 @@ else
> > > > >    endif
> > > > >    export srctree OUTPUT RM CC CXX LD AR CFLAGS CXXFLAGS V BISON FLEX AWK
> > > > > -export HOSTCC HOSTLD HOSTAR
> > > > > +export HOSTCC HOSTLD HOSTAR HOSTCFLAGS
> > > > >    include $(srctree)/tools/build/Makefile.include
> > > > > diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> > > > > index a055dee6a46a..d5c287f069a2 100644
> > > > > --- a/tools/perf/pmu-events/Build
> > > > > +++ b/tools/perf/pmu-events/Build
> > > > > @@ -1,7 +1,7 @@
> > > > >    hostprogs := jevents
> > > > >    jevents-y	+= json.o jsmn.o jevents.o
> > > > > -HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include
> > > > > +HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include $(HOSTCFLAGS)
> > > > so the the host cflags are made of:
> > > >
> > > > host_c_flags = -Wp,-MD,$(depfile) -Wp,-MT,$@ $(KBUILD_HOSTCFLAGS) -D"BUILD_STR(s)=\#s" $(HOSTCFLAGS_$(basetarget).o) $(HOSTCFLAGS_$(obj))
> > >
> > > ok, so IIRC, then the rule for building .o from .c in
> > > tools/build/Makefile.build will pick up HOSTCFLAGS through this variable, so
> > > we then don't need to explicitly mention it in the per-target rule, so can
> > > have this as before in pmu-events/Build
> > >
> > > HOSTCFLAGS_jevents.o	= -I$(srctree)/tools/include
> > >
> > > right?
> > >
> > > (Indeed I guess that we can get rid of -I$(srctree)/tools/include as well)
> >
> > hm, the -I.. should stay no? I don't see that
> > it's being added soem other way
> >
> > jirka
>
> Probably this change from KBUILD_HOSTCFLAGS back to HOSTCFLAGS should
> come with this;
>
> Cc: Laura Abbott <labbott@xxxxxxxxxx>
> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> Fixes: 96f14fe738b69dd9 ("kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS")
>
> Right?

Maybe, but then renaming back from KBUILD_HOSTCFLAGS -> HOSTCFLAGS seems 
odd as a fix

Anyway, now that this original series is in perf/core, I'll send patches 
on top with this change, cc'ing Laura and Masahiro

Thanks!