Re: [Qemu-devel] [PATCH v5 2/9] make: ensure all members of libqemuutil.a are linked

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Aug 26, 2015 at 09:25:39AM -0600, Eric Blake wrote:
> On 08/26/2015 09:05 AM, Daniel P. Berrange wrote:
> > The libqemuutil.a archive may contain QOM objects which are
> > only indirectly referenced via __attribute__((constructor))
> > annotations. Despite the constructor annotation the linker
> > will think these objects are unused by the executable and
> > so drop them when linking, to the system emulator. As a
> > result the objects in question will be missing from QOM.
> > 
> > Using the -Wl,--whole-archive flag instructs the linker
> > to pull in everything in libqemuutil.a regardless of
> > whether it thinks it is used or not.
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> > ---
> >  Makefile.target | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Makefile.target b/Makefile.target
> > index 3e7aafd..5b08f0f 100644
> > --- a/Makefile.target
> > +++ b/Makefile.target
> > @@ -180,8 +180,13 @@ all-obj-$(CONFIG_SOFTMMU) += $(block-obj-y)
> >  $(QEMU_PROG_BUILD): config-devices.mak
> >  
> >  # build either PROG or PROGW
> > +# We must use --whole-archive with libqemuutil.a otherwise the
> > +# linker will drop any objects from the archive which are only
> > +# indirectly referenced via __attribute__(constructor) annotations
> >  $(QEMU_PROG_BUILD): $(all-obj-y) ../libqemuutil.a ../libqemustub.a
> > -	$(call LINK, $(filter-out %.mak, $^))
> > +	$(call LINK, $(filter-out %.mak, $(sort $(all-obj-y)))) \
> 
> Why the added $(sort)? Should that be a separate patch?

$(all-obj-y) has some .o's listed multiple times. $^ removes
duplicates, avoiding this problem, but if we use $(all-obj-y)
we must now remove duplicates ourselves. $(sort) removes
duplicates and AFAICT, there's no built-in make function
that can remove duplicates without sorting.

> 
> > +		-Wl,--whole-archive ../libqemuutil.a -Wl,--no-whole-archive \
> > +		../libqemustub.a
> 
> Otherwise makes sense to me.
> Reviewed-by: Eric Blake <eblake@redhat.com>



Regards,
Daniel
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