Re: [PATCH v4 04/18] ui: avoid warnings about directdb on Alpine / musl libc

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

On Wed, Nov 24, 2021 at 02:32:56PM +0100, Thomas Huth wrote:
> On 24/11/2021 14.01, Daniel P. Berrangé wrote:
> > On Alpine, SDL is built with directfb support and this triggers warnings
> > during QEMU build
> > 
> > In file included from /usr/include/directfb/direct/thread.h:38,
> >                   from /usr/include/directfb/direct/debug.h:43,
> >                   from /usr/include/directfb/direct/interface.h:36,
> >                   from /usr/include/directfb/directfb.h:49,
> >                   from /usr/include/SDL2/SDL_syswm.h:80,
> >                   from /builds/berrange/qemu/include/ui/sdl2.h:8,
> >                   from ../ui/sdl2-gl.c:31:
> > /usr/include/directfb/direct/os/waitqueue.h:41:25: error: redundant redeclaration of 'direct_waitqueue_init' [-Werror=redundant-decls]
> >     41 | DirectResult DIRECT_API direct_waitqueue_init        ( DirectWaitQueue *queue );
> >        |                         ^~~~~~~~~~~~~~~~~~~~~
> 
> I think that's a bug in the SDL2 package of Alpine. I've had trouble with
> that one in the past already ... so not sure whether it's our job now to
> work around bugs in that crappy Alpine package... I'd prefer if we simply do
> not compile-test SDL on Alpine instead.

It is a harmless bug in directfb headers, which has no ill
effects other than producing a warning when some app uses
-Wredundant-decls.  Of course Alpine would ideally get this
patched, but at the same time it is reasonable for Alpine
users to want SDL and if someone has this package installed
already we don't want QEMU build to break due to -Werror.

Case in point, as we auto-generate dockerfiles to ensure
all pre-requisites are installed in all dockerfiles,  the
Alpine dockerfile gains SDL and exposes this bug. We could
turn off -Werror but that's a overly big hammer compared
to this targetted fix.

Regards,
Daniel
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