[Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Peter Maydell]

On non-x86 hosts with SDL2 2.0.8, configure fails:


config-host.mak is out-of-date, running configure

ERROR: configure test passed without -Werror but failed with -Werror.
       This is probably a bug in the configure script. The failing command
       will be at the bottom of config.log.
       You can run configure with --disable-werror to bypass this check.

The relevant configure test is the SDL one:
#include <SDL.h>
#undef main /* We don't want SDL to override our main() */
int main( void ) { return SDL_Init (SDL_INIT_VIDEO); }

and it fails because on non-x86 platforms one of the SDL headers
triggers a -Wundef warning:

cc -Wundef -o zz9.o -I /usr/include/SDL2 -c qemu-conf.c
In file included from /usr/include/SDL2/SDL.h:38:0,
                 from qemu-conf.c:1:
/usr/include/SDL2/SDL_cpuinfo.h:63:5: warning: "HAVE_IMMINTRIN_H" is
not defined, evaluates to 0 [-Wundef]
 #if HAVE_IMMINTRIN_H && !defined(SDL_DISABLE_IMMINTRIN_H)
     ^~~~~~~~~~~~~~~~

I've reported the bug to debian:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=892087
(who will probably forward it upstream), but since this version
of SDL is already released, I guess we need to work around it it
QEMU...

Any suggestions for how to do a workaround?

thanks
-- PMM

Re: [Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Daniel P. Berrangé]

On Mon, Mar 05, 2018 at 10:24:41AM +0000, Peter Maydell wrote:
> On non-x86 hosts with SDL2 2.0.8, configure fails:
> 
> 
> config-host.mak is out-of-date, running configure
> 
> ERROR: configure test passed without -Werror but failed with -Werror.
>        This is probably a bug in the configure script. The failing command
>        will be at the bottom of config.log.
>        You can run configure with --disable-werror to bypass this check.
> 
> The relevant configure test is the SDL one:
> #include <SDL.h>
> #undef main /* We don't want SDL to override our main() */
> int main( void ) { return SDL_Init (SDL_INIT_VIDEO); }
> 
> and it fails because on non-x86 platforms one of the SDL headers
> triggers a -Wundef warning:
> 
> cc -Wundef -o zz9.o -I /usr/include/SDL2 -c qemu-conf.c
> In file included from /usr/include/SDL2/SDL.h:38:0,
>                  from qemu-conf.c:1:
> /usr/include/SDL2/SDL_cpuinfo.h:63:5: warning: "HAVE_IMMINTRIN_H" is
> not defined, evaluates to 0 [-Wundef]
>  #if HAVE_IMMINTRIN_H && !defined(SDL_DISABLE_IMMINTRIN_H)
>      ^~~~~~~~~~~~~~~~

Ewwww, even ignoring the -Wundef issue, this is a really unpleasant
approach from SDL.  All these HAVE_* symbols SDL2 tests & defines
are polluting the global header namespace and could easily clash
with symbols defined by QEMU / $APP's own configure.ac script :-(

> Any suggestions for how to do a workaround?

Drop -Wundef when running the configiure test, or override it with -Wno-undef

If the actual ui/sdl* files fail for same reason, we could use a gcc
pragma top disable -Wundef in just those files, or set -Wno-undef in
CFLAGS on a per-.o file basis in Makefile.objs

Regards,
Daniel
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Re: [Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Gerd Hoffmann]

  Hi,

> > Any suggestions for how to do a workaround?
> 
> Drop -Wundef when running the configiure test, or override it with -Wno-undef
> 
> If the actual ui/sdl* files fail for same reason, we could use a gcc
> pragma top disable -Wundef in just those files, or set -Wno-undef in
> CFLAGS on a per-.o file basis in Makefile.objs

What is the status here?  Could you try this peter?  Don't have a test
box with SDL 2.0.8 at hand ...

Any reaction from debian/upstream?  Given that this probably affects
pretty much any SDL user and 2.0.8 is a few days old only a quick 2.0.9
bugfix release would be the best solution I guess.

cheers,
  Gerd

Re: [Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Peter Maydell]

On 7 March 2018 at 14:11, Gerd Hoffmann <kraxel@redhat.com> wrote:
>   Hi,
>
>> > Any suggestions for how to do a workaround?
>>
>> Drop -Wundef when running the configiure test, or override it with -Wno-undef
>>
>> If the actual ui/sdl* files fail for same reason, we could use a gcc
>> pragma top disable -Wundef in just those files, or set -Wno-undef in
>> CFLAGS on a per-.o file basis in Makefile.objs
>
> What is the status here?  Could you try this peter?  Don't have a test
> box with SDL 2.0.8 at hand ...

Haven't tried it, but I'm pretty sure it would work. For the
moment I just passed --disable-sdl to configure...

> Any reaction from debian/upstream?  Given that this probably affects
> pretty much any SDL user and 2.0.8 is a few days old only a quick 2.0.9
> bugfix release would be the best solution I guess.

Nothing from Debian yet; haven't tried to contact upstream
(feel free to do that yourself).

thanks
-- PMM

Re: [Qemu-devel] QEMU fails to configure on non-x86 hosts with recent SDL2

[Gerd Hoffmann]

On Wed, Mar 07, 2018 at 02:18:02PM +0000, Peter Maydell wrote:
> On 7 March 2018 at 14:11, Gerd Hoffmann <kraxel@redhat.com> wrote:
> >   Hi,
> >
> >> Drop -Wundef when running the configiure test, or override it with -Wno-undef
> >>
> >> If the actual ui/sdl* files fail for same reason, we could use a gcc
> >> pragma top disable -Wundef in just those files, or set -Wno-undef in
> >> CFLAGS on a per-.o file basis in Makefile.objs
> >
> > What is the status here?  Could you try this peter?  Don't have a test
> > box with SDL 2.0.8 at hand ...
> 
> Haven't tried it, but I'm pretty sure it would work. For the
> moment I just passed --disable-sdl to configure...

Ok, fedora rawhide has updated packages too.  With that recompiled I can
reproduce the issue.  The workaround is a one-liner, for both configure
and the sdl object builds.

cheers,
  Gerd