Re: [Qemu-devel] [PATCH] configure: Let SDL support be optional on OpenBSD

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

On Tue, Jan 22, 2019 at 07:20:35PM +0000, Peter Maydell wrote:
> On Tue, 22 Jan 2019 at 19:05, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> >
> > Currently if we try to build QEMU on OpenBSD with SDL disabled, we get:
> >
> >   $ ./configure --cc=x86_64-unknown-openbsd6.1-gcc-4.9.4 --python=python2.7 --disable-sdl
> >
> >   ERROR: sdl not found or disabled, can not use sdl audio driver
> >
> > Since SDL is not a requirement for OpenBSD, let it be optional (we remove
> > it from $audio_drv_list but it stays available in $audio_possible_drivers).
> > If no audio backends are available, QEMU falls back to the null driver.
> 
> > --- a/configure
> > +++ b/configure
> > @@ -828,7 +828,7 @@ NetBSD)
> >  OpenBSD)
> >    bsd="yes"
> >    make="${MAKE-gmake}"
> > -  audio_drv_list="sdl"
> > +  audio_drv_list=""
> >    audio_possible_drivers="sdl"
> >    HOST_VARIANT_DIR="openbsd"
> >    supported_os="yes"
> 
> This will mean that configure will by default not enable
> a real audio backend, even if we do have sdl.
> 
> Looking at the logic, "audio_possible_drivers" is only
> used for printing the help message. The thing that drives
> which audio drivers to test with is "audio_drv_list",
> and the expectation is that you put things on that only
> if it's possible to build with them. (For instance
> we only add 'dsound' for mingw if the dsound.h header is
> present, and so on.)
> 
> So we need to do one of:
>  (1) only put "sdl" into audio_drv_list if SDL is
>      available (this probably doesn't work as we haven't
>      probed for SDL at the point where we initialize it)
>  (2) have the sdl probe delete "sdl" from audio_drv_list
>      if the probe fails

This one sounds reasonable to me.

>  (3) some more complicated restructuring :-)
>      (eg rather than having audio_drv_list be set to an
>      initial list based on the host OS, just have a full
>      list of drivers, insist that each has a proper probe
>      routine, and use whichever ones we can successfully
>      probe)


Regards,
Daniel
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