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From: Anshul Makkar <anshul.makkar@profitbricks.com>
Date: Fri, 4 Jul 2014 11:24:22 +0200
Message-ID: <CAM4NYE8MJiCovNO1-1OdFOKBfSvrVVLmvE3UtUCP+MS29_hjBw@mail.gmail.com>
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Subject: Re: [Qemu-devel] Help debugging audio problem
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To: Markus Armbruster <armbru@redhat.com>
Cc: Programmingkid <programmingkidx@gmail.com>, qemu-devel <qemu-devel@nongnu.org>

Use of glue is heavily uses in audio code. I completely redesigned it
for Virtualbox and removed all the hard to understand glue code :) .

Not sure if this glue magic is such heavily used anywhere else also.

Moreover audio code uses one big monolythic big audio file audio.c .
So bringing modularity was another aim of my redesigning.

Anshul Makkar

On Thu, Jul 3, 2014 at 9:10 AM, Markus Armbruster <armbru@redhat.com> wrote:
> Programmingkid <programmingkidx@gmail.com> writes:
>
>> What does this code mean?
>>
>>  if (!glue (s->nb_hw_voices_, TYPE)) {
>>         return NULL;
>>     }
>>
>> The code is found in audio_template.h at line 244.
>>
>> I tried using GDB to figure out what it was doing, but had little luck.
>>
>> The AC97 sound card does not work, and I'm trying to change that.
>>
>> Any help would be great. Thanks.
>
> Definition of macro glue is in osdep.h.  It glues together its
> arguments.  Consult your textbook on C to understand how that kind of
> arcane preprocessor magic works.
>
> The audio subsystem is exceedingly fond of magic.
>
> In actual use, macro TYPE has either value in or out, thus the result is
> either s->nb_hw_voices_in or s->nb_hw_voices_out.
>