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Subject: Re: [Qemu-devel] Questions on audio_atexit(), possibly bugs
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From: Markus Armbruster <armbru@redhat.com>
Date: Fri, 02 Oct 2009 00:40:42 +0200
In-Reply-To: <Pine.LNX.4.64.0910020124370.2172@linmac.oyster.ru> (malc's
	message of "Fri\, 2 Oct 2009 01\:26\:24 +0400 \(MSD\)")
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To: malc <av1474@comtv.ru>
Cc: qemu-devel@nongnu.org

malc <av1474@comtv.ru> writes:

> On Thu, 1 Oct 2009, Markus Armbruster wrote:
>
>> malc <av1474@comtv.ru> writes:
>> 
>> > On Thu, 1 Oct 2009, Markus Armbruster wrote:
>> >
>> >> malc <av1474@comtv.ru> writes:
>> >> 
>> >> > On Wed, 30 Sep 2009, Markus Armbruster wrote:
>> >> >
>> >
>> > [..snip..]
>> >
> [..snip..]
>
>> 
>> The ctl_out() and ctl_in() callbacks I checked (ALSA, OSS), get the
>> variable argument unconditionally.
>> 
>> Getting more variable arguments than the caller passed is undefined
>> behavior (C99 7.15.1.1), although in practice is usually gets some
>> unpredictable value, which is harmless as long as it's not actually
>> used.
>
> I wasn't aware of that, thank you for pointing that out.
>
>> 
>> Not getting all variable arguments the caller passed is fine.
>> 
>> So, the calls you fixed up weren't broken in the first place, and the
>> change isn't worth the trouble, in my opinion.
>> 
>> However, there are calls with undefined behavior, because they pass two
>> arguments (two fixed, zero variable), and at least some callees use
>> three (two fixed, one variable).  Fix for that below.
>> 
>
> I'd much rather fix oss and alsa, they should look for poll_mode only in
> case of enable, one more time thanks for heads up.

Makes sense.

Better check the other drivers as well, because I didn't.