[FFmpeg-devel] [PATCH 1/4] x86inc: Support arbitrary stack alignments

[Hendrik Leppkes]

On Mon, Aug 3, 2015 at 10:31 AM, Henrik Gramner <henrik at gramner.com> wrote:
> On Mon, Aug 3, 2015 at 2:18 AM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>> So, I think the code changes themselves look mostly healthy. Is there a
>> behavioural difference before/after this patch? (Like: were there bugs in
>> the original code, or does this change behaviour of previous code in a
>> significant way?)
>
> Should only be what's in the commit message; "Previously alignment
> would occur either before or after allocating stack space depending on
> whether manual alignment was required or not." which I guess you could
> classify as a bug (it certainly wasn't a sensible behavior). It's the
> reason for why the weird deblock stack allocation for example existed
> in the first place.
>
> So anything relying on the previous alignment behavior of automatic
> stack allocation using cglobal would be affected, other than that it
> shouldn't make any difference since ffmpeg doesn't use >16-byte stack
> alignment.
>
> I can only compile ffmpeg with --disable-programs when using
> msys2/msvc2015 (ffmpeg.c(437): error C2039: '_cnt': is not a member of
> '_iobuf'). Not sure if I'm doing something wrong, but if someone is
> able to test that better that would be nice.

msvc2015 support is unfortunately still broken. I'll send a patch
later for this.

Otherwise, I tested the patch with msvc 2013 32-bit, and fate passed fine.
If there is something else I should specifically test which may not be
covered by fate, let me know.

- Hendrik