[FFmpeg-devel] [PATCH] configure: Remove av_restrict

[Andreas Rheinhardt]

Martin Storsjö:
> On Sun, 10 Mar 2024, Andreas Rheinhardt wrote:
> 
>> All versions of MSVC that support C11 (namely >= v19.27)
>> also support the restrict keyword, therefore av_restrict
>> is no longer necessary since 75697836b1db3e0f0a3b7061be6be28d00c675a0.
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
>> ---
>> Untested except via godbolt.
>> MSVC actually uses it for optimizations: https://godbolt.org/z/3EzPnff9T
> 
> This change looks good overall, thanks! Fate runs successfully both with
> an old version of MSVC targeting x86_64 and a new one targeting aarch64.
> 
> However, MSVC 19.27 (aka 2019 16.7) can't successfully build ffmpeg at
> the moment - it regressed in ec1b6e0cd404b2f7f4d202802b1c0a40d52fc9b0.
> Now building fails with this error:
> 
> src/libavcodec/ccaption_dec.c(186): error C2143: syntax error: missing
> ')' before 'sizeof'
> src/libavcodec/ccaption_dec.c(186): error C2143: syntax error: missing
> '{' before 'sizeof'
> src/libavcodec/ccaption_dec.c(186): error C2059: syntax error: 'sizeof'
> 
> This issue is not present with the following version, MSVC 2019 16.8
> (aka 19.28) though.
> 

Testing with Godbolt shows that MSVC 19.27 does not support
_Static_assert. But it supports static_assert (its synonym defined in
assert.h). So this is easy to fix.

>> Btw: The block about __declspec(restrict) was always unneeded
>> for FFmpeg due to 17fad33f81c7e9787fcdc17934fc1eee6c6aa4bf.
>> It came from Libav commit 17fad33f81c7e9787fcdc17934fc1eee6c6aa4bf.
> 
> This looks like a copypaste typo, I presume the latter should have been
> 0cff125200ab53fa3ae70d85b4f614f269fe3426. (The code it changed
> originated in dfa559bcbd41397b3408c59d016631c7c65e320f in libav.)
> 

Correct.

- Andreas