[FFmpeg-devel] [patch] Fix a warning in fft_mmx.asm on mac

[Nico Weber]

Hi Michael,

thank you for your reply.

>> If you don't think this revised patch can be landed, please let me
>> know what's missing.
>
> I think if there are still users around using old versions that need
> the workaround then the workaround should stay and no configure check
> should be added. (such check adds maintaince burden and its for a case
> that wont get tested so breakage is not unlikely)
>
> OTOH if all users, all platforms and such are using new enough versions
> then it just can be droped but
>
>> Yasm was fixed in its r2161 and yasm 0.8.0 (Apr 2010) contained this fix.
>> Nasm was fixed in 2.06 (Jun 2009):
>> https://groups.google.com/group/alt.lang.asm/browse_thread/thread/fcc85bbc3745d893
>
> Apr 2010 is not so long ago, i dont think this would have a zero effect

Sorry, I mistyped the year :-/ It's actually Apr 2009 (source:
http://yasm.tortall.net/Download.html) Not sure if this changes much
though.

> on our users. And i see nothing in your mail that would point to some
> research that all users & platforms would be using a recent enough
> version. But then this is huge work to do and the gain is fairly small

Note that this is a mac-only issue. People who build ffmpeg on mac
need to download / build yasm manually (yasm isn't included with
Xcode, and the nasm that is included doesn't pass the existing
configure script), so if configure told them to upgrade to a
less-than-three-years-old yasm, they would probably need to know what
to do.

Is there any research I can do to estimate how many people would be
affected by this change? What kind of data would you like to see that
I can realistically collect?

> Also if you are concerned about warnings, there are many that can be
> removed with less risk and troubble.

This is the last warning in all of chromium, including all third-party
code. (Admittedly, we disabled several harmless warnings that ffmpeg
doesn't seem to care about in the C parts. This yasm warning can't be
disabled though.)

Thanks,
Nico