[vlc-devel] [PATCH] contrib: ffmpeg: disable some inline assembler in win32 builds with LLVM

[Thomas Guillem]

On Thu, Jun 18, 2020, at 10:51, Rémi Denis-Courmont wrote:
> -O0 fails compile inline assembler on routine basis, disables optimisations that are likely to cause bugs (thus making debugging impossible anyway), and has terrible performance.
> 
> What's the point debugging a build that nothing to do with the production build?
> 
> Even -O0 can break tracing if you mess the stack enough. -Og is fine as long as you don't force some other trace-inhibiting parameters such as omit-frame-pointer.

I agree with you, specially if you want to debug race conditions.

But I already encountered unknow symbols in -Og builds, but it was maybe a PEBKAC.

> 
> Le 18 juin 2020 11:33:18 GMT+03:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>> On 2020-06-17 20:23, Rémi Denis-Courmont wrote:
>>> Le keskiviikkona 17. kesäkuuta 2020, 18.10.17 EEST Steve Lhomme a écrit :
>>>> Fun fact, it is fine when built in release mode. Probably the -O2 that
>>>> makes things easier. So I could force this flag for llvm-i686 in debug
>>>> builds.
>>> This has nothing to do with Win32. Even *VLC* can't build without
>>> optimisations on Linux/386 due to register shortage. Most likely not FFmpeg
>>> either.
>>> 
>>> As noted several times before, compiling with -O0 is _*STUPID*_, especially on
>>> 386. If you want debugable code, use -Og or equivalent.
>> 
>>  From my experience using -Og still has cases where you can't debug some 
>> code. Only -O0 ever worked reliably for me.vlc-devel mailing list
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