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

[Rémi Denis-Courmont]

-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.

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.
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