[FFmpeg-devel] [PATCH] lavf/wavdec.c: Fix unresolved symbols on Mac and VS2015 Update 3

[Hendrik Leppkes]

On Thu, Dec 15, 2016 at 8:43 PM, Matthew Wolenetz <wolenetz at chromium.org> wrote:
>>
>> This seems like a rather odd issue to be toolchain specific. Can you
>> please provide a configure command line that would result in a broken
>> build?
>
>
> I believe the link-time failures occurred with configs like these:
>
> IIRC, on Mac, Chromium build hit this with:
>
>    -
>    https://cs.chromium.org/chromium/src/third_party/ffmpeg/chromium/config/Chromium/mac/x64/config.h?rcl=0&l=4
>
> On Windows, one or both of the following hit this:
>
>    -
>    https://cs.chromium.org/chromium/src/third_party/ffmpeg/chromium/config/Chromium/win/ia32/config.h?rcl=0&l=4
>    -
>    https://cs.chromium.org/chromium/src/third_party/ffmpeg/chromium/config/Chromium/win/x64/config.h?rcl=0&l=4
>
> DCE is needed for FFmpeg compilation, this should get fixed by Steve
>> Lhomme's
>> configure patch.
>> I find it hard to understand why wavdec.c would be the only file
>> showing this issue...
>
>
> Notably, windows still hit this (VS2015 Update 3 19.00.24213.1) *even with
> -O2.*
>
>

You are using a custom build system, there is no way to verify any
issues for us unless you can provide a configure commandline that
fails on our own build-system.

The patches do look like they are trying to avoid the use of DCE - and
as Carl already pointed out, quite a lot of our code relies on DCE
being performed by the compiler/linker, so fixing it in one or two
isolated spots wouldn't really fix anything but your own customized
specific build, and make our code-base less consistent within itself.
DCE generally works fine with Visual Studio, and I do not know of any
configure setup that makes it fail - of course with the exception of
using --disable-optimizations, as that turns everything of for MSVC
right now, including DCE, which makes the build impossible.

- Hendrik