[FFmpeg-devel] CONFIG_W64_DEMUXER and dead-code elimination

Bruce Dawson brucedawson at google.com
Wed May 11 17:00:21 CEST 2016

Microsoft is aware of the issue and is working on it. They might fix it.
They might not, however, because regressions in non-standard behavior are
not as serious. We will see.

I'm committing a Chromium specific workaround because that allows us to
test Microsoft's new optimizer - I want to be able to report bugs and make
suggestions while it's not too late, and adding w64.c was a simple way to
unblock this testing.

Anyway, thought the ffmpeg team should know.

On Wed, May 11, 2016 at 10:51 AM, Hendrik Leppkes <h.leppkes at gmail.com>

> On Wed, May 11, 2016 at 4:19 PM, Bruce Dawson
> <brucedawson-at-google.com at ffmpeg.org> wrote:
> > The error is:
> >
> >     wavdec.obj : error LNK2001: unresolved external symbol
> _ff_w64_guid_data
> >
> > This happens because the compiler does not recognize early enough
> > that _ff_w64_guid_data is never actually needed, so it creates a
> reference
> > to it.
> >
> This sort of construct is used all the time in our code, so I would
> suggest to also report this to MS as a regression.
> Its important to keep in mind that they introduced a new optimizer
> just recently in the pre-release builds, so regressions are bound to
> happen, and hopefully disappear by the time it is released.
> Testing Update 3 right now, and possibly reacting to any changes it
> might require other then reporting regressions to MS, seems very
> premature.
> - Hendrik
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Bruce Dawson

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