[FFmpeg-devel] [PATCH] Workaround to build ffmpeg on MacOs 10.15

[Michael Niedermayer]

On Sat, Jan 04, 2020 at 09:25:40PM +0200, Martin Storsjö wrote:
> On Sat, 4 Jan 2020, Michael Niedermayer wrote:
> 
> >On Sat, Jan 04, 2020 at 12:06:55AM +0100, Henrik Gramner wrote:
> >>On Fri, Jan 3, 2020 at 7:37 PM Moritz Barsnick <barsnick at gmx.net> wrote:
> >>>On Fri, Jan 03, 2020 at 11:05:25 +0100, Timo Rothenpieler wrote:
> >>>>I think this was discussed on this list in the past.
> >>>>Not sure what the conclusion was, but I think an unconditional flag like
> >>>>this being added wasn't all that well received.
> >>>
> >>>Yes, discussed in this thread in November:
> >>>http://ffmpeg.org/pipermail/ffmpeg-devel/2019-November/253193.html
> >>
> >>Lmao "security feature". Just disable that flag and call it a day, it
> >>adds nothing of value (unless you consider crashing to be a "security
> >>feature"?).
> >
> >I dont know how effective this is or what exactly this option does, i
> >couldnt find documentation for it quickly what it does in clang on macosx.
> >google keeps pointing to gcc
> >but
> >
> >a crash is better than arbitrary code execution, which IIUC is the idea
> >here, if the stack of a thread grows too much, crash instead of overwriting
> >something that comes after it.
> >Not crashing when the stack overlapps another threads stack or heap is
> >unlikely to be better.
> 
> The point here is, disabling this "feature" is not a security regression -
> it's a new feature in apple's clang, which only is enabled when you target a
> new enough version of macOS. And that new security feature is broken to the
> point that the process crashes before you even get to code which may be
> misbehaving.
> 
> So disabling it isn't a regression, it just takes things back to how things
> were before, before this was introduced.

Is it difficult to detect if the compiler has this bug ?
Iam asking because disabling this feature only when needed avoids the
questions related to "what happens when it is fixed".

We could wait for it being fixed and then add a check on the
version number and then backport that to any release which may need it.
If it is difficult to add a check now

Also what is your oppinion about limiting disabling the flag for only
apple/clang ?

Thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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