Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Wang Bin]

>
> So how is it possible that clock_gettime() must not be defined to allow
> starting the executable, but this object has to be?


Because I build ffmpeg with cc and linker flag "-mmacosx-version-min=10.7"
to support lower os versions. If no such flag, the target os is the sdk
version you use, e.g. 10.x. Then the symbol is not compiled as a weak
symbol and it must be resolved at runtime.
You can see all weak symbols using `nm -mg libavcodec.dylib |grep -E
"undefined.*weak"`
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Carl Eugen Hoyos]

2017-02-05 3:12 GMT+01:00 Wang Bin :
>>
>> dyld: Symbol not found: _kVTCompressionPropertyKey_H264EntropyMode
>
> What system? kVTCompressionPropertyKey_H264EntropyMode is
> available since macOS 10.9 and iOS 10.8.

Indicating this is about 10.7.

> If targeting older system, we have to define it's value like
> kVTVideoDecoderSpecification_RequireHardwareAcceleratedVideoDecoder
> in videotoolbox.c

So how is it possible that clock_gettime() must not be defined to allow
starting the executable, but this object has to be?

Carl Eugen
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Wang Bin]

>
> dyld: Symbol not found: _kVTCompressionPropertyKey_H264EntropyMode


What system? kVTCompressionPropertyKey_H264EntropyMode is available since
macOS 10.9 and iOS 10.8. If targeting older system, we have to define it's
value
like kVTVideoDecoderSpecification_RequireHardwareAcceleratedVideoDecoder in
videotoolbox.c
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Carl Eugen Hoyos]

2017-01-03 7:26 GMT+01:00 Wang Bin :
> If ffmpeg is build with iOS 10 sdk, program will crash on iOS
> 9. This patch fixes the crash.

Does anybody know why clock_gettime() behaves differently than
kVTCompressionPropertyKey_H264EntropyMode in
libavcodec/videotoolboxenc.c?
Iiuc, the call to clock_gettime() crashes at runtime after a null
pointer dereference, trying to start ffmpeg on systems without
above symbol causes the following (I couldn't test myself):

dyld: Symbol not found: _kVTCompressionPropertyKey_H264EntropyMode

Carl Eugen
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Steven Liu]

2017-01-09 11:46 GMT+08:00 Steven Liu :

>
>
> 2017-01-09 11:06 GMT+08:00 Wang Bin :
>
>> ping
>>
>> 2017-01-03 14:26 GMT+08:00 Wang Bin :
>>
>> > If ffmpeg is build with iOS 10 sdk, program will crash on iOS 9. This
>> > patch fixes the crash.
>> >
>> ___
>> ffmpeg-devel mailing list
>> ffmpeg-devel@ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
>
> LGTM
>
>
[PATCH] avutil/tile: check clock_gettime at runtime for apple
 platforms

clock_gettime is avalible since macOS 10.12 and iOS 10.0. Because of
weak linking, clock_gettime can be build without error with new
macOS/iOS sdk, but the symbol may not exist on the target system.
Explicitly checking the symbol is required.
https://developer.apple.com/library/content/documentation/MacOSX/Conceptual/BPFrameworks/Concepts/WeakLinking.html

Signed-off-by: Wang Bin 
---
 libavutil/time.c | 18 +-
 1 file changed, 13 insertions(+), 5 deletions(-)



applied


Thanks
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Steven Liu]

2017-01-09 11:06 GMT+08:00 Wang Bin :

> ping
>
> 2017-01-03 14:26 GMT+08:00 Wang Bin :
>
> > If ffmpeg is build with iOS 10 sdk, program will crash on iOS 9. This
> > patch fixes the crash.
> >
> ___
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> ffmpeg-devel@ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel


LGTM
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Re: [FFmpeg-devel] mac, ios clock_gettime patch

[Wang Bin]

ping

2017-01-03 14:26 GMT+08:00 Wang Bin :

> If ffmpeg is build with iOS 10 sdk, program will crash on iOS 9. This
> patch fixes the crash.
>
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[FFmpeg-devel] mac, ios clock_gettime patch

[Wang Bin]

If ffmpeg is build with iOS 10 sdk, program will crash on iOS 9. This patch
fixes the crash.


0001-check-clock_gettime-at-runtime-for-apple-platforms.patch
Description: Binary data
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