[vlc-devel] [PATCH] Fix for crashes in several modules when running VLC on osx 10.6

[Rafaël Carré]

Le 28/10/2013 07:56, David Fuhrmann a écrit :
> 
> Am 28.10.2013 um 06:40 schrieb Rafaël Carré <funman at videolan.org>:
> 
>> Le 27/10/2013 18:51, David Fuhrmann a écrit :
>>> 
>>> Am 27.10.2013 um 18:33 schrieb Rémi Denis-Courmont 
>>> <remi at remlab.net>:
>>> 
>>>> Le dimanche 27 octobre 2013 18:02:19 David Fuhrmann a écrit
>>>> :
>>>>> Hi,
>>>>> 
>>>>> Since VLC 2.1, we noticed several crashes in different
>>>>> modules running on osx 10.6, if we compile the binary on
>>>>> osx 10.7 or later.
>>>> 
>>>> I don't know how the MacOS toolchain is designed.
>>>> 
>>>> But in general, the toolchain must be configured with the 
>>>> *oldest* supported OS version to provide binary compatiblity.
>>>> At least, that is how it works on Windows (through
>>>> _WIN32_WINNT) and on all ELF-based platforms (through custom
>>>> build roots).
>>> 
>>> Mac OS officially supports building on newer versions with
>>> newer osx SDKs, by giving a minimal version for osx which is
>>> supported at runtime.
>>> 
>>>> 
>>>>> As we have several features only working on 10.7 onwards,
>>>>> we need to compile the release binary on these newer
>>>>> versions. For 10.6, these features are deactivated.
>>>> 
>>>> Well, hmm, your "problems" very strongly suggest that you
>>>> failed to deactivate those "features". I think you answered
>>>> your own question.
>>> 
>>> These features are lion fullscreen and better window resizing, 
>>> concerning the interface module. Additionally, there is an 
>>> AVFoundation module only running on 10.7 onwards.
>>> 
>>> All of these features have absolutely _nothing_ to do with the 
>>> crashes we are experiencing. (Especially, the interface runs
>>> fine on all platforms. Crashes are only happening in
>>> completely unrelated and osx unspecific modules.)
>> 
>> Can you share backtraces of these crashes?
> 
> The backtraces are not really helpful. For example, from various
> tickets see: 
> https://trac.videolan.org/vlc/attachment/ticket/9140/crash-seeking-subs.txt
>
> 
https://trac.videolan.org/vlc/attachment/ticket/9527/vlc-crash-log.txt
> https://trac.videolan.org/vlc/attachment/ticket/9140/crash-libmp4.txt
>
>  It somehow looks like the integration of only the used functions
> from compat either does not work at all on osx, or it somehow
> interfers with the functions implemented in the standard libraries.
> For me it looks like they are not copied into the modules, and on
> osx 10.7 or later the system implementation is used.
> 
> j-b wrote that the concering functions are probably getdelim,
> strndup and strnlen.

If you build on 10.7 it will detect these functions as available and
not build replacements.

I am not sure why reverting this commit would fix the crashes though.

To let configure think those are not available you can use:

export ac_cv_func_strnlen=no
./configure ...

But then you will have double prototypes when building: one in OSX
headers and another one in vlc/include/vlc_fixups.h because vlc thinks
the prototype is not available in OSX.

If you are lucky the prototypes will match, but they could very well
be declared differently or #defined to something else like #define
strnlen(foo) strnlen_secure(foo, bar)

Well give it a try and see how it goes

23	0   ???                                 000000000000000000 0 + 0
24	1   libsubsdec_plugin.dylib             0x0000000102cf1672 HtmlPut + 34

This backtrace indeeds seems to be 'strnlen' missing.


24	0   ???                                 000000000000000000 0 + 0
25	1   libmp4_plugin.dylib                 0x000000011696b3d7
MP4_BoxGet_Internal + 167

Could be strndup

23	0   libSystem.B.dylib                   0x00007fff871ab2ea
__getdirentries64 + 10
24	1   libSystem.B.dylib                   0x00007fff871ab278
_readdir_unlocked$INODE64 + 79

No idea here :D