[FFmpeg-devel] [FFmpeg-cvslog] lavf/os_support.h: Fix for unicode filenames on windows.

[Matt Oliver]

On 13 June 2016 at 18:29, Benoit Fouet <benoit.fouet at free.fr> wrote:

> Hi,
>
>
>
> On 13/06/2016 10:21, Clément Bœsch wrote:
>
>> On Mon, Jun 13, 2016 at 05:50:18AM +0200, Matt Oliver wrote:
>>
>>> ffmpeg | branch: master | Matt Oliver <protogonoi at gmail.com> | Mon Jun
>>> 6 17:04:39 2016 +1000| [37787f261639c53998487400e874741c17e85fc6] |
>>> committer: Matt Oliver
>>>
>>> lavf/os_support.h: Fix for unicode filenames on windows.
>>>
>>> Fixes #819 #5256 #5281
>>>
>>> Signed-off-by: Matt Oliver <protogonoi at gmail.com>
>>>
>>>
>>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=37787f261639c53998487400e874741c17e85fc6
>>>>
>>> ---
>>>
>>>   libavformat/file.c       |    4 ++++
>>>   libavformat/os_support.h |   24 ++++++++++++++++++++++++
>>>   2 files changed, 28 insertions(+)
>>>
>>> diff --git a/libavformat/file.c b/libavformat/file.c
>>> index 5765ce7..264542a 100644
>>> --- a/libavformat/file.c
>>> +++ b/libavformat/file.c
>>> @@ -148,7 +148,11 @@ static int file_check(URLContext *h, int mask)
>>>               ret |= AVIO_FLAG_WRITE;
>>>   #else
>>>       struct stat st;
>>> +#   ifndef _WIN32
>>>       ret = stat(filename, &st);
>>> +#   else
>>> +    ret = win32_stat(filename, &st);
>>> +#   endif
>>>
>> why this chunk?
>>
>>       if (ret < 0)
>>>           return AVERROR(errno);
>>>   diff --git a/libavformat/os_support.h b/libavformat/os_support.h
>>> index a332911..9e312a5 100644
>>> --- a/libavformat/os_support.h
>>> +++ b/libavformat/os_support.h
>>> @@ -182,6 +182,29 @@ DEF_FS_FUNCTION(unlink, _wunlink, _unlink)
>>>   DEF_FS_FUNCTION(mkdir,  _wmkdir,  _mkdir)
>>>   DEF_FS_FUNCTION(rmdir,  _wrmdir , _rmdir)
>>>   +#define DEF_FS_FUNCTION2(name, wfunc, afunc, partype)     \
>>> +static inline int win32_##name(const char *filename_utf8, partype par) \
>>> +{                                                         \
>>> +    wchar_t *filename_w;                                  \
>>> +    int ret;                                              \
>>> +                                                          \
>>> +    if (utf8towchar(filename_utf8, &filename_w))          \
>>> +        return -1;                                        \
>>> +    if (!filename_w)                                      \
>>> +        goto fallback;                                    \
>>> +                                                          \
>>> +    ret = wfunc(filename_w, par);                         \
>>> +    av_free(filename_w);                                  \
>>> +    return ret;                                           \
>>> +                                                          \
>>> +fallback:                                                 \
>>> +    /* filename may be be in CP_ACP */                    \
>>> +    return afunc(filename_utf8, par);                     \
>>> +}
>>> +
>>> +DEF_FS_FUNCTION2(access, _waccess, _access, int)
>>> +DEF_FS_FUNCTION2(stat, _wstat64, _stat64, struct stat*)
>>> +
>>>   static inline int win32_rename(const char *src_utf8, const char
>>> *dest_utf8)
>>>   {
>>>       wchar_t *src_w, *dest_w;
>>> @@ -231,6 +254,7 @@ fallback:
>>>   #define rename      win32_rename
>>>   #define rmdir       win32_rmdir
>>>   #define unlink      win32_unlink
>>> +#define access      win32_access
>>>
>>>
>> ...instead of #define stat win32_stat here?
>>
>
> as already noted by someone else, this should be
> #define stat(a, b) win32_stat((a), (b))
> in order not to conflict with "struct stat" definition.
>

As stated in the original patch thread a define for the win32_stat function
can not be used as there is already a define for the 'stat' struct.
So using:
#define stat(a, b) win32_stat((a), (b))
clashes with the existing
#define stat _stat64

Since there is a stat function and a stat struct then a macro can only be
used for one of them and there is already an object macro for the stat
struct.
If the suggested "#define stat(a, b) win32_stat((a), (b))" was added this
overrides the struct macro causing the compiler not to use _stat64 and use
a 32 variant instead which results in memory corruption.