[FFmpeg-devel] [PATCH 1/2] avcodec/vda_h264: use multichar literal portably

[Ganesh Ajjanagadde]

On Sun, Sep 20, 2015 at 10:41 AM, wm4 <nfxjfg at googlemail.com> wrote:
> On Fri, 18 Sep 2015 18:16:18 -0400
> Ganesh Ajjanagadde <gajjanagadde at gmail.com> wrote:
>
>> Multichar literals are implementation defined, and thus trigger -Wmultichar:
>> http://fate.ffmpeg.org/log.cgi?time=20150918202532&log=compile&slot=x86_64-darwin-gcc-5.
>> http://www.zipcon.net/~swhite/docs/computers/languages/c_multi-char_const.html
>> gives a good summary of how to deal with them; in particular this patch
>> results in behavior identical to that generated by GCC (which I assume is correct this case).
>>
>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> ---
>>  libavcodec/vda_h264.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/vda_h264.c b/libavcodec/vda_h264.c
>> index 8c526c0..3279afa 100644
>> --- a/libavcodec/vda_h264.c
>> +++ b/libavcodec/vda_h264.c
>> @@ -339,7 +339,9 @@ int ff_vda_default_init(AVCodecContext *avctx)
>>      CFMutableDictionaryRef buffer_attributes;
>>      CFMutableDictionaryRef io_surface_properties;
>>      CFNumberRef cv_pix_fmt;
>> -    int32_t fmt = 'avc1', pix_fmt = vda_ctx->cv_pix_fmt_type;
>> +#define LE_CHR(a,b,c,d) ( ((a)<<24) | ((b)<<16) | ((c)<<8) | (d) )
>> +    int32_t fmt = LE_CHR( 'a', 'v', 'c', '1');
>> +    int32_t pix_fmt = vda_ctx->cv_pix_fmt_type;
>>
>>      // kCVPixelFormatType_420YpCbCr8Planar;
>>
>
> Sorry, but this is probably completely pointless. Apple and code using
> Apple APIs use this in a lot of places. Also, since this is Apple
> specific anyway (and thus runs on only 1 compiler and 1 platform), the
> portability argument doesn't make sense either.

please see patchv2.

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