[vorbis-dev] bug in vorbisfile with threads

[Martin Vogt]

Hello,

vorbisfile is not linked against pthreads:

>ldd /usr/lib/libvorbis.so
>        libm.so.6 => /lib/libm.so.6 (0x40034000)
>        libogg.so.0 => /usr/lib/libogg.so.0 (0x40057000)
>        libc.so.6 => /lib/libc.so.6 (0x4005c000)
>        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x80000000)

When vorbis is used in the KDE Media player (which uses vorbisfile
from a seperate thread) this code in vorbisfile makes trouble:

>static long _get_data(OggVorbis_File *vf){
>  errno=0;
>  if(vf->datasource){
>    char *buffer=ogg_sync_buffer(&vf->oy,CHUNKSIZE);
>    long bytes=(vf->callbacks.read_func)(buffer,1,CHUNKSIZE,vf->datasource);
>    if(bytes>0)ogg_sync_wrote(&vf->oy,bytes);
>    if(bytes==0 && errno)return(-1);
>    return(bytes);
>  }else
>    return(0);
>}

reason: errno is a global variable, but when you compile the code
        with include <pthreads.h> its replaced with a function call.

Thus the assumption that the read callback sets the errno variable
is wrong, when the callbacks are compiled with pthreads support.

This is the problem we see in the KDE Media player.

I think this solution would be fine:

- add another callback to the callback structure: errno_func
- this callback (if its != NULL) can be used to get the error condition
- if its not set : fallback to errno .

What do you think?

regards,

Martin

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