shithub: opusfile

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Fix to avoid technically undefined behavior.

The C standard says that calling library functions (including
 memcpy) with invalid arguments (including a NULL pointer) is
 undefined behavior unless otherwise noted (which memcpy doesn't).
op_filter_read_native() invokes op_read_native() with NULL for the
 _pcm buffer, which triggers such a memcpy invocation.
Even though it should be perfectly fine in practice to pass NULL to
 memcpy when copying zero bytes, don't do it.

Thanks to a person who did not wish to be credited for the report.

--- a/src/opusfile.c

+++ b/src/opusfile.c

@@ -2818,10 +2818,16 @@

       /*If we have buffered samples, return them.*/

       if(nsamples>0){

         if(nsamples*nchannels>_buf_size)nsamples=_buf_size/nchannels;

-        memcpy(_pcm,_of->od_buffer+nchannels*od_buffer_pos,

-         sizeof(*_pcm)*nchannels*nsamples);

-        od_buffer_pos+=nsamples;

-        _of->od_buffer_pos=od_buffer_pos;

+        /*Check nsamples again so we don't pass NULL to memcpy() if _buf_size

+           is zero.

+          That would technically be undefined behavior, even if the number of

+           bytes to copy were zero.*/

+        if(nsamples>0){

+          memcpy(_pcm,_of->od_buffer+nchannels*od_buffer_pos,

+           sizeof(*_pcm)*nchannels*nsamples);

+          od_buffer_pos+=nsamples;

+          _of->od_buffer_pos=od_buffer_pos;

+        }

         if(_li!=NULL)*_li=_of->cur_link;

         return nsamples;

       }