libavfilter/vf_overlay.c:341: error: Integer Overflow L2
  ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer`.

libavfilter/vf_overlay.c:341:5: Call
339. {
340.     avfilter_end_frame(inlink->dst->outputs[0]);
341.     avfilter_unref_buffer(inlink->cur_buf);
         ^
342. }
343. 

libavfilter/avfilter.c:71:1: <LHS trace>
69. }
70. 
71. void avfilter_unref_buffer(AVFilterBufferRef *ref)
    ^
72. {
73.     if (!(--ref->buf->refcount))

libavfilter/avfilter.c:71:1: Parameter `ref->buf->refcount`
  69. }
  70. 
  71. void avfilter_unref_buffer(AVFilterBufferRef *ref)
      ^
  72. {
  73.     if (!(--ref->buf->refcount))

libavfilter/avfilter.c:73:11: Binary operation: ([0, +oo] - 1):unsigned32 by call to `avfilter_unref_buffer` 
  71. void avfilter_unref_buffer(AVFilterBufferRef *ref)
  72. {
  73.     if (!(--ref->buf->refcount))
                ^
  74.         ref->buf->free(ref->buf);
  75.     av_free(ref->video);

void avfilter_unref_buffer(AVFilterBufferRef *ref)
{
    if (!(--ref->buf->refcount))
        ref->buf->free(ref->buf);
    av_free(ref->video);
    av_free(ref->audio);
    av_free(ref);
}
['static void end_frame(AVFilterLink *inlink)\n{\n    avfilter_end_frame(inlink->dst->outputs[0]);\n    avfilter_unref_buffer(inlink->cur_buf);\n}', 'void avfilter_unref_buffer(AVFilterBufferRef *ref)\n{\n    if (!(--ref->buf->refcount))\n        ref->buf->free(ref->buf);\n    av_free(ref->video);\n    av_free(ref->audio);\n    av_free(ref);\n}']