ffmpeg.c:3654: error: Null Dereference
  pointer `p` last assigned on line 3654 could be null and is dereferenced at line 3654, column 5.

ffmpeg.c:3639:1: start of procedure opt_streamid()
3637. 
3638. /* arg format is "output-stream-index:streamid-value". */
3639. static void opt_streamid(const char *opt, const char *arg)
      ^
3640. {
3641.     int idx;

ffmpeg.c:3645:5: 
3643.     char idx_str[16];
3644. 
3645.     strncpy(idx_str, arg, sizeof(idx_str));
          ^
3646.     idx_str[sizeof(idx_str)-1] = '\0';
3647.     p = strchr(idx_str, ':');

ffmpeg.c:3646:5: 
3644. 
3645.     strncpy(idx_str, arg, sizeof(idx_str));
3646.     idx_str[sizeof(idx_str)-1] = '\0';
          ^
3647.     p = strchr(idx_str, ':');
3648.     if (!p) {

ffmpeg.c:3647:5: 
3645.     strncpy(idx_str, arg, sizeof(idx_str));
3646.     idx_str[sizeof(idx_str)-1] = '\0';
3647.     p = strchr(idx_str, ':');
          ^
3648.     if (!p) {
3649.         fprintf(stderr,

ffmpeg.c:3648:10: Taking true branch
3646.     idx_str[sizeof(idx_str)-1] = '\0';
3647.     p = strchr(idx_str, ':');
3648.     if (!p) {
               ^
3649.         fprintf(stderr,
3650.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",

ffmpeg.c:3649:9: 
3647.     p = strchr(idx_str, ':');
3648.     if (!p) {
3649.         fprintf(stderr,
              ^
3650.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3651.                 arg, opt);

ffmpeg.c:3652:9: Skipping ffmpeg_exit(): empty list of specs
3650.                 "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
3651.                 arg, opt);
3652.         ffmpeg_exit(1);
              ^
3653.     }
3654.     *p++ = '\0';

ffmpeg.c:3654:5: 
3652.         ffmpeg_exit(1);
3653.     }
3654.     *p++ = '\0';
          ^
3655.     idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, MAX_STREAMS-1);
3656.     streamid_map[idx] = parse_number_or_die(opt, p, OPT_INT, 0, INT_MAX);
