libavcodec/aac.c:1553: error: Null Dereference
  pointer `&gb->buffer` last assigned on line 1551 could be null and is dereferenced by call to `show_bits()` at line 1553, column 9.

libavcodec/aac.c:1545:1: start of procedure aac_decode_frame()
1543. }
1544. 
1545. static int aac_decode_frame(AVCodecContext * avccontext, void * data, int * data_size, const uint8_t * buf, int buf_size) {
      ^
1546.     AACContext * ac = avccontext->priv_data;
1547.     GetBitContext gb;

libavcodec/aac.c:1546:5: 
1544. 
1545. static int aac_decode_frame(AVCodecContext * avccontext, void * data, int * data_size, const uint8_t * buf, int buf_size) {
1546.     AACContext * ac = avccontext->priv_data;
          ^
1547.     GetBitContext gb;
1548.     enum RawDataBlockType elem_type;

libavcodec/aac.c:1551:5: 
1549.     int err, elem_id, data_size_tmp;
1550. 
1551.     init_get_bits(&gb, buf, buf_size*8);
          ^
1552. 
1553.     if (show_bits(&gb, 12) == 0xfff) {

libavcodec/bitstream.h:741:1: start of procedure init_get_bits()
  739.  * @param bit_size the size of the buffer in bits
  740.  */
  741. static inline void init_get_bits(GetBitContext *s,
       ^
  742.                    const uint8_t *buffer, int bit_size)
  743. {

libavcodec/bitstream.h:744:5: 
  742.                    const uint8_t *buffer, int bit_size)
  743. {
  744.     int buffer_size= (bit_size+7)>>3;
           ^
  745.     if(buffer_size < 0 || bit_size < 0) {
  746.         buffer_size = bit_size = 0;

libavcodec/bitstream.h:745:8: Taking true branch
  743. {
  744.     int buffer_size= (bit_size+7)>>3;
  745.     if(buffer_size < 0 || bit_size < 0) {
              ^
  746.         buffer_size = bit_size = 0;
  747.         buffer = NULL;

libavcodec/bitstream.h:746:9: 
  744.     int buffer_size= (bit_size+7)>>3;
  745.     if(buffer_size < 0 || bit_size < 0) {
  746.         buffer_size = bit_size = 0;
               ^
  747.         buffer = NULL;
  748.     }

libavcodec/bitstream.h:747:9: 
  745.     if(buffer_size < 0 || bit_size < 0) {
  746.         buffer_size = bit_size = 0;
  747.         buffer = NULL;
               ^
  748.     }
  749. 

libavcodec/bitstream.h:750:5: 
  748.     }
  749. 
  750.     s->buffer= buffer;
           ^
  751.     s->size_in_bits= bit_size;
  752.     s->buffer_end= buffer + buffer_size;

libavcodec/bitstream.h:751:5: 
  749. 
  750.     s->buffer= buffer;
  751.     s->size_in_bits= bit_size;
           ^
  752.     s->buffer_end= buffer + buffer_size;
  753. #ifdef ALT_BITSTREAM_READER

libavcodec/bitstream.h:752:5: 
  750.     s->buffer= buffer;
  751.     s->size_in_bits= bit_size;
  752.     s->buffer_end= buffer + buffer_size;
           ^
  753. #ifdef ALT_BITSTREAM_READER
  754.     s->index=0;

libavcodec/bitstream.h:754:5: 
  752.     s->buffer_end= buffer + buffer_size;
  753. #ifdef ALT_BITSTREAM_READER
  754.     s->index=0;
           ^
  755. #elif defined LIBMPEG2_BITSTREAM_READER
  756.     s->buffer_ptr = (uint8_t*)((intptr_t)buffer&(~1));

libavcodec/bitstream.h:764:1: return from a call to init_get_bits
  762.     skip_bits_long(s, 0);
  763. #endif
  764. }
       ^
  765. 
  766. static inline void align_get_bits(GetBitContext *s)

libavcodec/aac.c:1553:9: 
1551.     init_get_bits(&gb, buf, buf_size*8);
1552. 
1553.     if (show_bits(&gb, 12) == 0xfff) {
              ^
1554.         if ((err = parse_adts_frame_header(ac, &gb)) < 0) {
1555.             av_log(avccontext, AV_LOG_ERROR, "Error decoding AAC frame header.\n");

libavcodec/bitstream.h:652:1: start of procedure show_bits()
  650.  * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
  651.  */
  652. static inline unsigned int show_bits(GetBitContext *s, int n){
       ^
  653.     register int tmp;
  654.     OPEN_READER(re, s)

libavcodec/bitstream.h:654:5: 
  652. static inline unsigned int show_bits(GetBitContext *s, int n){
  653.     register int tmp;
  654.     OPEN_READER(re, s)
           ^
  655.     UPDATE_CACHE(re, s)
  656.     tmp= SHOW_UBITS(re, s, n);

libavcodec/bitstream.h:655:5: 
  653.     register int tmp;
  654.     OPEN_READER(re, s)
  655.     UPDATE_CACHE(re, s)
           ^
  656.     tmp= SHOW_UBITS(re, s, n);
  657. //    CLOSE_READER(re, s)
