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h264: fix invalid pointer arithmetic

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Subtracting a (positive) value from the address of an array violates
C99 section 6.5.6:

  If both the pointer operand and the result point to elements of the
  same array object, or one past the last element of the array object,
  the evaluation shall not produce an overflow; otherwise, the
  behavior is undefined.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard
2012-10-26 21:18:33 +01:00
parent 50be207759
commit c4cccc8d3f
1 changed files with 5 additions and 5 deletions
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10
libavcodec/h264_cavlc.c
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@@ -566,13 +566,13 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
else{ else{
if (max_coeff <= 8) { if (max_coeff <= 8) {
if (max_coeff == 4) if (max_coeff == 4)
zeros_left = get_vlc2(gb, (chroma_dc_total_zeros_vlc-1)[total_coeff].table, zeros_left = get_vlc2(gb, chroma_dc_total_zeros_vlc[total_coeff - 1].table,
CHROMA_DC_TOTAL_ZEROS_VLC_BITS, 1); CHROMA_DC_TOTAL_ZEROS_VLC_BITS, 1);
else else
zeros_left = get_vlc2(gb, (chroma422_dc_total_zeros_vlc-1)[total_coeff].table, zeros_left = get_vlc2(gb, chroma422_dc_total_zeros_vlc[total_coeff - 1].table,
CHROMA422_DC_TOTAL_ZEROS_VLC_BITS, 1); CHROMA422_DC_TOTAL_ZEROS_VLC_BITS, 1);
} else { } else {
zeros_left= get_vlc2(gb, (total_zeros_vlc-1)[ total_coeff ].table, TOTAL_ZEROS_VLC_BITS, 1); zeros_left= get_vlc2(gb, total_zeros_vlc[total_coeff - 1].table, TOTAL_ZEROS_VLC_BITS, 1);
} }
} }
@@ -582,7 +582,7 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
((type*)block)[*scantable] = level[0]; \ ((type*)block)[*scantable] = level[0]; \
for(i=1;i<total_coeff && zeros_left > 0;i++) { \ for(i=1;i<total_coeff && zeros_left > 0;i++) { \
if(zeros_left < 7) \ if(zeros_left < 7) \
run_before= get_vlc2(gb, (run_vlc-1)[zeros_left].table, RUN_VLC_BITS, 1); \ run_before= get_vlc2(gb, run_vlc[zeros_left - 1].table, RUN_VLC_BITS, 1); \
else \ else \
run_before= get_vlc2(gb, run7_vlc.table, RUN7_VLC_BITS, 2); \ run_before= get_vlc2(gb, run7_vlc.table, RUN7_VLC_BITS, 2); \
zeros_left -= run_before; \ zeros_left -= run_before; \
@@ -597,7 +597,7 @@ static int decode_residual(H264Context *h, GetBitContext *gb, DCTELEM *block, in
((type*)block)[*scantable] = ((int)(level[0] * qmul[*scantable] + 32))>>6; \ ((type*)block)[*scantable] = ((int)(level[0] * qmul[*scantable] + 32))>>6; \
for(i=1;i<total_coeff && zeros_left > 0;i++) { \ for(i=1;i<total_coeff && zeros_left > 0;i++) { \
if(zeros_left < 7) \ if(zeros_left < 7) \
run_before= get_vlc2(gb, (run_vlc-1)[zeros_left].table, RUN_VLC_BITS, 1); \ run_before= get_vlc2(gb, run_vlc[zeros_left - 1].table, RUN_VLC_BITS, 1); \
else \ else \
run_before= get_vlc2(gb, run7_vlc.table, RUN7_VLC_BITS, 2); \ run_before= get_vlc2(gb, run7_vlc.table, RUN7_VLC_BITS, 2); \
zeros_left -= run_before; \ zeros_left -= run_before; \