[FFmpeg-devel] [PATCH 1/2] avcodec/h264_parser: Fix undefined left shift

[Andreas Rheinhardt]

Use an uint32_t for the NAL unit size of an AVC H.264 NAL unit instead
of an int as a left shift of a signed value is undefined behaviour
if the result doesn't fit into the target type.

Also make the log message never output negative lengths.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/h264_parser.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
index d9249e578d..1d2ce3870c 100644
--- a/libavcodec/h264_parser.c
+++ b/libavcodec/h264_parser.c
@@ -84,12 +84,13 @@ static int h264_find_frame_end(H264ParseContext *p, const uint8_t *buf,
 
     for (i = 0; i < buf_size; i++) {
         if (i >= next_avc) {
-            int nalsize = 0;
+            uint32_t nalsize = 0;
             i = next_avc;
             for (j = 0; j < p->nal_length_size; j++)
                 nalsize = (nalsize << 8) | buf[i++];
-            if (nalsize <= 0 || nalsize > buf_size - i) {
-                av_log(logctx, AV_LOG_ERROR, "AVC-parser: nal size %d remaining %d\n", nalsize, buf_size - i);
+            if (!nalsize || nalsize > buf_size - i) {
+                av_log(logctx, AV_LOG_ERROR, "AVC-parser: nal size %"PRIu32" "
+                       "remaining %d\n", nalsize, buf_size - i);
                 return buf_size;
             }
             next_avc = i + nalsize;
-- 
2.20.1