[FFmpeg-devel] [PATCH 1/4] avcodec/startcode: Use AV_RN due to UBSan warning about unaligned access

[Andreas Rheinhardt]

when directly accessing a buffer via a pointer to uint8_t cast to a
pointer to uint64_t/uint32_t. This happened only if HAVE_FAST_UNALIGNED
was set, so it was ok, but UBSan nevertheless complained about unaligned
accesses. So simply use AV_RNxx to read the buffer; this also improves
readability.

This affected many FATE-tests (namely 228 of them; e.g. the cbs-h264
tests) and it has also been reported in tickets #8138 and #8485.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/startcode.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libavcodec/startcode.c b/libavcodec/startcode.c
index 9efdffe8c6..d84f326521 100644
--- a/libavcodec/startcode.c
+++ b/libavcodec/startcode.c
@@ -25,6 +25,7 @@
  * @author Michael Niedermayer <michaelni at gmx.at>
  */
 
+#include "libavutil/intreadwrite.h"
 #include "startcode.h"
 #include "config.h"
 
@@ -38,14 +39,14 @@ int ff_startcode_find_candidate_c(const uint8_t *buf, int size)
      */
 #if HAVE_FAST_64BIT
     while (i < size &&
-            !((~*(const uint64_t *)(buf + i) &
-                    (*(const uint64_t *)(buf + i) - 0x0101010101010101ULL)) &
+            !((~AV_RN64(buf + i) &
+                    (AV_RN64(buf + i) - 0x0101010101010101ULL)) &
                     0x8080808080808080ULL))
         i += 8;
 #else
     while (i < size &&
-            !((~*(const uint32_t *)(buf + i) &
-                    (*(const uint32_t *)(buf + i) - 0x01010101U)) &
+            !((~AV_RN32(buf + i) &
+                    (AV_RN32(buf + i) - 0x01010101U)) &
                     0x80808080U))
         i += 4;
 #endif
-- 
2.20.1