[FFmpeg-cvslog] avutil/mem: use GCC builtins to check for overflow in av_size_mult()

[James Almer]

ffmpeg | branch: master | James Almer <jamrial at gmail.com> | Thu May 27 11:58:57 2021 -0300| [baf5cc5b7a016efaa0d9bf3dfe62ad74ef4ffafe] | committer: James Almer

avutil/mem: use GCC builtins to check for overflow in av_size_mult()

Signed-off-by: James Almer <jamrial at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=baf5cc5b7a016efaa0d9bf3dfe62ad74ef4ffafe
---

 libavutil/mem.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/libavutil/mem.h b/libavutil/mem.h
index e21a1feaae..c876111afb 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -674,11 +674,18 @@ void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
  */
 static inline int av_size_mult(size_t a, size_t b, size_t *r)
 {
-    size_t t = a * b;
+    size_t t;
+
+#if (!defined(__INTEL_COMPILER) && AV_GCC_VERSION_AT_LEAST(5,1)) || AV_HAS_BUILTIN(__builtin_mul_overflow)
+    if (__builtin_mul_overflow(a, b, &t))
+        return AVERROR(EINVAL);
+#else
+    t = a * b;
     /* Hack inspired from glibc: don't try the division if nelem and elsize
      * are both less than sqrt(SIZE_MAX). */
     if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)
         return AVERROR(EINVAL);
+#endif
     *r = t;
     return 0;
 }