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| author | Mans Rullgard <mans@mansr.com> | 2011-10-09 12:57:08 +0100 |
|---|---|---|
| committer | Mans Rullgard <mans@mansr.com> | 2011-10-13 15:40:16 +0100 |
| commit | f59bb3d8f3eb50aa182b0d7ae209848b94a507cc (patch) | |
| tree | d87c68c7d16ab3cc02ff1585f30e32788c885607 /libavcodec/mathops.h | |
| parent | 42feaf40700246d9afb9c27ef09a0022ddfdb998 (diff) | |
| download | ffmpeg-f59bb3d8f3eb50aa182b0d7ae209848b94a507cc.tar.gz | |
mathops: remove undefined behaviour from sign_extend()
This function intentionally overflows the signed range on
the left shift. Using this type-punning avoids errors from
the overflow checker without disabling this test globally.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Diffstat (limited to 'libavcodec/mathops.h')
| -rw-r--r-- | libavcodec/mathops.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/libavcodec/mathops.h b/libavcodec/mathops.h index ec76eaae29..45b1ecf1ae 100644 --- a/libavcodec/mathops.h +++ b/libavcodec/mathops.h @@ -116,7 +116,9 @@ static inline av_const int mid_pred(int a, int b, int c) #ifndef sign_extend static inline av_const int sign_extend(int val, unsigned bits) { - return (val << ((8 * sizeof(int)) - bits)) >> ((8 * sizeof(int)) - bits); + unsigned shift = 8 * sizeof(int) - bits; + union { unsigned u; int s; } v = { (unsigned) val << shift }; + return v.s >> shift; } #endif |