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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>
Mans Rullgard authored on 2011/10/09 20:57:08Showing 1 changed files
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@@ -116,7 +116,9 @@ static inline av_const int mid_pred(int a, int b, int c) |
| 116 | 116 |
#ifndef sign_extend |
| 117 | 117 |
static inline av_const int sign_extend(int val, unsigned bits) |
| 118 | 118 |
{
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- return (val << ((8 * sizeof(int)) - bits)) >> ((8 * sizeof(int)) - bits); |
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+ unsigned shift = 8 * sizeof(int) - bits; |
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+ union { unsigned u; int s; } v = { (unsigned) val << shift };
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+ return v.s >> shift; |
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} |
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#endif |
| 122 | 124 |
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