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38 lines
1.3 KiB
38 lines
1.3 KiB
7 years ago
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Backport the check_mul_overflow_size_t function from this upstream commit:
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commit 2e0bbbfbf95fc9e22692e93658a6fbdd2d4554da
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Author: Dennis Wölfing <denniswoelfing@gmx.de>
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Date: Tue May 30 18:26:19 2017 -0300
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Add reallocarray function
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diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h
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index b830d3f58fe74ca3..6ffa091ba3292901 100644
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--- a/malloc/malloc-internal.h
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+++ b/malloc/malloc-internal.h
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@@ -28,5 +28,24 @@ void __malloc_fork_unlock_parent (void) internal_function attribute_hidden;
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/* Called in the child process after a fork. */
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void __malloc_fork_unlock_child (void) internal_function attribute_hidden;
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+/* Set *RESULT to LEFT * RIGHT. Return true if the multiplication
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+ overflowed. */
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+static inline bool
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+check_mul_overflow_size_t (size_t left, size_t right, size_t *result)
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+{
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+#if __GNUC__ >= 5
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+ return __builtin_mul_overflow (left, right, result);
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+#else
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+ /* size_t is unsigned so the behavior on overflow is defined. */
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+ *result = left * right;
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+ size_t half_size_t = ((size_t) 1) << (8 * sizeof (size_t) / 2);
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+ if (__glibc_unlikely ((left | right) >= half_size_t))
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+ {
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+ if (__glibc_unlikely (right != 0 && *result / right != left))
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+ return true;
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+ }
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+ return false;
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+#endif
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+}
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#endif /* _MALLOC_PRIVATE_H */
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