diff options
Diffstat (limited to 'support')
| -rw-r--r-- | support/blob_repeat.c | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/support/blob_repeat.c b/support/blob_repeat.c index 16c1e448b9..718846d81d 100644 --- a/support/blob_repeat.c +++ b/support/blob_repeat.c @@ -34,6 +34,26 @@ optimization because mappings carry a lot of overhead. */ static const size_t maximum_small_size = 4 * 1024 * 1024; +/* Set *RESULT to LEFT * RIGHT. Return true if the multiplication + overflowed. See <malloc/malloc-internal.h>. */ +static inline bool +check_mul_overflow_size_t (size_t left, size_t right, size_t *result) +{ +#if __GNUC__ >= 5 + return __builtin_mul_overflow (left, right, result); +#else + /* size_t is unsigned so the behavior on overflow is defined. */ + *result = left * right; + size_t half_size_t = ((size_t) 1) << (8 * sizeof (size_t) / 2); + if (__glibc_unlikely ((left | right) >= half_size_t)) + { + if (__glibc_unlikely (right != 0 && *result / right != left)) + return true; + } + return false; +#endif +} + /* Internal helper for fill. */ static void fill0 (char *target, const char *element, size_t element_size, @@ -118,8 +138,8 @@ minimum_stride_size (size_t page_size, size_t element_size) common multiple, it appears only once. Therefore, shift one factor. */ size_t multiple; - if (__builtin_mul_overflow (page_size >> common_zeros, element_size, - &multiple)) + if (check_mul_overflow_size_t (page_size >> common_zeros, element_size, + &multiple)) return 0; return multiple; } @@ -255,7 +275,7 @@ support_blob_repeat_allocate (const void *element, size_t element_size, size_t count) { size_t total_size; - if (__builtin_mul_overflow (element_size, count, &total_size)) + if (check_mul_overflow_size_t (element_size, count, &total_size)) { errno = EOVERFLOW; return (struct support_blob_repeat) { 0 }; |