From 0c1719e65b2a5a80331d4f635612799f853b0479 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Sat, 15 Dec 2018 18:58:09 +0100 Subject: support: Do not require overflow builtin in support/blob_repeat.c It is only available in GCC 5 and later. Tested-by: Romain Naour --- ChangeLog | 6 ++++++ support/blob_repeat.c | 26 +++++++++++++++++++++++--- 2 files changed, 29 insertions(+), 3 deletions(-) diff --git a/ChangeLog b/ChangeLog index 3dd9054e58..90e9f8f2d2 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2018-12-15 Florian Weimer + + * support/blob_repeat.c (check_mul_overflow_size_t): New function. + (minimum_stride_size): Use it. + (support_blob_repeat_allocate): Likewise. + 2018-12-14 Joseph Myers * sysdeps/x86/fpu/bits/mathinline.h (asinh): Remove inline 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 . */ +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 }; -- cgit v1.2.3-70-g09d2