diff options
| author | Jim Huang <jserv.tw@gmail.com> | 2019-07-07 12:56:40 +0800 |
|---|---|---|
| committer | daan <daanl@outlook.com> | 2019-07-23 14:59:49 -0700 |
| commit | 8dba36bcecf33aaa743e75baf5996bfb9f898ead (patch) | |
| tree | c824cec1d23f429108509ccaabb9946ff912bc8f /include/mimalloc-internal.h | |
| parent | 46b11fa0a48ed34bb753470668bff5c6551dfab9 (diff) | |
Use checked unsigned multiplication extension of GCC/Clang
Most processors have carry flags which they set on addition overflow, so
it is a good idea to access them whenever possible. Most of them also
have widening multiply instructions that can be used to detect overflow
of the non-widening version. Both GCC and Clang offer a way to detect an
overflow for security critical applications.
Reference:
https://clang.llvm.org/docs/LanguageExtensions.html#checked-arithmetic-builtins
Diffstat (limited to 'include/mimalloc-internal.h')
| -rw-r--r-- | include/mimalloc-internal.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h index 1d380e8..cbed590 100644 --- a/include/mimalloc-internal.h +++ b/include/mimalloc-internal.h @@ -117,6 +117,9 @@ bool _mi_page_is_valid(mi_page_t* page); #define mi_likely(x) (x) #endif +#ifndef __has_builtin +#define __has_builtin(x) 0 +#endif #if defined(_MSC_VER) #define mi_decl_noinline __declspec(noinline) @@ -149,9 +152,17 @@ bool _mi_page_is_valid(mi_page_t* page); // Overflow detecting multiply #define MI_MUL_NO_OVERFLOW ((size_t)1 << (4*sizeof(size_t))) // sqrt(SIZE_MAX) static inline bool mi_mul_overflow(size_t size, size_t count, size_t* total) { +#if __has_builtin(__builtin_umul_overflow) || __GNUC__ >= 5 +#if (MI_INTPTR_SIZE == 4) + return __builtin_umul_overflow(size, count, total); +#else + return __builtin_umull_overflow(size, count, total); +#endif +#else /* __builtin_umul_overflow is unavailable */ *total = size * count; return ((size >= MI_MUL_NO_OVERFLOW || count >= MI_MUL_NO_OVERFLOW) && size > 0 && (SIZE_MAX / size) < count); +#endif } // Align a byte size to a size in _machine words_, |