commit 0d8abf5365cc39e7ea91bddfeb207e8d4d233544 Author: Nick Mathewson nickm@torproject.org Date: Sun Nov 2 11:42:33 2014 -0500

Switch to a < comparison for our calloc check; explain how it works --- src/common/util.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/common/util.c b/src/common/util.c index 74a538e..006fd80 100644 --- a/src/common/util.c +++ b/src/common/util.c @@ -195,14 +195,18 @@ tor_malloc_zero_(size_t size DMALLOC_PARAMS) return result; }

-/* Estimate the square root of SIZE_MAX. */ -#define SQRT_SIZE_MAX (((size_t) SIZE_MAX) >> (sizeof(size_t) * 8 / 2)) +/* The square root of SIZE_MAX + 1. If a is less than this, and b is less + * than this, then a*b is less than SIZE_MAX. (For example, if size_t is + * 32 bits, then SIZE_MAX is 0xffffffff and this value is 0x10000. If a and + * b are less than this, then their product is at most (65535*65535) == + * 0xfffe0001. */ +#define SQRT_SIZE_MAX_P1 (((size_t)1) << (sizeof(size_t)*4))

/** Return non-zero if and only if the product of the arguments is exact. */ static INLINE int size_mul_check(const size_t x, const size_t y) { - return ((x <= SQRT_SIZE_MAX && y <= SQRT_SIZE_MAX) || + return ((x < SQRT_SIZE_MAX_P1 && y < SQRT_SIZE_MAX_P1) || y == 0 || x <= SIZE_MAX / y); }