1 #if defined(_HAVE_BUILTIN_MUL_OVERFLOW) && !defined(__MSP430__) 2 // gcc should use the correct one here 3 #define mul_overflow __builtin_mul_overflow 4 #else 5 /** 6 * Since __builtin_mul_overflow doesn't seem to exist, 7 * use a (slower) software implementation instead. 8 * This is only implemented for size_t, so in case mallocr.c's INTERNAL_SIZE_T 9 * is non default, mallocr.c throws an #error. 10 */ mul_overflow_size_t(size_t a,size_t b,size_t * res)11static int mul_overflow_size_t(size_t a, size_t b, size_t *res) 12 { 13 // always fill the result (gcc doesn't define what happens here) 14 if (res) 15 *res = a * b; 16 17 // multiply with 0 can not overflow (and avoid div-by-zero): 18 if (a == 0 || b == 0) 19 return 0; 20 21 #ifdef __MSP430__ 22 volatile uint32_t ia = (uint32_t) a; 23 volatile uint32_t ib = (uint32_t) b; 24 25 // check if overflow would happen: 26 if ( (ia > SIZE_MAX / ib) || (ib > SIZE_MAX / ia)) { 27 return 1; 28 } 29 #else 30 // check if overflow would happen: 31 if ( (a > SIZE_MAX / b) || (b > SIZE_MAX / a)) { 32 return 1; 33 } 34 #endif 35 36 return 0; 37 } 38 #define mul_overflow mul_overflow_size_t 39 #endif 40
