These functions respectively add, subtract or multiply a and b with arbitrary precision and store the result in *result. Where type1, type2 and type3 are any integer type. Starting with C23, the standard header provides the following three function-like macros: bool ckd_add(type1 *result, type2 a, type3 b) īool ckd_sub(type1 *result, type2 a, type3 b) īool ckd_mul(type1 *result, type2 a, type3 b) If (x != 0 & a < INT_MIN / x) // `a * x` would underflowįor division (except for the INT_MIN and -1 special case), there isn't any possibility of going over INT_MIN or INT_MAX. If (x != 0 & a > INT_MAX / x) // `a * x` would overflow If (x = -1 & a = INT_MIN) // `a * x` (or `a / x`) can overflow If (a = -1 & x = INT_MIN) // `a * x` can overflow If one number is -1 and another is INT_MIN, multiplying them we get abs(INT_MIN) which is 1 higher than INT_MAX There may be a need to check for -1 for two's complement machines. If (x INT_MAX + x) // `a - x` would overflow If (x > 0 & a > INT_MAX - x) // `a + x` would overflow With signed integers, once there has been overflow, undefined behaviour (UB) has occurred and your program can do anything (for example: render tests inconclusive). so, at least for C, your point is moot :) By definition, in C (I don't know about C++), unsigned arithmetic does not overflow.
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