NAME

stdckdint — checked integer arithmetic

SYNOPSIS

#include <stdckdint.h>

bool
ckd_add(type1 *result, type2 a, type3 b);

bool
ckd_sub(type1 *result, type2 a, type3 b);

bool
ckd_mul(type1 *result, type2 a, type3 b);

DESCRIPTION

The function-like macros ckd_add, ckd_sub, and ckd_mul perform checked integer addition, subtraction, and multiplication, respectively. If the result of adding, subtracting, or multiplying a and b as if their respective types had infinite range fits in type1, it is stored in the location pointed to by result and the macro evaluates to false. Otherwise, the macro evaluates to true and the contents of the location pointed to by result is the result of the operation wrapped to the range of type1.

RETURN VALUES

The ckd_add, ckd_sub, and ckd_mul macros evaluate to true if the requested operation overflowed the result type and false otherwise.

EXAMPLES

#include <assert.h>
#include <limits.h>
#include <stdckdint.h>

int main(void)
{
	int result;

	assert(!ckd_add(&result, INT_MAX, 0));
	assert(result == INT_MAX);
	assert(ckd_add(&result, INT_MAX, 1));
	assert(result == INT_MIN);

	assert(!ckd_sub(&result, INT_MIN, 0));
	assert(result == INT_MIN);
	assert(ckd_sub(&result, INT_MIN, 1));
	assert(result == INT_MAX);

	assert(!ckd_mul(&result, INT_MAX / 2, 2));
	assert(result == INT_MAX - 1);
	assert(ckd_mul(&result, INT_MAX / 2 + 1, 2));
	assert(result == INT_MIN);

	return 0;
}

HISTORY

The ckd_add, ckd_sub, and ckd_mul macros were first introduced in FreeBSD 14.0.

AUTHORS

The ckd_add, ckd_sub, and ckd_mul macros and this manual page were written by Dag-Erling Smørgrav <des@FreeBSD.org>.