Reference

checkint(3)

detect overflow in arithmetic

NAME

check_int32_add, check_uint32_add, check_int64_add, check_uint64_add, check_int32_sub, check_uint32_sub, check_int64_sub, check_uint64_sub, check_int32_mul, check_uint32_mul, check_int64_mul, check_uint64_mul, check_int32_div, check_uint32_div, check_int64_div, check_uint64_div, – detect overflow in arithmetic

SYNOPSIS

#include <checkint.h>

int32_t

check_int32_add(int x, int y, int *err);

uint32_t

check_uint32_add(int x, int y, int *err);

int64_t

check_int64_add(int x, int y, int *err);

uint64_t

check_uint64_add(int x, int y, int *err);

int32_t

check_int32_sub(int x, int y, int *err);

uint32_t

check_uint32_sub(int x, int y, int *err);

int64_t

check_int64_sub(int x, int y, int *err);

uint64_t

check_uint64_sub(int x, int y, int *err);

int32_t

check_int32_mul(int x, int y, int *err);

uint32_t

check_uint32_mul(int x, int y, int *err);

int64_t

check_int64_mul(int x, int y, int *err);

uint64_t

check_uint64_mul(int x, int y, int *err);

int32_t

check_int32_div(int x, int y, int *err);

uint32_t

check_uint32_div(int x, int y, int *err);

int64_t

check_int64_div(int x, int y, int *err);

uint64_t

check_uint64_div(int x, int y, int *err);

DESCRIPTION

The check_<type>_<operation>(x, y, err) family of functions perform the specified arithmetic operation (addition, subtraction, multiplication, or division) with the left operand of x and right operand of y and return the arithmetic result with the specified type.

Either operand x or y (or both) can be of any type that is compatible to signed or unsigned 8-bit, 16-bit, 32-bit, or 64-bit integers.

The err argument is or'ed by flags in the function to indicate if an overflow has occurred. The possible flag values are:

CHECKINT_NO_ERROR		no overflow has occurred
CHECKINT_OVERFLOW_ERROR		overflow has occurred
CHECKINT_TYPE_ERROR		operand is of an incompatible type

The err argument is not cleared in calls to the check_<type>_<operation>(x, y, err) functions. Detected overflow persists in the err argument until err is reset to CHECKINT_NO_ERROR.

RETURN VALUES

If successful, the check_<type>_<operation>() functions will return the arithmetic result of performing the operation with left operand x and right operand y (even when overflow error occurs).

If any other error occurs, the return value is -1 and the argument err will be set to indicate the error.

EXAMPLES

/* Create a variable to store overflow flag */
int32_t err = CHECKINT_NO_ERROR;
/* Use checkint API to perform an arithmetic operation and
 * store result in variable. */
int32_t arithmetic_result = check_int32_add(UINT_MAX, 1, &err);
/* Check status of overflow flag */
if (err & CHECKINT_OVERFLOW_ERROR) {
    /* Perform overflow resolution code */
    fprintf(stderr, "Overflow detected!\n");
}
/* Check for type error */
else if (err & CHECKINT_TYPE_ERROR) {
    /* Deal with incompatible types error */
    fprintf(stderr, "Incompatible types!\n");
}
/* Reset overflow flag for next operation */
err = CHECKINT_NO_ERROR;

ERRORS

The check_<type>_<operation>() functions may fail if:

[CHECKINT_TYPE_ERROR]		operand is of an incompatible type

HISTORY

The checkint() API was introduced in Mac OS X 10.5.