NUM02-J. Ensure that division and remainder operations do not result in divide-by-zero errors

Division and remainder operations performed on integers are susceptible to divide-by-zero errors. Consequently, the divisor in a division or remainder operation on integer types must be checked for zero prior to the operation. Division and remainder operations performed on floating-point numbers are not subject to this rule.

Noncompliant Code Example (Division)

The result of the / operator is the quotient from the division of the first arithmetic operand by the second arithmetic operand. Division operations are susceptible to divide-by-zero errors. Overflow can also occur during two's-complement signed integer division when the dividend is equal to the minimum (negative) value for the signed integer type and the divisor is equal to −1 (see NUM00-J. Detect or prevent integer overflow for more information). This noncompliant code example can result in a divide-by-zero error during the division of the signed operands num1 and num2:

long num1, num2, result;

/* Initialize num1 and num2 */

result = num1 / num2;

Compliant Solution (Division)

This compliant solution tests the divisor to guarantee there is no possibility of divide-by-zero errors:

long num1, num2, result;

/* Initialize num1 and num2 */

if (num2 == 0) {
  // Handle error
} else {
  result = num1 / num2;
}

Noncompliant Code Example (Remainder)

The % operator provides the remainder when two operands of integer type are divided. This noncompliant code example can result in a divide-by-zero error during the remainder operation on the signed operands num1 and num2:

long num1, num2, result;

/* Initialize num1 and num2 */

result = num1 % num2;

Compliant Solution (Remainder)

This compliant solution tests the divisor to guarantee there is no possibility of a divide-by-zero error:

long num1, num2, result;

/* Initialize num1 and num2 */

if (num2 == 0) {
  // Handle error
} else {
  result = num1 % num2;
}

Risk Assessment

A division or remainder by zero can result in abnormal program termination and denial-of-service (DoS).

Automated Detection

Related Guidelines

Bibliography

[ISO/IEC 9899:1999]	Subclause 6.5.5, "Multiplicative Operators"
[Seacord 05]	Chapter 5, "Integers"
[Seacord 2015]	NUM02-J. Ensure that division and modulo operations do not result in divide-by-zero errors LiveLesson
[Warren 02]	Chapter 2, "Basics"