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

Division and modulo operations are susceptible to divide-by-zero errors. Consequently, the divisor in a division or modulo operation must be checked for zero prior to the operation.

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 rule 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.

This code 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 (Modulo)

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 (Modulo)

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 modulo by zero can result in abnormal program termination and denial of service (DoS).

Automated Detection

Automated detection exists for C and C++ but not for Java yet.

Related Guidelines

Bibliography

      03. Numeric Types and Operations (NUM)