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".)

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 suspect division operation 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 code 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

This compliant solution tests the suspect remainder operation 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 divide-by-zero can result in abnormal program termination and denial of service.

Automated Detection

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

Related Guidelines

Bibliography

NUM01-J. Avoid performing bitwise and arithmetic operations on the same data      03. Numeric Types and Operations (NUM)