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Division and modulo remainder operations performed on integers are susceptible to divide-by-zero errors. Consequently, the divisor in a division or modulo 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 rule −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.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) {
  // handleHandle 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) {
  // handleHandle error
} else {
  result = num1 % num2;
}

Risk Assessment

A division or modulo remainder 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

Related Guidelines

Bibliography

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[

[ISO/IEC 9899:1999

AA. Bibliography#ISO/IEC 9899-1999]

]

Section

Subclause 6.5.5,

Multiplicative Operators

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[[Seacord 05

AA. Bibliography#Seacord 05]]

"Multiplicative Operators"
[Seacord 05]	Chapter 5, "Integers"

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[[Warren 02

AA. Bibliography#Warren 02]]

Chapter 2, Basics

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[Seacord 2015]	Image Added NUM02-J. Ensure that division and modulo operations do not result in divide-by-zero errors LiveLesson
[Warren 02]	Chapter 2, "Basics"

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