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

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Division and remainder operations are susceptible to divide-by-zero errors. Consequently, the divisor in a division or remainder 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 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).

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

NUM02-J

Low

Likely

Medium

P6

L2

## Automated Detection

Tool
Version
Checker
Description
Coverity7.5DIVIDE_BY_ZEROImplemented
Parasoft Jtest
10.3
BD.PB.ZERO
SonarQube

6.7

S3518Zero should not be a possible denominator

## Bibliography

 Subclause 6.5.5, "Multiplicative Operators" Chapter 5, "Integers" [Seacord 2015] NUM02-J. Ensure that division and modulo operations do not result in divide-by-zero errors LiveLesson Chapter 2, "Basics"