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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 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".)

Noncompliant Code Example

This code for more information). This noncompliant code example can result in a divide-by-zero error during the division of the signed operands sl1 num1 and sl2. num2:

signed long sl1num1, sl2num2, result;

/* Initialize sl1num1 and sl2num2 */

result = sl1num1 / sl2num2;

Compliant Solution (Division)

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

signed long sl1num1, sl2num2, result;

/* Initialize sl1num1 and sl2num2 */

if (num2 (sl2 == 0) ) {
  //* handleHandle error condition */
}
 else {
  result = sl1num1 / sl2num2;
}

...

Noncompliant Code Example (Remainder)

The % operator provides the remainder when two operands of integer type are divided.

Noncompliant Code Example

This noncompliant code example can result in a divide-by-zero error during the remainder operation on the signed operands sl1 num1 and sl2. num2:

signed long sl1num1, sl2num2, result;

/* Initialize sl1num1 and sl2num2 */

result = sl1num1 % sl2num2;

Compliant Solution (Remainder)

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

signed long sl1num1, sl2num2, result;

/* Initialize sl1num1 and sl2num2 */

if ( (sl2num2 == 0 ) ) {
  /*/ handleHandle error condition */
}
 else {
  result = sl1num1 % sl2num2;
}

Risk Assessment

A divide-division or 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 Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Other Languages

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Related Guidelines

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Related Guidelines

Bibliography

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]

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

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[[Warren 02

AA. Bibliography#Warren 02]

[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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