CERT C: Rec. INT09-C

Ensure enumeration constants map to unique values

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Description

Rule Definition

Ensure enumeration constants map to unique values.¹

Polyspace Implementation

The rule checker checks for Enumeration constants map to same value.

Examples

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Enumeration constants map to same value

Issue

The issue occurs when, within an enumerator list, the value of an implicitly-specified enumeration constants are not unique.

The rule checker flags an enumeration if it has an implicitly specified enumeration constant with the same value as another enumeration constant.

Risk

An implicitly specified enumeration constant has a value one greater than its predecessor. If the first enumeration constant is implicitly specified, then its value is 0. An explicitly specified enumeration constant has the specified value.

If implicitly and explicitly specified constants are mixed within an enumeration list, it is possible for your program to replicate values. Such replications can be unintentional and can cause unexpected behavior.

Example - Replication of Value in Implicitly Specified Enum Constants

enum color1 {red_1, blue_1, green_1};   /* Compliant */
enum color2 {red_2 = 1, blue_2 = 2, green_2 = 3};       /* Compliant */
enum color3 {red_3 = 1, blue_3, green_3};     /* Compliant */
enum color4 {red_4, blue_4, green_4 = 1};     /* Non Compliant */
enum color5 {red_5 = 2, blue_5, green_5 = 2};     /* Compliant */
enum color6 {red_6 = 2, blue_6, green_6 = 2, yellow_6};     /* Non Compliant */

Compliant situations:

color1: All constants are implicitly specified.
color2: All constants are explicitly specified.
color3: Though there is a mix of implicit and explicit specification, all constants have unique values.
color5: The implicitly specified constants have unique values.

Noncompliant situations:

color4: The implicitly specified constant blue_4 has the same value as green_4.
color6: The implicitly specified constant blue_6 has the same value as yellow_6.

Check Information

Group: Rec. 04. Integers (INT)

Version History

Introduced in R2019a

¹ This software has been created by MathWorks incorporating portions of: the “SEI CERT-C Website,” © 2017 Carnegie Mellon University, the SEI CERT-C++ Web site © 2017 Carnegie Mellon University, ”SEI CERT C Coding Standard – Rules for Developing safe, Reliable and Secure systems – 2016 Edition,” © 2016 Carnegie Mellon University, and “SEI CERT C++ Coding Standard – Rules for Developing safe, Reliable and Secure systems in C++ – 2016 Edition” © 2016 Carnegie Mellon University, with special permission from its Software Engineering Institute.

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