SEI CERT C Coding Standard

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The following table summarizes some of the differences between const-qualified objects, enumeration constants, and object-like macro definitions.

Method

Evaluated At

Consumes Memory

Viewable by Debuggers

Type Checking

Compile-Time Constant Expression

Enumerations

Compile time

No

Yes

Yes

Yes

const-qualified

Runtime

Yes

Yes

Yes

No

Macros

Preprocessor

No

No

No

Yes

Noncompliant Code Example

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Using numeric literals makes code more difficult to read and understand. Buffer overruns are frequently a consequence of a magic number being changed in one place (such as in an array declaration) but not elsewhere (such as in a loop through an array).

Recommendation

Severity

Likelihood

Remediation Cost

Priority

Level

DCL06-C

Low

Unlikely

Medium

P2

L3

Automated Detection

Tool

Version

Checker

Description

Axivion Bauhaus Suite

Include Page
Axivion Bauhaus Suite_V
Axivion Bauhaus Suite_V

CertC-DCL06
Compass/ROSE

 

 



Could detect violations of this recommendation merely by searching for the use of "magic numbers" and magic strings in the code itself. That is, any number (except a few canonical numbers: −1, 0, 1, 2) that appears in the code anywhere besides where assigned to a variable is a magic number and should instead be assigned to a const integer, enum, or macro. Likewise, any string literal (except "" and individual characters) that appears in the code anywhere besides where assigned to a char* or char[] is a magic string

ECLAIR

Include Page
ECLAIR_V
ECLAIR_V

CC2.DCL06

Fully implemented

Helix QAC

Include Page
Helix QAC_V
Helix QAC_V

C3120, C3121, C3122, C3123, C3131, C3132


LDRA tool suite
Include Page
LDRA_V
LDRA_V

201 S

Fully implemented

Parasoft C/C++test
9.5CODSTA-26Fully implementedPRQA QA-C Include PagePRQA QA-C_vPRQA QA-C_v

3120
3121
3122
3123
3131
3132

Partially implemented
Include Page
Parasoft_V
Parasoft_V

CERT_C-DCL06-a

Use meaningful symbolic constants to represent literal values

Polyspace Bug Finder

Include Page
Polyspace Bug Finder_V
Polyspace Bug Finder_V

CERT C: Rec. DCL06-C


Checks for:

  • Hard-coded buffer size
  • Hard-coded loop boundary

Rec. fully covered.

Related Vulnerabilities

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

Related Guidelines

SEI CERT C++ Coding StandardVOID DCL06-CPP. Use meaningful symbolic constants to represent literal values in program logic
MITRE CWECWE-547, Use of hard-coded, security-relevant constants

Bibliography

[Henricson 1992]Chapter 10, "Constants"
[Saks 2001a]
 

[Saks 2001b]
 

[Saks 2002]
 

[Summit 2005]Question 10.5b

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