Use visually distinct identifiers to eliminate errors resulting from misrecognizing the spelling of an identifier during the development and review of code. Depending on the fonts used, certain characters are visually similar or even identical:
- 1 (one) and l (lower case el)
- 0 (zero) and O (capital o)
- 2 (two) and Z (capital Z)
- 5 (five) and S (capital S)
- 8 (eight) and B (capital B)
Do not define multiple identifiers that vary only with respect to one or more visually similar characters.
Make the initial portions of long identifiers unique for easier recognition. This also helps prevent errors resulting from nonunique identifiers (see DCL32-C. Guarantee that mutually visible identifiers are unique).
Risk Analysis
Failing to use visually distinct identifiers can result in the wrong variable being used, causing unexpected program behavior.
Recommendation |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
|---|---|---|---|---|---|
DCL02-C |
low |
unlikely |
medium |
P2 |
L3 |
Automated Detection
Compass/ROSE can detect violations of this recommendation.
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Other Languages
This rule appears in the C++ Secure Coding Standard as DCL02-CPP. Use visually distinct identifiers.
References
[[ISO/IEC 9899:1999]] Section 5.2.4.1, "Translation limits"
[[ISO/IEC PDTR 24772]] "AJN Choice of Filenames and other External Identifiers," "BRS Leveraging human experience," and "NAI Choice of Clear Names"
[[MISRA 04]] Rule 5.6
02. Declarations and Initialization (DCL)