Lowercase letter l (ell) can easily be confused with the digit 1 (one). This can be particularly confusing when indicating that an integer literal constant is a long value. This recommendation is similar to DCL02-C. Use visually distinct identifiers. Likewise, you should use uppercase LL rather than lowercase ll when indicating that an integer literal constant is a long long value.
To be precise when using modifiers to indicate the type of an integer literal, the first character may not be l. It may be L, u, or U. Subsequent characters have no strict case requirements.
Noncompliant Code Example
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Confusing a lowercase letter l (ell) with a digit 1 (one) when indicating that an integer denotation is a long value could lead to an incorrect value being written into code.
Recommendation | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
DCL16-C | Low | Unlikely | Low | P3 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Astrée |
| long-suffix | Fully checked | ||||||
| Axivion Bauhaus Suite |
| CertC-DCL16 | |||||||
| CodeSonar |
| LANG.TYPE.CSUF | Confusing literal suffix | ||||||
| CC2.DCL16 | Fully implemented | |||||||
| Helix QAC |
| C1280 | |||||||
| LDRA tool suite |
| 252 S | Fully implemented | ||||||
| Parasoft C/C++test |
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CERT_C-DCL16-a | The lowercase form of 'L' shall not be used as the first character in a literal suffix | ||||||||
| PC-lint Plus |
| 620 | Fully supported | ||||||
| Polyspace Bug Finder |
| CERT C: Rec. DCL16-C | Checks for use of lowercase "l" in literal suffix (rec. fully covered) |
| RuleChecker |
| long-suffix | Fully checked | ||||||
| SonarQube C/C++ Plugin |
| LiteralSuffix |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
| SEI CERT C++ Coding Standard | DCL16-CPP. Use "L," not "l," to indicate a long value |
| MISRA C:2012 | Rule 7.3 (required) |
Bibliography
| [Lockheed Martin 2005] | AV Rule 14, Literal suffixes shall use uppercase rather than lowercase letters |
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