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.
Noncompliant Code Example
This noncompliant example highlights the result of adding an integer and a long value even though it appears that two integers 1111 are being added:
printf("Sum is %ld\n", 1111 + 111l);
Compliant Solution
The compliant solution improvises by using an uppercase L instead of lowercase l to disambiguate the visual appearance:
printf("Sum is %ld\n", 1111 + 111L);
Risk Assessment
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 | 24.04 | long-suffix | Fully checked |
| CodeSonar | 8.1p0 | LANG.TYPE.CSUF | Confusing literal suffix |
1.2 | CC2.DCL16 | Fully implemented | |
| LDRA tool suite | 9.7.1 | 252 S | Fully implemented |
| Parasoft C/C++test | 2023.1 | CERT_C-DCL16-a | Use capital 'L' instead of lowercase 'l' to indicate long |
| PRQA QA-C | Unable to render {include} The included page could not be found. | 1280 | Fully implemented |
| RuleChecker | 24.04 | long-suffix | Fully checked |
| SonarQube C/C++ Plugin | 3.11 | 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 |
