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All occurrences in a source file of the following sequences of three characters (that is, trigraph sequences) are replaced with the corresponding single character.
??=
#
??)
]
??!
|
??(
[
??'
^
??>
}
??/
\
??<
{
??-
~
Noncompliant Code Example
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Inadvertent trigraphs can result in unexpected behavior. Some compilers provide options to warn when trigraphs are encountered or to disable trigraph expansion. Use the warning options, and ensure your code compiles cleanly. (See MSC00-C. Compile cleanly at high warning levels.)
Recommendation | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
PRE07-C | Low | Unlikely | Medium | P2 | L3 |
Automated Detection
| Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Astrée |
| trigraph | Fully checked | ||||||
| CC2.PRE07 | Fully implemented | |||||||
| GCC |
|
Can detect violation of this recommendation when the | |||||||||
| LDRA tool suite |
| 81 S | Fully implemented | ||||||
| Parasoft C/C++test |
|
|
| MISRA2004-4_2-3 | Partially implemented | |||||||
| PRQA QA-C |
| 3601 | Partially implemented | ||||||
| RuleChecker |
| trigraph | Fully checked | ||||||
| SonarQube C/C++ Plugin |
| TrigraphUsage |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
| SEI CERT C++ Coding Standard | VOID PRE07-CPP. Avoid using repeated question marks |
| MISRA C:2012 | Rule 4.2 (advisory) |
Bibliography
| [ISO/IEC 9899:2011] | Subclause 5.2.1.1, "Trigraph Sequences" |
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