MISRA C:2023 Rule 4.2
Trigraphs should not be used
Since R2024a
Description
Rule Definition
Trigraphs should not be used1 .
Rationale
You denote trigraphs with two question marks followed by a specific
third character (for instance,'??-' represents
a '~' (tilde) character and '??)' represents
a ']'). These trigraphs can cause accidental confusion
with other uses of two question marks.
Note
Digraphs (<: :>, <% %>, %:, %:%:)
are permitted because they are tokens.
Polyspace Implementation
The Polyspace® analysis converts trigraphs to the equivalent character for the defect analysis. However, Polyspace also raises a MISRA™ violation.
The standard requires that trigraphs must be transformed before comments are removed during preprocessing. Therefore, Polyspace raises a violation of this rule even if a trigraph appears in code comments.
Troubleshooting
If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.
Check Information
| Group: Character Sets and Lexical Conventions |
| Category: Advisory |
| AGC Category: Advisory |
Version History
Introduced in R2024a
1 All MISRA coding rules and directives are © Copyright The MISRA Consortium Limited 2021.
The MISRA coding standards referenced in the Polyspace Bug Finder™ documentation are from the following MISRA standards:
MISRA C:2004
MISRA C:2012
MISRA C:2023
MISRA C++:2008
MISRA C++:2023
MISRA and MISRA C are registered trademarks of The MISRA Consortium Limited 2021.
