This rule is part of MISRA C++:2023.
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Rule 4.1.1 - A program shall conform to ISO/IEC 14882:2017 (C++17)
[defns.well.formed]
[intro.compliance]
[MISRA Guidelines] / Table 3
[IEC 61508-7] / Table C.1
[ISO 26262-6] / Table 1
Category: Required
Analysis: Undecidable, System
Amplification
A conforming program shall be well-formed, meaning that it shall be constructed according to the syntax rules, diagnosable semantic rules,
and the one-definition rule, as specified for C++17 within ISO/IEC 14882:2017 . In addition, the program shall use only those features
of the C++ language and its library that are specified within the C++ Standard.
The use of language extensions is not permitted by this rule.
Note: a conforming implementation usually generates a diagnostic if a program is not well-formed, but be aware that:
- The C++ Standard does not require a diagnostic for all constructs that are not well-formed;
- A diagnostic need not necessarily be an error but could, for example, be a warning;
- The program may be translated and an executable generated, even if the program is not well-formed.
Rationale
Undesirable behaviours associated with language features that are extensions or which are specified outside of the C++ Standard have not been
considered during the development of the guidelines within this document.
The behaviour of a program that is not well-formed is unpredictable.
It is recognized that it is sometimes necessary to use language extensions in embedded systems. If an extension is used (subject to a deviation),
then appropriate steps shall be taken to guarantee predictable behaviour. This may be documented in a deviation permit to aid reuse, as explained in
MISRA Compliance .
Example
#warning "declaring an interrupt handler" // Non-compliant
__interrupt void handler(); // Non-compliant
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