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MISRA.md

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MISRA Compliance

The coreMQTT Agent library files conform to the MISRA C:2012 guidelines, with some noted exceptions. Compliance is checked with Coverity static analysis. Deviations from the MISRA standard are listed below:

Ignored by Coverity Configuration

Deviation Category Justification
Directive 4.5 Advisory Allow names that MISRA considers ambiguous (such as LogInfo and LogError)
Directive 4.8 Advisory Allow inclusion of unused types. Header files from coreMQTT may define types that are not used by the agent.
Directive 4.9 Advisory Allow inclusion of function like macros. The assert macro is used throughout the library for parameter validation, and logging is done using function like macros.
Rule 2.3 Advisory Allow unused types. Both the agent and coreMQTT headers define types that are not directly used by the library but are still intended to be used by the application.
Rule 2.4 Advisory Allow unused tags. Some compilers warn if types are not tagged.
Rule 2.5 Advisory Allow unused macros. Library headers may define macros intended for the application's use, but are not used by a specific file.
Rule 3.1 Required Allow nested comments. C++ style // comments are used in example code within Doxygen documentation blocks.
Rule 11.5 Advisory Allow casts from void *. Fields such as command parameters are passed as void * for generalization and must be cast to the correct data type before use.

Flagged by Coverity

Deviation Category Justification
Rule 8.7 Advisory API functions are not used by the library outside of the files they are defined; however, they must be externally visible in order to be used by an application.
Rule 8.13 Advisory Functions that are passed as pointers to coreMQTT or the agent must exactly match function signatures with the pointer type definition, so const modifiers cannot be added even if a specific function implementation does not modify a given parameter.

Suppressed with Coverity Comments

To find the deviation references in the source files run grep on the source code with ( Assuming rule 11.3 violation; with justification in point 1 ):

grep 'MISRA Ref 11.3.1' . -rI

Rule 11.3

Ref 11.3.1

  • MISRA C-2012 Rule 11.3 states that a cast shall not be performed between a pointer to to object type and a pointer to a different object type. In this library, the MQTT stack processes data as byte stream, requiring casting to specific data structure. However this casting is safe because the buffers are aligned to a 4-byte boundaries, ensuring that no unaligned memory access occurs.