The MISRA C and MISRA C++ documents are compilations of guidelines for coding in the C and C++ languages respectively.

They are widely used in the development of critical software systems when the requirements of a quality standard must be met. Many software projects specify that code quality should be assured by meeting the requirements of The Guidelines.

However, the meaning of the phrase “MISRA compliant” needs to be carefully defined.  In order for a claim of MISRA compliance to have meaning, it is necessary to establish:

• Use of a disciplined software development process;
• Exactly which guidelines are being applied;
• The effectiveness of the enforcement methods;
• The extent of any deviations from the guidelines;
• The status of any software components developed outside of the project.

The MISRA C and MISRA C++ guidelines recognize that, in some situations, it is unreasonable or even impossible to comply with a coding guideline and that it is necessary to deviate from its requirements. The freedom to deviate does not necessarily compromise claims of compliance, but it does carry with it great responsibility. In the absence of a disciplined development process, it is easy for that freedom to be abused. At best, that will undermine the credibility of any claims of MISRA compliance; at worst, it will compromise code quality, safety or security.