MISRA C

Since its launch in 1998, the uptake and usage of MISRA C has far exceeded the authors’s original expectations. MISRA C was originally developed to support the language requirements of the 1994 MISRA Guidelines, as noted above. Since that time, however, MISRA C has been adopted and used across a wide variety of industries and applications including the rail, aerospace, military and medical sectors. Furthermore, a significant number of tools are available that support enforcing the MISRA C rules. In Japan, a Japanese translation of MISRA C has been published by JSAE, and the MISRA C Study Group have produced a book (in Japanese) giving detailed explanations of the rules and additional code examples.

MISRA C:2004 (MISRA C2)

A considerable amount of feedback on the original version of MISRA C was received and it was recognized that a revision was appropriate, in particular to address the following:

  • Ensuring that the language used is consistent with the standard language
  • Replacing generalized rules for Undefined Behaviour with specific rules targeted at Undefined Behaviour only
  • Ensuring “one rule, one issue”; i.e. complex rules are split into atomic rules for ease of compliance
  • Adding to and improving the code examples
  • Removing the option for tool-less use.

In updating MISRA C, the aim was to avoid new material and to ensure backwards compatibility with the earlier version (MISRA C1 / MISRA C:1998) where possible. The second version of MISRA C is known as MISRA C:2004 and is titled “Guidelines for the use of the C language in critical systems.”

 

In July 2007 an Exemplar Suite was released. This is a set of code examples that demonstrate conforming and non-conforming code for the majority of the MISRA C rules. This Exemplar Suite is of value to users both in understanding the rules and also in evaluating the performance of rule-checking tools, although in this respect it must be understood that the Exemplar Suite is not a conformance testing suite.

 

In July 2007 a Technical Corrigendum was also issued, giving updates based on some of the most commonly-asked questions and also issues identified during the development of the Exemplar Suite. When MISRA C:2004 was reprinted in June 2008, the opportunity was taken to incorporate the text of the Technical Corrigendum.

MISRA C:2012 (MISRA C3)

MISRA C:2012 was published on 18 March 2013. MISRA C:2012 extends support to the C99 version of the language whilst maintaining guidelines for C90. Other improvements, many of which have been made as a result of user feedback, include: better rationales for every guideline, identified decidability so users can better interpret the output of checking tools, greater granularity of rules to allow more precise control, a number of expanded examples and integration of MISRA AC AGC. A cross reference for ISO 26262 has also been produced.