MISRA C:2012 - A Guide for Critical Systems Development

MISRA C is a set of guidelines for the use of the C language in critical systems, such as those found in the automotive, aerospace, medical and industrial sectors. The latest version of MISRA C, known as MISRA C:2012, was published in 2013 and covers the C99 and C90 standards. It also provides additional guidance for the use of C11 and C18 features in an amendment document published in 2020.

The main objectives of MISRA C are to facilitate code safety, security, portability and reliability in the context of embedded systems. MISRA C defines a subset of the C language that avoids certain constructs that are deemed to be risky or error-prone. It also provides rules and recommendations for good coding practices that can help to prevent or detect defects. MISRA C is widely adopted and supported by various tools and organizations across the world.

In this article, we will provide an overview of MISRA C:2012 and its benefits, as well as some resources for learning more about it.

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What is MISRA C:2012?

MISRA C:2012 is the third edition of the MISRA C guidelines, following MISRA C:1998 and MISRA C:2004. It consists of 143 rules and 16 directives that specify what features of the C language should or should not be used, and how they should be used. The rules and directives are classified into three categories:

Mandatory: Violations of these rules must be avoided at all costs, as they may lead to undefined or unspecified behavior, or compromise the safety or security of the system.

Required: Violations of these rules should be avoided as far as possible, as they may reduce the quality or maintainability of the code, or introduce potential errors or vulnerabilities.

Advisory: These rules provide suggestions for improving the style or readability of the code, or for avoiding possible issues in certain contexts.

The rules and directives are also grouped into eight chapters according to their topics:

Environment

Language extensions

Documentation

Character sets

Identifiers

Types

Constants

Declarations and definitions

Initialization

Arithmetic type conversions

Pointer type conversions

Expressions

Control statement expressions

Control flow

Switch statements

Functions

Pointers and arrays

Structures and unions

Preprocessing directives

Standard libraries

Run-time failures