MISRA provides coding guidelines for C and C++.

Consider this your guide to MISRA C and MISRA C++.

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What Is MISRA?

MISRA logo

MISRA provides coding standards for developing safety-critical systems.

MISRA is made up of manufacturers, component suppliers, and engineering consultancies. Experts from Perforce’s static code analysis team (formerly PRQA) are members of MISRA, too.

MISRA first developed coding guidelines in 1998. These were specific to the C programming language. Since then, MISRA has added a coding standard for C++.

 

Why Use MISRA Standards?

You can use MISRA standards to ensure your code is:

  • Safe
  • Secure
  • Reliable
  • Portable

 

[RELATED WHITE PAPER: WHAT IS MISRA? AN OVERVIEW OF THE MISRA STANDARD]

 

The MISRA C coding standard was originally written for the automotive industry. But today, MISRA standards for C and C++ are widely used by embedded industries — including aerospace and defense, telecommunications, medical devices, and rail.

Most of these industries have a compliance requirement to use a coding standard — such as ISO 26262 for automotive functional safety.

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3 Examples of Better Embedded Coding With MISRA

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Learn how embedded coding is better with MISRA — including in automotive, aerospace, and rail industries.

Important MISRA C Rules With Examples

MISRA C is the most widely used set of coding guidelines for C around the world. There have been three releases of the MISRA C standard.

MISRA C:1998

MISRA C:1998 was published in 1998 and remains widely used today. It was written for C90. There are 127 coding rules, including:

Rule 59
The statement forming the body of an "if", "else if", "else", "while", "do ... while", or "for" statement shall always be enclosed in braces

MISRA C:2004

MISRA C:2004 is the second edition of MISRA C, published in 2004. It was written for C90. There are 142 coding rules, including:

Rule 14.9

An if (expression) construct shall be followed by a compound statement. The else keyword shall be followed by either a compound statement, or another if statement.

Rule 14.10 

All if … else if constructs shall be terminated with an else clause.

MISRA C:2012

MISRA C:2012 is the third edition of MISRA C, published in 2012. It was written for C99. There are 143 rules, including:

Rule 18.1
A pointer resulting from arithmetic on a pointer operand shall address an element of the same array as that pointer operand

[RELATED WHITE PAPER: 6 KEY CHANGES IN MISRA:C 2012]

 

MISRA C:2012 Amendment 1

MISRA C 2012 Amendment 1 was released in 2016. With this amendment, MISRA C:2012 includes 156 rules and 17 directives for a total of 173 guidelines, including:

Rule 12.5

The sizeof operator shall not have an operand which is a function parameter declared as "array of type"

MISRA C:2012 Addenda

While the MISRA C standard was originally designed for functional safety, it also covers security. MISRA C:2012 includes addenda which strengthen security in coding. 

MISRA C:2012 — Addendum 2 shows how each MISRA rule maps to the C Secure rules in ISO/IEC TS 17961:2013.

MISRA C:2012 — Addendum 3 shows how each rule maps to the CERT C rules.

 

Watch: How to Secure Embedded Systems With MISRA C Rules

 

 

[RELATED WHITE PAPER: HOW TO WRITE SECURE CODE IN C]


Important MISRA C++ Rules With Examples

MISRA C++ is widely used by safety-critical developers. There’s one version of MISRA C++ rules available today.

MISRA C++2008

MISRA C++:2008 was published in 2008. It was written for C++03. There are 228 coding rules, including:

Rule 5-0-13

The condition of an if-statement and the condition of an iteration statement shall have type bool.

Looking for coding guidelines for C++11 or C++14? See AUTOSAR >


How to Achieve MISRA Compliance

Achieving MISRA compliance takes knowledge, skill, and the right tools.

Here are some steps you can take to comply with MISRA.

  1. Know the Rules

    You need to know the MISRA coding rules pertinent to which version of C or C++ you’re using.

  2. Check Your Code Constantly

    Continuously inspecting your code for violations is the best way to improve quality.

  3. Set Baselines

    Embedded systems come with legacy codebases. By setting baselines, you can focus on making sure your new code is compliant.

  4. Prioritize Violations Based on Risk

    You could have hundreds or even thousands of violations in your code. That’s why it’s important to prioritize rule violations based on risk severity. Some static code analysis tools can do this for you.

  5. Document Your Deviations

    Sometimes there are exceptions to the rule. But when it comes to compliance, every rule deviation needs to be well-documented.

  6. Monitor Your MISRA Compliance

    Keep an eye on how MISRA compliant your code is. Using a static code analyzer makes this easier by automatically generating a compliance report.

  7. Choose the Right Static Code Analyzer

    Choosing the right static code analyzer makes everything else easy. It takes care of scanning your code — new and legacy — for violations. It prioritizes vulnerabilities based on risk.

Complying with MISRA is important for many development teams today. Especially as virtualization rises. See how an automotive hypervisor complies with MISRA >>

But not all MISRA checkers are the same…

 

[RELATED WHITE PAPER: HOW TO COMPARE MISRA CHECKERS]


Using Helix QAC For MISRA Rules

Helix QAC finds and reports on violations of MISRA rules and directives in C and C++.

Why Use Helix QAC for MISRA Compliance?

  • Independently certified for use in the development of safety-critical software.
  • Fully documented rule enforcement and message interpretation.
  • Supplied with extensive example code.
  • Fully configurable rules processing.
  • Compliance reports for functional safety audits.

How Embedded Developers Use Helix QAC For MISRA

See how leaders in embedded industries — automotive, aerospace, and rail — use Helix QAC and MISRA.

 

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Try Helix QAC for MISRA C and C++

See why Helix QAC is the best static code analyzer for MISRA C and C++.