7.3 Using MISRA C 2004

MISRA C is a set of software development guidelines for the C programming language. It promotes best practices in developing safety-related electronic systems in road vehicles and other embedded systems. MISRA C was originally launched in 1998 by the Motor Industry Software Reliability Association, and has since been adopted across a wide variety of industries. A subsequent update to the guidelines was publishes as MISRA C:2004

You can alter your code to work with the MISRA C:2004 rules. The following options and pragmas can be used to enable/disable rules:

• The --check_misra option enables checking of the specified MISRA C:2004 rules. This compiler option must be used if you want to enable further control over checking using the CHECK_MISRA and RESET_MISRA pragmas.
• The CHECK_MISRA pragma enables/disables MISRA C:2004 rules at the source level. See Section 7.9.2.
• The RESET_MISRA pragma resets the specified MISRA C:2004 rules to their state before any CHECK_MISRA pragmas were processed. See Section 7.9.30.

The syntax of the option and the pragmas is:

The rulespec parameter is a comma-separated list of rule numbers to enable or disable.

Example: --check_misra=1.1,1.4,1.5,2.1,2.7,7.1,7.2,8.4

• Enables checking of rules 1.1, 1.4, 1.5, 2.1, 2.7, 7.1, 7.2, and 8.4.

Example: #pragma CHECK_MISRA("-7.1,-7.2,-8.4")

• Disables checking of rules 7.1, 7.2, and 8.4.

A typical use case is to use the --check_misra option on the command line to specify the rules that should be checked in most of your code. Then, use the CHECK_MISRA pragma with a rulespec to activate or deactivate certain rules for a particular region of code.

Two options control the severity of certain MISRA C:2004 rules:

• The --misra_required option sets the diagnostic severity for required MISRA C:2004 rules.
• The --misra_advisory option sets the diagnostic severity for advisory MISRA C:2004 rules.

The syntax for these options is: