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C Coding Directives and Rules Supported for Code Generation

When you generate C code from MATLAB® code, you can configure the code generator to maximize the compliance of the generated code with the required and mandatory coding rules in the MISRA™ C:2012 guidelines.

The following tables list all the required and mandatory coding directives and rules in MISRA C:2012 Main Document, MISRA C:2012 Amendment 1, and MISRA C:2012 Amendment 2. For each directive or rule, the Compliance column has one of these entries:

  • Compliant: Generated code is compliant with this directive/rule.

  • Not Compliant: In some situations, the generated code might not be compliant with this directive/rule.

  • Not Applicable: This directive/rule does not apply to the code generation process. For some of these directives/rules, the Additional Notes section suggests actions that you can take to improve the compliance of the generated code.


These tables assume that you have already followed these steps to maximize MISRA compliance of the generated code:

The generated code might include one or more files that are not compliant with MISRA guidelines. For a complete list of these files, see Scope of Code Generation Support.

In certain situations, you might be able to configure the code generator to avoid using the custom type definitions contained in the rtwtypes.h file in the generated code. For example, see Additional Settings for MISRA C++ Compliance.

The information in these tables does not apply to the C code generated for MATLAB code inside MATLAB Function blocks and MATLAB System blocks in Simulink® models. For information on the MISRA compliance of code generated from Simulink models, see MISRA C:2012 Compliance Summary Tables.

The code generator interprets these rules in the same way as the Polyspace® Bug Finder™ product. To learn about how the code generator interprets a particular coding rule, see the Polyspace Implementation section in the corresponding reference page in the Polyspace Bug Finder documentation: MISRA C:2012 Directives and Rules (Polyspace Bug Finder).

Compilation and Code Design Directives

DirectiveDescriptionComplianceAdditional Notes
D1.1Any implementation-defined behaviour on which the output of the program depends shall be documented and understood.Not Compliant 
D2.1All source files shall compile without any compilation errors.Compliant 
D3.1All code shall be traceable to documented requirements.Not Applicable

To make the generated code compliant, use Requirements Toolbox™ to include comments in the generated code that contain information about the requirements. See Requirements Traceability for Code Generated from MATLAB Code (Requirements Toolbox).

D4.1Run-time failures shall be minimized.Not Compliant 
D4.3Assembly language shall be encapsulated and isolated.Compliant 
D4.7If a function returns error information, then that error information shall be tested.Not Compliant

To reduce this violation, in your MATLAB code, include tests for the output of coder.ceval calls.

D4.10Precautions shall be taken in order to prevent the contents of a header file being included more than once.Compliant 
D4.11The validity of values passed to library functions shall be checked.Not Compliant

To reduce this violation, in your MATLAB code, check the validity of values that you pass to coder.ceval.

D4.12Dynamic memory allocation shall not be used.Compliant 
D4.14The validity of values received from external sources shall be checked.Not Compliant

To reduce this violation, in your MATLAB code, check the validity of values that coder.ceval returns.

1. Standard C Environment

RuleDescriptionComplianceAdditional Notes
1.1The program shall contain no violations of the standard C syntax and constraints, and shall not exceed the implementation's translation limits.Not Compliant 
1.3There shall be no occurrence of undefined or critical unspecified behaviour.Compliant 
1.4Emergent language features shall not be used.Compliant 

2. Unused Code

RuleDescriptionComplianceAdditional Notes
2.1A project shall not contain unreachable code.Not Compliant 
2.2There shall be no dead code.Not Compliant 


RuleDescriptionComplianceAdditional Notes
3.1The character sequences /* and // shall not be used within a comment.Not Compliant

To reduce this violation, make sure the comments that you include in your MATLAB code or external C/C+ code satisfies this rule.

Alternatively, consider disabling comment generation by setting the configuration property GenerateComments to false.

3.2Line-splicing shall not be used in // comments.Compliant 

4. Character Sets and Lexical Conventions

RuleDescriptionComplianceAdditional Notes
4.1Octal and hexadecimal escape sequences shall be terminated.Compliant 

5. Identifiers

RuleDescriptionComplianceAdditional Notes
5.1External identifiers shall be distinct.Not Compliant

To reduce this violation, make sure your MATLAB entry-point function names contain less than 5 characters.

5.2Identifiers declared in the same scope and name space shall be distinct.Compliant 
5.3An identifier declared in an inner scope shall not hide an identifier declared in an outer scope.Compliant 
5.4Macro identifiers shall be distinct.Compliant 
5.5Identifiers shall be distinct from macro names.Compliant 
5.6A typedef name shall be a unique identifier.Compliant 
5.7A tag name shall be a unique identifier.Compliant 
5.8Identifiers that define objects or functions with external linkage shall be unique.Compliant 

6. Types

RuleDescriptionComplianceAdditional Notes
6.1Bit-fields shall only be declared with an appropriate type.Compliant 
6.2Single-bit named bit fields shall not be of a signed type.Compliant 

7. Literals and Constants

RuleDescriptionComplianceAdditional Notes
7.1Octal constants shall not be used.Compliant 
7.2A "u" or "U" suffix shall be applied to all integer constants that are represented in an unsigned type.Compliant 
7.3The lowercase character "l" shall not be used in a literal suffix.Compliant 
7.4A string literal shall not be assigned to an object unless the object's type is "pointer to const-qualified char".Compliant 

8. Declarations and Definitions

RuleDescriptionComplianceAdditional Notes
8.1Types shall be explicitly specified.Compliant 
8.2Function types shall be in prototype form with named parameters.Compliant 
8.3All declarations of an object or function shall use the same names and type qualifiers.Compliant 
8.4A compatible declaration shall be visible when an object or function with external linkage is defined.Compliant 
8.5An external object or function shall be declared once in one and only one file.Compliant 
8.6An identifier with external linkage shall have exactly one external definition.Compliant 
8.8The static storage class specifier shall be used in all declarations of objects and functions that have internal linkage.Compliant 
8.10An inline function shall be declared with the static storage class.Compliant 
8.12Within an enumerator list, the value of an implicitly-specified enumeration constant shall be unique.Compliant 
8.14The restrict type qualifier shall not be used.Compliant 

9. Initialization

RuleDescriptionComplianceAdditional Notes
9.1The value of an object with automatic storage duration shall not be read before it has been set.Not Compliant 
9.2The initializer for an aggregate or union shall be enclosed in braces.Compliant 
9.3Arrays shall not be partially initialized.Compliant 
9.4An element of an object shall not be initialized more than once.Compliant 
9.5Where designated initializers are used to initialize an array object the size of the array shall be specified explicitly.Compliant 

10. The Essential Type Model

RuleDescriptionComplianceAdditional Notes
10.1Operands shall not be of an inappropriate essential type.Compliant 
10.2Expressions of essentially character type shall not be used inappropriately in addition and subtraction operations.Compliant 
10.3The value of an expression shall not be assigned to an object with a narrower essential type or of a different essential type category.Compliant 
10.4Both operands of an operator in which the usual arithmetic conversions are performed shall have the same essential type category.Compliant 
10.6The value of a composite expression shall not be assigned to an object with wider essential type.Compliant 
10.7If a composite expression is used as one operand of an operator in which the usual arithmetic conversions are performed then the other operand shall not have wider essential type.Compliant 
10.8The value of a composite expression shall not be cast to a different essential type category or a wider essential type.Compliant 

11. Pointer Type Conversion

RuleDescriptionComplianceAdditional Notes
11.1Conversions shall not be performed between a pointer to a function and any other type.Compliant 
11.2Conversions shall not be performed between a pointer to an incomplete type and any other type.Compliant 
11.3A cast shall not be performed between a pointer to object type and a pointer to a different object type.Not Compliant 
11.6A cast shall not be performed between pointer to void and an arithmetic type.Compliant 
11.7A cast shall not be performed between pointer to object and a non-integer arithmetic type.Compliant 
11.8A cast shall not remove any const or volatile qualification from the type pointed to by a pointer.Not Compliant 
11.9The macro NULL shall be the only permitted form of integer null pointer constant.Compliant 

12. Expressions

RuleDescriptionComplianceAdditional Notes
12.2The right hand operand of a shift operator shall lie in the range zero to one less than the width in bits of the essential type of the left hand operand.Not Compliant 
12.5The sizeof operator shall not have an operand which is a function parameter declared as "array of type".Compliant 

13. Side Effects

RuleDescriptionComplianceAdditional Notes
13.1Initializer lists shall not contain persistent side effects.Compliant 
13.2The value of an expression and its persistent side effects shall be the same under all permitted evaluation orders.Not Compliant 
13.5The right hand operand of a logical && or || operator shall not contain persistent side effects.Not Compliant

In certain situations, the code generator promotes local variables to static local variables to reduce the stack usage of the generated code. This promotion might cause the generated code to violate this rule.

Increasing the value of the StackUsageMax code configuration parameter might make the generated code compliant with this rule.

13.6The operand of the sizeof operator shall not contain any expression which has potential side effects.Compliant 

14. Control Statement Expressions

RuleDescriptionComplianceAdditional Notes
14.1A loop counter shall not have essentially floating type.Compliant 
14.2A for loop shall be well-formed.Compliant 
14.3Controlling expressions shall not be invariant.Not Compliant 
14.4The controlling expression of an if statement and the controlling expression of an iteration-statement shall have essentially Boolean type.Compliant 

15. Control Flow

RuleDescriptionComplianceAdditional Notes
15.2The goto statement shall jump to a label declared later in the same function.Compliant 
15.3Any label referenced by a goto statement shall be declared in the same block, or in any block enclosing the goto statement.Compliant 
15.6The body of an iteration-statement or a selection-statement shall be a compound-statement.Compliant 
15.7All if ... else if constructs shall be terminated with an else statement.Compliant 

16. Switch Statements

RuleDescriptionComplianceAdditional Notes
16.1All switch statements shall be well-formed.Compliant 
16.2A switch label shall only be used when the most closely-enclosing compound statement is the body of a switch statement.Compliant 
16.3An unconditional break statement shall terminate every switch-clause.Compliant 
16.4Every switch statement shall have a default label.Compliant 
16.5A default label shall appear as either the first or the last switch label of a switch statement.Compliant 
16.6Every switch statement shall have at least two switch-clauses.Compliant 
16.7A switch-expression shall not have essentially Boolean type.Compliant 

17. Functions

RuleDescriptionComplianceAdditional Notes
17.1The features of <stdarg.h> shall not be used.Compliant 
17.2Functions shall not call themselves, either directly or indirectly.Compliant 
17.3A function shall not be declared implicitly.Compliant 
17.4All exit paths from a function with non-void return type shall have an explicit return statement with an expression.Compliant 
17.6The declaration of an array parameter shall not contain the static keyword between the [ ].Compliant 
17.7The value returned by a function having non-void return type shall be used.Compliant 

18. Pointers and Arrays

RuleDescriptionComplianceAdditional Notes
18.1A pointer resulting from arithmetic on a pointer operand shall address an element of the same array as that pointer operand.Not Compliant 
18.2Subtraction between pointers shall only be applied to pointers that address elements of the same array.Compliant 
18.3The relational operators >, >=, < and <= shall not be applied to objects of pointer type except where they point into the same object.Compliant 
18.6The address of an object with automatic storage shall not be copied to another object that persists after the first object has ceased to exist.Not Compliant 
18.7Flexible array members shall not be declared.Compliant 
18.8Variable-length array types shall not be used.Compliant 

19. Overlapping Storage

RuleDescriptionComplianceAdditional Notes
19.1An object shall not be assigned or copied to an overlapping object.Compliant 

20. Preprocessing Directives

RuleDescriptionComplianceAdditional Notes
20.2The ', " or \ characters and the /* or // character sequences shall not occur in a header file name.Compliant 
20.3The #include directive shall be followed by either a <filename> or "filename"sequence.Compliant 
20.4A macro shall not be defined with the same name as a keyword.Compliant 
20.6Tokens that look like a preprocessing directive shall not occur within a macro argument.Compliant 
20.7Expressions resulting from the expansion of macro parameters shall be enclosed in parentheses.Compliant 
20.8The controlling expression of a #if or #elif preprocessing directive shall evaluate to 0 or 1.Compliant 
20.9All identifiers used in the controlling expression of #if or #elif preprocessing directives shall be #define'd before evaluation.Compliant 
20.11A macro parameter immediately following a # operator shall not immediately be followed by a ## operator.Compliant 
20.12A macro parameter used as an operand to the # or ## operators, which is itself subject to further macro replacement, shall only be used as an operand to these operators.Compliant 
20.13A line whose first token is # shall be a valid preprocessing directive.Compliant 
20.14All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if, #ifdef or #ifndef directive to which they are related.Compliant 

21. Standard Libraries

RuleDescriptionComplianceAdditional Notes
21.1#define and #undef shall not be used on a reserved identifier or reserved macro name.Compliant 
21.2A reserved identifier or reserved macro name shall not be declared.Not Compliant 
21.3The memory allocation and deallocation functions of <stdlib.h> shall not be used.Compliant 
21.4The standard header file <setjmp.h> shall not be used.Compliant 
21.5The standard header file <signal.h> shall not be used.Compliant 
21.6The Standard Library input/output functions shall not be used.Not Compliant

To reduce this violation, in your MATLAB code, avoid using functions such as fopen, fclose, fprintf, fscanf, fread, fwrite, and

21.7The Standard Library functions atof, atoi, atol and atoll of <stdlib.h> shall not be used.Compliant 
21.8The Standard Library termination functions of <stdlib.h> shall not be used.Compliant 
21.9The Standard Library functions bsearch and qsort of <stdlib.h> shall not be used.Compliant 
21.10The Standard Library time and date functions shall not be used.Not Compliant

To reduce this violation, in your MATLAB code, avoid using functions such as tic, toc, and pause.

21.11The standard header file <tgmath.h> shall not be used.Compliant 
21.13Any value passed to a function in <ctype.h> shall be representable as an unsigned char or be the value EOF.Compliant 
21.14The Standard Library function memcmp shall not be used to compare null terminated strings.Compliant 
21.15The pointer arguments to the Standard Library functions memcpy, memmove and memcmp shall be pointers to qualified or unqualified versions of compatible types.Not Compliant 
21.16The pointer arguments to the Standard Library function memcmp shall point to either a pointer type, an essentially signed type, an essentially unsigned type, an essentially Boolean type or an essentially enum type.Not Compliant 
21.17Use of the string handling functions from <string.h> shall not result in accesses beyond the bounds of the objects referenced by their pointer parameters.Compliant 
21.18The size_t argument passed to any function in <string.h> shall have an appropriate value.Not Compliant 
21.19The pointers returned by the Standard Library functions localeconv, getenv, setlocale or, strerror shall only be used as if they have pointer to const-qualified type.Compliant 
21.20The pointer returned by the Standard Library functions asctime, ctime, gmtime, localtime, localeconv, getenv, setlocale or strerror shall not be used following a subsequent call to the same function.Compliant 
21.21The Standard Library function system of <stdlib.h> shall not be used.Compliant 

22. Resources

RuleDescriptionComplianceAdditional Notes
22.1All resources obtained dynamically by means of Standard Library functions shall be explicitly released.Compliant 
22.2A block of memory shall only be freed if it was allocated by means of a Standard Library function.Compliant 
22.3The same file shall not be open for read and write access at the same time on different streams.Compliant 
22.4There shall be no attempt to write to a stream which has been opened as read-only.Compliant 
22.5A pointer to a FILE object shall not be dereferenced.Compliant 
22.6The value of a pointer to a FILE shall not be used after the associated stream has been closed.Compliant 
22.7The macro EOF shall only be compared with the unmodified return value from any Standard Library function capable of returning EOF.Compliant 
22.8The value of errno shall be set to zero prior to a call to an errno-setting-function.Compliant 
22.9The value of errno shall be tested against zero after calling an errno-setting-function.Compliant 
22.10The value of errno shall only be tested when the last function to be called was an errno-setting-function.Compliant 

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