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.

Note

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

• Set the code generation configuration properties to the recommended values. You can do this either at the command line or in the MATLAB Coder™ app. See Configure Code Generation Configuration Object Properties at Command Line and Configure MATLAB Coder App Settings.

• Make sure any user-written C/C++ files or third-party C/C++ files that you integrate with the generated code by using coder.ceval are compliant with the MISRA guidelines.

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

Directive	Description	Compliance	Additional Notes
D1.1	Any implementation-defined behaviour on which the output of the program depends shall be documented and understood.	Not Compliant
D2.1	All source files shall compile without any compilation errors.	Compliant
D3.1	All 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).
D4.1	Run-time failures shall be minimized.	Not Compliant
D4.3	Assembly language shall be encapsulated and isolated.	Compliant
D4.7	If 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.
D4.10	Precautions shall be taken in order to prevent the contents of a header file being included more than once.	Compliant
D4.11	The 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.
D4.12	Dynamic memory allocation shall not be used.	Compliant
D4.14	The 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

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

2. Unused Code

Rule	Description	Compliance	Additional Notes
2.1	A project shall not contain unreachable code.	Not Compliant
2.2	There shall be no dead code.	Not Compliant

3. Comments

Rule	Description	Compliance	Additional Notes
3.1	The 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.
3.2	Line-splicing shall not be used in // comments.	Compliant

4. Character Sets and Lexical Conventions

Rule	Description	Compliance	Additional Notes
4.1	Octal and hexadecimal escape sequences shall be terminated.	Compliant

5. Identifiers

Rule	Description	Compliance	Additional Notes
5.1	External identifiers shall be distinct.	Not Compliant	To reduce this violation, make sure your MATLAB entry-point function names contain less than 5 characters.
5.2	Identifiers declared in the same scope and name space shall be distinct.	Compliant
5.3	An identifier declared in an inner scope shall not hide an identifier declared in an outer scope.	Compliant
5.4	Macro identifiers shall be distinct.	Compliant
5.5	Identifiers shall be distinct from macro names.	Compliant
5.6	A typedef name shall be a unique identifier.	Compliant
5.7	A tag name shall be a unique identifier.	Compliant
5.8	Identifiers that define objects or functions with external linkage shall be unique.	Compliant

6. Types

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

7. Literals and Constants

Rule	Description	Compliance	Additional Notes
7.1	Octal constants shall not be used.	Compliant
7.2	A "u" or "U" suffix shall be applied to all integer constants that are represented in an unsigned type.	Compliant
7.3	The lowercase character "l" shall not be used in a literal suffix.	Compliant
7.4	A 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

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

9. Initialization

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

10. The Essential Type Model

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

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

12. Expressions

Rule	Description	Compliance	Additional Notes
12.2	The 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
12.5	The sizeof operator shall not have an operand which is a function parameter declared as "array of type".	Compliant

13. Side Effects

Rule	Description	Compliance	Additional Notes
13.1	Initializer lists shall not contain persistent side effects.	Compliant
13.2	The value of an expression and its persistent side effects shall be the same under all permitted evaluation orders.	Not Compliant
13.5	The 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.
13.6	The operand of the sizeof operator shall not contain any expression which has potential side effects.	Compliant

14. Control Statement Expressions

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

15. Control Flow

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

16. Switch Statements

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

17. Functions

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

18. Pointers and Arrays

Rule	Description	Compliance	Additional Notes
18.1	A pointer resulting from arithmetic on a pointer operand shall address an element of the same array as that pointer operand.	Not Compliant
18.2	Subtraction between pointers shall only be applied to pointers that address elements of the same array.	Compliant
18.3	The relational operators >, >=, < and <= shall not be applied to objects of pointer type except where they point into the same object.	Compliant
18.6	The 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
18.7	Flexible array members shall not be declared.	Compliant
18.8	Variable-length array types shall not be used.	Compliant

19. Overlapping Storage

Rule	Description	Compliance	Additional Notes
19.1	An object shall not be assigned or copied to an overlapping object.	Compliant

20. Preprocessing Directives

Rule	Description	Compliance	Additional Notes
20.2	The ', " or \ characters and the /* or // character sequences shall not occur in a header file name.	Compliant
20.3	The #include directive shall be followed by either a <filename> or "filename"sequence.	Compliant
20.4	A macro shall not be defined with the same name as a keyword.	Compliant
20.6	Tokens that look like a preprocessing directive shall not occur within a macro argument.	Compliant
20.7	Expressions resulting from the expansion of macro parameters shall be enclosed in parentheses.	Compliant
20.8	The controlling expression of a #if or #elif preprocessing directive shall evaluate to 0 or 1.	Compliant
20.9	All identifiers used in the controlling expression of #if or #elif preprocessing directives shall be #define'd before evaluation.	Compliant
20.11	A macro parameter immediately following a # operator shall not immediately be followed by a ## operator.	Compliant
20.12	A 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
20.13	A line whose first token is # shall be a valid preprocessing directive.	Compliant
20.14	All #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

Rule	Description	Compliance	Additional Notes
21.1	#define and #undef shall not be used on a reserved identifier or reserved macro name.	Compliant
21.2	A reserved identifier or reserved macro name shall not be declared.	Not Compliant
21.3	The memory allocation and deallocation functions of <stdlib.h> shall not be used.	Compliant
21.4	The standard header file <setjmp.h> shall not be used.	Compliant
21.5	The standard header file <signal.h> shall not be used.	Compliant
21.6	The 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 coder.read.
21.7	The Standard Library functions atof, atoi, atol and atoll of <stdlib.h> shall not be used.	Compliant
21.8	The Standard Library termination functions of <stdlib.h> shall not be used.	Compliant
21.9	The Standard Library functions bsearch and qsort of <stdlib.h> shall not be used.	Compliant
21.10	The 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.
21.11	The standard header file <tgmath.h> shall not be used.	Compliant
21.13	Any value passed to a function in <ctype.h> shall be representable as an unsigned char or be the value EOF.	Compliant
21.14	The Standard Library function memcmp shall not be used to compare null terminated strings.	Compliant
21.15	The pointer arguments to the Standard Library functions memcpy, memmove and memcmp shall be pointers to qualified or unqualified versions of compatible types.	Not Compliant
21.16	The 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
21.17	Use 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
21.18	The size_t argument passed to any function in <string.h> shall have an appropriate value.	Not Compliant
21.19	The 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
21.20	The 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
21.21	The Standard Library function system of <stdlib.h> shall not be used.	Compliant

22. Resources

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