MISRA C:2023 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:2023 guidelines.

The MISRA C:2023 standard consolidates these guidelines:

• MISRA C:2012 rules and directives

• Clarifications added in MISRA C:2012 Technical Corrigendum 1 (TC1) and Technical Corrigendum 2 (TC2)

• New rules and modifications added in MISRA C:2012 Amendment 1 (AMD1), Amendment 2 (AMD2), Amendment 3 (AMD3), and Amendment 4 (AMD4)

The following tables list all the required and mandatory coding directives and rules in the MISRA C:2023 standard, except the rules in MISRA C:2012 Amendment 4 . The Category columns in these tables apply to automatically generated code as specified in the Appendix E of the MISRA guidelines.

For each directive or rule, the Compliance column has one of these entries:

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

• Noncompliant: 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:2023 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:2023 Directives and Rules (Polyspace Bug Finder).

The Implementation

Directive	Descriptiona	Category	Compliance	Additional Notes
Dir 1.1	Any implementation-defined behavior on which the output of the program depends shall be documented and understood.	Required	Noncompliant
a Copyright © The MISRA Consortium Limited, 2023.

Compilation and Build

Directive	Descriptiona	Category	Compliance	Additional Notes
Dir 2.1	All source files shall compile without any compilation errors.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Requirements Traceability

Directive	Descriptiona	Category	Compliance	Additional Notes
Dir 3.1	All code shall be traceable to documented requirements.	Required	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).
a Copyright © The MISRA Consortium Limited, 2023.

Code Design

Directive	Descriptiona	Category	Compliance	Additional Notes
Dir 4.1	Run-time failures shall be minimized.	Required	Noncompliant
Dir 4.3	Assembly language shall be encapsulated and isolated.	Required	Compliant
Dir 4.7	If a function returns error information, then that error information shall be tested.	Required	Noncompliant	To reduce this violation, in your MATLAB code, include tests for the output of coder.ceval calls.
Dir 4.10	Precautions shall be taken in order to prevent the contents of a header file being included more than once.	Required	Compliant
Dir 4.11	The validity of values passed to library functions shall be checked.	Required	Noncompliant	To reduce this violation, in your MATLAB code, check the validity of values that you pass to coder.ceval.
Dir 4.12	Dynamic memory allocation shall not be used.	Required	Compliant
Dir 4.14	The validity of values received from external sources shall be checked.	Required	Noncompliant	To reduce this violation, in your MATLAB code, check the validity of values that coder.ceval returns.
Dir 4.15	Evaluation of floating-point expressions shall not lead to the undetected generation of infinities and NaNs.	Required	Noncompliant
a Copyright © The MISRA Consortium Limited, 2023.

Standard C Environment

Rule	Descriptiona	Category	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.	Required	Compliant
1.3	There shall be no occurrence of undefined or critical unspecified behavior.	Required	Compliant
1.4	Emergent language features shall not be used.	Required	Compliant
1.5	Obsolescent language features shall not be used.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Unused Code

Rule	Descriptiona	Category	Compliance	Additional Notes
2.1	A project shall not contain unreachable code.	Required	Noncompliant
2.2	There shall be no dead code.	Required	Noncompliant
a Copyright © The MISRA Consortium Limited, 2023.

Comments

Rule	Descriptiona	Category	Compliance	Additional Notes
3.1	The character sequences /* and // shall not be used within a comment.	Required	Noncompliant	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.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Character Sets and Lexical Conventions

Rule	Descriptiona	Category	Compliance	Additional Notes
4.1	Octal and hexadecimal escape sequences shall be terminated.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Identifiers

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
5.1	External identifiers shall be distinct.	Required	Noncompliant	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.	Required	Compliant
5.3	An identifier declared in an inner scope shall not hide an identifier declared in an outer scope.	Advisory	Compliant
5.4	Macro identifiers shall be distinct.	Required	Compliant
5.5	Identifiers shall be distinct from macro names.	Required	Compliant
5.6	A typedef name shall be a unique identifier.	Required	Compliant
5.7	A tag name shall be a unique identifier.	Required	Compliant
5.8	Identifiers that define objects or functions with external linkage shall be unique.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 5.3 as Required for manually generated code.

Types

Rule	Descriptiona	Category	Compliance	Additional Notes
6.1	Bit-fields shall only be declared with an appropriate type.	Required	Compliant
6.2	Single-bit named bit fields shall not be of a signed type.	Required	Compliant
6.3	A bit field shall not be declared as a member of a union.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Literals and Constants

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
7.1	Octal constants shall not be used.	Advisory	Compliant
7.2	A "u" or "U" suffix shall be applied to all integer constants that are represented in an unsigned type.	Readability	Compliant
7.3	The lowercase character "l" shall not be used in a literal suffix.	Readability	Compliant
7.4	A string literal shall not be assigned to an object unless the object's type is "pointer to const-qualified char".	Required	Compliant
7.5	The argument of an integer constant macro shall have an appropriate form.	Mandatory	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rules 7.1, 7.2, and 7.3 as Required for manually generated code.

Declarations and Definitions

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
8.1	Types shall be explicitly specified.	Required	Compliant
8.2	Function types shall be in prototype form with named parameters.	Required	Compliant
8.3	All declarations of an object or function shall use the same names and type qualifiers.	Required	Compliant
8.4	A compatible declaration shall be visible when an object or function with external linkage is defined.	Advisory	Compliant
8.5	An external object or function shall be declared once in one and only one file.	Advisory	Compliant
8.6	An identifier with external linkage shall have exactly one external definition.	Required	Compliant
8.8	The static storage class specifier shall be used in all declarations of objects and functions that have internal linkage.	Required	Compliant
8.10	An inline function shall be declared with the static storage class.	Required	Compliant
8.12	Within an enumerator list, the value of an implicitly-specified enumeration constant shall be unique.	Required	Compliant
8.14	The restrict type qualifier shall not be used.	Advisory	Compliant
8.15	All declarations of an object with an explicit alignment specification shall specify the same alignment.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 8.4, 8.5, and 8.14 as Required for manually generated code.

Initialization

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
9.1	The value of an object with automatic storage duration shall not be read before it has been set.	Mandatory	Noncompliant
9.2	The initializer for an aggregate or union shall be enclosed in braces.	Readability	Compliant
9.3	Arrays shall not be partially initialized.	Readability	Compliant
9.4	An element of an object shall not be initialized more than once.	Required	Compliant
9.5	Where designated initializers are used to initialize an array object the size of the array shall be specified explicitly.	Readability	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 9.2, 9.3, and 9.5 as Required for manually generated code.

The Essential Type Model

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
10.1	Operands shall not be of an inappropriate essential type.	Advisory	Compliant
10.2	Expressions of essentially character type shall not be used inappropriately in addition and subtraction operations.	Advisory	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.	Advisory	Compliant
10.4	Both operands of an operator in which the usual arithmetic conversions are performed shall have the same essential type category.	Advisory	Compliant
10.6	The value of a composite expression shall not be assigned to an object with wider essential type.	Advisory	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.	Advisory	Compliant
10.8	The value of a composite expression shall not be cast to a different essential type category or a wider essential type.	Advisory	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 10.1, 10.2, 10.3, 10.4, 10.6, 10.7, and 10.8 as Required for manually generated code.

Pointer Type Conversion

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
11.1	Conversions shall not be performed between a pointer to a function and any other type.	Required	Compliant
11.2	Conversions shall not be performed between a pointer to an incomplete type and any other type.	Required	Compliant
11.3	A cast shall not be performed between a pointer to object type and a pointer to a different object type.	Required	Noncompliant
11.6	A cast shall not be performed between pointer to void and an arithmetic type.	Required	Compliant
11.7	A cast shall not be performed between pointer to object and a non-integer arithmetic type.	Required	Compliant
11.8	A cast shall not remove any const or volatile qualification from the type pointed to by a pointer.	Required	Noncompliant
11.9	The macro NULL shall be the only permitted form of integer null pointer constant.	Readability	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 11.9 as Required for manually generated code.

Expressions

Rule	Descriptiona	Category	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.	Required	Noncompliant
12.5	The sizeof operator shall not have an operand which is a function parameter declared as "array of type".	Mandatory	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Side Effects

Rule	Descriptiona	Category	Compliance	Additional Notes
13.1	Initializer lists shall not contain persistent side effects.	Required	Compliant
13.2	The value of an expression and its persistent side effects shall be the same under all permitted evaluation orders.	Required	Noncompliant
13.5	The right hand operand of a logical && or || operator shall not contain persistent side effects.	Required	Noncompliant	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.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Control Statement Expressions

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
14.1	A loop counter shall not have essentially floating type.	Advisory	Compliant
14.2	A for loop shall be well-formed.	Readability	Compliant
14.3	Controlling expressions shall not be invariant.	Required	Noncompliant
14.4	The controlling expression of an if statement and the controlling expression of an iteration-statement shall have essentially Boolean type.	Advisory	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 14.1, 14.2, and 14.4 as Required for manually generated code.

Control Flow

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
15.2	The goto statement shall jump to a label declared later in the same function.	Advisory	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.	Advisory	Compliant
15.6	The body of an iteration-statement or a selection-statement shall be a compound-statement.	Required	Compliant
15.7	All if ... else if constructs shall be terminated with an else statement.	Readability	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 15.2, 15.3, and 15.7 as Required for manually generated code.

Switch Statements

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
16.1	All switch statements shall be well-formed.	Advisory	Compliant
16.2	A switch label shall only be used when the most closely-enclosing compound statement is the body of a switch statement.	Advisory	Compliant
16.3	An unconditional break statement shall terminate every switch-clause.	Advisory	Compliant
16.4	Every switch statement shall have a default label.	Advisory	Compliant
16.5	A default label shall appear as either the first or the last switch label of a switch statement.	Advisory	Compliant
16.6	Every switch statement shall have at least two switch-clauses.	Advisory	Compliant
16.7	A switch-expression shall not have essentially Boolean type.	Advisory	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 16.1, 16.2, 16.3, 16.4, 16.5, 16.6, and 16.7 as Required for manually generated code.

Functions

Rule	Descriptiona	Categoryb	Compliance	Additional Notes
17.1	The features of <stdarg.h> shall not be used.	Required	Compliant
17.2	Functions shall not call themselves, either directly or indirectly.	Required	Compliant
17.3	A function shall not be declared implicitly.	Mandatory	Compliant
17.4	All exit paths from a function with non-void return type shall have an explicit return statement with an expression.	Mandatory	Compliant
17.5	The function argument corresponding to a parameter declared to have an array type shall have an appropriate number of elements.	Required	Compliant
17.6	The declaration of an array parameter shall not contain the static keyword between the [ ].	Mandatory	Compliant
17.7	The value returned by a function having non-void return type shall be used.	Readability	Compliant
17.9	A function declared with a _Noreturn function specifier shall not return to its caller.	Mandatory	Compliant
17.10	A function declared with a _Noreturn function specifier shall have void return type.	Required	Compliant
17.13	A function type shall not be type qualified.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023. b Guideline identifies Rule 17.7 as Required for manually generated code.

Pointers and Arrays

Rule	Descriptiona	Category	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.	Required	Noncompliant
18.2	Subtraction between pointers shall only be applied to pointers that address elements of the same array.	Required	Compliant
18.3	The relational operators >, >=, < and <= shall not be applied to objects of pointer type except where they point into the same object.	Required	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.	Required	Noncompliant
18.7	Flexible array members shall not be declared.	Required	Compliant
18.8	Variable-length array types shall not be used.	Required	Compliant
18.9	An object with temporary lifetime shall not undergo array-to-pointer conversion.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Overlapping Storage

Rule	Descriptiona	Category	Compliance	Additional Notes
19.1	An object shall not be assigned or copied to an overlapping object.	Mandatory	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Preprocessing Directives

Rule	Descriptiona	Category	Compliance	Additional Notes
20.2	The ', " or \ characters and the /* or // character sequences shall not occur in a header file name.	Required	Compliant
20.3	The #include directive shall be followed by either a <filename> or "filename"sequence.	Required	Compliant
20.4	A macro shall not be defined with the same name as a keyword.	Required	Compliant
20.6	Tokens that look like a preprocessing directive shall not occur within a macro argument.	Required	Compliant
20.7	Expressions resulting from the expansion of macro parameters shall be enclosed in parentheses.	Required	Compliant
20.8	The controlling expression of a #if or #elif preprocessing directive shall evaluate to 0 or 1.	Required	Compliant
20.9	All identifiers used in the controlling expression of #if or #elif preprocessing directives shall be #define'd before evaluation.	Required	Compliant
20.11	A macro parameter immediately following a # operator shall not immediately be followed by a ## operator.	Required	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.	Required	Compliant
20.13	A line whose first token is # shall be a valid preprocessing directive.	Required	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.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Standard Libraries

Rule	Descriptiona	Category	Compliance	Additional Notes
21.1	#define and #undef shall not be used on a reserved identifier or reserved macro name.	Required	Compliant
21.2	A reserved identifier or reserved macro name shall not be declared.	Required	Compliant
21.3	The memory allocation and deallocation functions of <stdlib.h> shall not be used.	Required	Compliant
21.4	The standard header file <setjmp.h> shall not be used.	Required	Compliant
21.5	The standard header file <signal.h> shall not be used.	Required	Compliant
21.6	The Standard Library input/output functions shall not be used.	Required	Noncompliant	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.	Required	Compliant
21.8	The Standard Library termination functions of <stdlib.h> shall not be used.	Required	Compliant
21.9	The Standard Library functions bsearch and qsort of <stdlib.h> shall not be used.	Required	Compliant
21.10	The Standard Library time and date functions shall not be used.	Required	Noncompliant	To reduce this violation, in your MATLAB code, avoid using functions such as tic, toc, and pause.
21.12	The standard header file <fenv.h> shall not be used.	Required	Compliant
21.13	Any value passed to a function in <ctype.h> shall be representable as an unsigned char or be the value EOF.	Mandatory	Compliant
21.14	The Standard Library function memcmp shall not be used to compare null terminated strings.	Required	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.	Required	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.	Required	Noncompliant
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.	Mandatory	Compliant
21.18	The size_t argument passed to any function in <string.h> shall have an appropriate value.	Mandatory	Noncompliant
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.	Mandatory	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.	Mandatory	Compliant
21.21	The Standard Library function system of <stdlib.h> shall not be used.	Required	Compliant
21.22	All operand arguments to any type-generic macros declared in <tgmath.h> shall have an appropriate essential type.	Mandatory	Compliant
21.23	All operand arguments to any multi-argument type-generic macros declared in <tgmath.h> shall have the same standard type.	Required	Compliant
21.24	The random number generator functions of <stdlib.h> shall not be used.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Resources

Rule	Descriptiona	Category	Compliance	Additional Notes
22.1	All resources obtained dynamically by means of Standard Library functions shall be explicitly released.	Required	Compliant
22.2	A block of memory shall only be freed if it was allocated by means of a Standard Library function.	Mandatory	Compliant
22.3	The same file shall not be open for read and write access at the same time on different streams.	Required	Compliant
22.4	There shall be no attempt to write to a stream which has been opened as read-only.	Mandatory	Compliant
22.5	A pointer to a FILE object shall not be dereferenced.	Mandatory	Compliant
22.6	The value of a pointer to a FILE shall not be used after the associated stream has been closed.	Mandatory	Compliant
22.7	The macro EOF shall only be compared with the unmodified return value from any Standard Library function capable of returning EOF.	Required	Compliant
22.8	The value of errno shall be set to zero prior to a call to an errno-setting-function.	Required	Compliant
22.9	The value of errno shall be tested against zero after calling an errno-setting-function.	Required	Compliant
22.10	The value of errno shall only be tested when the last function to be called was an errno-setting-function.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.

Generic Selections

Rule	Descriptiona	Category	Compliance	Additional Notes
23.2	A generic selection that is not expanded from a macro shall not contain potential side effects in the controlling expression.	Required	Compliant
23.4	A generic association shall list an appropriate type.	Required	Compliant
23.6	The controlling expression of a generic selection shall have an essential type that matches its standard type.	Required	Compliant
23.8	A default association shall appear as either the first or the last association of a generic selection.	Required	Compliant
a Copyright © The MISRA Consortium Limited, 2023.