MISRA C:2012 Rule 1.2

Language extensions should not be used

Description

Rule Definition

Language extensions should not be used¹ .

Rationale

If a program uses language extensions, its portability is reduced. Even if you document the language extensions, the documentation might not describe the behavior in all circumstances.

Polyspace Implementation

The rule checker flags these language extensions, depending on the version of the C standard used in the analysis. See C standard version (-c-version).

• C90:

  • long long int type including constants

  • long double type

  • inline keyword

  • _Bool keyword

  • Hexadecimal floating-point constants

  • Designated initializers

  • Local label declarations

  • typeof operator

  • Casts to union

  • Compound literals

  • Statements and declarations in expressions

  • __func__ predefined identifier

  • _Pragma preprocessing operator

  • Macros with variable arguments list

  • asm functions

  • Anonymous unions

  • Empty struct

• C99:

  • short long int type

  • Local label declarations

  • typeof operator

  • Casts to union

  • Statements and declarations in expressions

  • asm functions

  • Anonymous unions

  • Empty struct

Troubleshooting

If you expect a rule violation but do not see it, refer to Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Check Information

Group: Standard C Environment

Category: Advisory

AGC Category: Advisory

Version History

Introduced in R2014b

R2024b: Cast to union detected more precisely

The rule checker now detects cast to union more precisely. For example, in this code, Polyspace^® now detects that the cast pMyDataTypes->struct2.X = (InputDataStruct)pSdata->struct2.X is not a cast to union. A violation is no longer reported for this cast.

typedef unsigned short uint_16_type;
typedef float float_32_type;
typedef struct
{
	uint_16_type   X;
	uint_16_type   Y;

} InputDataStruct;

typedef struct
{
	uint_16_type       var1;
	InputDataStruct  struct2;
} data_struct_2;

typedef struct
{
	float_32_type       var1;
	InputDataStruct  struct2;

} data_struct;

int foo()
{
	data_struct MyDataTypes;
	data_struct *pMyDataTypes = &MyDataTypes;
	data_struct_2 SData;
	data_struct_2 *pSdata = &SData;


	pMyDataTypes->struct2.X  = (InputDataStruct)pSdata->struct2.X;  // Compliant
	return 0;
}

R2023a: Use of asm functions flagged

The rule checker reports violations of this rule if you use asm functions in your C90 or C99 code.

R2022b: Empty structs and anonymous unions flagged

The rule checker reports violations of this rule if you use empty structs or anonymous unions in your C90 or C99 code.