LANG.TYPE.BFSIGN : Bit-field Signedness Not Explicit

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A bit-field type is neither explicitly signed nor explicitly unsigned.

C99 bit-fields with _Bool type will not trigger warnings of this class.

Class Name

Bit-field Signedness Not Explicit

Significance

style

Mnemonic

LANG.TYPE.BFSIGN

Categories

MisraC2023	MisraC2023:6.1	Bit-fields shall only be declared with an appropriate type
Misra2012	Misra2012:6.1	Bit-fields shall only be declared with an appropriate type
Misra2004	Misra2004:6.4	Bit fields shall only be defined to be of type unsigned int or signed int
MisraC++2008	MisraC++2008:9-6-2	Bit-fields shall be either bool type or an explicitly unsigned or signed integral type.
	MisraC++2008:9-6-3	Bit-fields shall not have enum type.
MisraC++2023	MisraC++2023:12.2.1	Bit fields should not be declared
CERT-C	CERT-C:INT12-C	Do not make assumptions about the type of a plain int bit-field when used in an expression

Availability

Available for C and C++.

Enabling

Checks for this warning class are disabled by default, and require the unnormalized C ASTs for the project. To enable them, add the following WARNING_FILTER rule and RETAIN_UNNORMALIZED_C_AST specification to the project configuration file.

RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Bit-field Signedness Not Explicit"

Note that retaining the unnormalized ASTs will increase the disk space used to store the project representation, and may make the analysis take longer.

struct mystruct{
    int A               : 2; /* 'Bit-field Signedness Not Explicit' warning issued here */ 
    signed int B        : 2;                      /* explicitly signed */ 
    unsigned int C      : 2;                      /* explicitly unsigned */ 
};

typedef int plainint;
typedef signed int signedint;

struct myotherstruct{
    plainint D          : 2; /* 'Bit-field Signedness Not Explicit' warning issued here */ 
    signedint E         : 2;                      /* explicitly signed (in typedef) */ 
};

The following configuration file parameters affect checks for this warning class.

LANG.TYPE.BFSIGN : Bit-field Signedness Not Explicit

Summary

Properties

Example

Relevant Configuration File Parameters