Ambiguously signed bit-field member¶
ID: cpp/ambiguously-signed-bit-field
Kind: problem
Security severity:
Severity: warning
Precision: high
Tags:
- reliability
- readability
- language-features
- external/cwe/cwe-190
Query suites:
- cpp-security-and-quality.qls
Click to see the query in the CodeQL repository
The signedness of a plain char, short, int, or long bit field is implementation-specific in C and in older versions of C++, and declaring their signedness explicitly removes the ambiguity and ensures portability.
Recommendation¶
Declare all members of the bit field with explicit signedness.
Example¶
struct {
int s : 4; //wrong: behavior of bit-field members with implicit signage vary across compilers
unsigned int : 24; //correct: explicitly unsigned
signed int : 4; //correct: explicitly signed
} bits;
References¶
AV Rule 154, Joint Strike Fighter Air Vehicle C++ Coding Standards. Lockheed Martin Corporation, 2005.
Common Weakness Enumeration: CWE-190.