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C

C static code analysis

Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code

  • All rules 315
  • Vulnerability13
  • Bug76
  • Security Hotspot19
  • Code Smell207

  • Quick Fix 19
Filtered: 13 rules found
lock-in
    Impact
      Clean code attribute
        1. "<time.h>" should not be used

           Code Smell
        2. "<stdio.h>" should not be used in production code

           Code Smell
        3. "<signal.h>" should not be used

           Bug
        4. Preprocessor operators "#" and "##" should not be used

           Code Smell
        5. Bitwise operators should not be applied to signed operands

           Bug
        6. Bit fields should be declared with appropriate types

           Code Smell
        7. Multicharacter literals should not be used

           Code Smell
        8. Arguments evaluation order should not be relied on

           Bug
        9. "#include_next" should not be used

           Code Smell
        10. GNU extensions should not be used

           Code Smell
        11. The "sizeof" and "alignof" operator should not be used with operands of a "void" type

           Bug
        12. Keywords introduced in later specifications should not be used as identifiers

           Code Smell
        13. Control should not be transferred into a complex logic block using a "goto" or a "switch" statement

           Code Smell

        Bitwise operators should not be applied to signed operands

        intentionality - logical
        reliability
        Bug
        • cwe
        • based-on-misra
        • lock-in
        • bad-practice
        • cert

        Why is this an issue?

        More Info

        Most built-in bitwise operators (~, >>, >>=, &, &=, ^, ^=, |, and |=) have implementation-dependent results when performed on signed operands, and bitwise left shift (<< and <<=) has unspecified or undefined behavior when performed on negative operands.

        Therefore, bitwise operations should not be performed on signed operands.

        Starting with C++20, the behaviors have been defined more accurately (negative values have to be represented using two’s complement), and therefore this rule will only report an issue when the second operand of a shift operator is signed (shifting by a negative value is still undefined behavior).

        Noncompliant code example

        if ( ( uint16_a & int16_b ) == 0x1234U ) // Noncompliant until C++20
        if ( ~int16_a == 0x1234U ) // Noncompliant until C++20
        
        auto f(int i) {
            return 1 << i; // Noncompliant
        }
        

        Compliant solution

        if ( ( uint16_a | uint16_b ) == 0x1234U )
        if ( ~uint16_a == 0x1234U )
        
        auto f(unsigned int i) {
            return 1 << i;
        }
        

        Exceptions

        When used as bit flags, it is acceptable to use preprocessor macros as arguments to the & and | operators even if the value is not explicitly declared as unsigned.

        fd = open(file_name, UO_WRONLY | UO_CREAT | UO_EXCL | UO_TRUNC, 0600);
        

        If the right-side operand to a shift operator is known at compile time, it is acceptable for the value to be represented with a signed type provided it is positive.

        #define SHIFT 24
        foo = 15u >> SHIFT;
        

        When combining several bitwise operations, even if all leaf operands are unsigned, if they are smaller than an int, some intermediate results will be of type signed int, due to integral promotion. However, this situation is usually not an issue, and is an exception for this rule:

        unsigned int f(unsigned short src) {
          return (src >> 3) & 0x1F; // (src >> 3) is of type signed int
        }
        
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