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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: 37 rules found
suspicious
    Impact
      Clean code attribute
        1. "offsetof" macro should not be used

           Code Smell
        2. "errno" should not be used

           Code Smell
        3. Function names should be used either as a call with a parameter list or with the "&" operator

           Code Smell
        4. "enum" values should not be used as operands to built-in operators other than [ ], =, ==, !=, unary &, and the relational operators <, <=, >, >=

           Code Smell
        5. "bool" expressions should not be used as operands to built-in operators other than =, &&, ||, !, ==, !=, unary &, and the conditional operator

           Code Smell
        6. A cast shall not remove any const or volatile qualification from the type of a pointer or reference

           Code Smell
        7. Trigraphs should not be used

           Code Smell
        8. "#pragma pack" should be used correctly

           Bug
        9. Only valid arguments should be passed to UNIX/POSIX functions

           Code Smell
        10. Only valid arguments should be passed to stream functions

           Code Smell
        11. "^" should not be confused with exponentiation

           Code Smell
        12. Size of variable length arrays should be greater than zero

           Code Smell
        13. "mktemp" family of functions templates should have at least six trailing "X"s

           Code Smell
        14. Unevaluated operands should not have side effects

           Code Smell
        15. Size argument of memory functions should be consistent

           Code Smell
        16. Return value of "nodiscard" functions should not be ignored

           Code Smell
        17. Implicit casts should not lower precision

           Code Smell
        18. Appropriate size arguments should be passed to "strncat" and "strlcpy"

           Code Smell
        19. User-defined types should not be passed as variadic arguments

           Bug
        20. Array values should not be replaced unconditionally

           Bug
        21. A conditionally executed single line should be denoted by indentation

           Code Smell
        22. Conditionals should start on new lines

           Code Smell
        23. "case" ranges should cover multiple values

           Code Smell
        24. "switch" statements should cover all cases

           Code Smell
        25. Redundant pointer operator sequences should be removed

           Code Smell
        26. Conditionally executed code should be reachable

           Bug
        27. Flexible array members should not be declared

           Code Smell
        28. Track parsing failures

           Code Smell
        29. Recursion should not be infinite

           Bug
        30. Two branches in a conditional structure should not have exactly the same implementation

           Code Smell
        31. Pre-defined macros should not be defined, redefined or undefined

           Code Smell
        32. Switch cases should end with an unconditional "break" statement

           Code Smell
        33. "switch" statements should not contain non-case labels

           Code Smell
        34. Methods should not be empty

           Code Smell
        35. Assignments should not be made from within conditions

           Code Smell
        36. Variables should not be shadowed

           Code Smell
        37. Nested blocks of code should not be left empty

           Code Smell

        Variables should not be shadowed

        intentionality - clear
        maintainability
        Code Smell
        • based-on-misra
        • cert
        • suspicious
        • pitfall

        Why is this an issue?

        More Info

        Variable shadowing happens when a variable declared in a specific scope has the same name as a variable in an outer scope.

        This can lead to three main problems:

        • Confusion: The same name can refer to different variables in different parts of the scope, making the code hard to read and understand.
        • Unintended Behavior: You might accidentally use the wrong variable, leading to hard-to-detect bugs.
        • Maintenance Issues: If the inner variable is removed or renamed, the code’s behavior might change unexpectedly because the outer variable is now being used.

        To avoid these problems, rename the shadowing, shadowed, or both variables to accurately represent their purpose with unique and meaningful names.

        The examples below show typical situations in which shadowing can occur.

        • Parameter shadowing
          void f(int x, bool b) {
            int y = 4;
            if (b) {
              int x = 7; // Noncompliant: the parameter "x" is shadowed.
              int y = 9; // Noncompliant: the local variable "y" is shadowed.
              // ...
            }
          }
          
        • Member variable shadowing
          class Foo {
          private:
            int myField;
          
          public:
            void doSomething() {
              int myField = 0; // Noncompliant: Foo::myField is shadowed.
              // ...
            }
          };
          
        • Global variable shadowing
          namespace ns {
            int state;
          
            void bar() {
              int state = 0; // Noncompliant: the namespace variable is shadowed.
            }
          }
          

        Exceptions

        It is common practice to have constructor arguments shadowing the fields they initialize in the member initializer list. This pattern avoids the need to select new names for the constructor arguments and will not be reported by this rule.

        class Point {
        public:
          Point(int x, int y)
            : x(x) // Compliant by exception: the parameter "x" is used
                   // in the member initializer list.
          {
            y = y; // Noncompliant: the parameter is assigned to itself
                   // and the member "y" is not initialized.
          }
        
        private:
          int x;
          int y;
        };
        

        Caveats

        Shadowing in if, else if, and else

        Variables can be introduced in the condition of an if statement. Their scope includes the optional else statement, which may be surprising. Consequently, such variables can be shadowed in an else if statement. This can be even more confusing and result in unintended behavior, as illustrated in this example:

        using ExpectedData = std::expected<std::string, std::error_code>;
        
        if (ExpectedData e = readData()) {
          printMessage(e.value());
        } else if (ExpectedData e = readFallbackSource()) { // Noncompliant
          printMessage(e.value());
        } else {
          logError(
            "Initial source failed with: ",
            e.error() // Contrary to the intention, the second "e" is used.
          );
        }
        

        Shadowing of inaccessible declarations

        This rule also raises issues on some variables, although they do not shadow another variable according to a strict interpretation of the C++ language. There are mainly two reasons for this.

        1. Primarily, the readability and maintainability of the code are impaired. Readers need an advanced understanding of the C++ language to understand the subtle differences.
        2. Secondly, a small change can lead to actual shadowing. This can lead to subtle bugs when updating the code.

        Here is an example with nested classes:

        class A {
        public:
          int x;
          class B;
        };
        
        class A::B {
          void f(int x) { // Noncompliant: The parameter "x" shadows the field "A::x".
            // ...
          }
        };
        

        In the above example, A::x cannot be used from A::B member functions because it is not a static field. This can lead to surprising effects when moving code around, particularly if the declaration of A::x was changed from int x; to static int x;.

        You should always avoid shadowing to avoid any confusion and increase the maintainability of your code.

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