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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
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  • Code Smell207

  • Quick Fix 19
Filtered: 10 rules found
cppcoreguidelines
    Impact
      Clean code attribute
        1. Function-like macros should not be used

           Code Smell
        2. Boolean operations should not have numeric operands, and vice versa

           Bug
        3. A cast shall not remove any const or volatile qualification from the type of a pointer or reference

           Code Smell
        4. Loop variables should be declared in the minimal possible scope

           Code Smell
        5. Relational and subtraction operators should not be used with pointers to different arrays

           Bug
        6. Arguments evaluation order should not be relied on

           Bug
        7. User-defined types should not be passed as variadic arguments

           Bug
        8. Local variables and member data should not be volatile

           Code Smell
        9. Types and variables should be declared in separate statements

           Code Smell
        10. Type specifiers should be listed in a standard order

           Code Smell

        User-defined types should not be passed as variadic arguments

        intentionality - complete
        reliability
        Bug
        • suspicious
        • based-on-misra
        • cppcoreguidelines
        • cert

        Why is this an issue?

        More Info

        Variadic arguments allow a function to accept any number of arguments (in this rule, we are not talking about variadic templates, but about functions with ellipses). But these arguments have to respect some criteria to be handled properly.

        The standard imposes some requirements on the class types that can be passed as variadic arguments, and those requirements vary according to the C++ standard version in use:

        • Before C++11, the standard only allows POD types to be used as variadic arguments.
        • In C++11, the rules are relaxed such that any class type with an eligible non-trivial copy constructor, an eligible non-trivial move constructor, or a non-trivial destructor can be used in variadic arguments.

        The rule detects any violations of these requirements since they can trigger undefined behavior.

        Additionally, since using an incorrect type to access the passed parameter within the variadic function can lead to undefined behavior, the rule goes a step further and reports all cases when class types are passed as variadic arguments. The rationale is that, most likely, the user forgot to call a method on the object being passed (std::string_view::data() for example) that would get a member of a built-in type.

        When in need to pass class types to functions that take a variable number of arguments, consider using modern type-safe alternatives like C++11 parameter packs instead of variadic functions.

        Noncompliant code example

        void my_log(const char* format, ...);
        
        void f() {
          std::string someStr = "foo";
          my_log("%s", someStr);  // Noncompliant; the C++11 standard requires types passed as variadic arguments to have a trivial copy constructor. The user probably meant to pass someStr.c_str() here
        
          std::string_view someStrView = "bar";
          my_log("%s", someStrView); // Noncompliant; the user probably meant to pass someText.data()
          std::chrono::duration<float> duration;
          my_log("%f", duration); // Noncompliant, the user probably meant to pass duration.count()
        }
        

        Compliant solution

        void my_log(const char* format, ...);
        
        void f() {
          std::string someStr = "foo";
          my_log("%s", someStr.c_str());  // Compliant
        
          std::string_view someStrView = "bar";
          my_log("%s", someStrView.data()); // Compliant
          std::chrono::duration<float> duration;
          my_log("%f", duration.count()); // Compliant
        }
        

        Exceptions

        The rule doesn’t report an issue in the following cases:

        • When the called variadic function doesn’t have any non-variadic parameters. This is a common pattern when the function is used as a catch-all net for an overload set. This is also guaranteed to be safe since there is no portable to access the passed arguments.
        • When the called variadic function is known to accept a class type object as a variadic argument (e.g., the semctl system call).
        // This variadic function is used as a catch-all net to terminate recursion
        std::size_t elementsCount(...) { return 1u; }
        
        template<typename T>
        std::size_t elementsCount(const std::vector<T>& vec) {
          // Sum the elements of all nested vectors recursively
          return std::accumulate(vec.begin(), vec.end(), 0u, [] (const std::size_t count, const T& element) {
            return count + elementsCount(element); // Compliant (the callee doesn't have non-variadic arguments)
          });
        }
        
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