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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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  • Quick Fix 19
Filtered: 3 rules found
since-c++11
    Impact
      Clean code attribute
        1. A single L in a literal suffix should only be used for long values

           Code Smell
        2. Functions which do not return should be declared as "noreturn"

           Code Smell
        3. Local variables and member data should not be volatile

           Code Smell

        Local variables and member data should not be volatile

        consistency - conventional
        maintainability
        Code Smell
        • cppcoreguidelines
        • c11
        • multi-threading
        • cert
        • since-c++11

        Why is this an issue?

        More Info

        The main intended use-case for volatile in C and C++ is to access data that can be modified by something external to the program, typically some hardware register. In contrast with some other languages with a volatile keyword, it does not provide any useful guarantees related to atomicity, memory ordering, or inter-thread synchronization. It is only really needed for the kind of low-level code found in kernels or embedded software, i.e. using memory-mapped I/O registers to manipulate hardware directly.

        According to the C standard:

        volatile is a hint to the implementation to avoid aggressive optimization involving the object because the value of the object might be changed by means undetectable by an implementation.

        Local variables and data members are completely controlled by the C++ language. This means they can’t change their value without the compiler knowing about it. Therefore, it doesn’t make sense for them to be marked as volatile.

        If the intent is to share those variables between threads, race conditions can be avoided by using synchronization primitives (such as std::mutex) or atomic types (_Atomic in C11, std::atomic<T> in C++11).

        This rule raises an issue when a local variable or class data member is declared as volatile (at the top level of the type, pointers to volatile are not reported).

        Noncompliant code example

        volatile int counter; // Noncompliant
        User * volatile vpUser; // Noncompliant; pointer is volatile
        User volatile * pvUser;  // Compliant; User instance is volatile, not the pointer
        

        Compliant solution

        atomic_int counter;
        std::atomic<User*> vpUser;
        User volatile * pvUser;
        
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