# V1096. Variable with static storage duration is declared inside the inline function with external linkage. This may lead to ODR violation.

The analyzer has detected a situation in which a static variable is declared inside the 'inline' function defined in the header file. This may lead to the ODR violation.

Example:

    // sample.h

    class MySingleton
    {
    public:
      static MySingleton& GetInstance()
      {
        static MySingleton Instance; // <=
        return Instance;
      }
    };

The 'MySingleton' class contains the 'GetInstance' member function, which returns an instance of the 'Instance' static variable. Since the function is defined in the same place where it is declared, the compiler will implicitly mark it as 'inline'. In this case, the linker will combine the 'GetInstance' function definitions in all translation units.

However, this will not happen if definitions are combined between an executable program module and a dynamic library. As a result, when executing the program, two instances of the 'Instance' static variable will already be created. This violates the ODR.

To fix this situation, the declaration and method definition need to be separated between the header file and the source code file.

Fixed code:

    // sample.h

    class MySingleton
    {
    public:
      static MySingleton& GetInstance();
    };

    // sample.cpp

    MySingleton& MySingleton::GetInstance()
    {
      static MySingleton Instance;
      return Instance;
    }