Question

Usually, when I try to initialize a static variable

class Test2 {
public:
    static vector<string> stringList;
private:
    static bool __init;
    static bool init() {
        stringList.push_back("string1");
        stringList.push_back("string2");
        stringList.push_back("string3");

        return true;
    }
};

// Implement
vector<string> Test2::stringList;
bool Test2::__init = Test2::init();

1. Is the following code thread safe, during static variable initialization?
2. Is there any better way to static initialize stringlist, instead of using a seperate static function (init)?

Although the initialization shall happen before main function (Hence, there can be no threads to simultaneous access the init), my concern is that :

1. I have an exe application.
2. My exe application will load a.dll, b.dll and c.dll
3. a/b/c.dll, in turn will load common.dll. The above code are inside common.dll
4. I had already verify. Since 3 dll are within single process, they will be referring to the same static variable (vector).
5. In this case, to prevent 3 dlls from simultaneous access init (Can I view them as 3 threads? Although doesn’t make sense at first thought), for the init function, shall I use a critical section to protect it?

I am using Windows XP, VC6 and VC2008 compiler.

Answer 1

I asked a similar question a while back:

LoadLibrary and Static Globals

When it comes to DLLs, static initialization and the call to DllMain is bracketed by an internal critical section, so they are thread-safe. A second thread will wait until the first is done before it loads the DLL.

So in short, your static init is safe.