Question

Suppose I have a free function called InitFoo. I’d like to protect this function from being called multiple times by accident. Without much thought I wrote the following:

void InitFoo()
{
    {
        static bool flag = false;
        if(flag) return;
        flag = true;
    }

    //Actual code goes here.
}

This looks like a big wart, though. InitFoo does not need to preserve any other state information. Can someone suggest a way to accomplish the same goal without the ugliness?

Macros don’t count, of course.

Answer 1

You can do it with some different ugliness:

struct InitFoo
{
     InitFoo()
     {
         // one-time code goes here
     }
};

void Foo()
{
    static InitFoo i;
}

You’re still using static, but now you don’t need to do your own flag checking – static already puts in a flag and a check for it, so it only constructs i once.