Best way to run lazy global initialization code only once

[hard raptor]

So I have a function like this that does lazy initialization:

Wrapper& getWrapper() {
  // initialization code
  
  return gWrapper;
}

But the initialization code isn't trivial and I want to only run it that once im actually constructing the gWrapper. Other times, it should just return gWrapper immediately. How can I best do this?

[spark ferry]

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[rare halo]

sounds like a singleton

[knotty grail]

you just write

Wrapper& getWrapper() {
  static Wrapper gWrapper /*whatever initializer here*/;
  return gWrapper;
}

and let Wrapper's constructor initialize it

[fervent salmon]

Or if you don't want to do that in Wrapper's constructor for some reason, you can use an immediately invoked lambda:

Wrapper &getWrapper()
{
    static Wrapper ret = []{
        Wrapper w;
        // do something to `w`
        return w;
    }();
    return ret;
}

[hard raptor]

Oh true, this fits my purpose thansk

!solved