[SOLVED] If a variable is assigned an object returned by a function, is it copied or created in-place?

If a variable is assigned an object returned by a function, is it copied or created in-place?

I have something like this in my CPP file to initialize an object outside any class. I've simplified it but the point is there is some complex initialization going on but I want a single instance created:

static MyBigObject o = []()
{
  MyBigObject ret;
  ret.Init();
  return ret; 
}();

My question is, does this object get copied from ret to o or created in-place due to compiler cleverness? There might be a proper term for "created in place" - emplaced?

I am working in C++17, if it's pertinent (i.e. the answer depends on language version). Is there a definite answer, or could this be a compiler-specific optimisation?

Solution

In this case: this depends on your compiler. This is named return value optimization, which is optionally elided. C++17 allows, but not requires, the copy to be elided even if the object has observable side effects in its copy/move constructors (and its destructor).