C++ class name as class member

Question

What's the meaning of the postfix expression AttrNode().AttrNode in main in the following code? Both gcc and clang can compile the code without any error. Seems it is legal in C++ standards. But what's the meaning of such code? Why does the C++ standards allow such usage?

#include <stdio.h>

struct AttrNode {
public:
     AttrNode() {}
     static void make() {}
};

int main() {
    AttrNode().AttrNode::make();
    return 0;
}

Thanks!

Answer 1

AttrNode:: is qualifying the name make, to explicitly call AttrNode::make and not any other function called make.

In this case, that's redundant; AttrNode().make() would do exactly the same thing: create a temporary object, call the function, then destroy the object. Since it's a static function, you would usually call it without making an object, AttrNode::make().

It makes a difference if it's a virtual function, causing a non-virtual call to the function in the specified class, rather than a virtual call the final override. The syntax can also be used to access a name in the base class that's been hidden in a derived class.