Question

I am puzzled why this one is right. The return value is reference type int&,
but the the h() function return a value int type in sentence return x. So, how does the int return change to a int &?

This is the code snippet and compiles fine with the C++ compiler.

int& h() {
 int q;
 static int x;
 return x;
}

Answer 1

This returns a reference to a static int. The x is initialized the first time the function h is called. Use it like this:

int& href = h();
++href; // increments the static variable
int& href2 = h(); // another reference to the same static variable

The variable q should have no effect and I would consider it dubious.