Question

Possible Duplicate:
How is reference implemented internally?

void f (int& a)
{
    a ++;
}

int main ()
{
    int b = 5;
    f(b);
    cout << b << endl; //prints 6
}

When I saw the syntax for references in C++, it initially looked like the variable b (if it were an object) would be copied into f. How do these references actually work under the hood? (Some simple asm would be great.)

Answer 1

In this case, the pass-by-reference most likely uses pointer semantics – i.e. the address of the object is probably passed as the parameter.\

When I saw the syntax for references in C++, it initially looked like the variable b (if it were an object) would be copied into f.

Nope. That’s one of the upsides of references – no copying.

    f(b);
00DF1405  lea         eax,[b]  
00DF1408  push        eax  
00DF1409  call        f (0DF1177h)  
00DF140E  add         esp,4  

eax will contain the address of b, and is then pushed onto the function argument stack.