C++ 左值引用

Question

So recently I revisited references on the type declaration but I didn't quite understand them.

Consider this dummy code:

int ia = 10;
int& ref = ia;

Now, my questions are:

1. how do these int& ref work internally, does it mean here that the address of ref is assigned the address of ia and thus equal to &ia if not then what does the compiler do upon seeing these references?
2. Why aren't these references compiled in a c++ program?

Answer 1

You don't have to think of addresses at all. ref is just another name for ia , or put another way, ref is an alias to ia . Just syntactic sugar for your code.

The compiler in this case doesn't have to do much at all, just keep track of when the code contains ref , replace it with ia .

Answer 2

C++ standard doesn't specify how reference should be implemented by the compiler. A lot of people think they are just aliases, but in fact, under the hood they are just implemented as const pointers.

C++ references are const pointers under the hood. So:

int ia = 10;
int& ref = ia;
ref++; // ia is 11 now

might be converted by the compiler to:

int ia = 10;
int* const ref = ia;
(*ref)++; // ia is 11 now

They need initialization because constants must be initialized.