A C++ reference is basically a pointer that pretends to not be a pointer. If they have any efficiency advantage over const-correct pointers, I've never heard of it (though I'm at best an intermediate C++ programmer).

Points often cited as disadvantages of references include:

- There's nothing that clearly distinguishes them from regular variables at the point of use. They can therefore obscure the fact that you're not passing by value or mutating a local/member variable (particularly if you don't have good IDE support, and good IDE support for C++ is damn hard for some environments/toolchains/targets)

- There is no concept of a null reference, which can create friction with interfaces that use NULL for optional parameters

These points are also often cited as crucial advantages of references. So it goes.