Question

Where in the process of creating the program, compiler, linker etc., is the overriding of functions and operator overloading done?

I’m particularly interested where it is done in C++, Ruby and Python.

Answer 1

Function overloading is (at least in C++) handled internally inside the compiler. The idea is that the code that the compiler ultimately generates will be hardcoded to call the appropriate function, as if the functions all had different names and you called the function uniquely suited to the arguments. More generally, in most compiled languages that support overloading, the overload resolution is done at compile-time and the emitted code will always call the indicated function. For example, Haskell supports compile-time overloading this way.

Operator overloading is a special case of general overloading, so it’s usually handled the same way.

Function overriding (a term that arises in OOP when a derived class inherits from a base class and redefines one of its methods) is almost always resolved at runtime, since a compiler can’t always tell which function is going to be invoked without actually knowing about the types at runtime. Some compilers might be able to statically prove that a certain object has a specific type and can then optimize the dynamic dispatch away, but it’s impossible to do this in all cases.

I am not aware of any dynamic languages that support overloading, since in theory you could introduce new overload candidates as the program was running. I would love to be enlightened if such a language exists.