在C ++中定义具有相同签名的两个函数

Question

Why can we define two functions with the same signature in the following way?

extern void print(int *ia, int sz);
void print(int *array, int size);

Answer 1

Those are not definitions, they are (redundant) declarations . If you would turn them both into definitions by providing a function body, you would certainly get an error from your compiler.

Answer 2

"Declaration" in C and C++ just tell the name, and type of that name.

"Definition" in C and C++ actually brings things into existence. Space for a variable gets allocated and the initial value set, a function code gets generated etc (ok, this is a bit simplified version).

Those two are declarations , because they lack function body. And since they are functions, extern is unnecessary so they are equal. You can declare same thing as many times as you want, as long as there's not conflict. And since functions allow overloading based on parameters in C++, you can only get conflict if you make functions which have same parameters but different return type. With variables or C functions you can't have name clashes.