What is the point of defining a calling convention?

Question

For example:

int WINAPI WinMain ( HINSTANCE instance, HINSTANCE prev_instance, PSTR cmd_line, int cmd_show )

WINAPI is a a define that looks li

Answer 1

Because the WINAPI calling convention is not guaranteed to be __stdcall. Code that uses WINAPI will still be correct even when it isn't.

You can write the function as in your latter example, and it'd work fine - it's just not good practice and would not be portable to a platform where the calling convention is something else.