windows - What does a "CALLBACK" declaration in C do?

Question

I was looking through some code from the SDL library and came across a function declared like this:

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)

Now, I'm a Delphi coder. No hablo C muy bien, senor. But I remember enough syntax from my college courses to read it like this:

Function name is WndProc. Argument list is pretty self-explanatory. Function return type is LRESULT. But what in the world is that "CALLBACK" doing there? In Delphi, any function can be used as a callback; you just need to pass the right type of function pointer. Is there any particular reason why C doesn't work that way? Or does it mean something different?

Answer 1

The "CALLBACK" is a calling convention. There are other kinds of calling conventions. CALLBACK is the same as __stdcall.

http://www.codeguru.com/cpp/cpp/cpp_mfc/callbacks/article.php/c10557

Some more information at Raymond Chen's blog:

http://blogs.msdn.com/oldnewthing/archive/2004/01/08/48616.aspx