Thread: Function types in C

I'm fairly familiar with C but I cannot seem to figure out the function definitions below.

Obviously i do not expect you to understand the context, kindly help me to understand the structure / Style.

This is actually extracted from the Lua source code.

what type of functions are these ?
I do not understand the LUA_API keyword. Is this another return type in addition to int? is it some sort of a macro?

Code:

LUA_API int lua_absindex (lua_State *L, int idx) {

....

LUA_API void lua_remove (lua_State *L, int idx) {

I noticed something similar below - this is a function definition extracted from a win32 api tutorial.

if WinMain is the function name, and int is the return type, then what is WINAPI.

Code:

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,     LPSTR lpCmdLine, int nCmdShow){

I cannot seem to place this style of coding.

It is a macro that expands into some special calling conventions or keywords that all Lua API functions should have. Remember, a macro in C is just fancy text substitution. According to this site: Lua: 5.2 source code - luaconf.h, it just expands to the extern keyword. But if they ever want to change the Lua API, it can be done by modifying one place, the LUA_API definition, instead of hundreds of functions.

WINAPI is the same idea, though probably a bit more complicated.

This practice is fairly common in libraries, when writing language extensions, etc.

Cheers.