这个问题在我的 Blog 上写文章讨论过。这里给出代码：

#include "lua.h"
#include <malloc.h>
#include <windows.h>
 
typedef void* (__stdcall *func_call)();
 
static int api_call(lua_State *L)
{
	int i,type;
	int n=lua_gettop(L);
	func_call fc=(func_call)lua_touserdata(L,lua_upvalueindex(2));
	void *ret;
	do {
		void **arg=(void **)_alloca(n*sizeof(void *));
		for (i=0;i<n;i++) {
			type=lua_type(L,i+1);
			switch(type) {
				case LUA_TNIL:
					arg[i]=0;
					break;
				case LUA_TNUMBER:
					arg[i]=(void*)lua_tointeger(L,i+1);
					break;
				case LUA_TBOOLEAN:
					arg[i]=(void*)lua_toboolean(L,i+1);
					break;
				case LUA_TSTRING:
					arg[i]=(void *)lua_tostring(L,i+1);
					break;
				case LUA_TLIGHTUSERDATA:
					arg[i]=lua_touserdata(L,i+1);
					break;
				default:
					lua_pushstring(L,"unknown argument type");
					lua_error(L);
					break;
			}
		}
		ret=fc();
	} while(0);
	switch(lua_type(L,lua_upvalueindex(1))) {
	case LUA_TNIL:
		lua_pushlightuserdata(L,ret);
		break;
	case LUA_TNUMBER:
		lua_pushinteger(L,(int)ret);
		break;
	case LUA_TBOOLEAN:
		lua_pushboolean(L,(int)ret);
		break;
	case LUA_TSTRING:
		lua_pushstring(L,(const char*)ret);
		break;
	default:
		lua_pushstring(L,"unknown return value type");
		lua_error(L);
		break;
	}
	return 1;
}
 
static int open_dll(lua_State *L)
{
	const char *name=lua_tostring(L,1);
	HMODULE hm=LoadLibrary(name);
	lua_pushlightuserdata(L,hm);
	return 1;
}
 
static int get_procaddress(lua_State *L)
{
	HMODULE hm=(HMODULE)lua_touserdata(L,1);
	const char *name=lua_tostring(L,2);
	void *func=GetProcAddress(hm,name);
	lua_pushvalue(L,3);
	lua_pushlightuserdata(L,func);
	lua_pushcclosure(L,api_call,2);
	return 1;
}
 
__declspec(dllexport) int luaopen_api_procaddress(lua_State *L)
{
	lua_pushcfunction(L,get_procaddress);
	return 1;
}
 
__declspec(dllexport) int luaopen_api_opendll(lua_State *L)
{
	lua_pushcfunction(L,open_dll);
	return 1;
}

下面，我们可以在 lua 中调用 windows 的 api 了，用法大约是这样的：

opendll = require("api.opendll")
getprocaddress =require("api.procaddress")
user32=opendll("user32.dll")
MessageBox=getprocaddress(user32,"MessageBoxA")
MessageBox(nil,"hello","hehe",0)