I am writing a program with Lua and SDL.They are Lua5.1 and SDL 1.3.
My problem is: when I call the "SDL_SetVideoMode" function to get SDL_Surface, the "luagetstring" function will make an error at lua_call(L, 1, 1); If I write "lua_pcall(L,1,1,0);" instead of lua_call(L, 1, 1), there is the same result. But if the SDL_SetVideoMode not execute, there is no problem. I will get the right result by calling luagetstring(L, 1,str );
There is no problem when I call SDL_SetVideoMode in SDL 1.2.
Is it a conflict between SDL 1.3 with Lua? Or is there anything I missed?

=======================================================
data.lua
=======================================================
wndres = {
{ type = "tga", x = 100, y = 200, width = 0, height = 0},
{ type = "tga", x = 100, y = 200, width = 0, height = 0},
}

=======================================================
testfromlua.lua
=======================================================
function add ( x )
return wndres[x].x
end

function gettablelen()
return #wndres 
end

function getwndtype( idx )
return wndres[idx].type
end

function getX( idx )
return wndres[idx].x
end

function getY( idx )
return wndres[idx].y
end
=======================================================
testnewlua.cpp
=======================================================
// testnewlua.cpp : Defines the entry point for the console application.
//
#include "SDL.h"
#include "SDL_image.h"

extern "C"
{
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
}
#include <iostream>
#include <string>

static void luagetstring(lua_State *L, int idx, std::string& str )
{
lua_getglobal(L,"getwndtype");;
lua_pushnumber(L, idx);
lua_call(L, 1, 1);
size_t number = 0;
str = lua_tolstring(L, -1,&number);
lua_pop(L, 1);
}

int main(int argc, char* args[])
{
lua_State *L;

L = luaL_newstate();

luaL_openlibs(L);
int base = lua_gettop(L) - 0;

std::string t;
luaL_loadfile(L, "data.lua") || lua_pcall(L, 0, 1,base);
luaL_loadfile(L, "testfromlua.lua") || lua_pcall(L, 0, 1,base);


if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
{
return false;
}
//Set up the screen
SDL_Surface* g_pScreen = SDL_SetVideoMode( 300, 300, 32, SDL_SWSURFACE );

for( size_t i = 0; i < 2; i++ )
{
std::string str = "";
luagetstring(L, 1,str );
}
return 0;
}