Lua sandboxing

test-global-environment.cc

/*
	this quick and dirty example shows how a program can
	mount a new table as the global table, run some code,
	restore the original global table and then refer to the
	'child' global table as a regular ol' table in the parent
	global's scope.

	expected output:
		global
		type id 0
		is nil 1
		inner global: inner global
		outer global: global
		inner global: inner global
*/

#include <iostream>
#include "lua.hpp"

using namespace std;

int main() {
	lua_State *L = luaL_newstate();

	lua_pushstring(L, "global");
	lua_setglobal(L, "globalstring");

	lua_getglobal(L, "globalstring");
	cout << lua_tostring(L, -1) << endl;
	lua_pop(L, 1);

	lua_pushglobaltable(L);

	lua_newtable(L);
	lua_rawseti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS);
	lua_getglobal(L, "globalstring");

	if (lua_isstring(L, -1)) {
		cout << "string " << lua_tostring(L, -1) << endl;
	} else {
		cout << "type id " << lua_type(L, -1) << endl;
		cout << "is nil " << (lua_type(L, -1) == LUA_TNIL) << endl;
	}
	lua_pop(L, 1);

	lua_pushstring(L, "inner global");
	lua_setglobal(L, "globalstring");
	lua_getglobal(L, "globalstring");
	cout << "inner global: " << lua_tostring(L, -1) << endl;
	lua_pop(L, 1);

	lua_pushglobaltable(L);
	lua_pushvalue(L, -2);
	lua_remove(L, -3);
	lua_rawseti(L, LUA_REGISTRYINDEX, LUA_RIDX_GLOBALS);

	lua_getglobal(L, "globalstring");
	cout << "outer global: " << lua_tostring(L, -1) << endl;
	lua_pop(L, 1);
	lua_getfield(L, -1, "globalstring");
	cout << "inner global: " << lua_tostring(L, -1) << endl;
	lua_pop(L, 2);

	lua_close(L);

	return 0;
}