luaL_checkinteger
return luaL_opt(L, luaL_checkinteger, narg, def);
#define luaL_checkint(L,n) ((int)luaL_checkinteger(L, (n)))
#define luaL_checklong(L,n) ((long)luaL_checkinteger(L, (n)))
LUALIB_API lua_Integer (luaL_checkinteger) (lua_State *L, int numArg);
size_t start = posrelat(luaL_checkinteger(L, 2), l);