Re: Losing metatable reference

[Sean Conner <sean@...>]

It was thus said that the Great Murray S. Kucherawy once stated:
>
> However, lua_getmetatable() returns 0, apparently unable to find the
> associated metatable.  I've confirmed that the pointer created by func()
> is the same as the one being passed to use().
> 
> Any suggestions?  I'm really puzzled; it shouldn't be garbage collection
> because the script hasn't terminated and the values haven't been
> reassigned on the script side, so that pointer should still reference
> something valid (and I checked that too; it does).

  Did you register the metatable in the registry? 

	luaL_newmetatable(L,name);

  Looking into the source of Lua, luaL_getmetatable(L,n) is a macro for
lua_getfield(L,LUA_REGISTRYINDEX,n), which will return a nil value for a
non-existent field.  nil is a Lua value, which I assume is not to be
confused with C's NULL, so what you might be seeing is an actual nil value
on the stack.  Try:

ud = lua_touserdata(L, n);
if (ud != NULL)
  if (lua_getmetatable(L, n) != 0) {
    lua_getfield(L, LUA_REGISTRYINDEX, name);

    assert(!lua_isnil(L,-1));

    if (lua_rawequal(L, -1, -2)) {
      lua_pop(L, 2);
      return ud;
    }
  lua_pop(L, 2);
  }
}

return NULL;

and see if the assert() fires.

  -spc (That's be my guess ... )