Re: Howto return kind userdata from C to Lua?

[Sean Conner <sean@...>]

It was thus said that the Great Ranier Vilela once stated:
> Em dom., 8 de nov. de 2020 às 01:02, Ranier Vilela <ranier.vf@gmail.com>
> escreveu:
> 
> > Em sáb., 7 de nov. de 2020 às 22:07, Sean Conner <sean@conman.org>
> > escreveu:
> >   // You can solve this several ways---one is to call lua_pop(L,1) to pop
> >
> >>   // MyItem off the stack, or to use lua_pushvalue(L,-2) to copy MyValue
> >> to
> >>   // the top of the stack.  Another way is to generate the uservalues in
> >>   // reverse order, thus avoiding the lua_pop() or lua_pushvalue() calls.
> >>
> > Many thanks, I will try.
> > In reverse order, I think it is not possible, MyItem is part of MyValue.
> > But I think of using it (MyItem) independently of MyValue, when this is
> > possible.
> >
> 
> lua_pushvalue, works, but only if disable that:
> //luaL_getmetatable(L, MYITEM_REGISTRY);
> //lua_setmetatable(L, -2);
> lua_pushvalue(L, -2);
> 
> How to discover what MyValue position is?
> Why does the register metatable MYITEM_REGISTRY confuse MYVALUE_REGISTRY?

  When I need to figure out the Lua stack in C, I use this function:

static int cstack(lua_State *L)
{
  int max = lua_gettop(L);
  
  fprintf(stderr,"Stack dump\n");
  
  for (int i = 1 ; i <= max ; i++)
  {
    fprintf(
            stderr,
            "%d %d - %s %s\n",
            i,
            i - max - 1,
            luaL_typename(L,i),
            luaL_tolstring(L,i,NULL)
    );
    lua_pop(L,1);
  }
  
  fprintf(stderr,"Stack done\n");
  return max;
}

  Call it where ever you feel the need to see the contents of the Lua stack. 
As for your second question, I don't have any ideas for that.

  -spc