Re: lua_pop and garbage collection

[Shmuel Zeigerman <shmuz@...>]

On 27/05/2014 18:31, Roberto Ierusalimschy wrote:
> > If it cannot, is it guaranteed somewhere in the docs or is it
> > implementation dependent?
>
> It is implementation dependent. (Note that even the notion of "garbage
> collection cycle" is implementation dependent. Lua uses an incremental
> collector, which means that a cycle occurs distributed among several
> points in time.)
>
> Why do you need to know that?

A non-Lua application calls into a Lua plugin and expects to get from it 
a pointer to some C-struct filled with data (I cannot change this 
interface, it is predefined). It would be very handy to do something like:

  struct Info* info = lua_newuserdata(L, sizeof(struct Info));
  ..... // fill the fields of struct with data
  lua_pop(L,1);
  return info;

As it is known that the application uses the returned pointer 
immediately, it should be safe, unless 'info' is not collected.

--
Shmuel