Re: How two C-closures can share an upvalue??

[Asko Kauppi <askok@...>]

There is no memory management involved in David's code clip. There  
shouldn't.

'static' variable is not memory managed, and all the light user data  
are, are pointers to that memory location.

About your real question, I am still listening (don't know an answer  
myself). Maybe it's a twisted design, from your side. What exactly do  
you need the shared upvalues for? :)

-asko


slonik.az@gmail.com kirjoitti 14.8.2006 kello 3.03:

> Hi David,
> thanks a lot for your help and for your suggestion!!
> Unfortunately, your solution does not quite solve the problem because
> functions myfunc1 and myfunc2 do not really share upvalues. Each one
> has its own upvalue that happens to contain a pointer that points to
> some common memory block (or Lua table).
> Firstly, it introduces one extra level of redirection. Secondly, how
> the memory will be cleaned? Lightuserdata is not being garbage
> collected and no one else is pointing to that memory block?
>
> Is there a way to share a given upvalue amongst several C-closures the
> same way it happens with Lua closures??
>
> --Leo--
>
> On 8/13/06, D Burgess <dburgess@gmail.com> wrote:
> > Case 1
> >
> > static int val;
> > lua_pushlightuserdata(L, &val);
> > lua_pushcclosurer(L,  myfunc2, 1);
> > lua_pushlightuserdata(L, &val);
> > lua_pushcclosurer(L,  myfunc1, 1);
> >
> > Case 2
> > If its lua values you wish to share (rather than C) create the value
> > as a table entry and use the table for the upvalue.
> >
> > David B
> >
> > On 8/14/06, slonik.az@gmail.com <slonik.az@gmail.com> wrote:
> > > Hi Lua Experts,
> > > Lua closures can share their private state with each other by  
> > sharing
> > > their "outer local" variables. In the following code snippet "local
> > > cnt" is accessible by both cnt_step() and cnt_get() and no other
> > > function in the world could touch it.
> > >
> > > function cnt_init()
> > >    local cnt= 0
> > >    function cnt_step() cnt= cnt + 1 end
> > >    function cnt_get()  return cnt; end
> > > end
> > > cnt_init();
> > >
> > > I would like to achieve the same effect using C-closures. But I  
> > cannot
> > > figure out how?
> > > Roberto's book "Programming in Lua, 2-nd edition" that I recently
> > > bought shows how a C-closure stores its individual state in an  
> > upvalue
> > > (lua_pushcclosure). But here I need two functions to have an  
> > access to
> > > the same upvalue.
> > > Any help is greatly appreciated.
> > >
> > > Thanks and Best Regards,
> > > --Leo--
> > >