Re: Discarding shared_ptrs

If you keep a reference around in Lua you will have a use count for it.
You can set to nil to remove that reference but you need make sure you
set all references to that pointer to nil.

A slight gotcha is that Lua will only increase the count by 1 regardless
of how many references in Lua you have.  Kinda obvious if you think
about it for a moment, but not so obvious if are thinking about other
things! 

You could use a weak table in Lua if you don't want Lua to 'hold on' to
shared pointers, or perhaps you could actually use a boost::weak_ptr ( I
haven't tried this.)  Depends what you are doing.

For instance I use a "ward ptr" for some things, which basically is a
smart pointer that can be marked as invalid so later on if Lua tries to
use it, it throws an exception/Lua error rather than crashing.  Which is
nice. :-P  

HTH

Nigel

On Mon, 2011-06-06 at 22:40 +0100, Simon Pickles wrote:
> Hi,
> 
> I am passing boost::shared_ptr<T> to Lua functions, which works well.
> 
> Unfortunately, the shared_ptr then keeps an extra use_count (held in the 
> lua table), even if the function is finished. How do I release this usage?
> 
> Set to nil? Use a Policy? Pass some other sort of pointer? I'd love to 
> be able to use the functionality of boost::weak_ptr in lua!
> 
> Any advice welcome
> 
> thanks
> 
> Simon
> 
> 
> 
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