Re: smart pointers, slicing, and double deletion

Nigel Atkinson wrote:
> Smart pointers, slicing, and double deletion.
> 
> Sound's like a right mess doesn't it.  I finaly cracked it, and since
> I'm sure someone else will come across the same problem I had, I thought
> I'd share.
> 
> What I was trying to do:
> I have a GUI widget (Ogre3d if your wondering), that holds a list of its
> children widgets.  This widget class is the base for several Lua widget
> classes.  I'm using smart pointers to avoid adoption issues.
> 
> Originally using shared pointers, I found that when only C++ had a
> pointer to the instance, it would get 'sliced' if it was a Lua class.
> 
> Bring in shared_ptr_converter.hpp, and that fixes the slicing.  However
> because of part of the way it works, it causes double deletion albeit
> seemingly only at the shut down of a Lua thread. 

How so? Does the test case you attached show this if I replace
intrusive_ptr with shared_ptr?

> (Its not safe across Lua threads either, but that's easily fixed.)

Because it stores a handle with the thread lua_State*, which might later
be collected? Yes, nice catch. This should fix it:

diff --git a/luabind/shared_ptr_converter.hpp
b/luabind/shared_ptr_converter.hpp
index d35d805..afdc841 100644
--- a/luabind/shared_ptr_converter.hpp
+++ b/luabind/shared_ptr_converter.hpp
@@ -5,6 +5,7 @@
 #ifndef LUABIND_SHARED_PTR_CONVERTER_090211_HPP
 # define LUABIND_SHARED_PTR_CONVERTER_090211_HPP

+# include <luabind/get_main_thread.hpp>
 # include <luabind/handle.hpp>
 # include <luabind/detail/policy.hpp>
 # include <boost/shared_ptr.hpp>
@@ -17,7 +18,7 @@ namespace detail
   struct shared_ptr_deleter
   {
       shared_ptr_deleter(lua_State* L, int index)
-        : life_support(L, index)
+        : life_support(get_main_thread(L), index)
       {}

       void operator()(void const*)

-- 
Daniel Wallin
BoostPro Computing
http://www.boostpro.com

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