Re: [boost] Severe shared_ptr limitation WRT dynamically loaded libraries

Subject: Re: [boost] Severe shared_ptr limitation WRT dynamically loaded libraries
From: Emil Dotchevski (emil_at_[hidden])
Date: 2008-11-20 08:17:56

On Wed, Nov 19, 2008 at 2:37 PM, J.D. Herron <jotadehace_at_[hidden]> wrote:
> If I have a dynamically loaded factory interface that returns a
> shared_ptr, the factory implementation causes the templates to generate the
> virtual function code within the factory library.  Everything is fine as
> long as the library stays loaded but if the library is unloaded, any client
> code holding the shared pointer to an object generated by that factory now
> has an invalid virtual function table for the sp_counted_base it holds.  So
> when the reference count goes to zero an access violation is generated.

One solution is to "inject" the shared_ptr that would crash if a DLL
is unloaded with another shared_ptr that keeps the DLL afloat. I've
also done this with the boost::function objects that are passed to the
client to be used as factories.

Another strategy which doesn't necessarily work in the case of
shared_ptr but works for other things (like std::type_infos obtained
from a DLL) is to use weak_ptr to detect that the DLL is gone and
accessing the object will crash the program, and throw an exception
instead.

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode