Re: [boost] boost::shared_ptr classes across DLL boundaries on Win32 issue

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-02-06 08:31:22

Greg Clayton wrote:
> I have been using the boost::shared_ptr class to add large classes to
> STL containers as shared pointers. I use many DLLs that all share the
> same heap (they all use multi-threaded DLL runtimes), and
> shared_ptr's are passed between DLLs.
>
> I am currently running into an issue where DLL "A" can build up a
> shared_ptr in a local variable, and hand ownership over to DLL "B"
> (which stores the shared pointer in a STL container). I get a crash
> when the STL container class in DLL B later destructs if DLL A has
> been unloaded. It seems all virtual functions in the vtable of the
> shared pointers are bogus at this point.

Yes, that's correct. A shared_ptr<X> remembers who created it (DLL A in this
case) and attempts to destroy itself using DLL A. This is by design; DLL B
may not be aware of the actual type of the shared_ptr, it may hold
shared_ptr<void> or shared_ptr<A> (where A is an abstract base of X). It's
even possible for X to not even exist outside DLL A. You need to make sure
that DLL A is still in memory when DLL B destroys its shared_ptr.