Re: [boost] Explicit instantiation of boost::shared_ptr<SomeClasss>

12 Mar 2004

      Greg Clayton wrote:
...
...
-----Original Message-----
From: Peter Dimov [mailto:pdimov@mmltd.net]
Sent: Thursday, March 11, 2004 4:48 PM
To: boost@lists.boost.org
Subject: Re: [boost] Explicit instantiation of
boost::shared_ptr<SomeClasss>
Greg Clayton wrote:
...
I am trying to do explicitly instantiate specific shared_ptr class
for export from a Win32 DLL (currently with MSVC6, and eventually in
VS2003).
First things first. Why do you need to do that? Have you
tried not exporting it, have you encountered any problems?
Yes, shared pointers can't be created and handed off from DLL to DLL
the way they are currently implemented. If DLL A has an STL container
of shared pointers, and DLL B gets _dynamically_ loaded and adds an
item to DLL A's container (creates a shared pointer to an object, and
DLL B adds that shared pointer through an interface it to DLL A's STL
container of shared pointers), DLL B can not be unloaded. If DLL B
does get unloaded you will crash when your STL container goes out of
scope (when it tries to delete the owned pointer).
Isn't it possible for the DLL C that contains the definition of SomeClass to
export

    shared_ptr<SomeClass> createSomeClass();

which DLL B can now call when it needs a SomeClass?

Since ~SomeClass lives in C, it must be available when the last
shared_ptr<SomeClass> is destroyed.