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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-03-12 13:24:08

Greg Clayton wrote:
>> -----Original Message-----
>> From: Peter Dimov [mailto:pdimov_at_[hidden]]
>> Sent: Thursday, March 11, 2004 4:48 PM
>> To: boost_at_[hidden]
>> 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.