[boost] shared_ptr, interface and dlls

From: Dirk Gregorius (dirk_at_[hidden])
Date: 2004-12-08 10:31:33

Hi,

is it possible to return a shared_ptr to an interface from a dl?. I 
thought of the following what unfortunately doesn't work:

// Interface.h - exe project
class Interface
{
public:
    vitrtual void f( void ) = 0;
    virtual void g( void ) = 0;

protected:
     ~Interface( void ) {}
}

typedef  shared_ptr<Interface> InterfacePtr;
InterfacePtr Create( void )
{
    // Load a special create function from the dll
    //....

    return DLLCreate();
}

// InterfaceImpl.h - dll project
#include Interface
class InterfaceImpl : public Interface
{
public:
    void f( void ) { /* ... */ };
    void g( void ) { /* ... */ };

private:
    // No copy operations
}

extern "C" InterfacePtr DLLCreate( void )
{
    return InterfacePtr( new InterfaceImpl );
}

At the moment this code doesn't compile because VS7.1 complains that it 
a function with extern "C" linkage can't return a shared_ptr<Interface> 
instance. How could I implement the desired behavior?

Some other related questions regarding this topic:

1.) I link to the multithreaded C run-time dll - is this allowed? I read 
in an older post that only static CRT linking is allowed.

2.) Does the above code - loading the factory from the DLL as well and 
(hopefully) constructing the instance there - solve the boundary 
problems? I read some articles regarding this issue, but to be honest I 
haven't completly understood the problems that may occure in this case 
so far.

Any help is greatly appreiciated..

-Dirk