Is it OK to use boost::shared ptr in DLL interface?

Question

Is it valid to develop a DLL in C++ that returns boost shared pointers and uses them as parameters?

So, is it ok to export functions like this?

1.) boost::shared_ptr<Connection> startConnection();
2.) void sendToConnection(boost::shared_ptr<Connection> conn, byte* data, int len);

In special: Does the reference count work across DLL boundaries or would the requirement be that exe and dll use the same runtime?

The intention is to overcome the problems with object ownership. So the object gets deleted when both dll and exe don't reference it any more.

Answer 1

DLLs do not normally own resources - the resources are owned by the processes that use the DLL. You are probably better off returning a plain pointer, which you then store in a shared pointer on the calling side. But without more info it's hard to be 100% certain about this.

Answer 2

In my opinion, if it's not in the standard and it's not an object/mechanism provided by your library, then it shouldn't be part of the interface to the library. You can create your own object to do the reference counting, and perhaps use boost underneath, but it shouldn't be explicitly exposed in the interface.

Answer 3

Something to lookout for if you expose raw pointers from a dll interface. It forces you to use the shared dll CRT, memory allocated in one CRT cannot be deallocated in a different CRT. If you use the shared dll CRT in all your modules ( dll's & exe's ) then you are fine, they all share the same heap, if you dont you will be crossing CRT's and the world will meltdown.

Aside from that issue, I agree with the accepted answer. The creation factory probably shouldn't define ownership & lifecycle management for the client code.