Re: [boost] News about proposed Boost.Application library

On Wed, Jul 30, 2014 at 1:29 PM, Peter Dimov wrote:

Klaim - Joël Lamotte wrote:

I might have misunderstood what Peter suggested: I thought he suggested

...

that get_symbol<> would return a smart pointer (not shared_ptr) that would _internally_ contain a shared_ptr to the plugin and the access to the data.

No, get_symbol returns a 'real' shared_ptr in my suggestion.

shared_ptr<library> p = load_library( "mylib.so" ); shared_ptr p2 = get_symbol( p, "myfunction" ); (*p2)(); // calls myfunction() in mylib.so

By creating p2 using the aliasing constructor of shared_ptr, you can have p2 and p share ownership of the loaded library.

template<class Y> shared_ptr(const shared_ptr<Y>& r, T *p) noexcept; Effects: Constructs a shared_ptr instance that stores p and shares ownership with r. Postconditions: get() == p && use_count() == r.use_count() [ Note: To avoid the possibility of a dangling pointer, the user of this constructor must ensure that p remains valid at least until the ownership group of r is destroyed. —end note ]

Ok, thanks now I see what you actually meant, sorry for the noise. Could you clarify what would happen here: shared_ptr p2; { shared_ptr<library> p = load_library( "mylib.so" ); p2 = get_symbol( p, "myfunction" ); } // p is destroyed (*p2)(); // ? A system-specific error or no error (which would mean that *p is kept alive)?

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