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

Rob Stewart wrote:

On July 29, 2014 3:39:16 AM EDT, "Klaim - Joël Lamotte" wrote:

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On 29 Jul 2014 02:33, "Rob Stewart" wrote: ...

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It would be nice if get_symbol returned a smart pointer that contained a shared_ptr to the library. When all such references are released, the library can be unloaded.

I disagree. In my experience it would be more useful if it contained a weak_ptr to the library, with a centralised system keeping all loaded libraries alive and allowing the used to unload the library explicitely. ... Please explain. Using a weak_ptr means each access must be tested, with synchronized access, to boot, versus assurance of validity with the shared_ptr.

It's possible to support both uses. If get_symbol is defined as class library; template<class F> shared_ptr<F> get_symbol( shared_ptr<library> pl ) { return shared_ptr<F>( pl, static_cast( ::dlsym( pl.get() ) ) ); } it will return a shared_ptr that is an alias for the library. You could then store the result in a weak_ptr, and it will expire when the library is unloaded. shared_ptr<library> pl = load_library( "mylib.so" ); weak_ptr pf = get_symbol( "myfunction" ); // void myfunction() pl.reset(); assert( pf.expired() );