Re: Rebirthing an object... just making sure

From:

"Tom1s # hilidhe" <toe@lavabit.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 10 Jan 2008 16:57:19 GMT

Message-ID:

<Xns9A21AC799ECC5toelavabitcom@194.125.133.14>

"Tom1s # hilidhe" <toe@lavabit.com> wrote in comp.lang.c++:

And of course, if the constructor of T throws, you still leak
the memory. You really need something like:

    template< typename T >
    void
    renewObject( T*& obj )
    {
        // Fail if object has a derived type...
        assert( typeid( *obj ) == typeid( T ) ) ;
        obj->~T() ;
        try {
            new( obj ) T ;
        } catch ( ... ) {
            ::operator delete( obj ) ;
            obj = NULL ;
            throw ;
        }
    }

I'm intending for there to be a leak, because the dialog's class code
deletes its controls automatically when the dialog is closed.

Wups a daisy... about five seconds after I posted that I realised I'd
need a catch to set the pointer to null to avoid the dialog's class from
calling the destructor on an object that's already been destructed.

Anyway, in my own particular program, it's a fatal error if you can't
rebirth an object, so I think I'll go with:

template<class T>
void Rebirth(T &obj)
{
obj.~T();

try { ::new(&obj) T(); } catch (...) { exit(EXIT_FAILURE); };
}

--
Tom1s # hilidhe