Re: Rebirthing an object... just making sure

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 11 Jan 2008 01:35:59 -0800 (PST)

Message-ID:

<556d6215-6572-41ed-9cf2-d78c2a3cef38@t1g2000pra.googlegroups.com>

On Jan 10, 5:57 pm, "Tom=E1s =D3 h=C9ilidhe" <t...@lavabit.com> wrote:

"Tom=E1s =D3 h=C9ilidhe" <t...@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.

Yes. And if you set the pointer to null, the dialog's class
can't free the memory, because it has no pointer to it. So you
need the ::operator delete( obj ) in the catch as well.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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