Re: gtkmm 3.0.

[Murray Cumming <murrayc murrayc com>]

On Sun, 2010-03-28 at 14:07 +0100, Chris Vine wrote:
> On Thu, 25 Mar 2010 23:20:28 +0000
> Chris Vine <chris cvine freeserve co uk> wrote:
> > On Thu, 25 Mar 2010 23:45:24 +0100
> > Murray Cumming <murrayc murrayc com> wrote:
> > > Also, I understand the previous examples that check before
> > > dereferencing, but I'm concerned that any part of my code could
> > > potentially cause the TreeView to be deleted, so all my code will
> > > look like this
> > > 
> > > if(ptr)
> > >   ptr->do_something();
> > > if(ptr)
> > >   ptr->do_next_thing();
> > > if(ptr)
> > >   ptr->do_third_thing();
> > > 
> > > And that will be particularly awful when it forces us to declare
> > > variables apart form their initialization, and make special efforts
> > > to always clean up properly.
> > 
> > Your point is a good one if it is the case that accessing the methods
> > of the TreeSelection for a non-existent TreeView does not cause the
> > program to blow up (and you can live with the copious warnings that
> > would no doubt be emitted were it not to cause memory faults).  I
> > suppose the best test of this would be to construct a test case and
> > run it under valgrind.
> 
> I can easily provoke g_critical() warnings but I have not been able to
> provoke a memory fault.
> 
> I agree you would need separate 'if' blocks for, or be prepared for a
> throw at, each dereference as in your example if do_something() or
> do_next_thing() might delete the TreeView (although of course they
> wouldn't because TreeSelections don't delete TreeViews, but you are
> presumably positing that a user class derived from TreeSelection might
> or there is some other intermediate code which might).
> 
> But frankly, if any of those functions might delete the TreeView, then
> the program really ought to check for that rather than just hope for the
> best and carry on as if all were well.

Actually, we probably need to find a better example. I think it's
generally agreed that there's no reason for TreeSelection to be a
separate class from TreeView.


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