Re: Gtk::SpinButton crash

[Ian Martin <martin_id vodafone co nz>]

Hi John,
Hope you don't mind me jumping in.  I'm curious why you want to do your 
own memory management:  Gtk::manage takes all the work out of your hands 
safely, and stops you deleting widgets in an inappropriate order.  If 
you want to make a program that you have to do all your memory 
management manually, C is probably a better choice- but if you work at 
it you can manage it in C++.  It's a bit archaic, though, and the only 
use I can see for it is a teaching exercise (to make sure you never want 
to do it again).

Program size isn't a good excuse; if you're that desperate you should be 
using C.  So why bother?

Ian

On 26/11/13 10:05, John Emmas wrote:
> Hi Kjell,
>
> Many thanks for sending me your versions of those files.  The good 
> news is that with only the exception of some commented sections, your 
> versions are identical to mine.  Both versions exhibit the same 
> behaviour (and unfortunately, the same problems).
>
> I'm wondering now if I've been fooling myself to think that this 
> SpinButton/Adjuster issue is somehow related to the previous one that 
> got solved.  For various reasons it does look a bit similar - but I'm 
> now starting to think that the SpinButton/Adjuster problem is actually 
> a clearly defined issue in its own right.  The reason I'm wondering is 
> that this sequence crashes:-
>
>         Create a SpinButton
>         Create an Adjustment
>         Attach the Adjustment to the SpinButton
>         Delete the Adjustment
>         Delete the SpinButton   // Remember that the (deleted) 
> Adjustment is still attached !!
>
> OTOH this sequence doesn't crash:-
>
>         Create a SpinButton
>         Create an Adjustment
>         Attach the Adjustment to the SpinButton
>         Delete the SpinButton  // Adjustment hasn't been deleted yet !!
>         Delete the Adjustment
>
> But wait a minute...  during my tests I discovered some evidence to 
> suggest that this sequence wouldn't crash either:-
>
>         Create a SpinButton
>         Create an Adjustment
>         Attach the Adjustment to the SpinButton
>         Detach the Adjustment (using 
> 'Gtk::SpinButton::unset_adjustment()')
>
>         Delete the Adjustment  // These two deletions can now
>         Delete the SpinButton   // get done (safely) in either order
>
> So I guess I'm questioning the safety of deleting a Gtk::SpinButton 
> whilst it has an (invalid) Gtk::Adjustment attached.  I don't know 
> enough about the gtkmm spec to know whether that should (or should 
> not) be safe.  It certainly isn't safe at present, from what I can 
> tell.  Would it help for me to try the same thing with a plain GTK+ 
> app?  If it's safe to do with GTK+ I'd assume it should also be safe 
> with gtkmm....
>
> John
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