[Gtk-sharp-list] widget destruction

"Andrés G. Aragoneses" knocte at gmail.com
Wed Mar 9 17:27:23 EST 2011

+1 for just writing a Warning on the finalizer. It has to be the 
developer who disposes things, not the GC. For that, we also have things 
like Gendarme's EnsureLocalDisposal rule or other helpers.

Plus, I think there's no class in the .NET class libraries which behaves 
like this.

On 09/03/11 16:54, Nicholas Frechette wrote:
> On Wed, Mar 9, 2011 at 6:39 AM, Lluis Sanchez Gual
> <slluis.devel at gmail.com <mailto:slluis.devel at gmail.com>> wrote:
>     Subclasses may need to free their own unmanaged resources, which may not
>     be related to gtk at all. For example, I could implement a widget
>     subclass which pinvokes a C api to get some data, which has to be
>     explicitly freed. I would free that data in the finalizer, but since the
>     finalizer will not be called if the object is explicitly disposed, I
>     also have to free that data in the Dispose method. So, I will end having
>     a DeleteMyData method which is called from the finalizer and from
>     Dispose.
>     The Dispose pattern provides an standard solution to the above scenario.
>     It states the need for a Dispose(bool disposing) method, to be called
>     from Dispose and from the finalizer. The 'disposing' parameter is 'true'
>     when calling from Dispose, meaning that it is safe to access other
>     reference objects, and it is 'false' when called from the finalizer,
>     meaning that only unmanaged data should be accessed.
>     There is some documentation about this pattern here:
>     http://msdn.microsoft.com/en-us/library/b1yfkh5e.aspx
> I disagree strongly with the implicit destruction of managed resources
> through the use of that pattern and the finalizer. Having worked
> extensively on embedded systems where tight control over memory is
> always required, in my experience, it is always better to provide tools
> for programmers to fix bad usage than it is to brush it under the rug
> and do their job for them. The finalizer should be there only to warn
> that memory is leaking and if you must, free that memory, but the
> warning is key so that the code can be fixed. Finalizers add a cost that
> can be very hard to measure.
> All objects that have managed resources to discard should implement
> Dispose and call base. Destroy should probably call Dispose (and not the
> other way around). Either way, documentation has to state clearly which
> is which and how to properly subclass widgets/other things.
> Nicholas
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