GC BUG: Referenced object destroyed before released

[Steven Schveighoffer]

"Koroskin Denis" in message
> On Mon, 17 Mar 2008 01:28:04 +0300, Graham St Jack  wrote:
>> I agree that this is a problem. Who cares if the two objects in question
>> aren't referenced and more - their destructors should be called in the
>> right order if it is possible to do so.
>
> Yep.
>
>> I guess the work-around (and maybe permanent) is to not reference any
>> garbage-collected objects in your destructors.
>>
>
> Nope. This is against RAII pattern.

The issue is with the usage of the destructor to clean up memory.  Do not 
worry about cleaning up memory in destructors, that is what we have the 
garbage collector for.

In your example, all the members of Resource are GC allocated and so will be 
cleaned up when Resource is cleaned up.  You shouldn't care what the order 
is.

If you have an OS resource, such as an open file, that should be cleaned up 
in the destructor of the object which owns the OS handle.  This is what 
destructors are for.

The only missing piece is if you wanted to have an array of OS resources. 
In order to make sure the elements in this array are cleaned up properly, 
you would need to allocate the array using an alternate memory allocator 
that does not get cleaned up automatically, or else use wrapper classes to 
store the OS resources.  A way to fix this would be to always deallocate 
arrays last in the GC, and allow using the array elements (not objects 
pointed to by those elements) in the destructors.

-Steve