GC and dtors ~ a different approach?

[kris]

Bruno Medeiros wrote:
> kris wrote:
> 
>> Bruno Medeiros wrote:
>>
>>>
>>>
>>> All of those pros you mention are valid. But you'd have one serious con:
>>> * Any class which required cleanup would have to be manually memory 
>>> managed.
>>>
>>
> 
> Just one addendum: I was just pointing out that con, I wasn't saying it 
> was or was not, a bad idea overall.
> 
>>
>> First, let's change the verbiage of "valid" and "unspecified" to be 
>> "deterministic" and "non-deterministic" respectively (per Don C).
>>
> 
> Let's not. *g*  See my reply to the Don.

heheh :)

> 
>>
>> To get to your assertion: under the suggested model, any class with 
>> resources that need to be released should either be 'delete'd at some 
>> appropriate point, or have raii applied to it. Classes with dtors that 
>> are not cleaned up in this manner can be treated as "leaks" (and can 
>> be identified at runtime).
>>
>> Thus, the term "manually memory managed" is not as clear as it might 
>> be: raii can be used to clean up, and scope(exit) can be used to 
>> cleanup. An explicit 'delete' can be used to cleanup. There's no 
>> malloc() or anything like that invoved.
>>
> 
> Those are all manual memory management. (Even if auto and scope() are 
> much better than plain malloc/free).
> [Note: RAII's auto = scope(exit)]
> You would have an automatic leak/failure detection, true.
> 
>> The truly serious problem with a 'lazy' cleanup is that the dtor will 
>> wind up invoked with non-determinstic state (typically leading to a 
>> serious error). The other concern with lazy cleanup is what Mike 
>> addresses (if the resource needs cleaning up, it should be done in a 
>> timely manner ~ not at some arbitrary point in the future).
>>
> 
> The state is *undefined*, it is not "non-deterministic" nor 
> "deterministic". This is the kind of terminology blur up that I was 
> leery of. :P

:-D

Terminology aside; with the current implementation, invocation of dtors 
during a collection often causes serious problems. That's why we see the 
use of close/dispose patterns in D. It would be great to avoid both of 
those things :p