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RFC: Proposal: Deterministic Object Destruction


On 3/4/18 6:55 PM, Ned Batchelder wrote:
> On 3/4/18 5:25 PM, Ooomzay wrote:
>> On Sunday, 4 March 2018 14:37:30 UTC, Ned Batchelder? wrote:
>>> Are you including cyclic references in your assertion that CPython
>>> behaves as you want?
>> Yes. Because the only behaviour required for RAII is to detect and 
>> debug such cycles in order to eliminate them. It is a design 
>> error/resource leak to create an orphan cycle containing RAII objects.
>>
>> def main():
>> gc,disable
>>
>>
>>
>
> This isn't a reasonable position.? Cycles exist, and the gc exists for 
> a reason.? Your proposal isn't going to go anywhere if you just 
> naively ignore cycles.
>
> --Ned.

While Ooomzay seems to want to say that all cycles are bad, I think it 
is fair to say that in general in Python they are unavoidable, in part 
because I can't see any good way to create the equivalent of a 'weak 
reference' (names aren't objects so don't have properties). The? best I 
can think of is to create some sort of magical object that can refer to 
another object, but that reference 'doesn't count'. This seems very 
unPythonic.

What I think can be said is that it should be possible (enforced by the 
programmer, not the language) to use these RAII objects in ways that 
don't create cycles (or maybe that the program knows of the cycles and 
makes the effort to break them when it is important). So perhaps it can 
be said that cycle that involve major resource RAII objects should exist.

-- 
Richard Damon