nagle at animats.com
Sun Sep 5 07:23:44 CEST 2010
On 9/4/2010 6:44 PM, Lawrence D'Oliveiro wrote:
> In message<4c82b097$0$1661$742ec2ed at news.sonic.net>, John Nagle wrote:
>> Personally, I'd like to have reference counting only, an enforced
>> prohibition on loops (backpointers must be weak pointers), RAII,
>> and reliably ordered finalization.
> Is there a cheap way of checking at runtime for circular structures?
It's an interesting technical problem to design a system where
circular references are detected immediately, at the moment
of creation. However, Python already detects loops during
garbage collection. If you set
all the loops show up in "gc.garbage".
>> A big advantage of reference counting is that finalization happens
>> in the thread that releases the object, and in the correct order.
>> GC and finalization/destructors do not play well together at all.
>> Microsoft once tried to get the hard cases to work right. See
>> "managed C++". Not a happy story.
> Thank you for that. Another arrow for my anti-GC quiver. :)
Unoptimized reference counting, which is what CPython does, isn't
all that great either. The four big bottlenecks in Python are boxed
numbers, attribute lookups, reference count updates, and the GIL.
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