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From: paavo512 <paavo@osa.pri.ee>
Newsgroups: comp.lang.c++,comp.lang.c
Subject: Re: "White House to Developers: Using C or C++ Invites Cybersecurity
 Risks"
Date: Mon, 29 Apr 2024 12:45:35 +0300
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On 29.04.2024 03:05, Lawrence D'Oliveiro wrote:
> On Fri, 8 Mar 2024 14:41:16 +0200, Paavo Helde wrote:
> 
>> AFAIK CPython uses reference counting ...
> 
> Combination of reference-counting as a first resort, with full garbage
> collection to deal with those less common cases where you have reference
> cycles. Trying to get the best of both worlds.
> 
> The trouble with reference-counting is it impacts multithreading
> performance. 

Maybe only in case of heavy contention. If there is little contention 
and the reference counter is implemented as an atomic variable, there is 
no measurable hit on performance. I know this because I was suspicious 
myself and measured this recently.

Anyway, multithreading performance is a non-issue for Python so far as 
the Python interpreter runs in a single-threaded regime anyway, under a 
global GIL lock. They are planning to get rid of GIL, but this work is 
still in development AFAIK. I'm sure it will take years to stabilize the 
whole Python zoo without GIL.


However, the CPython developers have a scheme to deal with
> this, by making the reference counts a little less deterministic (i.e.
> there may be a slight delay before they become fully correct). I think
> this is a complicated idea, and it may take them some time to get it fully
> implemented.