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From: "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Atomic caching of smart pointers
Date: Mon, 16 Sep 2024 13:34:58 -0700
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On 9/16/2024 9:23 AM, Marcel Mueller wrote:
> Am 16.09.24 um 08:01 schrieb Paavo Helde:
>> Meanwhile I think I found a bug in my posted code, I should probably 
>> use compare_exchange_strong() instead of compare_exchange_weak().
> 
> Indeed. With ..._weak you most likely need a loop. But if you already 
> have a loop for other purposes using the _weak function could avoid an 
> additional loop in the implementation of the function.

The problem with weak is that it can spuriously fail. So, yup you need a 
loop. The strong one can be used for some older state machine algorithms 
I have seen. If a cas failed its simply because the comparands were 
different, not because of anything else...


> 
>> I somehow thought the latter would err on the safe side, but it does 
>> not. In my test harness there seems to be no difference.
> 
> On many platforms the underlying CAS primitives already are strong. In 
> this cases both function are identical.
> 
> 
> Marcel