RetroBBS - comp.lang.c++ - Re: Why is there lock

Why is there lock_guard ?

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From: Bonita.Montero@gmail.com (Bonita Montero)
Newsgroups: comp.lang.c++
Subject: Why is there lock_guard ?
Date: Sat, 17 Feb 2024 20:15:33 +0100
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by: Bonita Montero - Sat, 17 Feb 2024 19:15 UTC

Re: Why is there lock_guard ?

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From: chris.m.thomasson.1@gmail.com (Chris M. Thomasson)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Sat, 17 Feb 2024 15:40:15 -0800
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by: Chris M. Thomasson - Sat, 17 Feb 2024 23:40 UTC

On 2/17/2024 11:15 AM, Bonita Montero wrote:
> Why is there lock_guard when unique_lock can anything lock_guard
> can do but far more ?

lock_guard is meant for its purpose. Only use unique_lock when you need
to. And be careful, you can shoot yourself in the foot with it...

Re: Why is there lock_guard ?

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From: Bonita.Montero@gmail.com (Bonita Montero)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Sun, 18 Feb 2024 07:59:10 +0100
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by: Bonita Montero - Sun, 18 Feb 2024 06:59 UTC

Am 18.02.2024 um 00:40 schrieb Chris M. Thomasson:
> On 2/17/2024 11:15 AM, Bonita Montero wrote:
>> Why is there lock_guard when unique_lock can anything lock_guard
>> can do but far more ?
>
> lock_guard is meant for its purpose. ...

You easily could do ...

template<typename Lock>
using std::lock_guard = std::unique_lock<Lock>;

.... without any problems.

For me lock_guard doesn't make sense.

Re: Why is there lock_guard ?

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From: chris.m.thomasson.1@gmail.com (Chris M. Thomasson)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Sun, 18 Feb 2024 12:13:26 -0800
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by: Chris M. Thomasson - Sun, 18 Feb 2024 20:13 UTC

On 2/17/2024 10:59 PM, Bonita Montero wrote:
> Am 18.02.2024 um 00:40 schrieb Chris M. Thomasson:
>> On 2/17/2024 11:15 AM, Bonita Montero wrote:
>>> Why is there lock_guard when unique_lock can anything lock_guard
>>> can do but far more ?
>>
>> lock_guard is meant for its purpose. ...
>
> You easily could do ...
>
> template<typename Lock>
> using std::lock_guard = std::unique_lock<Lock>;
>
> ... without any problems.
>
> For me lock_guard doesn't make sense.

It has its purpose. If you did this then std::lock_guard would be
moveable even though its not meant to be. That's just one point...

Re: Why is there lock_guard ?

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From: Bonita.Montero@gmail.com (Bonita Montero)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Mon, 19 Feb 2024 06:50:38 +0100
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by: Bonita Montero - Mon, 19 Feb 2024 05:50 UTC

Am 18.02.2024 um 21:13 schrieb Chris M. Thomasson:
> On 2/17/2024 10:59 PM, Bonita Montero wrote:
>> Am 18.02.2024 um 00:40 schrieb Chris M. Thomasson:
>>> On 2/17/2024 11:15 AM, Bonita Montero wrote:
>>>> Why is there lock_guard when unique_lock can anything lock_guard
>>>> can do but far more ?
>>>
>>> lock_guard is meant for its purpose. ...
>>
>> You easily could do ...
>>
>> template<typename Lock>
>> using std::lock_guard = std::unique_lock<Lock>;
>>
>> ... without any problems.
>>
>> For me lock_guard doesn't make sense.
>
> It has its purpose. ...

.... which unique_lock also fulfills.

Re: Why is there lock_guard ?

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From: chris.m.thomasson.1@gmail.com (Chris M. Thomasson)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
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by: Chris M. Thomasson - Mon, 19 Feb 2024 19:56 UTC

On 2/18/2024 9:50 PM, Bonita Montero wrote:
> Am 18.02.2024 um 21:13 schrieb Chris M. Thomasson:
>> On 2/17/2024 10:59 PM, Bonita Montero wrote:
>>> Am 18.02.2024 um 00:40 schrieb Chris M. Thomasson:
>>>> On 2/17/2024 11:15 AM, Bonita Montero wrote:
>>>>> Why is there lock_guard when unique_lock can anything lock_guard
>>>>> can do but far more ?
>>>>
>>>> lock_guard is meant for its purpose. ...
>>>
>>> You easily could do ...
>>>
>>> template<typename Lock>
>>> using std::lock_guard = std::unique_lock<Lock>;
>>>
>>> ... without any problems.
>>>
>>> For me lock_guard doesn't make sense.
>>
>> It has its purpose. ...
>
> ... which unique_lock also fulfills.
>
>

lock_guard is highly restricted when compared to unique_lock... ;^)

Re: Why is there lock_guard ?

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From: andreytarasevich@hotmail.com (Andrey Tarasevich)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Thu, 29 Feb 2024 20:50:47 -0800
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by: Andrey Tarasevich - Fri, 1 Mar 2024 04:50 UTC

On 02/17/24 11:15 AM, Bonita Montero wrote:
> Why is there lock_guard when unique_lock can anything lock_guard
> can do but far more ?

If you really want to ask about it, you should probably consider
`scoped_lock` instead of `lock_guard` anyway. The rest can be found here

https://stackoverflow.com/a/60172828

--
Best regards,
Andrey

Re: Why is there lock_guard ?

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From: Bonita.Montero@gmail.com (Bonita Montero)
Newsgroups: comp.lang.c++
Subject: Re: Why is there lock_guard ?
Date: Fri, 1 Mar 2024 14:49:13 +0100
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by: Bonita Montero - Fri, 1 Mar 2024 13:49 UTC

Am 01.03.2024 um 05:50 schrieb Andrey Tarasevich:
> On 02/17/24 11:15 AM, Bonita Montero wrote:
>> Why is there lock_guard when unique_lock can anything lock_guard
>> can do but far more ?
>
> If you really want to ask about it, you should probably consider
> `scoped_lock` instead of `lock_guard` anyway. The rest can be found here

scoped_lock is only necessary if you need to lock multiple mutexes. The
mutexes are internally sorted according to their addresses, resulting in
no deadlocks as long as all competing threads do it the same way. You
can not defer locking or adopt already locked mutexes with scoped_lock,
so there's something essentially missing with scoped_lock.

Professional wrestling: ballet for the common man.

devel / comp.lang.c++ / Re: Why is there lock_guard ?

Subject	Author
Why is there lock_guard ?	Bonita Montero
Re: Why is there lock_guard ?	Chris M. Thomasson
Re: Why is there lock_guard ?	Bonita Montero
Re: Why is there lock_guard ?	Chris M. Thomasson
Re: Why is there lock_guard ?	Bonita Montero
Re: Why is there lock_guard ?	Chris M. Thomasson
Re: Why is there lock_guard ?	Andrey Tarasevich
Re: Why is there lock_guard ?	Bonita Montero