From: Florian Weimer <fweimer@redhat.com>
To: Peng Yu <pengyu.ut@gmail.com>
Cc: Peng Yu via Libc-help <libc-help@sourceware.org>
Subject: Re: What is the point of IPC_PRIVATE of shmget?
Date: Mon, 12 Apr 2021 18:18:55 +0200 [thread overview]
Message-ID: <87o8ejiihc.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <87sg3viio7.fsf@oldenburg.str.redhat.com> (Florian Weimer's message of "Mon, 12 Apr 2021 18:14:48 +0200")
* Florian Weimer:
> * Peng Yu:
>
>> On Mon, Apr 12, 2021 at 11:07 AM Florian Weimer <fweimer@redhat.com> wrote:
>>>
>>> * Peng Yu via Libc-help:
>>>
>>> > I don't get the point of IPC_PRIVATE of shmget(). Since it is just
>>> > used by the current process, why not just use malloc?
>>> >
>>> > Can anybody give a real example in which IPC_PRIVATE must be used, but
>>> > malloc or other variant of *alloc functions are not appropriate to
>>> > use? Thanks.
>>>
>>> shmget(2) says this:
>>>
>>> | BUGS
>>> | The name choice IPC_PRIVATE was perhaps unfortunate, IPC_NEW
>>> | would more clearly show its function.
>>>
>>> Does this answer your question?
>>
>> No. That is just a naming issue. It is still privately used by the
>> current process instead of other processes.
>
> Oh, it can be shared if the process forks. With malloc, you'd lose the
> sharing.
There is also this part:
| RETURN VALUE
| On success, a valid shared memory identifier is returned. On
| error, -1 is returned, and errno is set to indicate the error.
That is, IPC_PRIVATE provides the identifier for future invocations.
Florian
next prev parent reply other threads:[~2021-04-12 16:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 15:54 Peng Yu
2021-04-12 16:06 ` tomas
2021-04-12 16:07 ` Florian Weimer
2021-04-12 16:12 ` Peng Yu
2021-04-12 16:14 ` Florian Weimer
2021-04-12 16:18 ` Florian Weimer [this message]
2021-04-12 17:23 ` Peng Yu
2021-04-12 18:17 ` J Lumby
2021-04-12 17:55 ` Manfred
2021-04-12 19:05 ` Peng Yu
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