Re: What is the point of IPC_PRIVATE of shmget?

[Manfred <mx2927@gmail.com>]

On 4/12/2021 6:14 PM, Florian Weimer via Libc-help wrote:
> * 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.

Out of curiosity,
Does it need to fork? Can the identifier be shared in some other way?

Thanks,
Manfred

> 
> Thanks,
> Florian
>