[ELDK] Posix Shared Memory

[Detlev Zundel]

Hi Daniel and Markus,

> "Daniel Stonier" <d.stonier at gmail.com> writes:
>
>> In your experience, is there any reason to favour SYSV over Posix? We
>> only chose posix keeping in mind that we may wish to port to QNX in the
>> future.
>
> Good question. SYSV is a lot heavier than POSIX shared memory and has
> some features that POSIX hasn't (get number of attached processes).
>
> Nevertheless i would choose the POSIX variant because shared memory
> objects are files that can be addressed through the file system instead
> of their own namespace(ftok, ipcs(1) ...)

The SystemV IPC calls are really going out of use.  The main reason is
that they do not fit into the Unix mind set.  For one, they do not yield
file descriptors that can for example be passed to select (only relevant
for message queues).  The other is that they have _persistent_
ressources, like global variables something one should not use
lightheartedly.

Cheers
  Detlev

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