[Trivial] Add dragonfly implementation for shared memory

[dkgroot]

This one was overlooked (and noticed by @joakim-noah in backporting to ldc-ltsmaster)

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[joakim-noah]

Properly scoped, LGTM.

[wilzbach]

Don't you want to target stable?

[wilzbach]

DStyle: void* (also do you have any resource where it's __shm_internal. I did a quick search, but could only find shm_internal like it's for FreeBSD.

[dkgroot]

On Dfly, /usr/include/sys/shm.h looks like:

struct shmid_ds {
    struct ipc_perm shm_perm;   /* operation permission structure */
    size_t          shm_segsz;  /* size of segment in bytes */
    pid_t           shm_lpid;   /* process ID of last shared memory op */
    pid_t           shm_cpid;   /* process ID of creator */
    shmatt_t    shm_nattch; /* number of current attaches */
    time_t          shm_atime;  /* time of last shmat() */
    time_t          shm_dtime;  /* time of last shmdt() */
    time_t          shm_ctime;  /* time of last change by shmctl() */
    void           *shm_internal;   /* sysv stupidity */
};

Have not looked at the use or implementation of this header file. I did have to gloss over the comment for this pointer (Logically it would be the opaque pointer to an internal representation/expansion for this struct,). But i thought size might matter (doesn't it always).

[wilzbach]

Thanks.
I would suggest to keep the shm_internal name then. You could set it to private though?

But i thought size might matter

Yes.

[dkgroot]

@wilzbach > Don't you want to target stable?
Sorry i don't understand, what do you mean ?

[wilzbach]

Sorry i don't understand, what do you mean ?

The master -> stable branch-off already happened. If you target stable, it will be part of the 2.079 tag.

[wilzbach]

For reference, when retargeting a PR to stable it needs to be rebased locally too:

git rebase --onto upstream/stable upstream/master

Also if you depend on this in master, you can simply run merge_stable yourself and get the changes back into master.

[wilzbach]

FYI: I squashed your PR + fixed the DStyle (void* not void *)

[dkgroot]

Thanks @wilzbach / @joakim-noah