Re: Emacs20 and mail file locking.

[Rob Browning <rlb@cs.utexas.edu>]

karlheg@bittersweet.inetarena.com (Karl M. Hegbloom) writes:

>  I volunteer to try rolling those patches into XEmacs 20.5.  I think
>  that configure ought to detect `liblockfile' and compile `movemail'
>  accordingly.  Sound right?

Sounds good, but perhaps it should just fail to build on a debian
system if liblockfile-dev's not installed.  Otherwise, without source
dependencies, it would be easy for a non-maintainer release (if there
ever is one) to be built broken, such that mail could be lost.  Given
this possibility, messing with configure might be overkill.  Just hard
code the -llockfile, and be done with it.

I guess you could go so far as to have a configure option that forces
the use of liblockfile, and then put that in the rules file, but that
may be more trouble than it's worth.

In any case, let me know how it goes.  I'd like to be able to steal
your work for incorporation into the emacs 20 package, if possible.

>     Rob> I'm under the impression that liblockfile handles everything,
>     Rob> including nfs.  I believe libnfslock is transitional, for use
>     Rob> until everything's migrated to liblockfile.
> 
>  Yes, that seems right... I looked them over once a few months ago.  I
>  think after I've finished reading the two W. Richard Stevens Unix
>  programming books I've just begun, I will go over them again with
>  better understanding, and thus, better recollection.

I don't think you even need to go that far; if the man page is to be
believed, NFS is handled by liblockfile:

    DESCRIPTION
       The maillock function tries to create a lockfile  for  the
       users  mailbox.  This  mailbox  is  typically  located  in
       /var/spool/mail.  The name of the  lockfile  then  becomes
       /var/spool/mail/username.lock.   Maillock uses an NFS safe
       algorithm that is documented in lockfile_create(3).

-- 
Rob Browning <rlb@cs.utexas.edu>
PGP fingerprint = E8 0E 0D 04 F5 21 A0 94  53 2B 97 F5 D6 4E 39 30


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