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Date: Sun, 2 Jun 2013 12:31:25 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: sqlite3: bug with monotone
Message-ID: <20130602103125.GE13934@calimero.vinschen.de>
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References: <51A6B6EB.6050309@users.sourceforge.net> <loom.20130530T122354-144@post.gmane.org> <51A7862F.1070507@etr-usa.com> <51A7D47E.3050502@users.sourceforge.net> <51A7F547.6020509@etr-usa.com> <20130531092228.GB30659@calimero.vinschen.de> <51A900EF.2020606@etr-usa.com> <20130601105741.GC30659@calimero.vinschen.de>
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User-Agent: Mutt/1.5.21 (2010-09-15)

Hi Warren,

On Jun  1 12:57, Corinna Vinschen wrote:
> If F_MDLCK is not such a bright idea, maybe another fcntl is?  Something
> along these lines:
> 
>     fd = open ("my.db", ...);
>   #ifdef __CYGWIN__
>     fcntl (fd, F_SETLK_MAND, 1);
>   #endif
> 
> As for the user, we could add the g+S,g-x stuff additionally at one point,
> but I'm rather reluctant to provide these means at all.  See below.
> [...]
> There's a lot to recommend not using mandatory locking at all, unless in
> very limited circumstances where interoperability with native
> applications using mandatory locking is required. [...]

I just applied a patch to implement mandatory locking.  It also supports
F_GETLK, with limited usability due to Windows restrictions, as I
explained in other mail.  It does NOT yet support BSD flock locking,
only POSIX fcntl locking.

I dropped the F_MDLCK idea. Instead I implemented a specific fcntl code
to switch to mandatory locking on a file descriptor:

  fcntl (fd, F_LCK_MANDATORY, 1);

The name F_SETLK_MAND didn't seem right.  Anyway, afterwards, you can
use the usual locking fcntls, but with Windows mandatory locking
semantics.

I didn't add a way for the user to switch on mandatory locking for now,
and I don't intend to do that for 1.7.19.  Hope that helps, nevertheless.

I'm just about to generate a 2013-06-02 developer snapshot for 32 bit,
a 64 bit DLL will follow tomorrow.

Please give the 32 bit snapshot a try ASAP.  I intend to release 1.7.19
very soon, probably tomorrow or Tuesday.


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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