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Date: Tue, 2 Mar 2004 14:02:29 -0600 (CST)
From: Brian Ford <ford@vss.fsi.com>
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To: Claude.Barrouil@onera.fr
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Subject: Re: problem linking SHM functions
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I'm digging out of my list backlog, and I noticed you didn't get a reply.
So, this is just in case you haven't figured it out yet.

On Wed, 14 Jan 2004 Claude.Barrouil@onera.fr wrote:

> I have a program that uses shared memory functions shmget() and shmat() and
> that works fine under Linux.
>
> My problem is that I couldn't find how to link it with Cygwin, although I
> installed le last full package, cygwin1.dll is in the PATH, any other
> compilations and linkages works fine.
>
> All the info I could find is the thread starting at
> http://www.cygwin.com/ml/cygwin/2002-08/msg01296.html, and the links to
> cygipc and cygserver. But this info does not address this (supposed to be
> trivial) linkage problem.
>
> Where is the relevant info ?
>
At the time you wrote this, your best option was cygipc.  You could have
read: /usr/share/doc/Cygwin/cygipc-*.README for details

Five days later, cygwin-1.5.6 was released with System V shm, sem, msg
handling in cygserver.  It then became the prefered option.  But,
cygserver and the documentation was accidentally left out of that release.

On the last day of January, cygwin-1.5.7 was released and included the
missing files.  See /usr/share/doc/Cygwin/cygserver.README for details.

Finally, on February 09, cygipc was updated to happily cooexist with the
cygserver implementation.

</end history lesson>

So, get Cygwin 1.5.7 or newer and read its docs listed above.

> Thanks,
> Claude Barrouil
>
> --------------- the relevant part of the codee -----------------
> ...
> #include <cygwin/shm.h>
> ...
> ShmId = shmget(ShmKey, ShmSiz, 0666)
> ...
> SharedData = shmat(ShmId,NULL,0)
> ...
> --------------- the linkage failure-----------------------------
> gcc  myprog.c -lm -o myprog.exe
> {}/Temp/ccj8s9oV.o(.text+0x67):myprog.c: undefined reference to `_shmget'
> {}/Temp/ccj8s9oV.o(.text+0xa3):myprog.c: undefined reference to `_shmat'
> collect2: ld returned 1 exit status
> ---------------- the end ---------------------------------------
>

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
Phone: 314-551-8460
Fax:   314-551-8444

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