On 19/06/2013 23:39, Yaakov (Cygwin/X) wrote:
There appears to be a bug in the MIT-SHM extension with the 64-bit
xserver; both XWin and Xvfb have manifested this so far. The easiest way to
trigger this is to install gnome-themes-standard, add
gtk-theme-name="Adwaita" to your ~/.gtkrc-2.0, then start a GTK+2 program
(e.g. gtk-demo), but GTK+3 programs also show this. Starting the server
with -extension MIT-SHM, or using a 32-bit server even with MIT-SHM, works
fine.
On 06/07/2013 15:28, Jon TURNEY wrote:
On 06/07/2013 12:46, Ken Brown wrote:
On 64bit Cygwin, if I try to run emacs under X11 while cygserver is running,
emacs fails to connect to the X server. The error message from the X server is
BadShmSeg (invalid shared segment parameter) on protocol request 131
To reproduce:
1. Install the current version of emacs-X11 (24.3-4).
2. Start the (64bit) cygserver service.
3. Start the (64bit) X server, e.g., by typing "startxwin" in a Cygwin Terminal.
4. In the resulting xterm, try to start emacs:
$ emacs-X11.exe -Q &
The result is that emacs displays the error message above and then aborts.
emacs-X11 works fine if the X server is started when cygserver is not running.
Yup, there's some kind of bug which affects SHM use by the X server on 64bit.
I am looking into it.
You can also work around this by starting the X server with '-extension MIT-SHM'
After going around in circles on this a few times, this is what I now think I
know:
The proximate cause of this error is that the x86_64 libcairo2 package appears
to be built with IPC_RMID_DEFERRED_RELEASE defined, which should only happen
on systems which allow processes to shmat() to a shared memory segment which
has already been marked for deletion with shmctl(IPC_RMID) (A non-portable
Linux behaviour)
(This behaviour can be turned on in cygwin by setting the
'kern.ipc.shm_allow_removed' to 'yes' in /etc/cygserver.conf, so that is also
a work around)
Attached is the configure test extracted from cairo, which for some reason
functions incorrectly on x86_64.
$ uname -a
CYGWIN_NT-5.1 byron 1.7.20(0.266/5/3) 2013-06-07 11:11 i686 Cygwin
$ ./shmtest ; echo $?
1
$ uname -a
CYGWIN_NT-6.1 allegra 1.7.21(0.267/5/3) 2013-07-15 13:50 x86_64 Cygwin
$ ./shmtest ; echo $?
0