Thanks for the bug report.  

Unfortunately line 186 isn't in the function greeter_item_ulist_setup in the file greeter_item_ulist.c in GDM 2.18 branch.  I'm guessing Ubuntu may be patching the code to change the line number?  Could you give me more information about what specific line is triggering the problem and what is causing the SEGV?  Is it an invalid pointer reference or something?

I'm wondering if this problem might be triggered by a specific configuration that might cause the problem.  Would be useful if you shared the configuration that triggers the problem.

The original bug report doesn't have any useful information besides the stack trace.  No description of when GDM is crashing (does it always crash on startup or when a specific interaction happens).  Can you replicate this problem?  

the corresponding line in the source of the package is "		if (usr->gecos && strcmp (usr->gecos, "") != 0) {", the optimized backtraces are not always accurate on the function names though. I don't get the bug, I'll ask informations to the submitter though

does the user have non-utf8 in their passwd file?

If so, might be a duplicate of bug 426647

More info?  I really need to understand what is going on here to fix this bug.

distribution comment:

"Yep, standard ascii:

$ tr -d ' ().,/:[0-9A-Za-z]-' < /etc/passwd | hexdump -C
00000000 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a 0a |................|
*
00000020 0a 0a 0a 0a 0a 0a 0a 0a |........|
00000028"

No ideas here.  Is there any information in the GDM debug log?  If you set DOING_GDM_DEVELOPMENT=1 and run gdmgreeter from the command line does it crash also?  If so, can you run it in a debugger and see if you can track down what might be triggering this core dump?

also attaching /etc/passwd, /etc/nsswitch.conf, and custom.conf might be useful.

If it's crashing on the line posted, then presumably usr or usr->gecos is NULL (or there is memory corruption) ?

Another bug with a similar backtrace on https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/145037

I've reported this bug on LaunchPad:
  https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/279902
and got directed here. Let's see if I can help.

Both /etc/passwd and /etc/nsswitch.conf are pure ASCII, according to `file`. I don't know what (or where) is custom.conf.

I tried running /usr/lib/gdm/gdmgreeter from the command-line while logged in, but all I get is this warning:
  The greeter version (2.20.8) does not match the daemon version. You have probably just upgraded GDM. Please restart the GDM daemon or the computer.

...but I've just restarted my computer.

Any other hints?

When I try to access the link you provided, I don't have access to view the page, so I'm unsure what problem you are having.  It is normal for /usr/lib/gdm/gdmgreeter to not allow you to run it from the command line.  It is only intended to be run via the GDM daemon.  You can set the environment variable "DOING_GDM_DEVELOPMENT=1" and run gdmgreeter for debug purposes, though this is really just for testing GUI changes.  But it might highlight a problem if there is an issue with the binary starting up (such as a missing library).

I'd recommend turning on debug in the GDM configuration and sharing any GDM-related messages or errors from your system log (/var/log/messages or /var/adm/messages), that might highlight any problems you might be seeing.

> When I try to access the link you provided, I don't have access to view the
page, so I'm unsure what problem you are having.

Sorry, reports in Launchpad seem to default to private. I've opened it.

I ran gdmgreeter in development mode, and other than writing to stdout the username, clicking a user in the list does nothing, and typing a username manually disables the input box when I press Enter (i.e., without getting to the password input). I turned on debug/Enable, but from a quick glance there's nothing interesting in the debug messages. I was suspicious of the extra characters which were appearing in stdout, but after a quick check I found they're actually expected (function greeter_item_ulist_select_user).

I also tried logging off and rebooting a few times to see if I could get a crash with gdm debug enabled, but had no luck. I'll keep it enabled, though.

I'm closing this bug since there hasn't been any feedback since 2008.  If there is still an issue, then please reopen or file a new bug.