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Re: bzr emacs( crashes when using auto-revert-tail-mode

On 6/20/2014 10:32 AM, Eli Zaretskii wrote:
Date: Fri, 20 Jun 2014 15:27:14 +0100
From: Ken Brown

Why did you need to step through the Glib code?  AFAIU, the file
monitor did trigger, so what I would first look at is the data it
delivers back to Emacs, not how the monitor works internally.  Did you
try that?

Yes, that's what I tried first.  I get a SEGV right after the call to g_file_monitor:

(gdb) b Fgfile_add_watch
Breakpoint 3 at 0x5f7a3f: file /usr/src/debug/emacs-24.3.91-2/src/gfilenotify.c, line 170.
(gdb) r -Q
Breakpoint 3, Fgfile_add_watch (file=-2146927663, flags=12352654,
     at /usr/src/debug/emacs-24.3.91-2/src/gfilenotify.c:170
170       GFileMonitorFlags gflags = G_FILE_MONITOR_NONE;
(gdb) n
173       CHECK_STRING (file);
(gdb) n
174       file = Fdirectory_file_name (Fexpand_file_name (file, Qnil));
(gdb) n
175       if (NILP (Ffile_exists_p (file)))
(gdb) n
178       CHECK_LIST (flags);
(gdb) n
180       if (!FUNCTIONP (callback))
(gdb) n
184       gfile = g_file_new_for_path (SSDATA (ENCODE_FILE (file)));
(gdb) n
[New Thread 6112.0x974]
[New Thread 6112.0x4c4]
187       if (!NILP (Fmember (Qwatch_mounts, flags)))
(gdb) n
188         gflags |= G_FILE_MONITOR_WATCH_MOUNTS;
(gdb) n
189       if (!NILP (Fmember (Qsend_moved, flags)))
(gdb) n
190         gflags |= G_FILE_MONITOR_SEND_MOVED;
(gdb) n
193       monitor = g_file_monitor (gfile, gflags, NULL, NULL);
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? ()
(gdb) bt full
#0  0x00000000 in ?? ()
No symbol table info available.
#1  0x610f842f in pthread_mutex::lock (this=0x0)
     at /usr/src/debug/cygwin-1.7.30-1/winsup/cygwin/
         self = <optimized out>
         result = <optimized out>
         __PRETTY_FUNCTION__ = "int pthread_mutex::lock()"
#2  0x00000201 in ?? ()
No symbol table info available.

Then I guess rebuilding Glib and pthreads with -O0 -g3 is the way to
go.  the above looks like pthreads tried to lock a mutex for a thread
that was not created correctly, or maybe exited right away.  But
that's a guess, and without debug info it's hard to say something

This turns out to be a Glib/Cygwin bug, having nothing to do with Emacs. I've started a new thread to report this:


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