Re: VM crashes on big INBOX file ==> problem found!!!

[Baoqiu.Cui@yahoo.com]

Baoqiu.Cui@yahoo.com writes:

> Reiner Steib <reinersteib+from-uce@imap.cc> writes:
>
>>>>I also tried splitting this big folder into two (one with 44MB and
>>>>one with 35MB), and VM can also crash on the small ones sometimes.
>>
>> Please clarify if *Emacs* or *VM* crashes.  (What to you mean by
>> "crash"?)
>
> It is Emacs that crashes...  Everything is gone except a line of
> "Segmentation fault    emacs" on the console.  I can easily recreate
> this using the 79MB folder.

OK.  After running GDB on Emacs, I finally found the real cause for the
crash.  The problem is that, when VM is visiting the huge 79MB folder,
garbage collection is triggered and function mark_object() (in alloc.c)
is recursively called about 29,885 times (see the backtrace info
below)!!!  So many levels of mark_object() calls make the stack
overflow, causing a segmentation fault.

Since I am running Emacs on Cygwin, I had to change the following line
in src/Makefile

  LD=$(CC) -Wl,--image-base,0x20000000

to

  LD=$(CC) -Wl,--image-base,0x20000000,--stack,8000000

to increase the stack limit to ~8MB and have the problem resolved.
After making this change and rebuilding Emacs, now I am able to read the
huge folder without any problem.

I hope Emacs can do a better job in adjusting the stack limit, or at
least add some document in etc/PROBLEMS.

Here is the backtrace information before Emacs crashes:
------------------------------------------------------------------------
Current directory is ~/tmp/emacs-22.1/src/
GNU gdb 6.5.50.20060706-cvs (cygwin-special)
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i686-pc-cygwin"...
DISPLAY = localhost:0.0
TERM = dumb
Breakpoint 1 at 0x2009ff96: file emacs.c, line 431.
Breakpoint 2 at 0x200b9ed9: file sysdep.c, line 1385.
(gdb) r
Starting program: /cygdrive/c/tmp/emacs-22.1/src/emacs.exe -geometry 80x40+0+0
Loaded symbols for /cygdrive/c/WINDOWS/system32/ntdll.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/kernel32.dll
Loaded symbols for /usr/bin/cygncurses-8.dll
Loaded symbols for /usr/bin/cygwin1.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/advapi32.dll
Loaded symbols for /cygdrive/c/WINDOWS/system32/rpcrt4.dll
Loaded symbols for /usr/bin/cygjpeg-62.dll
Loaded symbols for /usr/bin/cygpng12.dll
Loaded symbols for /usr/bin/cygz.dll
Loaded symbols for /usr/bin/cygtiff-5.dll
Loaded symbols for /usr/bin/cygungif-4.dll
Loaded symbols for /usr/X11R6/bin/cygX11-6.dll
Loaded symbols for /usr/X11R6/bin/cygICE-6.dll
Loaded symbols for /usr/X11R6/bin/cygSM-6.dll
Loaded symbols for /usr/X11R6/bin/cygXaw3d-7.dll
Loaded symbols for /usr/X11R6/bin/cygXext-6.dll
Loaded symbols for /usr/X11R6/bin/cygXmu-6.dll
Loaded symbols for /usr/X11R6/bin/cygXt-6.dll
Loaded symbols for /usr/X11R6/bin/cygXpm-4.dll

Breakpoint 3 at 0x20080c86: file xterm.c, line 7861.

Program received signal SIGSEGV, Segmentation fault.
mark_object (arg=567788100) at alloc.c:5700
5700		    mark_object (ptr->contents[i]);
(gdb) where
#0  mark_object (arg=567788100) at alloc.c:5700
#1  0x200f4c9d in mark_object (arg=567788132) at alloc.c:5700
#2  0x200f4707 in mark_object (arg=564785749) at alloc.c:5825
#3  0x200f4883 in mark_object (arg=567803073) at alloc.c:5712
#4  0x200f4c9d in mark_object (arg=567807364) at alloc.c:5700
#5  0x200f4c9d in mark_object (arg=567788036) at alloc.c:5700
#6  0x200f4707 in mark_object (arg=564785805) at alloc.c:5825
#7  0x200f4883 in mark_object (arg=567803145) at alloc.c:5712
#8  0x200f4c9d in mark_object (arg=567807236) at alloc.c:5700
#9  0x200f4c9d in mark_object (arg=567787940) at alloc.c:5700
#10 0x200f4707 in mark_object (arg=564785861) at alloc.c:5825
#11 0x200f4883 in mark_object (arg=567803217) at alloc.c:5712
#12 0x200f4c9d in mark_object (arg=567807108) at alloc.c:5700
#13 0x200f4c9d in mark_object (arg=567787844) at alloc.c:5700
#14 0x200f4707 in mark_object (arg=564785917) at alloc.c:5825
#15 0x200f4883 in mark_object (arg=567803289) at alloc.c:5712
#16 0x200f4c9d in mark_object (arg=567806980) at alloc.c:5700
#17 0x200f4c9d in mark_object (arg=567787748) at alloc.c:5700
#18 0x200f4707 in mark_object (arg=564785973) at alloc.c:5825
#19 0x200f4883 in mark_object (arg=567803361) at alloc.c:5712
#20 0x200f4c9d in mark_object (arg=567806852) at alloc.c:5700
#21 0x200f4c9d in mark_object (arg=567787652) at alloc.c:5700

...

#29884 0x200f4707 in mark_object (arg=560521157) at alloc.c:5825
#29885 0x200f4899 in mark_object (arg=565795341) at alloc.c:5714
#29886 0x20145e0d in traverse_intervals_noorder (tree=0x21a518c4, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:218
#29887 0x20145e36 in traverse_intervals_noorder (tree=0x21a518e0, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
#29888 0x20145e36 in traverse_intervals_noorder (tree=0x21b9c8c4, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
#29889 0x20145e36 in traverse_intervals_noorder (tree=0x21b9d380, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
#29890 0x20145e36 in traverse_intervals_noorder (tree=0x21ba0588, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
#29891 0x20145e36 in traverse_intervals_noorder (tree=0x21bbf534, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
#29892 0x20145e36 in traverse_intervals_noorder (tree=0x21bce4fc, 
    function=0x200f4d80 <mark_interval>, arg=539875329) at intervals.c:223
Debugger finished
------------------------------------------------------------------------

Thanks to all of you for the help!

Regards,
Baoqiu