次のようにすると core を吐きます。

% ./ruby -e '
d = Dir.new("/")
pos = Object.new
class << pos; self end.send(:define_method, :to_int) {
  d.instance_eval { initialize "/zzz" rescue nil }
  0
}
d.seek(pos)
'
-e:8: [BUG] Segmentation fault
ruby 1.9.0 (2004-11-21) [i686-linux]

zsh: abort (core dumped)  ./ruby -e 
% gdb ruby core 
GNU gdb 6.1-debian
Copyright 2004 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 "i386-linux"...Using host libthread_db library "/lib/libthread_db.so.1".

Core was generated by `./ruby -e 
d = Dir.new("/")
pos = Object.new
class << pos; self end.send(:defin'.
Program terminated with signal 6, Aborted.
Reading symbols from /lib/libdl.so.2...done.
Loaded symbols for /lib/libdl.so.2
Reading symbols from /lib/libcrypt.so.1...done.
Loaded symbols for /lib/libcrypt.so.1
Reading symbols from /lib/libm.so.6...done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /lib/libc.so.6...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
#0  0x4009e6b1 in kill () from /lib/libc.so.6
(gdb) bt
#0  0x4009e6b1 in kill () from /lib/libc.so.6
#1  0x4009e435 in raise () from /lib/libc.so.6
#2  0x4009f978 in abort () from /lib/libc.so.6
#3  0x080d55d6 in rb_bug (fmt=0x0) at error.c:214
#4  0x080b2642 in sigsegv (sig=11) at signal.c:446
#5  <signal handler called>
#6  0x40118624 in seekdir () from /lib/libc.so.6
#7  0x080d1e09 in dir_seek (dir=1075463712, pos=0) at dir.c:606
#8  0x0806a902 in call_cfunc (func=0x80d1dc0 <dir_seek>, recv=1075607796, len=0, argc=1075659456, argv=0xbffff118)
    at eval.c:5383
#9  0x0805e872 in rb_call0 (klass=1075626216, recv=1075607796, id=7633, oid=0, argc=1, argv=0xbffff118, body=0x401cbef4, 
    nosuper=0) at eval.c:5527
#10 0x0805eb28 in rb_call (klass=1075626216, recv=1075607796, mid=7633, argc=1, argv=0xbffff118, scope=0) at eval.c:5748
#11 0x080598ea in rb_eval (self=1075673536, n=0x0) at ruby.h:635
#12 0x08055e3d in ruby_exec_internal () at eval.c:1466
#13 0x08055e56 in ruby_exec () at eval.c:1484
#14 0x08055ea0 in ruby_run () at eval.c:1501
#15 0x08053ea5 in main (argc=0, argv=0x0, envp=0xbffff8f4) at main.c:38
(gdb)
-- 
[田中 哲][たなか あきら][Tanaka Akira]