次のようにすると core を吐きます。

% ./ruby -rsocket -e '
s = UDPSocket.new
host = Object.new
class << host; self end.send(:define_method, :to_str) {
  s.close
  "127.0.0.1"
}
s.connect(host, 1)
'
-e:8: [BUG] Segmentation fault
ruby 1.9.0 (2004-12-04) [i686-linux]

zsh: abort (core dumped)  ./ruby -rsocket -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 -rsocket -e 
s = UDPSocket.new
host = Object.new
class << host; self end'.
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
Reading symbols from /home/akr/ruby/head-ruby/lib/ruby/1.9/i686-linux/socket.so...done.
Loaded symbols for /home/akr/ruby/head-ruby/lib/ruby/1.9/i686-linux/socket.so
#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  0x080d5ba6 in rb_bug (fmt=0x0) at error.c:214
#4  0x080b2c12 in sigsegv (sig=11) at signal.c:446
#5  <signal handler called>
#6  0x400db426 in fileno_unlocked () from /lib/libc.so.6
#7  0x4001c843 in udp_connect (sock=0, host=0, port=0) at socket.c:1467
#8  0x0806ad1a in call_cfunc (func=0x4001c7e0 <udp_connect>, recv=1075604776, len=135544840, argc=1075439996, 
    argv=0xbffff118) at eval.c:5404
#9  0x0805ea32 in rb_call0 (klass=1075607376, recv=1075604776, id=10617, oid=0, argc=2, argv=0xbffff118, body=0x401c7700, 
    nosuper=0) at eval.c:5545
#10 0x0805ecf8 in rb_call (klass=1075607376, recv=1075604776, mid=10617, argc=2, argv=0xbffff118, scope=0) at eval.c:5767
#11 0x080598ba in rb_eval (self=1075673536, n=0x0) at ruby.h:635
#12 0x08055e8d in ruby_exec_internal () at eval.c:1470
#13 0x08055ea6 in ruby_exec () at eval.c:1488
#14 0x08055ef0 in ruby_run () at eval.c:1505
#15 0x08053ef5 in main (argc=0, argv=0x0, envp=0xbffff8f8) at main.c:38
(gdb) 
-- 
[田中 哲][たなか あきら][Tanaka Akira]