次のようにすると core を吐きます。

% ./ruby -e '
name = "A" * 0x20000
S1 = Struct.new(name, :a)
class << $stderr; self end.send(:define_method, :write) {|s|
  name.clear
}
S2 = Struct.new(name, :a)
'
-e:7: [BUG] Segmentation fault
ruby 1.9.0 (2004-12-18) [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 
name = "A" * 0x20000
S1 = Struct.new(name, :a)
class << $stderr; sel'.
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  0x080d5966 in rb_bug (fmt=0x0) at error.c:214
#4  0x080b2922 in sigsegv (sig=11) at signal.c:446
#5  <signal handler called>
#6  strhash (string=0x401d9008 <Address 0x401d9008 out of bounds>) at st.c:563
#7  0x080b5247 in st_lookup (table=0x810e780, key=1075679240, value=0xbfffe7f8) at st.c:258
#8  0x0809aab4 in rb_intern (name=0x401d9008 <Address 0x401d9008 out of bounds>) at parse.y:7912
#9  0x080cfc67 in rb_define_class_under (outer=1075641116, name=0x401d9008 <Address 0x401d9008 out of bounds>, 
    super=1075641116) at class.c:244
#10 0x080bd68b in make_struct (name=1075607756, members=1075607296, klass=1075641116) at struct.c:201
#11 0x080bd92e in rb_struct_s_def (argc=135256872, argv=0x80fdb28, klass=135256872) at struct.c:318
#12 0x0806ae3a in call_cfunc (func=0x80bd8c0 <rb_struct_s_def>, recv=1075641116, len=135325568, argc=1075679240, 
    argv=0xbfffeac8) at eval.c:5418
#13 0x0805eab2 in rb_call0 (klass=1075641096, recv=1075641116, id=3377, oid=135256872, argc=2, argv=0xbfffeac8, 
    body=0x401cfacc, nosuper=0) at eval.c:5559
#14 0x0805ed78 in rb_call (klass=1075641096, recv=1075641116, mid=3377, argc=2, argv=0xbfffeac8, scope=0) at eval.c:5781
#15 0x0805989a in rb_eval (self=1075673536, n=0x80fdb28) at ruby.h:635
#16 0x08059235 in rb_eval (self=1075673536, n=0x80fdb28) at eval.c:3405
#17 0x08055e6d in ruby_exec_internal () at eval.c:1470
#18 0x08055e86 in ruby_exec () at eval.c:1488
#19 0x08055ed0 in ruby_run () at eval.c:1505
#20 0x08053ed5 in main (argc=135256872, argv=0x80fdb28, envp=0xbffff8f4) at main.c:38
(gdb) 
-- 
[田中 哲][たなか あきら][Tanaka Akira]