次のようにすると core を吐きます。

% ./ruby -e '
r, w = IO.pipe
str = ""
Thread.new { Thread.pass; str.replace ""; w << "a" * 4096 }
r.read(4096, str)
p str
'
816885936
-e:6: [BUG] Segmentation fault
ruby 1.9.0 (2004-09-27) [i686-linux]

-e:6: [BUG] Segmentation fault
ruby 1.9.0 (2004-09-27) [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 
r, w = IO.pipe
str = ""
Thread.new { Thread.pass; str.replace ""; w'.
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  0x4009e721 in kill () from /lib/libc.so.6
(gdb) bt
#0  0x4009e721 in kill () from /lib/libc.so.6
#1  0x4009e4c5 in raise () from /lib/libc.so.6
#2  0x4009f9e8 in abort () from /lib/libc.so.6
#3  0x080d1e46 in rb_bug (fmt=0x0) at error.c:214
#4  0x080afeb2 in sigsegv (sig=11) at signal.c:446
#5  <signal handler called>
#6  0x400e1aee in _IO_adjust_column () from /lib/libc.so.6
#7  0x4009fa38 in abort () from /lib/libc.so.6
#8  0x080d1e46 in rb_bug (fmt=0x2 <Address 0x2 out of bounds>) at error.c:214
#9  0x080afeb2 in sigsegv (sig=11) at signal.c:446
#10 <signal handler called>
#11 0x0806645c in rb_thread_schedule () at eval.c:10178
#12 0x08066f85 in rb_thread_fd_writable (fd=1) at eval.c:10412
#13 0x080755fe in io_fflush (f=0x4019df60, fptr=0x812dd00) at io.c:322
#14 0x080759cd in rb_io_flush (io=1075634136) at io.c:539
#15 0x080799c3 in rb_f_p (argc=1, argv=0xbffff158) at io.c:3780
#16 0x08069f2a in call_cfunc (func=0x8079970 <rb_f_p>, recv=1075673496, len=0, argc=0, argv=0xbffff158) at eval.c:5368
#17 0x0805e147 in rb_call0 (klass=1075678376, recv=1075673496, id=7417, oid=0, argc=1, argv=0xbffff158, body=0x401cea3c, 
    nosuper=0) at eval.c:5509
#18 0x0805e3f8 in rb_call (klass=1075678376, recv=1075673496, mid=7417, argc=1, argv=0xbffff158, scope=1) at eval.c:5730
#19 0x08059328 in rb_eval (self=1075673496, n=0x0) at ruby.h:635
#20 0x080558bb in ruby_exec () at eval.c:1458
#21 0x08055900 in ruby_run () at eval.c:1484
#22 0x080539c5 in main (argc=0, argv=0x0, envp=0xbffff934) at main.c:38
(gdb) 

# [BUG] Segmentation fault がふたつ出るのははじめて見た...
-- 
[田中 哲][たなか あきら][Tanaka Akira]