make test-all すると core を吐くようです。

% make test-all
./miniruby ./runruby.rb --extout=.ext -- -C "./test" runner.rb --runner=console 
Loaded suite .
Started
.............................................................................................................................................................................................../tmp/z/ruby/lib/drb/drb.rb:907: [BUG] Segmentation fault
ruby 1.9.0 (2004-07-31) [i686-linux]

EEEEEEEEEEEEEE/tmp/z/ruby/lib/drb/drb.rb:907: [BUG] Segmentation fault
ruby 1.9.0 (2004-07-31) [i686-linux]

E/tmp/z/ruby/lib/drb/extservm.rb:78:in `stop': Interrupt        from /tmp/z/ruby/lib/drb/extservm.rb:78:in `invoke_service'
        from /tmp/z/ruby/lib/drb/extservm.rb:38:in `service'
        from /tmp/z/ruby/test/drb/drbtest.rb:67:in `setup'
        from /tmp/z/ruby/lib/test/unit/testcase.rb:69:in `run'
        from /tmp/z/ruby/lib/test/unit/testsuite.rb:34:in `run'
        from /tmp/z/ruby/lib/test/unit/testsuite.rb:33:in `each'
        from /tmp/z/ruby/lib/test/unit/testsuite.rb:33:in `run'
        from /tmp/z/ruby/lib/test/unit/testsuite.rb:34:in `run'
         ... 8 levels...
        from /tmp/z/ruby/lib/test/unit/ui/testrunnerutilities.rb:29:in `run'
        from /tmp/z/ruby/lib/test/unit/autorunner.rb:185:in `run'
        from /tmp/z/ruby/lib/test/unit/autorunner.rb:13:in `run'
        from runner.rb:8
make: *** [test-all] Error 1

% gdb ruby test/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 `/tmp/z/ruby/ruby /tmp/z/ruby/test/drb/ut_drb.rb druby://serein:41054 ut_drb.rb'.
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 /tmp/z/ruby/.ext/i686-linux/socket.so...done.
Loaded symbols for /tmp/z/ruby/.ext/i686-linux/socket.so
Reading symbols from /tmp/z/ruby/.ext/i686-linux/fcntl.so...done.
Loaded symbols for /tmp/z/ruby/.ext/i686-linux/fcntl.so
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
#0  0x4009d721 in kill () from /lib/libc.so.6
(gdb) where
#0  0x4009d721 in kill () from /lib/libc.so.6
#1  0x4009d4c5 in raise () from /lib/libc.so.6
#2  0x4009e9e8 in abort () from /lib/libc.so.6
#3  0x080d05d6 in rb_bug (fmt=0x0) at error.c:214
#4  0x080aee42 in sigsegv (sig=11) at signal.c:446
#5  <signal handler called>
#6  is_defined (self=1076044024, node=0x401b88e4, buf=0xbfff8b00 "\003", noeval=0) at ruby.h:664
#7  0x0805aa49 in rb_eval (self=1076044024, n=0x70000) at eval.c:3875
#8  0x08057eac in rb_eval (self=1076044024, n=0x70000) at eval.c:2775
#9  0x0805dd1b in rb_call0 (klass=1076065644, recv=1076044024, id=11241, oid=458752, argc=0, argv=0xbfff98cc, 
    body=0x401b88a8, nosuper=0) at eval.c:5658
#10 0x0805e4b8 in rb_call (klass=1076065644, recv=1076044024, mid=11241, argc=1, argv=0xbfff98c8, scope=1) at eval.c:5751
#11 0x080593f8 in rb_eval (self=1076044024, n=0x70000) at ruby.h:634
#12 0x0805dd1b in rb_call0 (klass=1076065644, recv=1076044024, id=2969, oid=458752, argc=0, argv=0xbfffa394, 
    body=0x401b9f50, nosuper=0) at eval.c:5658
#13 0x0805e4b8 in rb_call (klass=1076065644, recv=1076044024, mid=2969, argc=3, argv=0xbfffa388, scope=1) at eval.c:5751
#14 0x0805e8da in rb_funcall2 (recv=0, mid=458752, argc=458752, argv=0x70000) at ruby.h:634
#15 0x08061078 in rb_obj_call_init (obj=458752, argc=458752, argv=0x70000) at eval.c:7170
#16 0x08086a5c in rb_class_new_instance (argc=458752, argv=0x70000, klass=458752) at object.c:1540
#17 0x08069e8a in call_cfunc (func=0x8086a30 <rb_class_new_instance>, recv=1076065644, len=0, argc=-1073772600, 
    argv=0xbfffa388) at eval.c:5390
#18 0x0805e207 in rb_call0 (klass=1075674360, recv=1076065644, id=3377, oid=458752, argc=3, argv=0xbfffa388, 
    body=0x401d6ac4, nosuper=0) at eval.c:5530
#19 0x0805e4b8 in rb_call (klass=1075674360, recv=1076065644, mid=3377, argc=3, argv=0xbfffa388, scope=0) at eval.c:5751
#20 0x080593f8 in rb_eval (self=1076065644, n=0x70000) at ruby.h:634
#21 0x0805dd1b in rb_call0 (klass=1076065284, recv=1076065644, id=11089, oid=458752, argc=0, argv=0xbfffabe0, 
    body=0x401ba9c8, nosuper=0) at eval.c:5658
#22 0x0805e4b8 in rb_call (klass=1076065284, recv=1076065644, mid=11089, argc=2, argv=0xbfffabd8, scope=0) at eval.c:5751
#23 0x080593f8 in rb_eval (self=1076065984, n=0x70000) at ruby.h:634
#24 0x0805aec5 in rb_eval (self=1076065984, n=0x70000) at eval.c:3172
#25 0x08058a8a in rb_eval (self=1076065984, n=0x70000) at eval.c:3035
#26 0x0805c283 in rb_yield_0 (val=1076065644, self=1076065984, klass=1075561980, flags=0, avalue=0) at eval.c:4731
#27 0x0805c769 in rb_yield (val=458752) at eval.c:4813
#28 0x080c389f in rb_ary_each (ary=1076064544) at array.c:1224
#29 0x08069e91 in call_cfunc (func=0x80c3870 <rb_ary_each>, recv=1076064544, len=0, argc=-1073772600, argv=0x0)
    at eval.c:5393
#30 0x0805e207 in rb_call0 (klass=1075643680, recv=1076064544, id=3873, oid=458752, argc=0, argv=0x0, body=0x401d00fc, 
    nosuper=0) at eval.c:5530
#31 0x0805e4b8 in rb_call (klass=1075643680, recv=1076064544, mid=3873, argc=0, argv=0x0, scope=0) at eval.c:5751
---Type <return> to continue, or q <return> to quit---
#32 0x080593f8 in rb_eval (self=1076065984, n=0x70000) at ruby.h:634
#33 0x080587a8 in rb_eval (self=1076065984, n=0x70000) at eval.c:2948
#34 0x0805dd1b in rb_call0 (klass=1076065564, recv=1076065984, id=11089, oid=458752, argc=0, argv=0xbfffd130, 
    body=0x401bc354, nosuper=0) at eval.c:5658
#35 0x0805e4b8 in rb_call (klass=1076065564, recv=1076065984, mid=11089, argc=2, argv=0xbfffd128, scope=0) at eval.c:5751
#36 0x080593f8 in rb_eval (self=1076044404, n=0x70000) at ruby.h:634
#37 0x08058d5c in rb_eval (self=1076044404, n=0x70000) at eval.c:3418
#38 0x0805dd1b in rb_call0 (klass=1076063704, recv=1076044404, id=2969, oid=458752, argc=0, argv=0xbfffe244, 
    body=0x401b3204, nosuper=0) at eval.c:5658
#39 0x0805e4b8 in rb_call (klass=1076063704, recv=1076044404, mid=2969, argc=3, argv=0xbfffe238, scope=1) at eval.c:5751
#40 0x0805e8da in rb_funcall2 (recv=0, mid=458752, argc=458752, argv=0x70000) at ruby.h:634
#41 0x08061078 in rb_obj_call_init (obj=458752, argc=458752, argv=0x70000) at eval.c:7170
#42 0x08086a5c in rb_class_new_instance (argc=458752, argv=0x70000, klass=458752) at object.c:1540
#43 0x08069e8a in call_cfunc (func=0x8086a30 <rb_class_new_instance>, recv=1076063704, len=0, argc=-1073772600, 
    argv=0xbfffe238) at eval.c:5390
#44 0x0805e207 in rb_call0 (klass=1075674360, recv=1076063704, id=3377, oid=458752, argc=3, argv=0xbfffe238, 
    body=0x401d6ac4, nosuper=0) at eval.c:5530
#45 0x0805e4b8 in rb_call (klass=1075674360, recv=1076063704, mid=3377, argc=3, argv=0xbfffe238, scope=0) at eval.c:5751
#46 0x080593f8 in rb_eval (self=1076067784, n=0x70000) at ruby.h:634
#47 0x08058d5c in rb_eval (self=1076067784, n=0x70000) at eval.c:3418
#48 0x0805dd1b in rb_call0 (klass=1076058564, recv=1076067784, id=10641, oid=458752, argc=0, argv=0xbffff0d0, 
    body=0x401ae240, nosuper=0) at eval.c:5658
#49 0x0805e4b8 in rb_call (klass=1076058564, recv=1076067784, mid=10641, argc=2, argv=0xbffff0c8, scope=0) at eval.c:5751
#50 0x080593f8 in rb_eval (self=1075669400, n=0x70000) at ruby.h:634
#51 0x0805586b in ruby_exec () at eval.c:1459
#52 0x080558b0 in ruby_run () at eval.c:1480
#53 0x08053985 in main (argc=458752, argv=0x70000, envp=0xbffff8e8) at main.c:38
(gdb) 

backtrace にある is_defined というのが、ruby-cvs:12401 および
ruby-cvs:12408 との関係を示唆しているように思われます。
-- 
[田中 哲][たなか あきら][Tanaka Akira]