こんばんは、sheepman です。
以下のクラスのいずれかを dup すると core を吐きます。

 YARVCore::VM::Binding
 YARVCore::VM::Proc
 YARVCore::VM::Env
 YARVCore::VM::Thread
 YARVCore::VM
 UnboundMethod
 Method
 Process::Status
 MatchData
 Struct
 Float
 Integer
 FalseClass
 TrueClass
 Data
 Symbol
 NilClass
 Class

$ ruby-2.0 -ve 'Class.dup'
ruby 2.0.0 (Base: Ruby 1.9.0 2006-04-08) [i686-linux]
YARVCore 0.4.1 Rev: 527 (2006-07-19) [opts: [direct threaded code] [inline method cache] ]
-- stack frame ------------
0000 (0x402b3008): 00000004
0001 (0x402b300c): 00000005
0002 (0x402b3010): 00000004
0003 (0x402b3014): 00000001
0004 (0x402b3018): 402b2d1c
0005 (0x402b301c): 00000004
0006 (0x402b3020): 00000001
0007 (0x402b3024): 00000004
0008 (0x402b3028): 00000001 <- lfp <- dfp
-- control frame ----------
c:0005 p:---- s:0009 b:0009 l:000008 d:000008 CFUNC  :initialize_copy
c:0004 p:---- s:0007 b:0007 l:000006 d:000006 CFUNC  :dup
c:0003 p:0013 s:0004 b:0004 l:000003 d:000003 TOP    -e:1
c:0002 p:---- s:0002 b:0002 l:000001 d:000001 FINISH
c:0001 p:---- s:0000 b:-001 l:000000 d:000000 ------
---------------------------
DBG> : "-e:1:in `dup'"
DBG> : "-e:1:in `<main>'"
[BUG] Segmentation fault
ruby 2.0.0 (2006-04-08) [i686-linux]

zsh: abort      ruby-2.0 -ve 'Class.dup'

$ ruby-2.0 -ve 'MatchData.dup'
ruby 2.0.0 (Base: Ruby 1.9.0 2006-04-08) [i686-linux]
YARVCore 0.4.1 Rev: 527 (2006-07-19) [opts: [direct threaded code] [inline method cache] ]
-- stack frame ------------
0000 (0x402b3008): 00000004
0001 (0x402b300c): 00000005
0002 (0x402b3010): 00000004
0003 (0x402b3014): 00000001
0004 (0x402b3018): 402a6bd4
0005 (0x402b301c): 00000004
0006 (0x402b3020): 00000001
0007 (0x402b3024): 00000004
0008 (0x402b3028): 00000001 <- lfp <- dfp
-- control frame ----------
c:0005 p:---- s:0009 b:0009 l:000008 d:000008 CFUNC  :initialize_copy
c:0004 p:---- s:0007 b:0007 l:000006 d:000006 CFUNC  :dup
c:0003 p:0013 s:0004 b:0004 l:000003 d:000003 TOP    -e:1
c:0002 p:---- s:0002 b:0002 l:000001 d:000001 FINISH
c:0001 p:---- s:0000 b:-001 l:000000 d:000000 ------
---------------------------
DBG> : "-e:1:in `dup'"
DBG> : "-e:1:in `<main>'"
[BUG] Segmentation fault
ruby 2.0.0 (2006-04-08) [i686-linux]

zsh: abort      ruby-2.0 -ve 'MatchData.dup'


-- 
sheepman / TAMURA Takashi
sheepman sheepman.sakura.ne.jp 

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