斎藤と申します。

自分自身の評価結果を返すメソッドを呼ぶとcoreを吐くようです。

$ ruby-trunk -ve 'def a; a; end; a'
ruby 1.9.0 (2007-12-07 patchlevel 0) [i686-linux]
-e:1: -- control frame ----------
c:7710 p:0007 s:23127 b:23126 l:003125 d:003125 METHOD -e:1
c:7709 p:0007 s:23123 b:23123 l:003122 d:003122 METHOD -e:1
c:7708 p:0007 s:23120 b:23120 l:003119 d:003119 METHOD -e:1
c:7707 p:0007 s:23117 b:23117 l:003116 d:003116 METHOD -e:1
c:7706 p:0007 s:23114 b:23114 l:003113 d:003113 METHOD -e:1
c:7705 p:0007 s:23111 b:23111 l:003110 d:003110 METHOD -e:1
(snip)
c:0009 p:0007 s:0023 b:0023 l:000022 d:000022 METHOD -e:1
c:0008 p:0007 s:0020 b:0020 l:000019 d:000019 METHOD -e:1
c:0007 p:0007 s:0017 b:0017 l:000016 d:000016 METHOD -e:1
c:0006 p:0007 s:0014 b:0014 l:000013 d:000013 METHOD -e:1
c:0005 p:0007 s:0011 b:0011 l:000010 d:000010 METHOD -e:1
c:0004 p:0007 s:0008 b:0008 l:000007 d:000007 METHOD -e:1
c:0003 p:0012 s:0005 b:0005 l:000004 d:000004 TOP    -e:1
c:0002 p:---- s:0003 b:0003 l:000002 d:000002 FINISH :inherited
c:0001 p:---- s:0001 b:-001 l:000000 d:000000 ------
---------------------------
DBG> : "-e:1:in `a'"
DBG> : "-e:1:in `a'"
DBG> : "-e:1:in `a'"
(snip)
DBG> : "-e:1:in `a'"
DBG> : "-e:1:in `a'"
DBG> : "-e:1:in `<main>'"
-- backtrace of native function call (Use addr2line) --
0xb7ece4f7
0xb7e17eb5
0xb7e17f99
0xb7e2ce2f
0xb7ec2e7d
0xb7e2ce3e
0xb7ec2dfd
0xb7e92d5f
0xb7ec31fd
0xb7e2ce3e
0xb7e2d720
0xb7e2e0c5
0xb7e98942
0xb7e989ed
0xb7e8f217
0xb7e90057
0xb7ec4162
0xb7e1a6b6
0xb7e1e107
0xb7e1e233
0xb7ec5ce9
0xb7ec8ee1
0xb7eccb91
0xb7eccf10
0xb7e1b80b
0xb7e2011a
0x80486ce
0xb7c41ea8
0x80485e1
-------------------------------------------------------
[BUG] rb_gc_mark(): unknown data type 0x18(0xb7bc0968) non object
ruby 1.9.0 (2007-12-07) [i686-linux]


また、無限ループのつもりでカウントすると、falseに化けました。


$ ruby-trunk -ve '$i=0; def a; p $i += 1; a; end; a'
ruby 1.9.0 (2007-12-07 patchlevel 0) [i686-linux]
1
2
3
(snip)
7704
7705
7706
false
-e:1: -- control frame ----------
c:7710 p:-33706527 s:302957567 b:23126 l:003125 d:003125 METHOD -e:1
c:7709 p:0023 s:23123 b:23123 l:003122 d:003122 METHOD -e:1
c:7708 p:0023 s:23120 b:23120 l:003119 d:003119 METHOD -e:1
c:7707 p:0023 s:23117 b:23117 l:003116 d:003116 METHOD -e:1
c:7706 p:0023 s:23114 b:23114 l:003113 d:003113 METHOD -e:1
c:7705 p:0023 s:23111 b:23111 l:003110 d:003110 METHOD -e:1
c:7704 p:0023 s:23108 b:23108 l:003107 d:003107 METHOD -e:1
(snip)


なお1.8では、SystemStackErrorとなります。

-- 
斎藤ただし