From: Tanaka Akira <akr@...>
Date: 2007-06-25T16:08:04+09:00
Subject: [ruby-dev:31046] Conditional jump or move depends on uninitialised value(s) in TOPLEVEL_BINDING

valgrind をかけたところとりあえず最初のが

==32482== Conditional jump or move depends on uninitialised value(s)
==32482==    at 0x80E1880: th_make_env_each (vm.c:255)
==32482==    by 0x80E1DDF: th_make_env_object (vm.c:413)
==32482==    by 0x805EBE1: rb_binding_new (proc.c:190)
==32482==    by 0x80E93EC: rb_thread_eval (vm.c:1853)
==32482==    by 0x80EB8EE: yarvcore_eval_iseq (yarvcore.c:98)
==32482==    by 0x80EB9E6: yarvcore_eval_parsed (yarvcore.c:130)
==32482==    by 0x80EBA1C: yarvcore_eval (yarvcore.c:138)
==32482==    by 0x80F0AA4: Init_Thread (thread.c:2936)
==32482==    by 0x8063D6C: rb_call_inits (inits.c:89)
==32482==    by 0x8059ADD: ruby_init (eval.c:88)
==32482==    by 0x80570A5: main (main.c:48)

だったので調べてみると、

Index: yarvcore.c
===================================================================
--- yarvcore.c	(revision 12610)
+++ yarvcore.c	(working copy)
@@ -328,6 +328,7 @@ th_init2(rb_thread_t *th)
 
     /* allocate thread stack */
     th->stack = ALLOC_N(VALUE, RUBY_VM_THREAD_STACK_SIZE);
+    int i; for (i = 0; i < RUBY_VM_THREAD_STACK_SIZE; i++) th->stack[i] = Qundef;
 
     th->stack_size = RUBY_VM_THREAD_STACK_SIZE;
     th->cfp = (void *)(th->stack + th->stack_size);

というように初期化されていないメモリをとある値に設定すると次
のように SEGV するようです。

% ./ruby -ve 'p eval("a", TOPLEVEL_BINDING)'
ruby 1.9.0 (2007-06-25 patchlevel 0) [i686-linux]
-e:1: -- control frame ----------
c:0004 p:---- s:0011 b:0011 l:000010 d:000010 CFUNC  :eval
c:0003 p:0017 s:0006 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 ------ :(null)
---------------------------
DBG> : "-e:1:in `<main>'"
-- backtrace of native function call (Use addr2line) --
0x80da515
0x80f3740
0x80b2510
0xb7fe8420
0x805b2f5
0x80d133e
0x80d8ec9
0x80d4d90
0x80d8064
0x80d8459
0x8059062
0x8059086
0x805d611
0x8056d38
0xb7e51ea8
0x8056c51
-------------------------------------------------------
[BUG] Segmentation fault
ruby 1.9.0 (2007-06-25) [i686-linux]
-- 
[田中 哲][たなか あきら][Tanaka Akira]