なかだです。

Procは$SAFEを保存しますが、呼び出し側よりも低いレベルに戻すこと
ができるのは危険ではないかといわれました。
説得力のある意見ではないかと思うのですが、どうでしょうか。


Index: eval.c
===================================================================
RCS file: /pub/cvs/ruby/src/ruby/eval.c,v
retrieving revision 1.673
diff -U2 -p -d -r1.673 eval.c
--- eval.c	22 Jun 2004 14:59:25 -0000	1.673
+++ eval.c	25 Jun 2004 01:35:41 -0000
@@ -7900,10 +7900,15 @@ proc_get_safe_level(data)
 }
 
-static void
+static int
 proc_set_safe_level(data)
     VALUE data;
 {
-    if (!proc_safe_level_p(data)) return;
-    ruby_safe_level = proc_get_safe_level(data);
+    int old, safe;
+
+    if (!proc_safe_level_p(data)) return -1;
+    old = ruby_safe_level;
+    safe = proc_get_safe_level(data);
+    if (safe > old) ruby_safe_level = safe;
+    return old;
 }
 
@@ -8040,5 +8045,5 @@ proc_invoke(proc, args, self, klass)
     volatile VALUE result = Qundef;
     int state;
-    volatile int safe = ruby_safe_level;
+    volatile int safe;
     volatile VALUE old_wrapper = ruby_wrapper;
     struct RVarmap * volatile old_dvars = ruby_dyna_vars;
@@ -8072,7 +8077,7 @@ proc_invoke(proc, args, self, klass)
     ruby_frame->iter = ITER_CUR;
     PUSH_TAG(pcall ? PROT_LAMBDA : PROT_NONE);
+    safe = proc_set_safe_level(proc);
     state = EXEC_TAG();
     if (state == 0) {
-	proc_set_safe_level(proc);
 	result = rb_yield_0(args, self, (self!=Qundef)?CLASS_OF(self):0,
 			    pcall | YIELD_PROC_CALL, avalue);
@@ -8086,5 +8091,5 @@ proc_invoke(proc, args, self, klass)
     ruby_wrapper = old_wrapper;
     ruby_dyna_vars = old_dvars;
-    if (proc_safe_level_p(proc)) ruby_safe_level = safe;
+    if (safe >= 0) ruby_safe_level = safe;
 
     switch (state) {
@@ -8370,5 +8375,6 @@ block_pass(self, node)
     int state;
     volatile int orphan;
-    volatile int safe = ruby_safe_level;
+    volatile int oldsafe;
+    int safe;
 
     if (NIL_P(proc)) {
@@ -8414,8 +8420,9 @@ block_pass(self, node)
 
     PUSH_TAG(PROT_LOOP);
+    oldsafe = proc_set_safe_level(proc);
+    safe = ruby_safe_level;
     state = EXEC_TAG();
     if (state == 0) {
       retry:
-	proc_set_safe_level(proc);
 	if (safe > ruby_safe_level)
 	    ruby_safe_level = safe;
@@ -8433,5 +8440,5 @@ block_pass(self, node)
     POP_ITER();
     ruby_block = old_block;
-    if (proc_safe_level_p(proc)) ruby_safe_level = safe;
+    if (oldsafe >= 0) ruby_safe_level = safe;
 
     switch (state) {/* escape from orphan block */


-- 
--- 僕の前にBugはない。
--- 僕の後ろにBugはできる。
    中田 伸悦