[ruby-dev:25038] Continuation protection (Re: Re: IO#flush dumps core again)

なかだです。

At Thu, 2 Dec 2004 14:57:14 +0900,
Yukihiro Matsumoto wrote in [ruby-dev:25029]:
> |rb_protect()自体をこうしてしまったほうがいいような気がしてきま
> |した。rb_protect()を使うようなところからcallccを外部に持ち出せ
> |て嬉しいというか、安全な状況はあまりないと思います。
> 
> 賛成です。コミット希望。

スレッドを考慮してませんでした。

protectはrb_protect()を呼ぶグローバルメソッドとして

  $ cat ext/protect/protect.c
  #include "ruby.h"

  static VALUE
  call_protect(argc, argv)
      int argc;
      VALUE *argv;
  {
      VALUE val;
      int state;

      rb_scan_args(argc, argv, "01", &val);
      val = rb_protect(rb_yield, val, &state);
      if (state) rb_jump_tag(state);
      return val;
  }

  void
  Init_protect()
  {
      rb_define_global_function("protect", call_protect, -1);
  }

途中で別スレッドでrb_protect()を使うと対応が合わなくなります。

  $ ruby -rprotect -e '
  trap("INT"){c=nil;(puts; c.call(false)) if callcc{|c|
  Thread.pass;print "."; true}}
  Thread.new{protect{Process.kill("INT", $$)}}.join'
  .
  -e:2:in `call': continuation called across trap (RuntimeError)
          from -e:2
          from -e:2:in `call'
          from -e:4:in `initialize'
          from -e:4:in `new'
          from -e:4

また、外部の継続も呼び出せないのはちょっと制限がきついかもとい
う気がして来ました。

  $ ruby -rprotect -e '
  c=nil
  protect{puts; c.call(false)} if callcc{|c| print "."; true}'
  -e:3:in `call': continuation called across trap (RuntimeError)
          from -e:3
          from -e:3:in `protect'
          from -e:3


Index: eval.c
===================================================================
RCS file: /cvs/ruby/src/ruby/eval.c,v
retrieving revision 1.741
diff -U2 -p -d -r1.741 eval.c
--- eval.c	2 Dec 2004 15:17:35 -0000	1.741
+++ eval.c	3 Dec 2004 05:01:23 -0000
@@ -1298,4 +1298,7 @@ static int thread_set_raised();
 static int thread_reset_raised();
 
+static void thread_push_cont_protect();
+static void thread_pop_cont_protect();
+
 static VALUE exception_error;
 static VALUE sysstack_error;
@@ -5147,6 +5150,4 @@ rb_rescue(b_proc, data1, r_proc, data2)
 }
 
-static VALUE cont_protect;
-
 VALUE
 rb_protect(proc, data, state)
@@ -5159,9 +5160,9 @@ rb_protect(proc, data, state)
 
     PUSH_TAG(PROT_NONE);
-    cont_protect = (VALUE)rb_node_newnode(NODE_MEMO, cont_protect, 0, 0);
+    thread_push_cont_protect();
     if ((status = EXEC_TAG()) == 0) {
 	result = (*proc)(data);
     }
-    cont_protect = ((NODE *)cont_protect)->u1.value;
+    thread_pop_cont_protect();
     POP_TAG();
     if (state) {
@@ -9585,4 +9586,5 @@ struct thread {
 
     VALUE thread;
+    NODE *cont_protect;
 };
 
@@ -9657,4 +9659,20 @@ thread_reset_raised()
 }
 
+static void
+thread_push_cont_protect()
+{
+    NODE *c = curr_thread->cont_protect;
+    curr_thread->cont_protect =
+	rb_node_newnode(NODE_MEMO, (VALUE)c, Qtrue, 0);
+}
+
+static void
+thread_pop_cont_protect()
+{
+    NODE *c = curr_thread->cont_protect;
+    curr_thread->cont_protect = c->u1.node;
+    c->u2.value = Qfalse;
+}
+
 static void rb_thread_ready _((rb_thread_t));
 
@@ -9785,4 +9803,5 @@ thread_mark(th)
     rb_mark_tbl(th->locals);
     rb_gc_mark(th->thgroup);
+    rb_gc_mark((VALUE)th->cont_protect);
 
     /* mark data in copied stack */
@@ -11336,4 +11355,5 @@ rb_thread_group(thread)
     th->locals = 0;\
     th->thread = 0;\
+    th->cont_protect = 0;\
 } while (0)
 
@@ -12274,5 +12294,5 @@ rb_callcc(self)
     }
     th->thread = curr_thread->thread;
-    th->thgroup = cont_protect;
+    th->cont_protect = curr_thread->cont_protect;
 
     for (vars = ruby_dyna_vars; vars; vars = vars->next) {
@@ -12316,6 +12336,6 @@ rb_cont_call(argc, argv, cont)
 	rb_raise(rb_eRuntimeError, "continuation called across threads");
     }
-    if (th->thgroup != cont_protect) {
-	rb_raise(rb_eRuntimeError, "continuation called across trap");
+    if (th->cont_protect && !RTEST(th->cont_protect->u2.value)) {
+	rb_raise(rb_eRuntimeError, "continuation called across context");
     }
     switch (argc) {


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