eval_intern.h: refine stack overflow detection

* eval_intern.h (TH_PUSH_TAG, TH_EXEC_TAG): refine stack overflow
  detection.  chain local tag after setjmp() successed on it, because
  calling setjmp() also can overflow the stack.
  [ruby-dev:47804] [Bug #9109]
* vm_eval.c (rb_catch_obj): now th->tag points previous tag until
  TH_EXEC_TAG().


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43707 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,4 +1,12 @@
-Mon Nov 18 22:47:11 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Mon Nov 18 22:47:54 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* eval_intern.h (TH_PUSH_TAG, TH_EXEC_TAG): refine stack overflow
+	  detection.  chain local tag after setjmp() successed on it, because
+	  calling setjmp() also can overflow the stack.
+	  [ruby-dev:47804] [Bug #9109]
+
+	* vm_eval.c (rb_catch_obj): now th->tag points previous tag until
+	  TH_EXEC_TAG().
 
 	* thread_pthread.c (ruby_init_stack): set stack_start properly by
 	  get_main_stack() if possible.

eval_intern.h

@@ -95,8 +95,7 @@ extern int select_large_fdset(int, fd_set *, fd_set *, fd_set *, struct timeval
   rb_thread_t * const _th = (th); \
   struct rb_vm_tag _tag; \
   _tag.tag = 0; \
-  _tag.prev = _th->tag; \
-  _th->tag = &_tag;
+  _tag.prev = _th->tag;
 
 #define TH_POP_TAG() \
   _th->tag = _tag.prev; \
@@ -129,7 +128,7 @@ rb_threadptr_tag_jump(rb_thread_t *th, int st)
   [ISO/IEC 9899:1999] 7.13.1.1
 */
 #define TH_EXEC_TAG() \
-    (ruby_setjmp(_th->tag->buf) ? rb_threadptr_tag_state(_th) : 0)
+    (ruby_setjmp(_tag.buf) ? rb_threadptr_tag_state(_th) : (_th->tag = &_tag, 0))
 
 #define EXEC_TAG() \
   TH_EXEC_TAG()

test/ruby/test_exception.rb

@@ -477,6 +477,14 @@ end.join
     assert_raise(SystemStackError){m}
   end
 
+  def test_machine_stackoverflow
+    bug9109 = '[ruby-dev:47804] [Bug #9109]'
+    assert_separately([], <<-SRC)
+    h = {a: ->{h[:a].call}}
+    assert_raise(SystemStackError, #{bug9109.dump}) {h[:a].call}
+    SRC
+  end
+
   def test_cause
     msg = "[Feature #8257]"
     cause = nil

vm_eval.c

@@ -1823,7 +1823,7 @@ rb_catch_obj(VALUE t, VALUE (*func)(), VALUE data)
 
     TH_PUSH_TAG(th);
 
-    th->tag->tag = tag;
+    _tag.tag = tag;
 
     if ((state = TH_EXEC_TAG()) == 0) {
 	/* call with argc=1, argv = [tag], block = Qnil to insure compatibility */