Add support for debug break in Dart source.

tests/language/vm/debug_break_vm_test.dart

Index: tests/language/vm/debug_break_vm_test.dart
===================================================================
--- tests/language/vm/debug_break_vm_test.dart	(revision 0)
+++ tests/language/vm/debug_break_vm_test.dart	(working copy)
@@ -0,0 +1,22 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// VMOptions=--optimization-counter-threshold=5

[Ivan Posva, 2015/04/16 21:44:51]

Is there any particular reason for using a special optimization count threshold
in this test? Is so (optimized code?) then please add a comment.

[regis, 2015/04/16 22:17:04]

Yes and no.
Ideally, I would like to test two different flag configurations, which I could
specify with 2 lines:
// VMOptions=--optimization-counter-threshold=5
// VMOptions=--optimization-counter-threshold=5 --enable-debug-break

However, I cannot specify different expected results for the second line. In
that case, I do not expect a compile-time error, but I want to hit the debug
break at runtime. I also do not want to crash at compile time while optimizing
the new StopInstr. This actually happened with patch #1, because I wrongly
assumed that the optimizer would not see this instruction (see
intermediate_language.h in patch #1).

In short, the optimization count threshold is only useful when running this test
by hand and adding the --enable-debug-break flag. I allowed me to test and fix
patch #1.

I will add a comment.

 

+
+// A debug break is not valid Dart syntax unless --enable-debug-break.
+
+test(i) {
+  break "outside_loop";  /// 02: compile-time error
+  do {
+    if (i > 15) {
+      break "inside_loop";  /// 03: compile-time error
+    }
+  } while (false);
+}
+
+void main() {
+  break "gdb";   /// 01: compile-time error
+  for (var i = 0; i < 20; i++) {
+    test(i);
+  }
+}