Debugger: preserve stepping state after evaluating breakpoint condition.

R=ulan@chromium.org, yurys@chromium.org
BUG=chromium:467180
LOG=N

Review URL: https://codereview.chromium.org/1132643004

Cr-Commit-Position: refs/heads/master@{#28432}

src/debug.cc

@@ -897,6 +897,11 @@ Handle<Object> Debug::CheckBreakPoints(Handle<Object> break_point_objects) {
   Handle<FixedArray> break_points_hit;
   int break_points_hit_count = 0;
   DCHECK(!break_point_objects->IsUndefined());
+
+  // Break points are checked by calling into Javascript. This could change
+  // the stepping state we are currently in.
+  PreserveDebugState state(this);
+
   if (break_point_objects->IsFixedArray()) {
     Handle<FixedArray> array(FixedArray::cast(*break_point_objects));
     break_points_hit = factory->NewFixedArray(array->length());

src/debug.h

@@ -732,6 +732,27 @@ class Debug {
     Object** restarter_frame_function_pointer_;
   };
 
+
+  class PreserveDebugState {
+   public:
+    explicit PreserveDebugState(Debug* debug) : debug_(debug) {
+      size_t size = sizeof(debug_->thread_local_);
+      storage_ = NewArray<char>(size);
+      MemCopy(storage_, &debug_->thread_local_, size);
+    }
+
+    ~PreserveDebugState() {
+      size_t size = sizeof(debug_->thread_local_);
+      MemCopy(&debug_->thread_local_, storage_, size);
+      DeleteArray(storage_);
+    }
+
+   private:
+    Debug* debug_;
+    char* storage_;
+  };
+
+
   // Storage location for registers when handling debug break calls
   ThreadLocal thread_local_;
 

test/mjsunit/regress/regress-crbug-467180.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-debug-as debug
+
+function f() {
+  for (var i = 10; i < 14; i++) {  // 1
+    i;                             // 2
+  }
+}                                  // 3
+
+var state = "conditional";
+var log = [];
+var exception = null;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var label = +exec_state.frame(0).sourceLineText().substr(-1);
+    log.push(label);
+    if (label == 2) log.push(exec_state.frame(0).evaluate("i").value());
+    exec_state.prepareStep(Debug.StepAction.StepNext, 1);
+  } catch (e) {
+    exception = e;
+    print("Caught something. " + e + " " + e.stack);
+  };
+};
+
+
+var Debug = debug.Debug;
+Debug.setListener(listener);
+
+Debug.setBreakPoint(f, 2, 0, "i == 12");
+
+f();
+
+Debug.setListener(null);  // 4
+
+assertEquals([2,12,1,1,2,13,1,1,3,4], log);
+assertNull(exception);