Support tasks injection into a running VM.

test/cctest/test-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7378 matching lines @@
   CHECK_EQ(1, CountNativeContexts());
 
   v8::Debug::SetDebugEventListener(NopListener);
   CompileRun("debugger;");
   CHECK_EQ(2, CountNativeContexts());
 
   v8::Debug::SetDebugEventListener(NULL);
 }
 
 
+class DelayedTask : public v8::base::Thread {
+ public:
+  DelayedTask(v8::Isolate* isolate, v8::Debug::Task* task, int delay_ms)
+      : Thread(Options("DelayedTask")),
+        isolate_(isolate),
+        task_(task),
+        delay_ms_(delay_ms) {}
+  void Run() override {
+    v8::base::OS::Sleep(delay_ms_);

[yurys, 2014/12/17 14:25:03]

We can avoid this Sleep. E.g. "while" loop below can call a native function that
would on first call start this thread and after that would return false until
StopExecutionTask is executed and flips some flag.

[alph, 2014/12/17 15:05:46]

I would like to make sure the BreakAndRun is engaged when the VM loops in a pure
JS code (i.e. having no native callbacks).
I realize Sleep does not guarantee that, but it makes the signal fall into
random points of VM execution, i.e. it covers more cases. The test should not
fail in any case, so it is not a source of flakiness.

+    v8::Debug::BreakAndRun(isolate_, task_);

[yurys, 2014/12/17 14:25:03]

task_ = NULL?

[alph, 2014/12/17 15:05:46]

Done.

+  }
+
+ private:
+  v8::Isolate* isolate_;
+  v8::Debug::Task* task_;
+  int delay_ms_;
+};
+
+
+class StopExecutionTask : public v8::Debug::Task {
+ public:
+  explicit StopExecutionTask(LocalContext& context) : context_(context) {}
+  void Run() override {
+    context_->Global()->Set(v8_str("stop"), v8::True(context_->GetIsolate()));

[yurys, 2014/12/17 14:25:03]

We can use a static C++ variable instead, it would indicate that we can break
the loop.

[alph, 2014/12/17 15:05:46]

See my comment above. I'd like it to be a pure JS loop.

+  }
+
+ private:
+  LocalContext& context_;
+};
+
+
+TEST(RunTaskWhileLooping) {
+  LocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  v8::Debug::Task* task = new StopExecutionTask(env);
+  DelayedTask delayed_task(env->GetIsolate(), task, 100);

[yurys, 2014/12/17 14:25:03]

Or can we at least reduce the delay to 10 or something?

[alph, 2014/12/17 15:05:46]

Acknowledged.

+  CompileRun("var stop = false;");
+  delayed_task.Start();
+  CompileRun("while (!stop) {}");
+}
+
+
 TEST(LiveEditEnabled) {
   v8::internal::FLAG_allow_natives_syntax = true;
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());
   v8::Debug::SetLiveEditEnabled(env->GetIsolate(), true);
   CompileRun("%LiveEditCompareStrings('', '')");
 }
 
 
 TEST(LiveEditDisabled) {
@@ skipping 263 matching lines @@
       "let y = 2;               \n"
       "debugger;                \n"
       "x * y",
       30);
   ExpectInt32(
       "x = 1; y = 2; \n"
       "debugger;"
       "x * y",
       30);
 }