Make debugger step into bound callbacks passed to Array.forEach.

src/runtime/runtime-debug.cc

 // Copyright 2014 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/compiler.h"
 #include "src/debug.h"
@@ skipping 2720 matching lines @@
         break;
       }
     }
   }
 
   if (found.is_null()) return heap->undefined_value();
   return *Script::GetWrapper(found);
 }
 
 
-// Check whether debugger and is about to step into the callback that is passed
+// Check whether debugger is about to step into the callback that is passed
 // to a built-in function such as Array.forEach.
-RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
-  DCHECK(args.length() == 1);
+RUNTIME_FUNCTION(Runtime_DebugIsStepping) {
+  DCHECK(args.length() == 0);
   Debug* debug = isolate->debug();
   if (!debug->is_active() || !debug->IsStepping() ||
       debug->last_step_action() != StepIn) {
     return isolate->heap()->false_value();
   }
-  CONVERT_ARG_CHECKED(Object, callback, 0);
-  // We do not step into the callback if it's a builtin or not even a function.
-  return isolate->heap()->ToBoolean(callback->IsJSFunction() &&
-                                    !JSFunction::cast(callback)->IsBuiltin());

[Yang, 2015/03/24 07:27:15]

Can't we make this change a lot simpler by returning true here for callbacks
where JSFunction::cast(callback)->shared()->bound()?

+  return isolate->heap()->true_value();

[kozy, 2015/03/23 16:49:27]

Why can we eliminate callback function check?

 }
 
 
 // Set one shot breakpoints for the callback function that is passed to a
 // built-in function such as Array.forEach to enable stepping into the callback.
 RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   DCHECK(args.length() == 1);
   Debug* debug = isolate->debug();
   if (!debug->IsStepping()) return isolate->heap()->undefined_value();
 
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   RUNTIME_ASSERT(object->IsJSFunction() || object->IsJSGeneratorObject());
   Handle<JSFunction> fun;
   if (object->IsJSFunction()) {
     fun = Handle<JSFunction>::cast(object);
   } else {
     fun = Handle<JSFunction>(
         Handle<JSGeneratorObject>::cast(object)->function(), isolate);
   }
   // When leaving the function, step out has been activated, but not performed
   // if we do not leave the builtin.  To be able to step into the function
   // again, we need to clear the step out at this point.
   debug->ClearStepOut();
-  debug->FloodWithOneShot(fun);
+  debug->FloodWithOneShotGeneric(fun);
   return isolate->heap()->undefined_value();
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugPushPromise) {
   DCHECK(args.length() == 1);
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, promise, 0);
   isolate->PushPromise(promise);
   return isolate->heap()->undefined_value();
@@ skipping 31 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }
 }  // namespace v8::internal