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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Interfaces by which the embedding can interact with the Debugger API.
+
+#ifndef js_Debug_h
+#define js_Debug_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/MemoryReporting.h"
+
+#include "jsapi.h"
+#include "jspubtd.h"
+
+#include "js/GCAPI.h"
+#include "js/RootingAPI.h"
+#include "js/TypeDecls.h"
+
+namespace js {
+class Debugger;
+}  // namespace js
+
+namespace JS {
+namespace dbg {
+
+// [SMDOC] Debugger builder API
+//
+// Helping embedding code build objects for Debugger
+// -------------------------------------------------
+//
+// Some Debugger API features lean on the embedding application to construct
+// their result values. For example, Debugger.Frame.prototype.scriptEntryReason
+// calls hooks provided by the embedding to construct values explaining why it
+// invoked JavaScript; if F is a frame called from a mouse click event handler,
+// F.scriptEntryReason would return an object of the form:
+//
+//   { eventType: "mousedown", event: <object> }
+//
+// where <object> is a Debugger.Object whose referent is the event being
+// dispatched.
+//
+// However, Debugger implements a trust boundary. Debuggee code may be
+// considered untrusted; debugger code needs to be protected from debuggee
+// getters, setters, proxies, Object.watch watchpoints, and any other feature
+// that might accidentally cause debugger code to set the debuggee running. The
+// Debugger API tries to make it easy to write safe debugger code by only
+// offering access to debuggee objects via Debugger.Object instances, which
+// ensure that only those operations whose explicit purpose is to invoke
+// debuggee code do so. But this protective membrane is only helpful if we
+// interpose Debugger.Object instances in all the necessary spots.
+//
+// SpiderMonkey's compartment system also implements a trust boundary. The
+// debuggee and debugger are always in different compartments. Inter-compartment
+// work requires carefully tracking which compartment each JSObject or JS::Value
+// belongs to, and ensuring that is is correctly wrapped for each operation.
+//
+// It seems precarious to expect the embedding's hooks to implement these trust
+// boundaries. Instead, the JS::dbg::Builder API segregates the code which
+// constructs trusted objects from that which deals with untrusted objects.
+// Trusted objects have an entirely different C++ type, so code that improperly
+// mixes trusted and untrusted objects is caught at compile time.
+//
+// In the structure shown above, there are two trusted objects, and one
+// untrusted object:
+//
+// - The overall object, with the 'eventType' and 'event' properties, is a
+//   trusted object. We're going to return it to D.F.p.scriptEntryReason's
+//   caller, which will handle it directly.
+//
+// - The Debugger.Object instance appearing as the value of the 'event' property
+//   is a trusted object. It belongs to the same Debugger instance as the
+//   Debugger.Frame instance whose scriptEntryReason accessor was called, and
+//   presents a safe reflection-oriented API for inspecting its referent, which
+//   is:
+//
+// - The actual event object, an untrusted object, and the referent of the
+//   Debugger.Object above. (Content can do things like replacing accessors on
+//   Event.prototype.)
+//
+// Using JS::dbg::Builder, all objects and values the embedding deals with
+// directly are considered untrusted, and are assumed to be debuggee values. The
+// only way to construct trusted objects is to use Builder's own methods, which
+// return a separate Object type. The only way to set a property on a trusted
+// object is through that Object type. The actual trusted object is never
+// exposed to the embedding.
+//
+// So, for example, the embedding might use code like the following to construct
+// the object shown above, given a Builder passed to it by Debugger:
+//
+//    bool
+//    MyScriptEntryReason::explain(JSContext* cx,
+//                                 Builder& builder,
+//                                 Builder::Object& result)
+//    {
+//        JSObject* eventObject = ... obtain debuggee event object somehow ...;
+//        if (!eventObject) {
+//            return false;
+//        }
+//        result = builder.newObject(cx);
+//        return result &&
+//               result.defineProperty(cx, "eventType",
+//                                     SafelyFetchType(eventObject)) &&
+//               result.defineProperty(cx, "event", eventObject);
+//    }
+//
+//
+// Object::defineProperty also accepts an Object as the value to store on the
+// property. By its type, we know that the value is trusted, so we set it
+// directly as the property's value, without interposing a Debugger.Object
+// wrapper. This allows the embedding to builted nested structures of trusted
+// objects.
+//
+// The Builder and Builder::Object methods take care of doing whatever
+// compartment switching and wrapping are necessary to construct the trusted
+// values in the Debugger's compartment.
+//
+// The Object type is self-rooting. Construction, assignment, and destruction
+// all properly root the referent object.
+
+class BuilderOrigin;
+
+class Builder {
+  // The Debugger instance whose client we are building a value for. We build
+  // objects in this object's compartment.
+  PersistentRootedObject debuggerObject;
+
+  // debuggerObject's Debugger structure, for convenience.
+  js::Debugger* debugger;
+
+  // Check that |thing| is in the same compartment as our debuggerObject. Used
+  // for assertions when constructing BuiltThings. We can overload this as we
+  // add more instantiations of BuiltThing.
+#if DEBUG
+  void assertBuilt(JSObject* obj);
+#else
+  void assertBuilt(JSObject* obj) {}
+#endif
+
+ protected:
+  // A reference to a trusted object or value. At the moment, we only use it
+  // with JSObject*.
+  template <typename T>
+  class BuiltThing {
+    friend class BuilderOrigin;
+
+   protected:
+    // The Builder to which this trusted thing belongs.
+    Builder& owner;
+
+    // A rooted reference to our value.
+    PersistentRooted<T> value;
+
+    BuiltThing(JSContext* cx, Builder& owner_,
+               T value_ = SafelyInitialized<T>())
+        : owner(owner_), value(cx, value_) {
+      owner.assertBuilt(value_);
+    }
+
+    // Forward some things from our owner, for convenience.
+    js::Debugger* debugger() const { return owner.debugger; }
+    JSObject* debuggerObject() const { return owner.debuggerObject; }
+
+   public:
+    BuiltThing(const BuiltThing& rhs) : owner(rhs.owner), value(rhs.value) {}
+    BuiltThing& operator=(const BuiltThing& rhs) {
+      MOZ_ASSERT(&owner == &rhs.owner);
+      owner.assertBuilt(rhs.value);
+      value = rhs.value;
+      return *this;
+    }
+
+    explicit operator bool() const {
+      // If we ever instantiate BuiltThing<Value>, this might not suffice.
+      return value;
+    }
+
+   private:
+    BuiltThing() = delete;
+  };
+
+ public:
+  // A reference to a trusted object, possibly null. Instances of Object are
+  // always properly rooted. They can be copied and assigned, as if they were
+  // pointers.
+  class Object : private BuiltThing<JSObject*> {
+    friend class Builder;        // for construction
+    friend class BuilderOrigin;  // for unwrapping
+
+    typedef BuiltThing<JSObject*> Base;
+
+    // This is private, because only Builders can create Objects that
+    // actually point to something (hence the 'friend' declaration).
+    Object(JSContext* cx, Builder& owner_, HandleObject obj)
+        : Base(cx, owner_, obj.get()) {}
+
+    bool definePropertyToTrusted(JSContext* cx, const char* name,
+                                 JS::MutableHandleValue value);
+
+   public:
+    Object(JSContext* cx, Builder& owner_) : Base(cx, owner_, nullptr) {}
+    Object(const Object& rhs) = default;
+
+    // Our automatically-generated assignment operator can see our base
+    // class's assignment operator, so we don't need to write one out here.
+
+    // Set the property named |name| on this object to |value|.
+    //
+    // If |value| is a string or primitive, re-wrap it for the debugger's
+    // compartment.
+    //
+    // If |value| is an object, assume it is a debuggee object and make a
+    // Debugger.Object instance referring to it. Set that as the propery's
+    // value.
+    //
+    // If |value| is another trusted object, store it directly as the
+    // property's value.
+    //
+    // On error, report the problem on cx and return false.
+    bool defineProperty(JSContext* cx, const char* name, JS::HandleValue value);
+    bool defineProperty(JSContext* cx, const char* name,
+                        JS::HandleObject value);
+    bool defineProperty(JSContext* cx, const char* name, Object& value);
+
+    using Base::operator bool;
+  };
+
+  // Build an empty object for direct use by debugger code, owned by this
+  // Builder. If an error occurs, report it on cx and return a false Object.
+  Object newObject(JSContext* cx);
+
+ protected:
+  Builder(JSContext* cx, js::Debugger* debugger);
+};
+
+// Debugger itself instantiates this subclass of Builder, which can unwrap
+// BuiltThings that belong to it.
+class BuilderOrigin : public Builder {
+  template <typename T>
+  T unwrapAny(const BuiltThing<T>& thing) {
+    MOZ_ASSERT(&thing.owner == this);
+    return thing.value.get();
+  }
+
+ public:
+  BuilderOrigin(JSContext* cx, js::Debugger* debugger_)
+      : Builder(cx, debugger_) {}
+
+  JSObject* unwrap(Object& object) { return unwrapAny(object); }
+};
+
+// Finding the size of blocks allocated with malloc
+// ------------------------------------------------
+//
+// Debugger.Memory wants to be able to report how many bytes items in memory are
+// consuming. To do this, it needs a function that accepts a pointer to a block,
+// and returns the number of bytes allocated to that block. SpiderMonkey itself
+// doesn't know which function is appropriate to use, but the embedding does.
+
+// Tell Debuggers in |cx| to use |mallocSizeOf| to find the size of
+// malloc'd blocks.
+JS_PUBLIC_API void SetDebuggerMallocSizeOf(JSContext* cx,
+                                           mozilla::MallocSizeOf mallocSizeOf);
+
+// Get the MallocSizeOf function that the given context is using to find the
+// size of malloc'd blocks.
+JS_PUBLIC_API mozilla::MallocSizeOf GetDebuggerMallocSizeOf(JSContext* cx);
+
+// Debugger and Garbage Collection Events
+// --------------------------------------
+//
+// The Debugger wants to report about its debuggees' GC cycles, however entering
+// JS after a GC is troublesome since SpiderMonkey will often do something like
+// force a GC and then rely on the nursery being empty. If we call into some
+// Debugger's hook after the GC, then JS runs and the nursery won't be
+// empty. Instead, we rely on embedders to call back into SpiderMonkey after a
+// GC and notify Debuggers to call their onGarbageCollection hook.
+
+// Determine whether it's necessary to call FireOnGarbageCollectionHook() after
+// a GC. This is only required if there are debuggers with an
+// onGarbageCollection hook observing a global in the set of collected zones.
+JS_PUBLIC_API bool FireOnGarbageCollectionHookRequired(JSContext* cx);
+
+// For each Debugger that observed a debuggee involved in the given GC event,
+// call its `onGarbageCollection` hook.
+JS_PUBLIC_API bool FireOnGarbageCollectionHook(
+    JSContext* cx, GarbageCollectionEvent::Ptr&& data);
+
+// Return true if the given value is a Debugger object, false otherwise.
+JS_PUBLIC_API bool IsDebugger(JSObject& obj);
+
+// Append each of the debuggee global objects observed by the Debugger object
+// |dbgObj| to |vector|. Returns true on success, false on failure.
+JS_PUBLIC_API bool GetDebuggeeGlobals(JSContext* cx, JSObject& dbgObj,
+                                      MutableHandleObjectVector vector);
+
+// Hooks for reporting where JavaScript execution began.
+//
+// Our performance tools would like to be able to label blocks of JavaScript
+// execution with the function name and source location where execution began:
+// the event handler, the callback, etc.
+//
+// Construct an instance of this class on the stack, providing a JSContext
+// belonging to the runtime in which execution will occur. Each time we enter
+// JavaScript --- specifically, each time we push a JavaScript stack frame that
+// has no older JS frames younger than this AutoEntryMonitor --- we will
+// call the appropriate |Entry| member function to indicate where we've begun
+// execution.
+
+class MOZ_STACK_CLASS JS_PUBLIC_API AutoEntryMonitor {
+  JSContext* cx_;
+  AutoEntryMonitor* savedMonitor_;
+
+ public:
+  explicit AutoEntryMonitor(JSContext* cx);
+  ~AutoEntryMonitor();
+
+  // SpiderMonkey reports the JavaScript entry points occuring within this
+  // AutoEntryMonitor's scope to the following member functions, which the
+  // embedding is expected to override.
+  //
+  // It is important to note that |asyncCause| is owned by the caller and its
+  // lifetime must outlive the lifetime of the AutoEntryMonitor object. It is
+  // strongly encouraged that |asyncCause| be a string constant or similar
+  // statically allocated string.
+
+  // We have begun executing |function|. Note that |function| may not be the
+  // actual closure we are running, but only the canonical function object to
+  // which the script refers.
+  virtual void Entry(JSContext* cx, JSFunction* function,
+                     HandleValue asyncStack, const char* asyncCause) = 0;
+
+  // Execution has begun at the entry point of |script|, which is not a
+  // function body. (This is probably being executed by 'eval' or some
+  // JSAPI equivalent.)
+  virtual void Entry(JSContext* cx, JSScript* script, HandleValue asyncStack,
+                     const char* asyncCause) = 0;
+
+  // Execution of the function or script has ended.
+  virtual void Exit(JSContext* cx) {}
+};
+
+}  // namespace dbg
+}  // namespace JS
+
+#endif /* js_Debug_h */