Bug 1149987 - Part 1: Make it possible to send an ErrorResult that doesn't encode a JS exception through the IPDL layer; r=bzbarsky

dom/bindings/BindingUtils.cpp

@@ -46,6 +46,7 @@
 #include "mozilla/jsipc/CrossProcessObjectWrappers.h"
 #include "WorkerPrivate.h"
 #include "nsDOMClassInfo.h"
+#include "ipc/ErrorIPCUtils.h"
 
 namespace mozilla {
 namespace dom {
@@ -149,6 +150,31 @@ ErrorResult::ThrowErrorWithMessage(va_list ap, const dom::ErrNum errorNumber,
   mMessage = message;
 }
 
+void
+ErrorResult::SerializeMessage(IPC::Message* aMsg) const
+{
+  using namespace IPC;
+  MOZ_ASSERT(mMessage);
+  WriteParam(aMsg, mMessage->mArgs);
+  WriteParam(aMsg, mMessage->mErrorNumber);
+}
+
+bool
+ErrorResult::DeserializeMessage(const IPC::Message* aMsg, void** aIter)
+{
+  using namespace IPC;
+  nsAutoPtr<Message> readMessage(new Message());
+  if (!ReadParam(aMsg, aIter, &readMessage->mArgs) ||
+      !ReadParam(aMsg, aIter, &readMessage->mErrorNumber)) {
+    return false;
+  }
+  if (mMessage) {
+    delete mMessage;
+  }
+  mMessage = readMessage.forget();
+  return true;
+}
+
 void
 ErrorResult::ThrowTypeError(const dom::ErrNum errorNumber, ...)
 {

dom/bindings/ErrorIPCUtils.h

@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* vim: set ts=2 sw=2 et tw=79: */
+/* 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/. */
+
+#include "ipc/IPCMessageUtils.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Move.h"
+
+#ifndef IPC_ErrorIPCUtils_h
+#define IPC_ErrorIPCUtils_h
+
+namespace IPC {
+
+template<>
+struct ParamTraits<mozilla::dom::ErrNum> :
+  public ContiguousEnumSerializer<mozilla::dom::ErrNum,
+                                  mozilla::dom::ErrNum(0),
+                                  mozilla::dom::ErrNum(mozilla::dom::Err_Limit)> {};
+
+template<>
+struct ParamTraits<mozilla::ErrorResult>
+{
+  typedef mozilla::ErrorResult paramType;
+
+  static void Write(Message* aMsg, const paramType& aParam)
+  {
+    // It should be the case that mMightHaveUnreportedJSException can only be
+    // true when we're expecting a JS exception.  We cannot send such messages
+    // over the IPC channel since there is no sane way of transferring the JS
+    // value over to the other side.  Callers should never do that.
+    MOZ_ASSERT_IF(aParam.IsJSException(), aParam.mMightHaveUnreportedJSException);
+    if (aParam.IsJSException()
+#ifdef DEBUG
+        || aParam.mMightHaveUnreportedJSException
+#endif
+        ) {
+      MOZ_CRASH("Cannot encode an ErrorResult representing a Javascript exception");
+    }
+
+    WriteParam(aMsg, aParam.mResult);
+    WriteParam(aMsg, aParam.IsErrorWithMessage());
+    if (aParam.IsErrorWithMessage()) {
+      aParam.SerializeMessage(aMsg);
+    }
+  }
+
+  static bool Read(const Message* aMsg, void** aIter, paramType* aResult)
+  {
+    paramType readValue;
+    if (!ReadParam(aMsg, aIter, &readValue.mResult)) {
+      return false;
+    }
+    bool hasMessage = false;
+    if (!ReadParam(aMsg, aIter, &hasMessage)) {
+      return false;
+    }
+    if (hasMessage && !readValue.DeserializeMessage(aMsg, aIter)) {
+      return false;
+    }
+    *aResult = Move(readValue);
+    return true;
+  }
+};
+
+}
+
+#endif

dom/bindings/ErrorResult.h

@@ -18,6 +18,11 @@
 #include "nsStringGlue.h"
 #include "mozilla/Assertions.h"
 
+namespace IPC {
+class Message;
+template <typename> struct ParamTraits;
+}
+
 namespace mozilla {
 
 namespace dom {
@@ -161,6 +166,10 @@ private:
     JS::Value mJSException; // valid when IsJSException()
   };
 
+  friend struct IPC::ParamTraits<ErrorResult>;
+  void SerializeMessage(IPC::Message* aMsg) const;
+  bool DeserializeMessage(const IPC::Message* aMsg, void** aIter);
+
 #ifdef DEBUG
   // Used to keep track of codepaths that might throw JS exceptions,
   // for assertion purposes.

dom/bindings/moz.build

@@ -6,6 +6,10 @@
 
 TEST_DIRS += ['test']
 
+EXPORTS.ipc += [
+    'ErrorIPCUtils.h',
+]
+
 EXPORTS.mozilla += [
     'ErrorResult.h',
 ]