win: Add version to client registration request

util/win/registration_protocol_win.h

 // Copyright 2015 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 20 matching lines @@
   //! \brief The address of an EXCEPTION_POINTERS structure in the client
   //!     process that describes the exception.
   WinVMAddress exception_pointers;
 
   //! \brief The thread on which the exception happened.
   DWORD thread_id;
 };
 
 //! \brief A client registration request.
 struct RegistrationRequest {
+  //! \brief The expected value of `version`. This should be changed whenever
+  //!     the messages or ExceptionInformation are modified incompatibly.
+  enum { kMessageVersion = 1 };
+
+  //! \brief Version field to detect skew between client and server. Should be
+  //!     set to kMessageVersion.
+  int version;
+
+  //! \brief The PID of the client process.
+  DWORD client_process_id;

[Mark Mentovai, 2015/09/04 16:05:55]

Nice repacking. :)

[scottmg, 2015/09/04 18:50:00]

Tell me 20 or 30 times and eventually I remember. :)

+
   //! \brief The address, in the client process address space, of an
   //!     ExceptionInformation structure.
   WinVMAddress exception_information;
-
-  //! \brief The PID of the client process.
-  DWORD client_process_id;
 };
 
 //! \brief A message only sent to the server by itself to trigger shutdown.
 struct ShutdownRequest {
   //! \brief A randomly generated token used to validate the the shutdown
   //!     request was not sent from another process.
   uint64_t token;
 };
 
 //! \brief The message passed from client to server by
@@ skipping 40 matching lines @@
 //! CrashpadClient::SetHandler().
 //!
 //! \sa CrashpadClient::SetHandler()
 bool SendToCrashHandlerServer(const base::string16& pipe_name,
                               const ClientToServerMessage& message,
                               ServerToClientMessage* response);
 
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_WIN_REGISTRATION_PROTOCOL_WIN_H_