Implement off-the-wire validation scheme for enum types.

ipc/param_traits_write_macros.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IPC_PARAM_TRAITS_WRITE_MACROS_H_
 #define IPC_PARAM_TRAITS_WRITE_MACROS_H_
 
 // Null out all the macros that need nulling.
 #include "ipc/ipc_message_null_macros.h"
 
 // STRUCT declarations cause corresponding STRUCT_TRAITS declarations to occur.
-#undef IPC_STRUCT_BEGIN
 #undef IPC_STRUCT_BEGIN_WITH_PARENT
 #undef IPC_STRUCT_MEMBER
 #undef IPC_STRUCT_END
 #define IPC_STRUCT_BEGIN_WITH_PARENT(struct_name, parent) \
-  IPC_STRUCT_BEGIN(struct_name)
-#define IPC_STRUCT_BEGIN(struct_name) IPC_STRUCT_TRAITS_BEGIN(struct_name)
+  IPC_STRUCT_TRAITS_BEGIN(struct_name)
 #define IPC_STRUCT_MEMBER(type, name, ...) IPC_STRUCT_TRAITS_MEMBER(name)
 #define IPC_STRUCT_END() IPC_STRUCT_TRAITS_END()
 
 // Set up so next include will generate write methods.
 #undef IPC_STRUCT_TRAITS_BEGIN
 #undef IPC_STRUCT_TRAITS_MEMBER
 #undef IPC_STRUCT_TRAITS_PARENT
 #undef IPC_STRUCT_TRAITS_END
 #define IPC_STRUCT_TRAITS_BEGIN(struct_name) \
   void ParamTraits<struct_name>::Write(Message* m, const param_type& p) {
 #define IPC_STRUCT_TRAITS_MEMBER(name) WriteParam(m, p.name);
 #define IPC_STRUCT_TRAITS_PARENT(type) ParamTraits<type>::Write(m, p);
 #define IPC_STRUCT_TRAITS_END() }
 
-#undef IPC_ENUM_TRAITS
-#define IPC_ENUM_TRAITS(enum_name) \
+#undef IPC_ENUM_TRAITS_VALIDATE
+#define IPC_ENUM_TRAITS_VALIDATE(enum_name, validation_expression) \

[jam, 2013/05/31 23:00:17]

nit: for developer ease, perhaps test validation_expression here in debug
builds? because when the assert happens in the receiving process, it'd be a bit
of debugging to track down the sender

[Tom Sepez, 2013/05/31 23:01:54]

That's a great idea.  I'll add it.

   void ParamTraits<enum_name>::Write(Message* m, const param_type& p) { \
     m->WriteInt(static_cast<int>(p)); \
   }
 
 #endif  // IPC_PARAM_TRAITS_WRITE_MACROS_H_