Beware of print-read inconsistency when serializing GURLs.

content/public/common/common_param_traits.cc

 // 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.
 
 #include "content/public/common/common_param_traits.h"
 
 #include "content/public/common/content_constants.h"
 #include "content/public/common/referrer.h"
 #include "net/base/host_port_pair.h"
 #include "third_party/skia/include/core/SkBitmap.h"
@@ skipping 33 matching lines @@
   }
 };
 
 }  // namespace
 
 namespace IPC {
 
 void ParamTraits<GURL>::Write(Message* m, const GURL& p) {
   DCHECK(p.possibly_invalid_spec().length() <= content::kMaxURLChars);
   m->WriteString(p.possibly_invalid_spec());
+  m->WriteBool(p.is_valid());
   // TODO(brettw) bug 684583: Add encoding for query params.
 }
 
 bool ParamTraits<GURL>::Read(const Message* m, PickleIterator* iter, GURL* p) {
   std::string s;
   if (!m->ReadString(iter, &s) || s.length() > content::kMaxURLChars) {
     *p = GURL();
     return false;
   }
+
   *p = GURL(s);
+
+  // Backwards compatibility with automation bots: permit older messages
+  // that don't contain the is_valid flag without returing an error.
+  bool is_valid;
+  if (m->ReadBool(iter, &is_valid)) {
+    // GURL doesn't always have print-parse consistency; beware of an invalid
+    // URL magically become valid.
+    if (p->is_valid() && !is_valid) {
+      DLOG(WARNING) << "GURL string " << s << " (marked invalid) parsed valid.";
+      *p = GURL();

[brettw, 2012/12/17 18:53:23]

If we're going to do this, why not just have Write() write an empty string if
the URL is invalid and skip the flag?

We're going to do another pass where the serialization is done "properly",
right? Getting an empty GURL out the other makes me a bit worried about causing
regressions.

+    }
+  }
   return true;
 }
 
 void ParamTraits<GURL>::Log(const GURL& p, std::string* l) {
   l->append(p.spec());
 }
 
 void ParamTraits<net::HostPortPair>::Write(Message* m, const param_type& p) {
   WriteParam(m, p.host());
   WriteParam(m, p.port());
@@ skipping 231 matching lines @@
 #undef CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_MACROS_H_
 #include "content/public/common/common_param_traits_macros.h"
 }  // namespace IPC
 
 // Generate param traits log methods.
 #include "ipc/param_traits_log_macros.h"
 namespace IPC {
 #undef CONTENT_PUBLIC_COMMON_COMMON_PARAM_TRAITS_MACROS_H_
 #include "content/public/common/common_param_traits_macros.h"
 }  // namespace IPC