Fixing HttpPost deletion crash

components/copresence/rpc/rpc_handler.cc

 // Copyright 2014 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 "components/copresence/rpc/rpc_handler.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 300 matching lines @@
 }
 
 // Private methods
 
 void RpcHandler::RegisterResponseHandler(
     const SuccessCallback& init_done_callback,
     HttpPost* completed_post,
     int http_status_code,
     const std::string& response_data) {
   if (completed_post) {
-    DCHECK(pending_posts_.erase(completed_post));
+    int elements_erased = pending_posts_.erase(completed_post);
+    DCHECK(elements_erased);

[rkc, 2014/08/13 15:41:51]

This will probably throw an unused variable compile error on release builds.

[Charlie, 2014/08/13 15:48:27]

Nope, I've used this pattern before. There's even a comment about this when
DCHECK is defined:

https://code.google.com/p/chromium/codesearch#chromium/src/base/logging.h&l=616

     delete completed_post;
   }
 
   if (http_status_code != net::HTTP_OK) {
     init_done_callback.Run(false);
     return;
   }
 
   RegisterDeviceResponse response;
   if (!response.ParseFromString(response_data)) {
     LOG(ERROR) << "Invalid RegisterDeviceResponse:\n" << response_data;
     init_done_callback.Run(false);
     return;
   }
 
   if (CopresenceErrorLogged(response.header().status()))
     return;
   device_id_ = response.registered_device_id();
   DCHECK(!device_id_.empty());
   DVLOG(2) << "Device registration successful: id " << device_id_;
   init_done_callback.Run(true);
 }
 
 void RpcHandler::ReportResponseHandler(const StatusCallback& status_callback,
                                        HttpPost* completed_post,
                                        int http_status_code,
                                        const std::string& response_data) {
   if (completed_post) {
-    DCHECK(pending_posts_.erase(completed_post));
+    int elements_erased = pending_posts_.erase(completed_post);
+    DCHECK(elements_erased);
     delete completed_post;
   }
 
   if (http_status_code != net::HTTP_OK) {
     if (!status_callback.is_null())
       status_callback.Run(FAIL);
     return;
   }
 
   DVLOG(3) << "Received ReportResponse.";
@@ skipping 179 matching lines @@
     bool audible,
     const WhispernetClient::SamplesCallback& samples_callback) {
   WhispernetClient* whispernet_client = delegate_->GetWhispernetClient();
   if (whispernet_client) {
     whispernet_client->RegisterSamplesCallback(samples_callback);
     whispernet_client->EncodeToken(token, audible);
   }
 }
 
 }  // namespace copresence