Initialize |bytes_so_far| local variable in SaveFileManager::SaveFinished.

content/browser/download/save_file_manager.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 "build/build_config.h"
 
 #include "content/browser/download/save_file_manager.h"
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
@@ skipping 188 matching lines @@
 // fetching data. We forward the message to OnSaveFinished in UI thread.
 void SaveFileManager::SaveFinished(SaveItemId save_item_id,
                                    SavePackageId save_package_id,
                                    bool is_success) {
   DVLOG(20) << " " << __FUNCTION__ << "()"
             << " save_item_id = " << save_item_id
             << " save_package_id = " << save_package_id
             << " is_success = " << is_success;
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
 
-  int64_t bytes_so_far;
+  int64_t bytes_so_far = 0;

[Łukasz Anforowicz, 2016/03/24 18:23:28]

I think 0 is safe fallback here.  Initializing to some non-sensical value (like
-1 or int64-max-value) risks mishandling of the non-sense somewhere down the
code (i.e. in functions receiving this value).

PS. Before I was aware that the style guide mandates initialization everywhere,
I thought that not initializing might be preferable, because 1) the compiler can
catch it in simple cases [1] and 2) asan should catch it in more complex cases
(and after this CL this won't longer be true - the variable will always be
initialized to a "fallback" value).  Do you think this makes sense?  Does it
need a broader discussion (i.e. on chromium-dev) or is it not really worth it?

[Randy Smith (Not in Mondays), 2016/03/24 19:17:49]

I don't think a broader discussion is worth it.  This seems like a reasonable
default; I'm a bit inclined to skip the re-assignment below, and just implement
the semantic decision of "We got zero bytes unless the save file told us we got
more than zero."  

[Łukasz Anforowicz, 2016/03/24 19:25:58]

Makes sense - done.

   SaveFile* save_file = LookupSaveFile(save_item_id);
   if (save_file != nullptr) {
     DCHECK(save_file->InProgress());
     DVLOG(20) << " " << __FUNCTION__ << "()"
               << " save_file = " << save_file->DebugString();
     bytes_so_far = save_file->BytesSoFar();
     save_file->Finish();
     save_file->Detach();
   } else {
     // We got called before StartSave - this should only happen if
@@ skipping 201 matching lines @@
       SaveFile* save_file = it->second;
       DCHECK(!save_file->InProgress());
       base::DeleteFile(save_file->FullPath(), false);
       delete save_file;
       save_file_map_.erase(it);
     }
   }
 }
 
 }  // namespace content