Make string_util::WriteInto() DCHECK() that the supplied |length_with_null| > 1, meaning that the...

media/audio/win/audio_manager_win.cc

 // Copyright (c) 2011 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 "media/audio/audio_io.h"
 
 #include <windows.h>
 #include <objbase.h>  // This has to be before initguid.h
 #include <initguid.h>
 #include <mmsystem.h>
@@ skipping 172 matching lines @@
 string16 AudioManagerWin::GetAudioInputDeviceModel() {
   // Get the default audio capture device and its device interface name.
   DWORD device_id = 0;
   waveInMessage(reinterpret_cast<HWAVEIN>(WAVE_MAPPER),
                 DRVM_MAPPER_PREFERRED_GET,
                 reinterpret_cast<DWORD_PTR>(&device_id), NULL);
   ULONG device_interface_name_size = 0;
   waveInMessage(reinterpret_cast<HWAVEIN>(device_id),
                 DRV_QUERYDEVICEINTERFACESIZE,
                 reinterpret_cast<DWORD_PTR>(&device_interface_name_size), 0);
-  if (device_interface_name_size == 0)  // No audio capture device?
-    return string16();
+  size_t bytes_in_char16 = sizeof(string16::value_type);
+  DCHECK_EQ(0u, device_interface_name_size % bytes_in_char16);
+  if (device_interface_name_size <= bytes_in_char16)
+    return string16();  // No audio capture device.
 
   string16 device_interface_name;
   string16::value_type* name_ptr = WriteInto(&device_interface_name,
-      device_interface_name_size / sizeof(string16::value_type));
+      device_interface_name_size / bytes_in_char16);
   waveInMessage(reinterpret_cast<HWAVEIN>(device_id),
                 DRV_QUERYDEVICEINTERFACE,
                 reinterpret_cast<DWORD_PTR>(name_ptr),
                 static_cast<DWORD_PTR>(device_interface_name_size));
 
   // Enumerate all audio devices and find the one matching the above device
   // interface name.
   HDEVINFO device_info = SetupDiGetClassDevs(
       &AM_KSCATEGORY_AUDIO, 0, 0, DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);
   if (device_info == INVALID_HANDLE_VALUE)
@@ skipping 67 matching lines @@
     name.device_name = AudioManagerBase::kDefaultDeviceName;
     name.unique_id = "0";
     device_names->push_back(name);
   }
 }
 
 // static
 AudioManager* AudioManager::CreateAudioManager() {
   return new AudioManagerWin();
 }