Added DCHECK() to prevent NULL-pointer dereference

media/audio/win/wavein_input_win.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 "media/audio/win/wavein_input_win.h"
 
 #pragma comment(lib, "winmm.lib")
 
 #include "base/logging.h"
 #include "media/audio/audio_io.h"
@@ skipping 80 matching lines @@
     buffer_->dwBufferLength = buffer_size_;
     buffer_->dwBytesRecorded = 0;
     buffer_->dwUser = reinterpret_cast<DWORD_PTR>(last);
     buffer_->dwFlags = WHDR_DONE;
     buffer_->dwLoops = 0;
     if (ix == 0)
       first = buffer_;
     last = buffer_;
     ::waveInPrepareHeader(wavein_, buffer_, sizeof(WAVEHDR));
   }
+  DCHECK(first);

[Tyler Breisacher (Chromium), 2012/07/25 21:18:15]

This can only be NULL if num_buffers_ is 0, I think. Let's make sure that it's
impossible for num_buffers_ to be 0 rather than just adding a DCHECK?

[Kyle Horimoto, 2012/07/25 21:56:40]

num_buffers_ is only assigned to within the constructor. Thus, we can't be sure
what its value is.

   // Fix the first buffer to point to the last one.
   first->dwUser = reinterpret_cast<DWORD_PTR>(last);
 }
 
 void PCMWaveInAudioInputStream::FreeBuffers() {
   WAVEHDR* current = buffer_;
   for (int ix = 0; ix != num_buffers_; ++ix) {
     WAVEHDR* next = GetNextBuffer(current);
     if (current->dwFlags & WHDR_PREPARED)
       ::waveInUnprepareHeader(wavein_, current, sizeof(WAVEHDR));
@@ skipping 181 matching lines @@
     }
   } else if (msg == WIM_CLOSE) {
     // We can be closed before calling Start, so it is possible to have a
     // null callback at this point.
     if (obj->callback_)
       obj->callback_->OnClose(obj);
   }
 }
 
 }  // namespace media