Crash in DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/modules/desktop_capture/win/dxgi_output_duplicator.h"
 
 #include <string.h>
 
 #include <unknwn.h>
 #include <DXGIFormat.h>
 #include <Windows.h>
 
+#include <algorithm>
+
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/desktop_capture/win/dxgi_texture_mapping.h"
 #include "webrtc/modules/desktop_capture/win/dxgi_texture_staging.h"
 
 namespace webrtc {
 
 using Microsoft::WRL::ComPtr;
 
 namespace {
@@ skipping 238 matching lines @@
     dirty_rects_count--;
   }
 
   return true;
 }
 
 void DxgiOutputDuplicator::Setup(Context* context) {
   RTC_DCHECK(context->updated_region.is_empty());
   // Always copy entire monitor during the first Duplicate() function call.
   context->updated_region.AddRect(desktop_rect_);
-  for (size_t i = 0; i < contexts_.size(); i++) {
-    if (contexts_[i] == nullptr) {
-      contexts_[i] = context;
-      return;
-    }
-  }
-
   contexts_.push_back(context);

[Sergey Ulanov, 2016/11/11 22:57:35]

Maybe DCHECK here that context is not already in contexts_?

[Hzj_jie, 2016/11/11 23:28:23]

Done.

 }
 
 void DxgiOutputDuplicator::Unregister(const Context* const context) {
-  for (size_t i = 0; i < contexts_.size(); i++) {
-    if (contexts_[i] == context) {
-      contexts_[i] = nullptr;
-      return;
-    }
-  }
-
-  RTC_NOTREACHED();
+  // There is no ostream operator<< defined for std::vector::iterator, so
+  // RTC_DCHECK_EQ will trigger build break. Refer to webrtc/base/checks.h:130.

[Sergey Ulanov, 2016/11/11 22:57:35]

I don't think you really need this comment, it's a well known problem with
DCHECK_EQ.

[Hzj_jie, 2016/11/11 23:28:23]

Really, I thought it was not so common.

+  RTC_DCHECK(std::find(contexts_.begin(), contexts_.end(), context) !=

[Sergey Ulanov, 2016/11/11 22:57:35]

I'd prefer to save result of std::find() and use it here and in erase() call
below. This would make it clearer how DCHECK is related to the line below it and
the code would be simpler.

[Hzj_jie, 2016/11/11 23:28:23]

Done.

+             contexts_.end());
+  contexts_.erase(std::find(contexts_.begin(), contexts_.end(), context));
 }
 
 void DxgiOutputDuplicator::SpreadContextChange(const Context* const source) {
   for (Context* dest : contexts_) {
+    RTC_DCHECK(dest);
     if (dest != source) {
       dest->updated_region.AddRegion(source->updated_region);
     }
   }
 }
 
 DesktopRect DxgiOutputDuplicator::SourceRect(DesktopRect rect) {
   // |texture_|->AsDesktopFrame() starts from (0, 0).
   rect.Translate(-desktop_rect_.left(), -desktop_rect_.top());
   return rect;
 }
 
 DesktopRect DxgiOutputDuplicator::TargetRect(DesktopRect rect,
                                              DesktopVector offset) {
   rect = SourceRect(rect);
   rect.Translate(offset);
   return rect;
 }
 
 }  // namespace webrtc