Crash in DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

Index: webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
index b17c195340b0e495fa6e123a2b33c06141e9a2c5..bd321d5e1ef46d814622c66bede6d7cb8bc83de1 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
@@ -16,6 +16,8 @@
 #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"
@@ -274,29 +276,20 @@ 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);
     }