From 7449a77618fd11220b3a7b0535457c5f7c07863b Mon Sep 17 00:00:00 2001
From: Zhou Wang <zhouwang@microsoft.com>
Date: Thu, 15 Sep 2016 15:44:45 +0200
Subject: [PATCH] use struct-level static instead of local static as work
 around to ensure thread-safety in VS2013

---
 Makefile                          |  1 +
 Source/Common/Common.vcxproj      |  1 +
 Source/Common/Include/Sequences.h | 10 ++++++++--
 Source/Common/Sequences.cpp       | 18 ++++++++++++++++++
 4 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 Source/Common/Sequences.cpp

diff --git a/Makefile b/Makefile
index f44cf3819..185ebd0a2 100644
--- a/Makefile
+++ b/Makefile
@@ -274,6 +274,7 @@ COMMON_SRC =\
 	$(SOURCEDIR)/Common/File.cpp \
 	$(SOURCEDIR)/Common/TimerUtility.cpp \
 	$(SOURCEDIR)/Common/fileutil.cpp \
+	$(SOURCEDIR)/Common/Sequences.cpp \
 
 MATH_SRC =\
 	$(SOURCEDIR)/Math/BatchNormalizationEngine.cpp \
diff --git a/Source/Common/Common.vcxproj b/Source/Common/Common.vcxproj
index 6dce529d7..62933346a 100644
--- a/Source/Common/Common.vcxproj
+++ b/Source/Common/Common.vcxproj
@@ -67,6 +67,7 @@
     <ClCompile Include="fileutil.cpp" />
     <ClCompile Include="Globals.cpp" />
     <ClCompile Include="MPIWrapper.cpp" />
+    <ClCompile Include="Sequences.cpp" />
     <ClCompile Include="TimerUtility.cpp" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
diff --git a/Source/Common/Include/Sequences.h b/Source/Common/Include/Sequences.h
index b538eddc3..d08bea713 100644
--- a/Source/Common/Include/Sequences.h
+++ b/Source/Common/Include/Sequences.h
@@ -268,9 +268,11 @@ public:
     void SetAxisName(const std::wstring& name) { m_axisName = name; }
     void SetUniqueAxisName(std::wstring name) // helper for constructing
     {
-        // Unfortunatelly, the following initialization of local static variables is not thread-safe in VS2013.
+        // Unfortunatelly, initialization of local static variables is not thread-safe in VS2013.
+        // As workaround, it is moved to the struct level. 
+        // Todo: when upgraded to VS2013, change back to use the local static mutex, and remove also Sequences.cpp.
         // The mutex is need to make access to nameIndices be thread-safe.
-        static std::mutex nameIndiciesMutex;
+        // static std::mutex nameIndiciesMutex;
         static std::map<std::wstring, size_t> nameIndices;
         size_t index;
 
@@ -577,6 +579,10 @@ private:
     // For now only a string meant for debugging.
     std::wstring m_axisName;
 
+    // The mutex to searilize the access to nameIndices in SetUniqueAxisName().
+    // Todo: after upgraded to VS2015, move this static variable into SetUnqiueAxisName() as local static variable there.
+    static std::mutex nameIndiciesMutex;
+
 public:
 
     // special accessor for sequence training  --TODO: must be replaced by a different mechanism
diff --git a/Source/Common/Sequences.cpp b/Source/Common/Sequences.cpp
new file mode 100644
index 000000000..0ea304898
--- /dev/null
+++ b/Source/Common/Sequences.cpp
@@ -0,0 +1,18 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.md file in the project root for full license information.
+//
+
+#ifndef _CRT_SECURE_NO_WARNINGS
+#define _CRT_SECURE_NO_WARNINGS // "secure" CRT not available on all platforms  --add this at the top of all CPP files that give "function or variable may be unsafe" warnings
+#endif
+
+#include "Sequences.h"
+
+namespace Microsoft { namespace MSR { namespace CNTK {
+
+    // define the static member of MBLayout.
+    // Todo: After upgrade to VS2015, remove this when nameIndiciesMutex is moved into SetUnqiueAxisName as local static variable.
+    std::mutex MBLayout::nameIndiciesMutex;
+
+}}}
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