From 71edc49814448de0a3c3617b6664c0801abf3cdd Mon Sep 17 00:00:00 2001
From: tqchen <tianqi.tchen@gmail.com>
Date: Fri, 25 Sep 2015 21:00:07 -0700
Subject: [PATCH 1/2] [ENGINE] Change obj pool to normal struct instead of
 union, to support more compiler

---
 include/mxnet/base.h     | 3 ++-
 src/common/object_pool.h | 7 ++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/mxnet/base.h b/include/mxnet/base.h
index b5670070ae1a..1ef9c6bf8450 100644
--- a/include/mxnet/base.h
+++ b/include/mxnet/base.h
@@ -42,7 +42,8 @@
  *  Used to support g++-4.6 and g++4.7
  */
 #if DMLC_USE_CXX11 && defined(__GNUC__) && !defined(__clang_version__)
-#if __GNUC__ == 4 && __GNUC_MINOR__ == 6
+#if __GNUC__ == 4 && __GNUC_MINOR__ < 8
+#error "Currently we need g++ 4.8 or higher to fully support c++11 features"
 #define override
 #define final
 #endif
diff --git a/src/common/object_pool.h b/src/common/object_pool.h
index 43d309e24bf5..0306ed6ef355 100644
--- a/src/common/object_pool.h
+++ b/src/common/object_pool.h
@@ -46,10 +46,15 @@ class ObjectPool {
    * \brief Internal structure to hold pointers.
    */
   struct LinkedList {
+#if defined(_MSC_VER)
+    T t;
+    LinkedList* next{nullptr};
+#else
     union {
-      LinkedList* next{nullptr};
       T t;
+      LinkedList* next{nullptr};
     };
+#endif
   };
   /*!
    * \brief Page size of allocation.

From a801b3e36a3b2110df4252e5e67d27c13dddf560 Mon Sep 17 00:00:00 2001
From: tqchen <tianqi.tchen@gmail.com>
Date: Fri, 25 Sep 2015 23:16:13 -0700
Subject: [PATCH 2/2] Some update

---
 scripts/travis_script.sh      | 1 +
 src/engine/threaded_engine.cc | 6 ++++++
 src/engine/threaded_engine.h  | 6 +++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/scripts/travis_script.sh b/scripts/travis_script.sh
index 68f5a9211628..dd2a62c8b37b 100755
--- a/scripts/travis_script.sh
+++ b/scripts/travis_script.sh
@@ -81,6 +81,7 @@ if [ ${TASK} == "cpp_unittest" ]; then
     echo "GTEST_PATH="${CACHE_PREFIX} >> config.mk
     make test || exit -1
     export MXNET_ENGINE_TYPE=ThreadedEngine
+    export MXNET_ENGINE_INFO=true
     for test in tests/cpp/*_test; do
         ./$test || exit -1
     done
diff --git a/src/engine/threaded_engine.cc b/src/engine/threaded_engine.cc
index ea122a67becf..1f71e9154761 100644
--- a/src/engine/threaded_engine.cc
+++ b/src/engine/threaded_engine.cc
@@ -302,11 +302,17 @@ void ThreadedEngine::WaitForVar(VarHandle var) {
   if (threaded_var->ready_to_read()) return;
   std::atomic<bool> done{false};
   this->PushSync([this, &done](RunContext) {
+      if (engine_info_) {
+        LOG(INFO) << "Sync is executed";
+      }
       {
         std::unique_lock<std::mutex> lock{finished_m_};
         done.store(true);
       }
       finished_cv_.notify_all();
+      if (engine_info_) {
+        LOG(INFO) << "Sync is notified";
+      }
     }, Context::CPU(), {var}, {}, FnProperty::kNormal);
   {
     std::unique_lock<std::mutex> lock{finished_m_};
diff --git a/src/engine/threaded_engine.h b/src/engine/threaded_engine.h
index 13c55c6d5747..7a8708484f9c 100644
--- a/src/engine/threaded_engine.h
+++ b/src/engine/threaded_engine.h
@@ -249,7 +249,9 @@ class ThreadedEngine : public Engine {
     shutdown_phase_.store(true);
   }
 
-  ThreadedEngine() {}
+  ThreadedEngine() {
+    engine_info_ = dmlc::GetEnv("MXNET_ENGINE_INFO", false);
+  }
   ~ThreadedEngine() {
     {
       std::unique_lock<std::mutex> lock{finished_m_};
@@ -319,6 +321,8 @@ class ThreadedEngine : public Engine {
   std::atomic<bool> kill_{false};
   /*! \brief whether it is during shutdown phase*/
   std::atomic<bool> shutdown_phase_{false};
+  /*!\brief show more information from engine actions */
+  bool engine_info_{false};
   /*!
    * \brief Mutex and condition_variable,
    *  used to Notify waits for single or all variables.