SERVER-17655 polyfill make_unique in stdx

SConstruct

@@ -1770,6 +1770,29 @@ def doConfigure(myenv):
 
     myenv = conf.Finish()
 
+    def CheckCXX14MakeUnique(context):
+        test_body = """
+        #include <memory>
+        int main(int argc, char **argv) {
+            auto foo = std::make_unique<int>(5);
+            return 0;
+        }
+        """
+        context.Message('Checking for C++14 std::make_unique support... ')
+        ret = context.TryCompile(textwrap.dedent(test_body), '.cpp')
+        context.Result(ret)
+        return ret
+
+    # Check for std::make_unique support without using the __cplusplus macro
+    conf = Configure(myenv, help=False, custom_tests = {
+        'CheckCXX14MakeUnique': CheckCXX14MakeUnique,
+    })
+
+    if conf.CheckCXX14MakeUnique():
+        conf.env.Append(CPPDEFINES=['MONGO_HAVE_STD_MAKE_UNIQUE'])
+
+    myenv = conf.Finish()
+
     def CheckBoostMinVersion(context):
         compile_test_body = textwrap.dedent("""
         #include <boost/version.hpp>

src/mongo/db/db.cpp

@@ -93,6 +93,7 @@
 #include "mongo/db/ttl.h"
 #include "mongo/platform/process_id.h"
 #include "mongo/scripting/engine.h"
+#include "mongo/stdx/memory.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/cmdline_utils/censor_cmdline.h"
 #include "mongo/util/concurrency/task.h"
@@ -477,7 +478,7 @@ namespace mongo {
         }
 
         getGlobalEnvironment()->setGlobalStorageEngine(storageGlobalParams.engine);
-        getGlobalEnvironment()->setOpObserver(std::unique_ptr<OpObserver>(new OpObserver));
+        getGlobalEnvironment()->setOpObserver(stdx::make_unique<OpObserver>());
 
         const repl::ReplSettings& replSettings =
                 repl::getGlobalReplicationCoordinator()->getSettings();

src/mongo/stdx/memory.h

@@ -0,0 +1,55 @@
+/**
+ *    Copyright (C) 2015 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#if defined(MONGO_HAVE_STD_MAKE_UNIQUE)
+
+#include <memory>
+
+namespace mongo {
+namespace stdx {
+
+    using ::std::make_unique;
+
+}  // namespace stdx
+}  // namespace mongo
+
+#else
+
+#include <boost/smart_ptr/make_unique.hpp>
+
+namespace mongo {
+namespace stdx {
+
+    using boost::make_unique;
+
+}  // namespace stdx
+}  // namespace mongo
+
+#endif