--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/flags/flagSetting.hpp	Mon Apr 23 10:59:39 2018 -0500
@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP
+#define SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP
+
+#include "memory/allocation.hpp"
+
+// debug flags control various aspects of the VM and are global accessible
+
+// use FlagSetting to temporarily change some debug flag
+// e.g. FlagSetting fs(DebugThisAndThat, true);
+// restored to previous value upon leaving scope
+class FlagSetting : public StackObj {
+  bool val;
+  bool* flag;
+public:
+  FlagSetting(bool& fl, bool newValue) { flag = &fl; val = fl; fl = newValue; }
+  ~FlagSetting()                       { *flag = val; }
+};
+
+class UIntFlagSetting : public StackObj {
+  uint val;
+  uint* flag;
+public:
+  UIntFlagSetting(uint& fl, uint newValue) { flag = &fl; val = fl; fl = newValue; }
+  ~UIntFlagSetting()                       { *flag = val; }
+};
+
+class SizeTFlagSetting : public StackObj {
+  size_t val;
+  size_t* flag;
+public:
+  SizeTFlagSetting(size_t& fl, size_t newValue) { flag = &fl; val = fl; fl = newValue; }
+  ~SizeTFlagSetting()                           { *flag = val; }
+};
+
+// Helper class for temporarily saving the value of a flag during a scope.
+template <size_t SIZE>
+class FlagGuard {
+  unsigned char _value[SIZE];
+  void* const _addr;
+public:
+  FlagGuard(void* flag_addr) : _addr(flag_addr) { memcpy(_value, _addr, SIZE); }
+  ~FlagGuard()                                  { memcpy(_addr, _value, SIZE); }
+};
+
+#define FLAG_GUARD(f) FlagGuard<sizeof(f)> f ## _guard(&f)
+
+#endif // SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP