1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP
  26 #define SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 
  30 // debug flags control various aspects of the VM and are global accessible
  31 
  32 // use FlagSetting to temporarily change some debug flag
  33 // e.g. FlagSetting fs(DebugThisAndThat, true);
  34 // restored to previous value upon leaving scope
  35 class FlagSetting : public StackObj {
  36   bool val;
  37   bool* flag;
  38 public:
  39   FlagSetting(bool& fl, bool newValue) { flag = &fl; val = fl; fl = newValue; }
  40   ~FlagSetting()                       { *flag = val; }
  41 };
  42 
  43 class UIntFlagSetting : public StackObj {
  44   uint val;
  45   uint* flag;
  46 public:
  47   UIntFlagSetting(uint& fl, uint newValue) { flag = &fl; val = fl; fl = newValue; }
  48   ~UIntFlagSetting()                       { *flag = val; }
  49 };
  50 
  51 class SizeTFlagSetting : public StackObj {
  52   size_t val;
  53   size_t* flag;
  54 public:
  55   SizeTFlagSetting(size_t& fl, size_t newValue) { flag = &fl; val = fl; fl = newValue; }
  56   ~SizeTFlagSetting()                           { *flag = val; }
  57 };
  58 
  59 // Helper class for temporarily saving the value of a flag during a scope.
  60 template <size_t SIZE>
  61 class FlagGuard {
  62   unsigned char _value[SIZE];
  63   void* const _addr;
  64 public:
  65   FlagGuard(void* flag_addr) : _addr(flag_addr) { memcpy(_value, _addr, SIZE); }
  66   ~FlagGuard()                                  { memcpy(_addr, _value, SIZE); }
  67 };
  68 
  69 #define FLAG_GUARD(f) FlagGuard<sizeof(f)> f ## _guard(&f)
  70 
  71 #endif // SHARE_VM_RUNTIME_FLAGS_FLAGSETTING_HPP