JDK14/Java14源码在线阅读

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#ifndef SHARE_RUNTIME_FLAGS_FLAGSETTING_HPP
#define SHARE_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:

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