gt:             fallbackLinkers = Collections.singletonList(new BeansLinker());
context: /*
   * Copyright (c) 2010, 2013, 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.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * 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.
   */
  
  /*
   * This file is available under and governed by the GNU General Public
   * License version 2 only, as published by the Free Software Foundation.
   * However, the following notice accompanied the original version of this
   * file, and Oracle licenses the original version of this file under the BSD
   * license:
   */
  /*
     Copyright 2009-2013 Attila Szegedi
  
     Licensed under both the Apache License, Version 2.0 (the "Apache License")
     and the BSD License (the "BSD License"), with licensee being free to
     choose either of the two at their discretion.
  
     You may not use this file except in compliance with either the Apache
     License or the BSD License.
  
     If you choose to use this file in compliance with the Apache License, the
     following notice applies to you:
  
         You may obtain a copy of the Apache License at
  
             http://www.apache.org/licenses/LICENSE-2.0
  
         Unless required by applicable law or agreed to in writing, software
         distributed under the License is distributed on an "AS IS" BASIS,
         WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
         implied. See the License for the specific language governing
         permissions and limitations under the License.
  
     If you choose to use this file in compliance with the BSD License, the
     following notice applies to you:
  
         Redistribution and use in source and binary forms, with or without
         modification, are permitted provided that the following conditions are
         met:
         * Redistributions of source code must retain the above copyright
           notice, this list of conditions and the following disclaimer.
         * Redistributions in binary form must reproduce the above copyright
           notice, this list of conditions and the following disclaimer in the
           documentation and/or other materials provided with the distribution.
         * Neither the name of the copyright holder nor the names of
           contributors may be used to endorse or promote products derived from
           this software without specific prior written permission.
  
         THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
         IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
         TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
         PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
         BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
         CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
         SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
         BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
         WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
         OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
         ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
  
  package jdk.internal.dynalink;
  
  import java.lang.invoke.MutableCallSite;
  import java.security.AccessController;
  import java.security.PrivilegedAction;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Set;
  import jdk.internal.dynalink.beans.BeansLinker;
  import jdk.internal.dynalink.linker.GuardingDynamicLinker;
  import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;
  import jdk.internal.dynalink.linker.LinkRequest;
  import jdk.internal.dynalink.support.AutoDiscovery;
  import jdk.internal.dynalink.support.BottomGuardingDynamicLinker;
  import jdk.internal.dynalink.support.ClassLoaderGetterContextProvider;
  import jdk.internal.dynalink.support.CompositeGuardingDynamicLinker;
  import jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker;
  import jdk.internal.dynalink.support.DefaultPrelinkFilter;
  import jdk.internal.dynalink.support.LinkerServicesImpl;
  import jdk.internal.dynalink.support.TypeConverterFactory;
  
  /**
   * A factory class for creating {@link DynamicLinker}s. The most usual dynamic linker is a linker that is a composition
   * of all {@link GuardingDynamicLinker}s known and pre-created by the caller as well as any
   * {@link AutoDiscovery automatically discovered} guarding linkers and the standard fallback {@link BeansLinker} and a
   * {@link DefaultPrelinkFilter}. See {@link DynamicLinker} documentation for tips on how to use this class.
   *
   * @author Attila Szegedi
   */
  public class DynamicLinkerFactory {
  
      /**
       * Default value for {@link #setUnstableRelinkThreshold(int) unstable relink threshold}.
       */
      public static final int DEFAULT_UNSTABLE_RELINK_THRESHOLD = 8;
  
      private boolean classLoaderExplicitlySet = false;
      private ClassLoader classLoader;
  
      private List<? extends GuardingDynamicLinker> prioritizedLinkers;
      private List<? extends GuardingDynamicLinker> fallbackLinkers;
      private int runtimeContextArgCount = 0;
      private boolean syncOnRelink = false;
      private int unstableRelinkThreshold = DEFAULT_UNSTABLE_RELINK_THRESHOLD;
      private GuardedInvocationFilter prelinkFilter;
  
      /**
       * Sets the class loader for automatic discovery of available linkers. If not set explicitly, then the thread
       * context class loader at the time of {@link #createLinker()} invocation will be used.
       *
       * @param classLoader the class loader used for the autodiscovery of available linkers.
       */
      public void setClassLoader(ClassLoader classLoader) {
          this.classLoader = classLoader;
          classLoaderExplicitlySet = true;
      }
  
      /**
       * Sets the prioritized linkers. Language runtimes using this framework will usually precreate at least the linker
       * for their own language. These linkers will be consulted first in the resulting dynamic linker, before any
       * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the prioritized
       * linkers, it will be ignored and the explicit prioritized instance will be used.
       *
       * @param prioritizedLinkers the list of prioritized linkers. Null can be passed to indicate no prioritized linkers
       * (this is also the default value).
       */
      public void setPrioritizedLinkers(List<? extends GuardingDynamicLinker> prioritizedLinkers) {
          this.prioritizedLinkers =
                  prioritizedLinkers == null ? null : new ArrayList<>(prioritizedLinkers);
      }
  
      /**
       * Sets the prioritized linkers. Language runtimes using this framework will usually precreate at least the linker
       * for their own language. These linkers will be consulted first in the resulting dynamic linker, before any
       * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the prioritized
       * linkers, it will be ignored and the explicit prioritized instance will be used.
       *
       * @param prioritizedLinkers a list of prioritized linkers.
       */
      public void setPrioritizedLinkers(GuardingDynamicLinker... prioritizedLinkers) {
          setPrioritizedLinkers(Arrays.asList(prioritizedLinkers));
      }
  
      /**
       * Sets a single prioritized linker. Identical to calling {@link #setPrioritizedLinkers(List)} with a single-element
       * list.
       *
       * @param prioritizedLinker the single prioritized linker. Must not be null.
       * @throws IllegalArgumentException if null is passed.
       */
      public void setPrioritizedLinker(GuardingDynamicLinker prioritizedLinker) {
          if(prioritizedLinker == null) {
              throw new IllegalArgumentException("prioritizedLinker == null");
          }
          this.prioritizedLinkers = Collections.singletonList(prioritizedLinker);
      }
  
      /**
       * Sets the fallback linkers. These linkers will be consulted last in the resulting composite linker, after any
       * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the fallback
       * linkers, it will be ignored and the explicit fallback instance will be used.
       *
       * @param fallbackLinkers the list of fallback linkers. Can be empty to indicate the caller wishes to set no
       * fallback linkers.
       */
      public void setFallbackLinkers(List<? extends GuardingDynamicLinker> fallbackLinkers) {
          this.fallbackLinkers = fallbackLinkers == null ? null : new ArrayList<>(fallbackLinkers);
      }
  
      /**
       * Sets the fallback linkers. These linkers will be consulted last in the resulting composite linker, after any
       * autodiscovered linkers. If the framework also autodiscovers a linker of the same class as one of the fallback
       * linkers, it will be ignored and the explicit fallback instance will be used.
       *
       * @param fallbackLinkers the list of fallback linkers. Can be empty to indicate the caller wishes to set no
       * fallback linkers. If it is left as null, the standard fallback {@link BeansLinker} will be used.
       */
      public void setFallbackLinkers(GuardingDynamicLinker... fallbackLinkers) {
          setFallbackLinkers(Arrays.asList(fallbackLinkers));
      }
  
      /**
       * Sets the number of arguments in the call sites that represent the stack context of the language runtime creating
       * the linker. If the language runtime uses no context information passed on stack, then it should be zero
       * (the default value). If it is set to nonzero value, then every dynamic call site emitted by this runtime must
       * have the argument list of the form: {@code (this, contextArg1[, contextArg2[, ...]], normalArgs)}. It is
       * advisable to only pass one context-specific argument, though, of an easily recognizable, runtime specific type
       * encapsulating the runtime thread local state.
       *
       * @param runtimeContextArgCount the number of language runtime context arguments in call sites.
       */
      public void setRuntimeContextArgCount(int runtimeContextArgCount) {
          if(runtimeContextArgCount < 0) {
              throw new IllegalArgumentException("runtimeContextArgCount < 0");
          }
          this.runtimeContextArgCount = runtimeContextArgCount;
      }
  
      /**
       * Sets whether the linker created by this factory will invoke {@link MutableCallSite#syncAll(MutableCallSite[])}
       * after a call site is relinked. Defaults to false. You probably want to set it to true if your runtime supports
       * multithreaded execution of dynamically linked code.
       * @param syncOnRelink true for invoking sync on relink, false otherwise.
       */
      public void setSyncOnRelink(boolean syncOnRelink) {
          this.syncOnRelink = syncOnRelink;
      }
  
      /**
       * Sets the unstable relink threshold; the number of times a call site is relinked after which it will be
       * considered unstable, and subsequent link requests for it will indicate this.
       * @param unstableRelinkThreshold the new threshold. Must not be less than zero. The value of zero means that
       * call sites will never be considered unstable.
       * @see LinkRequest#isCallSiteUnstable()
       */
      public void setUnstableRelinkThreshold(int unstableRelinkThreshold) {
          if(unstableRelinkThreshold < 0) {
              throw new IllegalArgumentException("unstableRelinkThreshold < 0");
          }
          this.unstableRelinkThreshold = unstableRelinkThreshold;
      }
  
      /**
       * Set the pre-link filter. This is a {@link GuardedInvocationFilter} that will get the final chance to modify the
       * guarded invocation after it has been created by a component linker and before the dynamic linker links it into
       * the call site. It is normally used to adapt the return value type of the invocation to the type of the call site.
       * When not set explicitly, {@link DefaultPrelinkFilter} will be used.
       * @param prelinkFilter the pre-link filter for the dynamic linker.
       */
      public void setPrelinkFilter(GuardedInvocationFilter prelinkFilter) {
          this.prelinkFilter = prelinkFilter;
      }
  
      /**
       * Creates a new dynamic linker consisting of all the prioritized, autodiscovered, and fallback linkers as well as
       * the pre-link filter.
       *
       * @return the new dynamic Linker
       */
      public DynamicLinker createLinker() {
          // Treat nulls appropriately
          if(prioritizedLinkers == null) {
              prioritizedLinkers = Collections.emptyList();
          }
          if(fallbackLinkers == null) {
  