2 * Copyright (C) 2014, United States Government, as represented by the
3 * Administrator of the National Aeronautics and Space Administration.
6 * The Java Pathfinder core (jpf-core) platform is licensed under the
7 * Apache License, Version 2.0 (the "License"); you may not use this file except
8 * in compliance with the License. You may obtain a copy of the License at
10 * http://www.apache.org/licenses/LICENSE-2.0.
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
18 package gov.nasa.jpf.jvm.bytecode;
20 import gov.nasa.jpf.vm.ClassInfo;
21 import gov.nasa.jpf.vm.ElementInfo;
22 import gov.nasa.jpf.vm.Instruction;
23 import gov.nasa.jpf.vm.MethodInfo;
24 import gov.nasa.jpf.vm.ThreadInfo;
27 * this is an artificial bytecode that we use to deal with the particularities of
28 * <clinit> calls, which are never in the loaded bytecode but always directly called by
29 * the VM. The most obvious difference is that <clinit> execution does not trigger
30 * class initialization.
31 * A more subtle difference is that we save a wait() - if a class
32 * is concurrently initialized, both enter INVOKECLINIT (i.e. compete and sync for/on
33 * the class object lock), but once the second thread gets resumed and detects that the
34 * class is now initialized (by the first thread), it skips the method execution and
35 * returns right away (after deregistering as a lock contender). That's kind of hackish,
36 * but we have no method to do the wait in, unless we significantly complicate the
37 * direct call stubs, which would obfuscate observability (debugging dynamically
38 * generated code isn't very appealing).
40 public class INVOKECLINIT extends INVOKESTATIC {
42 public INVOKECLINIT (ClassInfo ci){
43 super(ci.getSignature(), "<clinit>", "()V");
47 public Instruction execute (ThreadInfo ti) {
48 MethodInfo callee = getInvokedMethod(ti);
49 ClassInfo ciClsObj = callee.getClassInfo();
50 ElementInfo ei = ciClsObj.getClassObject();
52 if (ciClsObj.isInitialized()) { // somebody might have already done it if this is re-executed
53 if (ei.isRegisteredLockContender(ti)){
54 ei = ei.getModifiableInstance();
55 ei.unregisterLockContender(ti);
60 // not much use to update sharedness, clinits are automatically synchronized
61 if (reschedulesLockAcquisition(ti, ei)){ // this blocks or registers as lock contender
65 // if we get here we still have to execute the clinit method
66 setupCallee( ti, callee); // this creates, initializes & pushes the callee StackFrame, then acquires the lock
67 ciClsObj.setInitializing(ti);
69 return ti.getPC(); // we can't just return the first callee insn if a listener throws an exception
73 public boolean isExtendedInstruction() {
77 public static final int OPCODE = 256;
80 public int getByteCode () {
85 public void accept(JVMInstructionVisitor insVisitor) {
86 insVisitor.visit(this);