EscapedThisReferenceChecker.java

package org.mutabilitydetector.checkers;

/*
 * #%L
 * MutabilityDetector
 * %%
 * Copyright (C) 2008 - 2014 Graham Allan
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the 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.
 * #L%
 */



import java.util.ArrayList;
import java.util.List;

import org.mutabilitydetector.MutabilityReason;
import org.mutabilitydetector.checkers.util.StackPushingOpcodes;
import org.mutabilitydetector.locations.CodeLocation.ClassLocation;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.FieldInsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;

public final class EscapedThisReferenceChecker extends AsmMutabilityChecker {

    @Override
    public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
        super.visitMethod(access, name, desc, signature, exceptions);
        return MethodIs.aConstructor(name)
                ? new ThisEscapingFromConstructorVistor(access, name, desc, signature, exceptions)
                : null;
    }

    private final class ThisEscapingFromConstructorVistor extends MethodNode {

        private final List<MethodInsnNode> methodCalls = new ArrayList<MethodInsnNode>();
        private final List<FieldInsnNode> fieldAssignmentsInConstructor = new ArrayList<FieldInsnNode>();

        private final StackPushingOpcodes stackPushingOpcodes = new StackPushingOpcodes();

        public ThisEscapingFromConstructorVistor(int access,
                String name,
                String desc,
                String signature,
                String[] exceptions) {
            super(Opcodes.ASM5, access, name, desc, signature, exceptions);
        }

        @Override
        public void visitMethodInsn(int opcode, String owner, String methodName, String methodDesc, boolean isInterface) {
            super.visitMethodInsn(opcode, owner, methodName, methodDesc, isInterface);
            if (MethodIs.aConstructor(methodName) && owner.equals("java/lang/Object")) { return; }
            methodCalls.add((MethodInsnNode) instructions.getLast());
        }

        @Override
        public void visitFieldInsn(int opcode, String owner, String fieldName, String fieldDesc) {
            super.visitFieldInsn(opcode, owner, fieldName, fieldDesc);

            if (opcode == Opcodes.PUTSTATIC || opcode == Opcodes.PUTFIELD) {
                fieldAssignmentsInConstructor.add((FieldInsnNode) instructions.getLast());
            }

        }

        @Override
        public void visitEnd() {
            super.visitEnd();

            checkForPassingThisReferenceAsParameter();
            checkForSettingFieldToThisReference();
        }

        private void checkForSettingFieldToThisReference() {
            if (fieldAssignmentsInConstructor.isEmpty()) { return; }

            for (FieldInsnNode fieldInstruction : fieldAssignmentsInConstructor) {
                checkFieldAssignment(fieldInstruction);
            }

        }

        private void checkFieldAssignment(FieldInsnNode assignment) {
            AbstractInsnNode previous = assignment.getPrevious();
            if (stackPushingOpcodes.includes(previous.getOpcode())) {
                checkForThisReferenceBeingPutOnStack(previous);
            }

        }

        private void checkForPassingThisReferenceAsParameter() {
            if (methodCalls.isEmpty()) { return; }

            for (MethodInsnNode methodInsnNode : methodCalls) {
                checkMethodCall(methodInsnNode);
            }
        }

        private void checkMethodCall(MethodInsnNode methodInsnNode) {
            AbstractInsnNode previous = methodInsnNode.getPrevious();
            Type[] argumentTypes = Type.getArgumentTypes(methodInsnNode.desc);
            int numberOfArguments = argumentTypes.length;

            for (int i = numberOfArguments - 1; i >= 0; i--) {
                if (instructionPushesSomethingElseOnTheStack(previous)) {
                    i = i + 1;
                }

                checkForThisReferenceBeingPutOnStack(previous);

                previous = previous.getPrevious();
            }
        }

        private boolean instructionPushesSomethingElseOnTheStack(AbstractInsnNode previous) {
            switch(previous.getOpcode()) {
            case Opcodes.DUP:
            case Opcodes.NEW:
                return true;
            default:
                return false;
            }
        }

        private void checkForThisReferenceBeingPutOnStack(AbstractInsnNode previous) {
            if (previous instanceof VarInsnNode) {
                VarInsnNode varInstruction = (VarInsnNode) previous;
                if (varInstruction.var == 0) {
                    thisReferencesEscapes();
                }
            }
        }

        private void thisReferencesEscapes() {
            setResult("The 'this' reference is passed outwith the constructor.",
                    ClassLocation.fromInternalName(ownerClass),
                    MutabilityReason.ESCAPED_THIS_REFERENCE);
        }
    }
}