infiniterecursiveloop.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004-2006 University of Maryland
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.detect;


import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XMethod;

public class InfiniteRecursiveLoop extends BytecodeScanningDetector implements 
		StatelessDetector {

	private BugReporter bugReporter;

	private boolean seenTransferOfControl;

	private boolean seenReturn;

	private boolean seenThrow;

	private boolean seenStateChange;

	private int largestBranchTarget;

	private final static boolean DEBUG = SystemProperties.getBoolean("irl.debug");

	public InfiniteRecursiveLoop(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}



	@Override
		 public void visit(JavaClass obj) {
	}


	@Override
		 public void visit(Method obj) {
		seenTransferOfControl = false;
		seenStateChange = false;
		seenReturn = false;
		seenThrow = false;
		largestBranchTarget = -1;
		try {
		stack.resetForMethodEntry(this);
		} catch (Throwable e) {
			throw new RuntimeException("error in " + getFullyQualifiedMethodName() + " " + e.getMessage(), e);
		}
		if (DEBUG) {
			System.out.println();
			System.out.println(" --- " + getFullyQualifiedMethodName());
			System.out.println();
		}
	}

	@Override
		 public void sawBranchTo(int seen) {
		if (largestBranchTarget < seen)
			largestBranchTarget = seen;
		seenTransferOfControl = true;
	}

	OpcodeStack stack = new OpcodeStack();

	/** Signal an infinite loop if either:
	 * we see a call to the same method with the same parameters, or
	 * we see a call to the same (dynamically dispatched method), and there
	 * has been no transfer of control.	
	 */
	@Override
		 public void sawOpcode(int seen) {
		stack.mergeJumps(this);
		if (seenReturn && seenTransferOfControl && seenStateChange)
			return;

		if (DEBUG) {
			System.out.println(stack);
			System.out.println(getPC() + " : " + OPCODE_NAMES[seen]);
		}

		if ((seen == INVOKEVIRTUAL || seen == INVOKEINTERFACE)
				&& getNameConstantOperand().equals("add")
				&& getSigConstantOperand().equals("(Ljava/lang/Object;)Z")
				&& stack.getStackDepth() >= 2) {
			OpcodeStack.Item it0 = stack.getStackItem(0);
			int r0 = it0.getRegisterNumber();
			OpcodeStack.Item it1 = stack.getStackItem(1);
			int r1 = it1.getRegisterNumber();
			if (r0 == r1 && r0 > 0)
				bugReporter.reportBug(new BugInstance(this, "IL_CONTAINER_ADDED_TO_ITSELF",
						NORMAL_PRIORITY).addClassAndMethod(this).addSourceLine(this));
		}

		if ((seen == INVOKEVIRTUAL || seen == INVOKESPECIAL || seen == INVOKEINTERFACE || seen == INVOKESTATIC)
				&& getNameConstantOperand().equals(getMethodName())
				&& getSigConstantOperand().equals(getMethodSig())
				&& (seen == INVOKESTATIC) == getMethod().isStatic()
				&& (seen == INVOKESPECIAL) == (getMethod().isPrivate() || getMethodName().equals("<init>"))
				) {
			Type arguments[] = getMethod().getArgumentTypes();
				// stack.getStackDepth() >= parameters
			int parameters = arguments.length;
			if (!getMethod().isStatic()) parameters++;
			XMethod xMethod = XFactory.createReferencedXMethod(this);
			if (DEBUG) {
				System.out.println("IL: Checking...");
				System.out.println(xMethod);
				System.out.println("vs. " + getClassName() + "." + getMethodName() + " : "
						+ getMethodSig());

			}
			if (xMethod.getClassName().replace('.','/').equals(getClassName()) || seen == INVOKEINTERFACE) {
				// Invocation of same method
				// Now need to see if parameters are the same
				int firstParameter = 0;
				if (getMethodName().equals("<init>"))
					firstParameter = 1;

				// match1 should be true if it is any call to the exact same method
				// and no state has been change. 
				// if match1 is true, the method may not always perform
				// a recursive infinite loop, but this particular method call is an infinite
				// recursive loop

				boolean match1 = !seenStateChange;
				for (int i = firstParameter; match1 && i < parameters; i++) {
					OpcodeStack.Item it = stack.getStackItem(parameters - 1 - i);
					if (!it.isInitialParameter() || it.getRegisterNumber() != i)
						match1 = false;
				}

				boolean sameMethod = seen == INVOKESTATIC
						|| getNameConstantOperand().equals("<init>");
				if (!sameMethod) {
					// Have to check if first parmeter is the same
					// know there must be a this argument
					if (DEBUG) 
						System.out.println("Stack is " + stack);
					OpcodeStack.Item p = stack.getStackItem(parameters - 1);
					if (DEBUG) 
						System.out.println("parameters = " + parameters + ", Item is " + p);
					String sig = p.getSignature(); 
					sameMethod =  p.isInitialParameter() && p.getRegisterNumber() == 0 && sig.equals("L" + getClassName() +";");

				}

				// match2 and match3 are two different ways of seeing if the call site
				// postdominates the method entry. 

				// technically, we use (!seenTransferOfControl || !seenReturn && largestBranchTarget < getPC())
				// as a check that the call site postdominates the method entry. If those are true,
				// and sameMethod is true, we have a guaranteed IL.

				boolean match2 = sameMethod && !seenTransferOfControl;
				boolean match3 = sameMethod && !seenReturn && largestBranchTarget < getPC();
				if (match1 || match2 || match3) {
					if (DEBUG)
						System.out.println("IL: " + sameMethod + " " + match1 + " " + match2 + " " + match3);
					int priority = HIGH_PRIORITY;
					if (!match1 && !match2 && seenThrow) priority = NORMAL_PRIORITY;
					if (seen == INVOKEINTERFACE) priority = NORMAL_PRIORITY;
					bugReporter.reportBug(new BugInstance(this, "IL_INFINITE_RECURSIVE_LOOP",
							HIGH_PRIORITY).addClassAndMethod(this).addSourceLine(this));
				}
			}
		}

		switch (seen) {
		case ARETURN:
		case IRETURN:
		case LRETURN:
		case RETURN:
		case DRETURN:
		case FRETURN:
			seenReturn = true;
			seenTransferOfControl = true;
			break;
		case ATHROW:
			seenThrow = true;
			seenTransferOfControl = true;
			break;
		case PUTSTATIC:
		case PUTFIELD:
		case IASTORE:
		case AASTORE:
		case DASTORE:
		case FASTORE:
		case LASTORE:
		case SASTORE:
		case CASTORE:
		case BASTORE:
		case INVOKEVIRTUAL:
		case INVOKESPECIAL:
		case INVOKEINTERFACE:
		case INVOKESTATIC:
			seenStateChange = true;
			break;
		}
		stack.sawOpcode(this, seen);
	}

}