atomicityproblem.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 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 java.util.HashSet;

import org.apache.bcel.Repository;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.ConstantNameAndType;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.Detector;
import edu.umd.cs.findbugs.MethodAnnotation;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.PruneUnconditionalExceptionThrowerEdges;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
import edu.umd.cs.findbugs.visitclass.DismantleBytecode;
import edu.umd.cs.findbugs.BytecodeScanningDetector;

/**
 *	if we get from a ConcurrentHashMap and assign to a variable...
 * 		and don't do anything else
 * 			and perform a null check on it...
 * 				and then do a set on it... (or anything else inside the if that modifies it?)
 * 					then we have a bug.
 * 
 * @author Michael Midgley-Biggs
 */
public class AtomicityProblem extends OpcodeStackDetector {

	int priority = IGNORE_PRIORITY;
	int lastQuestionableCheckTarget = -1;
	private BugReporter bugReporter;
	final static boolean DEBUG = false;

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

	@Override
	public void visit(Code obj) {
		if (DEBUG) {
			System.out.println("Checking " + obj);
		}
		lastQuestionableCheckTarget = -1;
		super.visit(obj);
	}

	/**
	 * This is the "dumb" version of the detector.  It may generate false positives, and/or not detect all instances of the bug.
	 * 
	 * @see edu.umd.cs.findbugs.visitclass.DismantleBytecode#sawOpcode(int)
	 */
	@Override
	public void sawOpcode(int seen) {
		if (DEBUG) {
			System.out.println(getPC() + " " + OPCODE_NAMES[seen]);
		}
		if (seen == IFNULL || seen == IFNONNULL) {
			OpcodeStack.Item top = stack.getStackItem(0);
			if (DEBUG) {
				System.out.println("Stack top: " + top);
			}
			XMethod m = top.getReturnValueOf();
			if (DEBUG) {
				System.out.println("Found null check");
			}
			if (m != null && m.getClassName().equals("java.util.concurrent.ConcurrentHashMap") && m.getName().equals("get")) {
				lastQuestionableCheckTarget = getBranchTarget();
				if (seen == IFNULL) {
					priority = LOW_PRIORITY;
				}
				else if (seen == IFNONNULL) {
					priority = NORMAL_PRIORITY;
				}
			}
		}
		if (seen == INVOKEVIRTUAL) {
			if(getDottedClassConstantOperand().equals("java.util.concurrent.ConcurrentHashMap")) {
				String methodName = getNameConstantOperand();
				if (methodName.equals("put")) {
					if((getPC() < lastQuestionableCheckTarget) && (lastQuestionableCheckTarget != -1)) {
						bugReporter.reportBug(new BugInstance("AT_CONCURRENTHASHMAP_GET_PUT", priority).addClassAndMethod(this).addSourceLine(this));
					}
				}
			}
		}
	}
}