initializationchain.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2003,2004 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.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;

import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.JavaClass;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.SystemProperties;

public class InitializationChain extends BytecodeScanningDetector {
	Set<String> requires = new TreeSet<String>();
	Map<String, Set<String>> classRequires = new TreeMap<String, Set<String>>();
	Set<String> staticFieldsAccessedInConstructor = new HashSet<String>();
	Map<String, BugInstance> staticFieldWritten = new HashMap<String, BugInstance>();
	private BugReporter bugReporter;
	private boolean instanceCreated;
	private int instanceCreatedPC;
	private boolean instanceCreatedWarningGiven;

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

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

	@Override
		 public void visit(Code obj) {
		instanceCreated = false;
		instanceCreatedWarningGiven = false;
		if (!getMethodName().equals("<clinit>") && !getMethodName().equals("<init>")) return;
		super.visit(obj);
		requires.remove(getDottedClassName());
		if (getDottedClassName().equals("java.lang.System")) {
			requires.add("java.io.FileInputStream");
			requires.add("java.io.FileOutputStream");
			requires.add("java.io.BufferedInputStream");
			requires.add("java.io.BufferedOutputStream");
			requires.add("java.io.PrintStream");
		}
		if (!requires.isEmpty()) {
			classRequires.put(getDottedClassName(), requires);
			requires = new TreeSet<String>();
		}
	}

	@Override
	public void visitAfter(JavaClass obj) {
		for(String name : staticFieldsAccessedInConstructor) {
			BugInstance bug = staticFieldWritten.get(name);
			if (bug != null) bugReporter.reportBug(bug);
		}
		staticFieldWritten.clear();
		staticFieldsAccessedInConstructor.clear();

	}

	@Override
		 public void sawOpcode(int seen) {

		if (getMethodName().equals("<init>")) {
			if (seen == GETSTATIC && getClassConstantOperand().equals(getClassName())) {
				staticFieldsAccessedInConstructor.add(getNameConstantOperand());
			}
			return;
		}


		if (seen == PUTSTATIC && getClassConstantOperand().equals(getClassName())) {
			// Don't do this check; it generates too many false
			// positives. We need to do a more detailed check
			// of which variables could be seen.
			if (instanceCreated && !instanceCreatedWarningGiven && !getSuperclassName().equals("java.lang.Enum")) {
				String okSig = "L" + getClassName() + ";";
				if (!okSig.equals(getSigConstantOperand())) {
					staticFieldWritten.put(getNameConstantOperand(), 
							new BugInstance(this, "SI_INSTANCE_BEFORE_FINALS_ASSIGNED", NORMAL_PRIORITY)
							.addClassAndMethod(this)
							.addReferencedField(this)
							.addSourceLine(this, instanceCreatedPC));
					instanceCreatedWarningGiven = true;
				}
			}
		} else if (seen == NEW && getClassConstantOperand().equals(getClassName())) {
			instanceCreated = true;
			instanceCreatedPC = getPC();
		} else if (seen == PUTSTATIC || seen == GETSTATIC || seen == INVOKESTATIC
				|| seen == NEW)
			if (getPC() + 6 < codeBytes.length)
				requires.add(getDottedClassConstantOperand());
	}

	public void compute() {
		Set<String> allClasses = classRequires.keySet();
		Set<String> emptyClasses = new TreeSet<String>();
		for (String c : allClasses) {
			Set<String> needs = classRequires.get(c);
			needs.retainAll(allClasses);
			Set<String> extra = new TreeSet<String>();
			for (String need : needs)
				extra.addAll(classRequires.get(need));
			needs.addAll(extra);
			needs.retainAll(allClasses);
			classRequires.put(c, needs);
			if (needs.isEmpty()) emptyClasses.add(c);
		}
		for (String c : emptyClasses) {
			classRequires.remove(c);
		}
	}

	@Override
		 public void report() {

		if (DEBUG) System.out.println("Finishing computation");
		compute();
		compute();
		compute();
		compute();
		compute();
		compute();
		compute();
		compute();
		Set<String> allClasses = classRequires.keySet();

		for (String c : allClasses) {
			if (DEBUG) System.out.println("Class " + c + " requires:");
			for (String needs : (classRequires.get(c))) {
				if (DEBUG) System.out.println("  " + needs);
				Set<String> s = classRequires.get(needs);
				if (s != null && s.contains(c) && c.compareTo(needs) < 0)
					bugReporter.reportBug(new BugInstance(this, "IC_INIT_CIRCULARITY", NORMAL_PRIORITY)
							.addClass(c)
							.addClass(needs));
			}
		}
	}

}