findmaskedfields.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004 Dave Brosius <[e-mail]>
 * 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.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;

import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.LocalVariable;
import org.apache.bcel.classfile.LocalVariableTable;
import org.apache.bcel.classfile.Method;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.FieldAnnotation;
import edu.umd.cs.findbugs.Priorities;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;

public class FindMaskedFields extends BytecodeScanningDetector {
	private BugReporter bugReporter;
	private int numParms;
	private Set<Field> maskedFields = new HashSet<Field>();
	private Map<String, Field> classFields = new HashMap<String, Field>();
	private boolean staticMethod;

	private Collection<RememberedBug> 
		rememberedBugs = new LinkedList<RememberedBug>();

	static class RememberedBug {
		BugInstance bug;
		XField maskingField, maskedField;
		RememberedBug(BugInstance bug, 
				FieldAnnotation maskingField, FieldAnnotation maskedField) {
			this.bug = bug;
			this.maskingField = XFactory.createXField(maskingField);
			this.maskedField = XFactory.createXField(maskedField);
		}
	}
	public FindMaskedFields(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}

	@Override
		 public void visitClassContext(ClassContext classContext) {
		JavaClass obj = classContext.getJavaClass();
		if (!obj.isInterface())
			classContext.getJavaClass().accept(this);
	}

	@Override
		 public void visit(JavaClass obj) {
		classFields.clear();

		Field[] fields = obj.getFields();
		String fieldName;
		for (Field field : fields) if (!field.isStatic() && !field.isPrivate()){
			fieldName = field.getName();
			classFields.put(fieldName, field);
		}

		// Walk up the super class chain, looking for name collisions
		try {
			JavaClass[] superClasses = org.apache.bcel.Repository.getSuperClasses(obj);
			for (JavaClass superClass : superClasses) {
				fields = superClass.getFields();
				for (Field fld : fields) {
					if (!fld.isStatic()
							&& !maskedFields.contains(fld)
							&& (fld.isPublic() || fld.isProtected())) {
						fieldName = fld.getName();
						if (fieldName.length() == 1)
							continue;
						if (fieldName.equals("serialVersionUID"))
							continue;
						String superClassName = superClass.getClassName();
						if (superClassName.startsWith("java.io") &&  
								(superClassName.endsWith("InputStream")
								&& fieldName.equals("in")
								|| superClassName.endsWith("OutputStream")
								&& fieldName.equals("out"))
								) continue;
						if (classFields.containsKey(fieldName)) {
							maskedFields.add(fld);
							Field maskingField = classFields.get(fieldName);
							String mClassName = getDottedClassName();
							FieldAnnotation fa = new FieldAnnotation(mClassName, maskingField.getName(),
									maskingField.getSignature(),
									maskingField.isStatic());
							int priority = NORMAL_PRIORITY;
							if (maskingField.isStatic()
									|| maskingField.isFinal())
								priority++;
							else if (fld.getSignature().charAt(0) == 'L'
									&& !fld.getSignature().startsWith("Ljava/lang/")
									|| fld.getSignature().charAt(0) == '[')
								priority--;
							if (!fld.getSignature().equals(maskingField.getSignature()))
								priority+=2;
							else if (fld.getAccessFlags()
									!= maskingField.getAccessFlags())
								priority++;


							FieldAnnotation maskedFieldAnnotation
									= FieldAnnotation.fromBCELField(superClassName, fld);
							BugInstance bug = new BugInstance(this, "MF_CLASS_MASKS_FIELD",
									priority)
									.addClass(this)
									.addField(fa)
									.describe("FIELD_MASKING")
									.addField(maskedFieldAnnotation)
									.describe("FIELD_MASKED");
							rememberedBugs.add(new RememberedBug(bug, fa, maskedFieldAnnotation));

						}
					}
				}
			}
		} catch (ClassNotFoundException e) {
			bugReporter.reportMissingClass(e);
		}

		super.visit(obj);
	}

	@Override
		 public void visit(Method obj) {
		super.visit(obj);
		numParms = getNumberMethodArguments();
		if (!obj.isStatic()) numParms++;
		// System.out.println(obj);
		// System.out.println(numParms);
		staticMethod = obj.isStatic();
	}

	/**
	 * This property enables production of warnings for
	 * locals which obscure fields.
	 */
	private static final boolean ENABLE_LOCALS =
		SystemProperties.getBoolean("findbugs.maskedfields.locals");

	@Override
		 public void visit(LocalVariableTable obj) {
		if (ENABLE_LOCALS) {
			if (staticMethod)
				return;

			LocalVariable[] vars = obj.getLocalVariableTable();
			// System.out.println("Num params = " + numParms);
			for (LocalVariable var : vars) {
				if (var.getIndex() < numParms)
					continue;
				String varName = var.getName();
				if (varName.equals("serialVersionUID"))
					continue;
				Field f = classFields.get(varName);
				// System.out.println("Checking " + varName);
				// System.out.println(" got " + f);
				// TODO: we could distinguish between obscuring a field in the same class
				// vs. obscuring a field in a superclass.  Not sure how important that is.
				if (f != null) {
					FieldAnnotation fa
							= FieldAnnotation.fromBCELField(getClassName(), f);
					if (true || var.getStartPC() > 0)
						bugReporter.reportBug(new BugInstance(this, "MF_METHOD_MASKS_FIELD", LOW_PRIORITY)
								.addClassAndMethod(this)
								.addField(fa)
								.addSourceLine(this, var.getStartPC() - 1));
				}
			}
		}
		super.visit(obj);
	}

	@Override
	public void report() {
		UnreadFields unreadFields = AnalysisContext.currentAnalysisContext().getUnreadFields();
		for(RememberedBug rb : rememberedBugs) {
			BugInstance bug = rb.bug;
			int score1 = 0;
			int score2 = 0;
			int priority = bug.getPriority();
			if (unreadFields.classesScanned.contains(rb.maskedField.getClassName())) {
				if (unreadFields.getReadFields().contains(rb.maskedField))
					score1++;
				if (unreadFields.getWrittenFields().contains(rb.maskedField))
					score1++;
				if (unreadFields.getWrittenOutsideOfConstructorFields().contains(rb.maskedField))
					score1++;
			} else score1 += 2;
			if (unreadFields.getReadFields().contains(rb.maskingField))
				score2++;
				if (unreadFields.getWrittenFields().contains(rb.maskingField))
				score2++;
			if (unreadFields.getWrittenOutsideOfConstructorFields().contains(rb.maskingField))
				score2++;
			int score = score1+score2;
			if (score1 == 0 || score2 == 0)
				bug.setPriority(priority+1);
			else if (score >= 5) 
				bug.setPriority(priority-1);
			else if (score < 3) 
				bug.setPriority(priority+1);
			bugReporter.reportBug(bug);
	}
	}
}

// vim:ts=4