/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2004-2005 Dave Brosius <dbrosius@users.sourceforge.net>
* Copyright (C) 2004-2005 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.Code;
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.StatelessDetector;
import edu.umd.cs.findbugs.visitclass.LVTHelper;
/**
* Find occurrences of a instanceof b where it can be determined statically
* whether this is true or false. This may signal a misunderstanding of the
* inheritance hierarchy in use, and potential bugs.
*
* @author Dave Brosius
*/
public class SuperfluousInstanceOf extends BytecodeScanningDetector implements StatelessDetector {
private static final int SEEN_NOTHING = 0;
private static final int SEEN_ALOAD = 1;
private final BugReporter bugReporter;
private LocalVariableTable varTable;
private int state;
private int register;
public SuperfluousInstanceOf(BugReporter bugReporter) {
this.bugReporter = bugReporter;
}
@Override
public void visit(Method obj) {
state = SEEN_NOTHING;
varTable = obj.getLocalVariableTable();
if (varTable != null) {
super.visit(obj);
}
}
@Override
public void visit(Code obj) {
if (varTable != null) {
super.visit(obj);
}
}
@Override
public void sawOpcode(int seen) {
switch (state) {
case SEEN_NOTHING:
if (seen == ALOAD) {
register = getRegisterOperand();
} else if ((seen >= ALOAD_0) && (seen <= ALOAD_3)) {
register = seen - ALOAD_0;
} else {
return;
}
state = SEEN_ALOAD;
break;
case SEEN_ALOAD:
try {
if (seen == INSTANCEOF) {
LocalVariable lv = LVTHelper.getLocalVariableAtPC(varTable, register, getPC());
if (lv != null) {
String objSignature = lv.getSignature();
if (objSignature.charAt(0) == 'L') {
objSignature = objSignature.substring(1, objSignature.length() - 1).replace('/', '.');
String clsSignature = getDottedClassConstantOperand();
if (clsSignature.charAt(0) != '[') {
if (org.apache.bcel.Repository.instanceOf(objSignature, clsSignature)) {
bugReporter.reportBug(new BugInstance(this, "SIO_SUPERFLUOUS_INSTANCEOF", LOW_PRIORITY)
.addClassAndMethod(this).addSourceLine(this));
}
}
}
}
}
} catch (ClassNotFoundException cnfe) {
bugReporter.reportMissingClass(cnfe);
}
state = SEEN_NOTHING;
break;
default:
break;
}
}
}