/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2005 Dave Brosius <dbrosius@users.sourceforge.net>
* Copyright (C) 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.JavaClass;
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.ba.ClassContext;
/**
* finds public classes that use 'this' as a semaphore, which can cause
* conflicts if clients of this class use an instance of this class as their own
* synchronization point. Frankly, Just calling synchronized on this, or
* defining synchronized methods is bad, but since that is so prevalent, don't
* warn on that.
*/
public class PublicSemaphores extends BytecodeScanningDetector implements StatelessDetector {
private static final int SEEN_NOTHING = 0;
private static final int SEEN_ALOAD_0 = 1;
private final BugReporter bugReporter;
private int state;
private boolean alreadyReported;
public PublicSemaphores(BugReporter bugReporter) {
this.bugReporter = bugReporter;
}
@Override
public void visitClassContext(ClassContext classContext) {
JavaClass cls = classContext.getJavaClass();
if ((!cls.isPublic()) || (cls.getClassName().indexOf('$') >= 0)) {
return;
}
alreadyReported = false;
super.visitClassContext(classContext);
}
@Override
public void visit(Code obj) {
Method m = getMethod();
if (m.isStatic() || alreadyReported) {
return;
}
state = SEEN_NOTHING;
super.visit(obj);
}
@Override
public void sawOpcode(int seen) {
if (alreadyReported) {
return;
}
switch (state) {
case SEEN_NOTHING:
if (seen == ALOAD_0) {
state = SEEN_ALOAD_0;
}
break;
case SEEN_ALOAD_0:
if ((seen == INVOKEVIRTUAL) && getClassConstantOperand().equals("java/lang/Object")) {
String methodName = getNameConstantOperand();
if ("wait".equals(methodName) || "notify".equals(methodName) || "notifyAll".equals(methodName)) {
bugReporter.reportBug(new BugInstance(this, "PS_PUBLIC_SEMAPHORES", NORMAL_PRIORITY).addClassAndMethod(this)
.addSourceLine(this));
alreadyReported = true;
}
}
state = SEEN_NOTHING;
break;
default:
break;
}
}
}