findselfcomparison2.java

A static analysis tool to find bugs in Java programs

package edu.umd.cs.findbugs.detect;

import static org.apache.bcel.Constants.*;

import java.util.BitSet;
import java.util.Iterator;

import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.MethodGen;

import edu.umd.cs.findbugs.BugAnnotation;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.Detector;
import edu.umd.cs.findbugs.FieldAnnotation;
import edu.umd.cs.findbugs.LocalVariableAnnotation;
import edu.umd.cs.findbugs.SourceLineAnnotation;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.CFGBuilderException;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Location;
import edu.umd.cs.findbugs.ba.MethodUnprofitableException;
import edu.umd.cs.findbugs.ba.SignatureParser;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;
import edu.umd.cs.findbugs.ba.npe.NullDerefAndRedundantComparisonFinder;
import edu.umd.cs.findbugs.ba.vna.ValueNumber;
import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;

public class FindSelfComparison2 implements Detector {

	private BugReporter bugReporter;

	public FindSelfComparison2(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}

	public void visitClassContext(ClassContext classContext) {
		Method[] methodList = classContext.getJavaClass().getMethods();

		for (Method method : methodList) {
			if (method.getCode() == null)
				continue;

			try {
				analyzeMethod(classContext, method);
			} catch (MethodUnprofitableException mue) {
				if (SystemProperties.getBoolean("unprofitable.debug")) // otherwise don't report
					bugReporter.logError("skipping unprofitable method in " + getClass().getName());
			} catch (CFGBuilderException e) {
				bugReporter.logError("Detector " + this.getClass().getName()
						+ " caught exception", e);
			} catch (DataflowAnalysisException e) {
				bugReporter.logError("Detector " + this.getClass().getName()
						+ " caught exception", e);
			}
		}
	}

	private void analyzeMethod(ClassContext classContext, Method method)
			throws CFGBuilderException, DataflowAnalysisException {
		CFG cfg = classContext.getCFG(method);
		ValueNumberDataflow valueNumberDataflow = classContext
				.getValueNumberDataflow(method);
		ConstantPoolGen cpg = classContext.getConstantPoolGen();
		MethodGen methodGen = classContext.getMethodGen(method);
		String sourceFile = classContext.getJavaClass().getSourceFileName();

		for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
			Location location = i.next();

			Instruction ins = location.getHandle().getInstruction();
			switch(ins.getOpcode()) {
			case INVOKEVIRTUAL:
			case INVOKEINTERFACE:
				InvokeInstruction iins = (InvokeInstruction) ins;
				String invoking = iins.getName(cpg);
				if (invoking.equals("equals") || invoking.equals("compareTo")) {
				if (methodGen.getName().toLowerCase().indexOf("test") >= 0) break;
				if (methodGen.getClassName().toLowerCase().indexOf("test") >= 0) break;
				if (classContext.getJavaClass().getSuperclassName().toLowerCase().indexOf("test") >= 0) break;

			   String sig = iins.getSignature(cpg);

			   SignatureParser parser = new SignatureParser(sig);
			   if (parser.getNumParameters() == 1 && 
					   (invoking.equals("equals") && sig.endsWith(";)Z")
					   || invoking.equals("compareTo")  && sig.endsWith(";)I")))
				   checkForSelfOperation(classContext, location, valueNumberDataflow, "COMPARISON", method, methodGen, sourceFile);


				}
				break;

			case LOR:
			case LAND:
			case LXOR:
			case LSUB:
			case IOR:
			case IAND:
			case IXOR:
			case ISUB:
				checkForSelfOperation(classContext, location, valueNumberDataflow, "COMPUTATION", method, methodGen, sourceFile);
				break;
			case FCMPG:
			case DCMPG:
			case DCMPL:
			case FCMPL:
				break;
			case LCMP:
			case IF_ACMPEQ:
			case IF_ACMPNE:
			case IF_ICMPNE:
			case IF_ICMPEQ:
			case IF_ICMPGT:
			case IF_ICMPLE:
			case IF_ICMPLT:
			case IF_ICMPGE: 
				checkForSelfOperation(classContext, location, valueNumberDataflow, "COMPARISON", method, methodGen, sourceFile);

			}


		}
	}

	/**
	 * @param classContext TODO
	 * @param location
	 * @param method TODO
	 * @param methodGen TODO
	 * @param sourceFile TODO
	 * @param string
	 * @throws DataflowAnalysisException 
	 */
	private void checkForSelfOperation(ClassContext classContext, Location location, ValueNumberDataflow valueNumberDataflow, String op, Method method, MethodGen methodGen, String sourceFile) throws DataflowAnalysisException {
		ValueNumberFrame frame = valueNumberDataflow.getFactAtLocation(location);
		if (!frame.isValid())  return;
		Instruction ins = location.getHandle().getInstruction();
		int opcode = ins.getOpcode();
		int offset = 1;
		if (opcode == LCMP || opcode == LXOR || opcode == LAND || opcode == LOR || opcode == LSUB)
			offset = 2;
		ValueNumber v0 = frame.getStackValue(0);
		ValueNumber v1 = frame.getStackValue(offset);
		if (!v1.equals(v0)) return;

		int priority = HIGH_PRIORITY;
		if (opcode == ISUB || opcode == LSUB || opcode == INVOKEINTERFACE || opcode == INVOKEVIRTUAL)
			priority = NORMAL_PRIORITY;
		XField field = NullDerefAndRedundantComparisonFinder.findXFieldFromValueNumber(method, location, v0, frame);
		BugAnnotation annotation;
		String prefix;
		if (field != null) {
			if (field.isVolatile()) return;
			if (true) return; // don't report these; too many false positives
			annotation = FieldAnnotation.fromXField(field);
			prefix = "SA_FIELD_SELF_";
		} else {
			annotation  = NullDerefAndRedundantComparisonFinder.findLocalAnnotationFromValueNumber(method, location, v0, frame);
			prefix = "SA_LOCAL_SELF_" ;
			if (opcode == ISUB) return; // only report this if simple detector reports it
		}
		if (annotation == null) return;
		SourceLineAnnotation sourceLine = SourceLineAnnotation.fromVisitedInstruction(classContext, methodGen, sourceFile, location.getHandle());
		int line = sourceLine.getStartLine();
		BitSet occursMultipleTimes = ClassContext.linesMentionedMultipleTimes(method);
		if (line > 0 && occursMultipleTimes.get(line)) return;
		BugInstance bug = new BugInstance(this, prefix + op, priority).addClassAndMethod(methodGen, sourceFile)
		.add(annotation).addSourceLine(classContext, methodGen, sourceFile, location.getHandle());
		bugReporter.reportBug(bug);
	}

	public void report() {
	}

}