Java Code Examples for org.apache.bcel.Const#IFNULL

@Override
public void sawOpcode(int seen) {

    if ((seen == Const.INVOKEVIRTUAL || seen == Const.INVOKEINTERFACE) && "notify".equals(getNameConstantOperand())
            && "()V".equals(getSigConstantOperand())) {
        sawNotify = true;
        notifyPC = getPC();
    }
    if (!(sawWait || sawAwait) && (seen == Const.INVOKEVIRTUAL || seen == Const.INVOKEINTERFACE)
            && (isMonitorWait() || isConditionAwait())) {

        if ("wait".equals(getNameConstantOperand())) {
            sawWait = true;
        } else {
            sawAwait = true;
        }
        waitHasTimeout = !"()V".equals(getSigConstantOperand());
        waitAt = getPC();
        earliestJump = getPC() + 1;
        return;
    }
    if (seen >= Const.IFEQ && seen <= Const.GOTO || seen >= Const.IFNULL && seen <= Const.GOTO_W) {
        earliestJump = Math.min(earliestJump, getBranchTarget());
    }
}
 

private Type nullCheck(short opcode, Edge edge, InstructionHandle last, BasicBlock sourceBlock)
        throws DataflowAnalysisException {
    if (DEBUG_NULL_CHECK) {
        System.out.println("checking for nullcheck on edge " + edge);
    }
    Type type = null;
    if ((opcode == Const.IFNULL && edge.getType() == EdgeTypes.IFCMP_EDGE)
            || (opcode == Const.IFNONNULL && edge.getType() == EdgeTypes.FALL_THROUGH_EDGE)) {
        Location location = new Location(last, sourceBlock);
        TypeFrame typeFrame = typeDataflow.getFactAtLocation(location);
        if (typeFrame.isValid()) {
            type = typeFrame.getTopValue();
            if (DEBUG_NULL_CHECK) {
                System.out.println("ifnull comparison of " + type + " to null at " + last);
            }
        }
    }
    return type;
}
 

public void printOpCode(int seen) {
    System.out.print("  " + this.getClass().getSimpleName() + ": [" + formatter.format(getPC()) + "]  " + Const.getOpcodeName(seen));
    if ((seen == Const.INVOKEVIRTUAL) || (seen == Const.INVOKESPECIAL) || (seen == Const.INVOKEINTERFACE) || (seen == Const.INVOKESTATIC)) {
        System.out.print("   " + getClassConstantOperand() + "." + getNameConstantOperand() + " " + getSigConstantOperand());
    } else if (seen == Const.LDC || seen == Const.LDC_W || seen == Const.LDC2_W) {
        Constant c = getConstantRefOperand();
        if (c instanceof ConstantString) {
            System.out.print("   \"" + getStringConstantOperand() + "\"");
        } else if (c instanceof ConstantClass) {
            System.out.print("   " + getClassConstantOperand());
        } else {
            System.out.print("   " + c);
        }
    } else if ((seen == Const.ALOAD) || (seen == Const.ASTORE)) {
        System.out.print("   " + getRegisterOperand());
    } else if ((seen == Const.GOTO) || (seen == Const.GOTO_W) || (seen == Const.IF_ACMPEQ) || (seen == Const.IF_ACMPNE)
            || (seen == Const.IF_ICMPEQ)
            || (seen == Const.IF_ICMPGE) || (seen == Const.IF_ICMPGT) || (seen == Const.IF_ICMPLE) || (seen == Const.IF_ICMPLT)
            || (seen == Const.IF_ICMPNE) || (seen == Const.IFEQ) || (seen == Const.IFGE) || (seen == Const.IFGT) || (seen == Const.IFLE)
            || (seen == Const.IFLT)
            || (seen == Const.IFNE) || (seen == Const.IFNONNULL) || (seen == Const.IFNULL)) {
        System.out.print("   " + getBranchTarget());
    } else if ((seen == Const.NEW) || (seen == Const.INSTANCEOF)) {
        System.out.print("   " + getClassConstantOperand());
    } else if ((seen == Const.TABLESWITCH) || (seen == Const.LOOKUPSWITCH)) {
        System.out.print("    [");
        int switchPC = getPC();
        int[] offsets = getSwitchOffsets();
        for (int offset : offsets) {
            System.out.print((switchPC + offset) + ",");
        }
        System.out.print((switchPC + getDefaultSwitchOffset()) + "]");
    }

    System.out.println();
}
 

public static boolean areOppositeBranches(int opcode1, int opcode2) {
    if (!isBranch(opcode1)) {
        throw new IllegalArgumentException(Const.getOpcodeName(opcode1) + " isn't a branch");
    }
    if (!isBranch(opcode2)) {
        throw new IllegalArgumentException(Const.getOpcodeName(opcode2) + " isn't a branch");
    }
    switch (opcode1) {
    case Const.IF_ACMPEQ:
    case Const.IF_ACMPNE:
    case Const.IF_ICMPEQ:
    case Const.IF_ICMPNE:
    case Const.IF_ICMPLT:
    case Const.IF_ICMPLE:
    case Const.IF_ICMPGT:
    case Const.IF_ICMPGE:
    case Const.IFNE:
    case Const.IFEQ:
    case Const.IFLT:
    case Const.IFLE:
    case Const.IFGT:
    case Const.IFGE:
        return ((opcode1 + 1) ^ 1) == opcode2 + 1;
    case Const.IFNONNULL:
        return opcode2 == Const.IFNULL;
    case Const.IFNULL:
        return opcode2 == Const.IFNONNULL;
    default:
        return false;

    }
}
 

@Override
public void sawOpcode(int seen) {
    if (seen == Const.INVOKEVIRTUAL && "indexOf".equals(getNameConstantOperand())
            && "java/lang/String".equals(getClassConstantOperand())
            && "(Ljava/lang/String;)I".equals(getSigConstantOperand())) {
        stringIndexOfOnTOS = true;
    } else if (stringIndexOfOnTOS) {
        if (seen == Const.IFLE || seen == Const.IFGT) {
            bugAccumulator.accumulateBug(
                    new BugInstance(this, "RV_CHECK_FOR_POSITIVE_INDEXOF", LOW_PRIORITY).addClassAndMethod(this), this);
        }
        stringIndexOfOnTOS = false;
    }

    if (seen == Const.INVOKEVIRTUAL && "readLine".equals(getNameConstantOperand())
            && "()Ljava/lang/String;".equals(getSigConstantOperand()) && getClassConstantOperand().startsWith("java/io")
            && !"java/io/LineNumberReader".equals(getClassConstantOperand())) {
        readLineOnTOS = true;
    } else if (readLineOnTOS) {
        if (seen == Const.IFNULL || seen == Const.IFNONNULL) {
            bugAccumulator.accumulateBug(
                    new BugInstance(this, "RV_DONT_JUST_NULL_CHECK_READLINE", NORMAL_PRIORITY).addClassAndMethod(this), this);
        }

        readLineOnTOS = false;
    }
}
 

private Obligation comparesObligationTypeToNull(Edge edge) throws DataflowAnalysisException {
    BasicBlock sourceBlock = edge.getSource();
    InstructionHandle last = sourceBlock.getLastInstruction();
    if (last == null) {
        if (DEBUG_NULL_CHECK) {
            System.out.println("no last instruction in source block of " + edge + " ???");
        }
        return null;
    }
    Type type = null;

    short opcode = last.getInstruction().getOpcode();
    switch (opcode) {
    case Const.IFNULL:
    case Const.IFNONNULL:
        type = nullCheck(opcode, edge, last, sourceBlock);
        break;

    case Const.IF_ACMPEQ:
    case Const.IF_ACMPNE:
        type = acmpNullCheck(opcode, edge, last, sourceBlock);
        break;
    default:
        break;
    }

    if (!(type instanceof ObjectType)) {
        return null;
    }

    try {
        // See if the type of value compared to null is an obligation type.
        return database.getFactory().getObligationByType((ObjectType) type);
    } catch (ClassNotFoundException e) {
        errorLogger.reportMissingClass(e);
        throw new MissingClassException(e);
    }

}
 

/**
 * Examine basic blocks for null checks and potentially-redundant null
 * comparisons.
 *
 * @throws DataflowAnalysisException
 * @throws CFGBuilderException
 */
private void examineBasicBlocks() throws DataflowAnalysisException, CFGBuilderException {
    // Look for null check blocks where the reference being checked
    // is definitely null, or null on some path
    Iterator<BasicBlock> bbIter = invDataflow.getCFG().blockIterator();
    while (bbIter.hasNext()) {
        BasicBlock basicBlock = bbIter.next();

        if (basicBlock.isNullCheck()) {
            analyzeNullCheck(invDataflow, basicBlock);
        } else if (!basicBlock.isEmpty()) {
            // Look for all reference comparisons where
            // - both values compared are definitely null, or
            // - one value is definitely null and one is definitely not null
            // These cases are not null dereferences,
            // but they are quite likely to indicate an error, so while
            // we've got
            // information about null values, we may as well report them.
            InstructionHandle lastHandle = basicBlock.getLastInstruction();
            Instruction last = lastHandle.getInstruction();
            switch (last.getOpcode()) {
            case Const.IF_ACMPEQ:
            case Const.IF_ACMPNE:
                analyzeRefComparisonBranch(basicBlock, lastHandle);
                break;
            case Const.IFNULL:
            case Const.IFNONNULL:
                analyzeIfNullBranch(basicBlock, lastHandle);
                break;
            default:
                break;
            }
        }
    }
}
 

@Override
public void sawOpcode(int seen) {

    // System.out.println("PC: " + PC + ", stage: " + stage1);
    switch (seen) {
    case Const.ALOAD_0:
    case Const.ALOAD_1:
    case Const.ALOAD_2:
    case Const.ALOAD_3:
    case Const.ALOAD:
        if (DEBUG) {
            System.out.println("   ALOAD at PC " + getPC());
        }
        start = getPC();
        stage = 1;
        break;
    case Const.GETSTATIC:
        if (DEBUG) {
            System.out.println("   getfield in stage " + stage);
        }
        lastFieldSeen = FieldAnnotation.fromReferencedField(this);
        start = getPC();
        stage = 2;
        break;
    case Const.GETFIELD:
        if (DEBUG) {
            System.out.println("   getfield in stage " + stage);
        }
        lastFieldSeen = FieldAnnotation.fromReferencedField(this);
        if (stage == 1 || stage == 2) {
            stage = 2;
        } else {
            stage = 0;
        }
        break;
    case Const.GOTO:
    case Const.IFNE:
    case Const.IFEQ:
    case Const.IFNULL:
    case Const.IFNONNULL:
        if (DEBUG) {
            System.out.println("   conditional branch in stage " + stage + " to " + getBranchTarget());
        }
        if (stage == 2 && getBranchTarget() == start) {
            bugReporter.reportBug(new BugInstance(this, "SP_SPIN_ON_FIELD", NORMAL_PRIORITY).addClassAndMethod(this)
                    .addReferencedField(lastFieldSeen).addSourceLine(this, start));
            stage = 0;
        } else if (getBranchTarget() < getPC()) {
            stage = 0;
        }
        break;
    default:
        stage = 0;
        break;
    }

}
 

@Override
public void sawOpcode(int seen) {
    int priority;
    switch (seen) {
    case Const.INVOKEINTERFACE:
    case Const.INVOKEVIRTUAL:
    case Const.INVOKESPECIAL:
    case Const.INVOKESTATIC:
        hq.pushHash(getClassConstantOperand());
        if (getNameConstantOperand().indexOf('$') == -1) {
            hq.pushHash(getNameConstantOperand());
        }
        hq.pushHash(getSigConstantOperand());

        priority = hq.getPriority();
        if (priority <= Priorities.LOW_PRIORITY) {
            accumulator.accumulateBug(new BugInstance(this, "NOISE_METHOD_CALL", priority).addClassAndMethod(this)
                    .addCalledMethod(this), this);
        }
        break;
    case Const.GETFIELD:
    case Const.PUTFIELD:
    case Const.GETSTATIC:
    case Const.PUTSTATIC:
        hq.pushHash(getClassConstantOperand());
        if (getNameConstantOperand().indexOf('$') == -1) {
            hq.pushHash(getNameConstantOperand());
        }
        hq.pushHash(getSigConstantOperand());
        priority = hq.getPriority();
        if (priority <= Priorities.LOW_PRIORITY) {
            accumulator.accumulateBug(new BugInstance(this, "NOISE_FIELD_REFERENCE", priority).addClassAndMethod(this)
                    .addReferencedField(this), this);
        }
        break;
    case Const.CHECKCAST:
    case Const.INSTANCEOF:
    case Const.NEW:
        hq.pushHash(getClassConstantOperand());
        break;
    case Const.IFEQ:
    case Const.IFNE:
    case Const.IFNONNULL:
    case Const.IFNULL:
    case Const.IF_ICMPEQ:
    case Const.IF_ICMPNE:
    case Const.IF_ICMPLE:
    case Const.IF_ICMPGE:
    case Const.IF_ICMPGT:
    case Const.IF_ICMPLT:
    case Const.IF_ACMPEQ:
    case Const.IF_ACMPNE:
    case Const.RETURN:
    case Const.ARETURN:
    case Const.IRETURN:
    case Const.MONITORENTER:
    case Const.MONITOREXIT:
    case Const.IINC:
    case Const.NEWARRAY:
    case Const.TABLESWITCH:
    case Const.LOOKUPSWITCH:
    case Const.LCMP:
    case Const.INEG:
    case Const.IADD:
    case Const.IMUL:
    case Const.ISUB:
    case Const.IDIV:
    case Const.IREM:
    case Const.IXOR:
    case Const.ISHL:
    case Const.ISHR:
    case Const.IUSHR:
    case Const.IAND:
    case Const.IOR:
    case Const.LAND:
    case Const.LOR:
    case Const.LADD:
    case Const.LMUL:
    case Const.LSUB:
    case Const.LDIV:
    case Const.LSHL:
    case Const.LSHR:
    case Const.LUSHR:
    case Const.AALOAD:
    case Const.AASTORE:
    case Const.IALOAD:
    case Const.IASTORE:
    case Const.BALOAD:
    case Const.BASTORE:
        hq.push(seen);
        priority = hq.getPriority();
        if (priority <= Priorities.LOW_PRIORITY) {
            accumulator.accumulateBug(
                    new BugInstance(this, "NOISE_OPERATION", priority).addClassAndMethod(this).addString(Const.getOpcodeName(seen)),
                    this);
        }
        break;
    default:
        break;
    }
}
 

@Override
public void sawOpcode(int seen) {
    // System.out.println(getPC() + " " + Const.getOpcodeName(seen) + " " +
    // currState);
    switch (currState) {
    case 0:
        if (seen == Const.GETFIELD || seen == Const.GETSTATIC) {
            syncField = FieldAnnotation.fromReferencedField(this);
            currState = 1;
        }
        break;
    case 1:
        if (seen == Const.DUP) {
            currState = 2;
        } else {
            currState = 0;
        }
        break;
    case 2:
        if (seen == Const.ASTORE || seen == Const.ASTORE_0 || seen == Const.ASTORE_1 || seen == Const.ASTORE_2 || seen == Const.ASTORE_3) {
            currState = 3;
        } else {
            currState = 0;
        }
        break;
    case 3:
        if (seen == Const.MONITORENTER) {
            currState = 4;
        } else {
            currState = 0;
        }
        break;
    case 4:
        if (seen == Const.GETFIELD || seen == Const.GETSTATIC) {
            gottenField = FieldAnnotation.fromReferencedField(this);
            currState = 5;
        } else {
            currState = 0;
        }
        break;
    case 5:
        if ((seen == Const.IFNONNULL || seen == Const.IFNULL) && gottenField.equals(syncField)) {
            BugInstance bug = new BugInstance(this, "NP_SYNC_AND_NULL_CHECK_FIELD", NORMAL_PRIORITY).addClass(this)
                    .addMethod(this).addField(syncField).addSourceLine(this);
            bugReporter.reportBug(bug);
        } else {
            currState = 0;
        }
        break;
    default:
        currState = 0;
    }
}
 

private void scanForBooleanValue(int seen) {
    switch (seen) {

    case Const.IAND:
    case Const.IOR:
        switch (prevOpcode) {
        case Const.ILOAD:
        case Const.ILOAD_0:
        case Const.ILOAD_1:
        case Const.ILOAD_2:
        case Const.ILOAD_3:
            clearAll();
            break;
        default:
            break;
        }
        break;
    case Const.ICONST_1:
        stage1 = 1;
        switch (prevOpcode) {
        case Const.IFNONNULL:
        case Const.IFNULL:
            sawNullTest = true;
            break;
        case Const.IF_ICMPGT:
        case Const.IF_ICMPGE:
        case Const.IF_ICMPLT:
        case Const.IF_ICMPLE:
            sawNumericTest = true;
            break;
        }

        break;
    case Const.GOTO:
        if (stage1 == 1) {
            stage1 = 2;
        } else {
            stage1 = 0;
            clearAll();
        }
        break;
    case Const.ICONST_0:
        if (stage1 == 2) {
            sawBooleanValue();
        }
        stage1 = 0;
        break;
    case Const.INVOKEINTERFACE:
    case Const.INVOKEVIRTUAL:
    case Const.INVOKESPECIAL:
    case Const.INVOKESTATIC:
        String sig = getSigConstantOperand();
        if (sig.endsWith(")Z")) {
            sawBooleanValue();
        }
        stage1 = 0;
        break;
    default:
        stage1 = 0;
    }
}
 

/** This is called for both IFNULL and IFNONNULL instructions. */
private void analyzeIfNullBranch(BasicBlock basicBlock, InstructionHandle lastHandle) throws DataflowAnalysisException {

    Location location = new Location(lastHandle, basicBlock);

    IsNullValueFrame frame = invDataflow.getFactAtLocation(location);

    if (!frame.isValid()) {
        // This is probably dead code due to an infeasible exception edge.
        return;
    }

    IsNullValue top = frame.getTopValue();

    // Find the line number.
    int lineNumber = getLineNumber(method, lastHandle);
    if (lineNumber < 0) {
        return;
    }

    if (!(top.isDefinitelyNull() || top.isDefinitelyNotNull())) {
        if (DEBUG) {
            System.out.println("Line " + lineNumber + " undetermined");
        }
        undeterminedBranchSet.set(lineNumber);
        return;
    }

    // Figure out if the branch is always taken
    // or always not taken.
    short opcode = lastHandle.getInstruction().getOpcode();
    boolean definitelySame = top.isDefinitelyNull();
    if (opcode != Const.IFNULL) {
        definitelySame = !definitelySame;
    }

    if (definitelySame) {
        if (DEBUG) {
            System.out.println("Line " + lineNumber + " always same");
        }
        definitelySameBranchSet.set(lineNumber);
    } else {
        if (DEBUG) {
            System.out.println("Line " + lineNumber + " always different");
        }
        definitelyDifferentBranchSet.set(lineNumber);
    }

    RedundantBranch redundantBranch = new RedundantBranch(location, lineNumber, top);

    // Determine which control edge is made infeasible by the redundant
    // comparison
    boolean wantNull = (opcode == Const.IFNULL);
    int infeasibleEdgeType = (wantNull == top.isDefinitelyNull()) ? EdgeTypes.FALL_THROUGH_EDGE : EdgeTypes.IFCMP_EDGE;
    Edge infeasibleEdge = invDataflow.getCFG().getOutgoingEdgeWithType(basicBlock, infeasibleEdgeType);
    redundantBranch.setInfeasibleEdge(infeasibleEdge);

    if (DEBUG) {
        System.out.println("Adding redundant branch: " + redundantBranch);
    }
    redundantBranchList.add(redundantBranch);
}
 

/** Create branch instruction by given opcode, except LOOKUPSWITCH and TABLESWITCH.
 * For those you should use the SWITCH compound instruction.
 */
public static BranchInstruction createBranchInstruction( final short opcode, final InstructionHandle target ) {
    switch (opcode) {
        case Const.IFEQ:
            return new IFEQ(target);
        case Const.IFNE:
            return new IFNE(target);
        case Const.IFLT:
            return new IFLT(target);
        case Const.IFGE:
            return new IFGE(target);
        case Const.IFGT:
            return new IFGT(target);
        case Const.IFLE:
            return new IFLE(target);
        case Const.IF_ICMPEQ:
            return new IF_ICMPEQ(target);
        case Const.IF_ICMPNE:
            return new IF_ICMPNE(target);
        case Const.IF_ICMPLT:
            return new IF_ICMPLT(target);
        case Const.IF_ICMPGE:
            return new IF_ICMPGE(target);
        case Const.IF_ICMPGT:
            return new IF_ICMPGT(target);
        case Const.IF_ICMPLE:
            return new IF_ICMPLE(target);
        case Const.IF_ACMPEQ:
            return new IF_ACMPEQ(target);
        case Const.IF_ACMPNE:
            return new IF_ACMPNE(target);
        case Const.GOTO:
            return new GOTO(target);
        case Const.JSR:
            return new JSR(target);
        case Const.IFNULL:
            return new IFNULL(target);
        case Const.IFNONNULL:
            return new IFNONNULL(target);
        case Const.GOTO_W:
            return new GOTO_W(target);
        case Const.JSR_W:
            return new JSR_W(target);
        default:
            throw new IllegalArgumentException("Invalid opcode: " + opcode);
    }
}