isnullvalueframemodelingvisitor.java

A static analysis tool to find bugs in Java programs

/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003-2005 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.ba.npe;

import java.util.Map;
import org.apache.bcel.generic.ACONST_NULL;
import org.apache.bcel.generic.ANEWARRAY;
import org.apache.bcel.generic.CHECKCAST;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.GETFIELD;
import org.apache.bcel.generic.GETSTATIC;
import org.apache.bcel.generic.INVOKEINTERFACE;
import org.apache.bcel.generic.INVOKESPECIAL;
import org.apache.bcel.generic.INVOKESTATIC;
import org.apache.bcel.generic.INVOKEVIRTUAL;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.LDC;
import org.apache.bcel.generic.LDC2_W;
import org.apache.bcel.generic.MULTIANEWARRAY;
import org.apache.bcel.generic.NEW;
import org.apache.bcel.generic.NEWARRAY;
import org.apache.bcel.generic.PUTFIELD;
import org.apache.bcel.generic.ReferenceType;
import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.AbstractFrameModelingVisitor;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.AssertionMethods;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Frame;
import edu.umd.cs.findbugs.ba.InstanceField;
import edu.umd.cs.findbugs.ba.NullnessAnnotation;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XField;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.ba.vna.AvailableLoad;
import edu.umd.cs.findbugs.ba.vna.ValueNumber;
import edu.umd.cs.findbugs.ba.vna.ValueNumberAnalysisFeatures;
import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;

public class IsNullValueFrameModelingVisitor extends AbstractFrameModelingVisitor<IsNullValue, IsNullValueFrame> {

	private static final boolean NO_ASSERT_HACK = SystemProperties.getBoolean("inva.noAssertHack");
	private static final boolean MODEL_NONNULL_RETURN = SystemProperties.getBoolean("fnd.modelNonnullReturn",true);
	private AssertionMethods assertionMethods;
	private ValueNumberDataflow vnaDataflow;
	private final boolean trackValueNumbers;
	private int slotContainingNewNullValue;

	public IsNullValueFrameModelingVisitor(
			ConstantPoolGen cpg,
			AssertionMethods assertionMethods,
			ValueNumberDataflow vnaDataflow,
			boolean trackValueNumbers) {
		super(cpg);
		this.assertionMethods = assertionMethods;
		this.vnaDataflow = vnaDataflow;
		this.trackValueNumbers = trackValueNumbers;
	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.ba.AbstractFrameModelingVisitor#analyzeInstruction(org.apache.bcel.generic.Instruction)
	 */
	@Override
	public void analyzeInstruction(Instruction ins) throws DataflowAnalysisException {
		slotContainingNewNullValue = -1;
		super.analyzeInstruction(ins);
	}

	/**
	 * @return Returns the slotContainingNewNullValue; or -1 if no new null value
	 *          was produced
	 */
	public int getSlotContainingNewNullValue() {
		return slotContainingNewNullValue;
	}

	@Override
	public IsNullValue getDefaultValue() {
		return IsNullValue.nonReportingNotNullValue();
	}

	// Overrides of specific instruction visitor methods.
	// ACONST_NULL obviously produces a value that is DEFINITELY NULL.
	// LDC produces values that are NOT NULL.
	// NEW produces values that are NOT NULL.

	// Note that all instructions that have an implicit null
	// check (field access, invoke, etc.) are handled in IsNullValueAnalysis,
	// because handling them relies on control flow (the existence of
	// an ETB and exception edge prior to the block containing the
	// instruction with the null check.)

	// Note that we don't override IFNULL and IFNONNULL.
	// Those are handled in the analysis itself, because we need
	// to produce different values in each of the control successors.

	private void produce(IsNullValue value) {
		IsNullValueFrame frame = getFrame();
		frame.pushValue(value);
		newValueOnTOS();
	}

	private void produce2(IsNullValue value) {
		IsNullValueFrame frame = getFrame();
		frame.pushValue(value);
		frame.pushValue(value);
	}

	/**
	 * Handle method invocations.
	 * Generally, we want to get rid of null information following a
	 * call to a likely exception thrower or assertion.
	 */
	private void handleInvoke(InvokeInstruction obj) {
		Type callType = obj.getLoadClassType(getCPG());
		Type returnType = obj.getReturnType(getCPG());
		String methodName = obj.getMethodName(getCPG());

		boolean stringMethodCall = callType.equals(Type.STRING) && returnType.equals(Type.STRING);

		// Determine if we are going to model the return value of this call.
		boolean modelCallReturnValue = MODEL_NONNULL_RETURN && returnType instanceof ReferenceType;


		if( !modelCallReturnValue) {
			// Normal case: Assume returned values are non-reporting non-null.
			handleNormalInstruction(obj);
		} else {
			// Special case: some special value is pushed on the stack for the return value
			IsNullValue pushValue = null;
			if (false && stringMethodCall) {
				// String methods always return a non-null value
				pushValue = IsNullValue.nonNullValue();
			} else  {
				// Check to see if this method is in either database
				XMethod calledMethod = XFactory.createXMethod(obj, getCPG());
				if (IsNullValueAnalysis.DEBUG) System.out.println("Check " + calledMethod + " for null return...");
				NullnessAnnotation annotation = AnalysisContext.currentAnalysisContext().getNullnessAnnotationDatabase().getResolvedAnnotation(calledMethod, false);
				Boolean alwaysNonNull =  AnalysisContext.currentAnalysisContext().getReturnValueNullnessPropertyDatabase().getProperty(calledMethod);
					if (annotation == NullnessAnnotation.CHECK_FOR_NULL) {
					if (IsNullValueAnalysis.DEBUG) {
						System.out.println("Null value returned from " + calledMethod);
					}
					pushValue = IsNullValue.nullOnSimplePathValue().markInformationAsComingFromReturnValueOfMethod(calledMethod);
				} else  if (annotation == NullnessAnnotation.NULLABLE)  {
					pushValue = IsNullValue.nonReportingNotNullValue();
				} else  if (annotation == NullnessAnnotation.NONNULL || alwaysNonNull != null && alwaysNonNull.booleanValue()) {
					// Method is declared NOT to return null
					if (IsNullValueAnalysis.DEBUG) {
						System.out.println("NonNull value return from " + calledMethod);
					}
					pushValue = IsNullValue.nonNullValue().markInformationAsComingFromReturnValueOfMethod(calledMethod);

				} else {
					pushValue = IsNullValue.nonReportingNotNullValue();
				}
			}

			modelInstruction(obj, getNumWordsConsumed(obj), getNumWordsProduced(obj), pushValue);
			newValueOnTOS();
		}

		if (!NO_ASSERT_HACK) {
			if (assertionMethods.isAssertionCall(obj)) {
				IsNullValueFrame frame = getFrame();
				for (int i = 0; i < frame.getNumSlots(); ++i) {
					IsNullValue value = frame.getValue(i);
					if (value.isDefinitelyNull() || value.isNullOnSomePath()) {
						frame.setValue(i, IsNullValue.nonReportingNotNullValue());
					}
				}
				for(Map.Entry<ValueNumber,IsNullValue> e : frame.getKnownValueMapEntrySet()) {
					IsNullValue value = e.getValue();
					if (value.isDefinitelyNull() || value.isNullOnSomePath()) 
						e.setValue(IsNullValue.nonReportingNotNullValue());

				}
			}
		}
	}

	/**
	 * Hook indicating that a new (possibly-null) value is on the
	 * top of the stack.
	 */
	private void newValueOnTOS() {
		IsNullValueFrame frame= getFrame();
		if (frame.getStackDepth() < 1) {
			return;
		}
		int tosSlot = frame.getNumSlots() - 1;
		IsNullValue tos = frame.getValue(tosSlot);
		if (tos.isDefinitelyNull()) {
			slotContainingNewNullValue = tosSlot;
		}
		if (trackValueNumbers) {
			try {
				ValueNumberFrame vnaFrameAfter = vnaDataflow.getFactAfterLocation(getLocation());
				if (vnaFrameAfter.isValid()) {
					ValueNumber tosVN = vnaFrameAfter.getTopValue();
					getFrame().setKnownValue(tosVN, tos);
					}
				} catch (DataflowAnalysisException e) {
					AnalysisContext.logError("error", e);
			}
		}
	}

	@Override
	public void visitPUTFIELD(PUTFIELD obj) {
		if (getNumWordsConsumed(obj) != 2) {
			super.visitPUTFIELD(obj);
			return;
		}

		IsNullValue nullValueStored = null;
		try {
			nullValueStored = getFrame().getTopValue();
		} catch (DataflowAnalysisException e1) {
			AnalysisContext.logError("Oops", e1);
		}
		super.visitPUTFIELD(obj);
		InstanceField field = (InstanceField) XFactory.createXField(obj, cpg);
		if (nullValueStored != null && ValueNumberAnalysisFeatures.REDUNDANT_LOAD_ELIMINATION)
			try {
			ValueNumberFrame vnaFrameBefore = vnaDataflow.getFactAtLocation(getLocation());
			ValueNumber refValue = vnaFrameBefore.getStackValue(1);
			AvailableLoad load = new AvailableLoad(refValue, field);
			ValueNumberFrame vnaFrameAfter = vnaDataflow.getFactAfterLocation(getLocation());
			ValueNumber [] newValueNumbersForField = vnaFrameAfter.getAvailableLoad(load);
			if (newValueNumbersForField != null && trackValueNumbers)
				for(ValueNumber v : newValueNumbersForField)
					getFrame().setKnownValue(v, nullValueStored);			
		} catch (DataflowAnalysisException e) {
			AnalysisContext.logError("Oops", e);
		}
	}

	@Override
	public void visitGETFIELD(GETFIELD obj) {
		if (getNumWordsProduced(obj) != 1) {
			super.visitGETFIELD(obj);
			return;
		}

		if (checkForKnownValue(obj)) {
			return;
		}

		XField field = XFactory.createXField(obj, cpg);

		NullnessAnnotation annotation = AnalysisContext.currentAnalysisContext().getNullnessAnnotationDatabase().getResolvedAnnotation(field, false);
		if (annotation == NullnessAnnotation.NONNULL) {
			modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
			produce(IsNullValue.nonNullValue());
		}
		else if (annotation == NullnessAnnotation.CHECK_FOR_NULL) {
				modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
				produce(IsNullValue.nullOnSimplePathValue().markInformationAsComingFromFieldValue(field));
		} else {

			super.visitGETFIELD(obj);
		}

	}

	/* (non-Javadoc)
	 * @see edu.umd.cs.findbugs.ba.AbstractFrameModelingVisitor#visitGETSTATIC(org.apache.bcel.generic.GETSTATIC)
	 */
	@Override
	public void visitGETSTATIC(GETSTATIC obj) {
		if (getNumWordsProduced(obj) != 1) {
			super.visitGETSTATIC(obj);
			return;
		}

		if (checkForKnownValue(obj)) {
			return;
		}
		XField field = XFactory.createXField(obj, cpg);
		if (field.getClassName().equals("java.util.logging.Level")
				&& field.getName().equals("SEVERE")
				|| field.getClassName().equals("org.apache.log4j.Level") 
				&& (field.getName().equals("ERROR") || field.getName().equals("FATAL")))
			getFrame().toExceptionValues();

		if (field.getName().startsWith("class$")) {
			produce(IsNullValue.nonNullValue());
			return;
		}
		NullnessAnnotation annotation = AnalysisContext
				.currentAnalysisContext().getNullnessAnnotationDatabase()
				.getResolvedAnnotation(field, false);
		if (annotation == NullnessAnnotation.NONNULL) {
			modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
			produce(IsNullValue.nonNullValue());
		} else if (annotation == NullnessAnnotation.CHECK_FOR_NULL) {
			modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
			produce(IsNullValue.nullOnSimplePathValue().markInformationAsComingFromFieldValue(field));
		} else {

			super.visitGETSTATIC(obj);
		}
	}

	/**
	 * Check given Instruction to see if it produces a known value.
	 * If so, model the instruction and return true.
	 * Otherwise, do nothing and return false.
	 * Should only be used for instructions that produce a single
	 * value on the top of the stack.
	 * 
	 * @param obj the Instruction the instruction
	 * @return true if the instruction produced a known value and was modeled,
	 *          false otherwise
	 */
	private boolean checkForKnownValue(Instruction obj) {
		if (trackValueNumbers) {
			try {
				// See if the value number loaded here is a known value
				ValueNumberFrame vnaFrameAfter = vnaDataflow.getFactAfterLocation(getLocation());
				if (vnaFrameAfter.isValid()) {
					ValueNumber tosVN = vnaFrameAfter.getTopValue();
					IsNullValue knownValue = getFrame().getKnownValue(tosVN);
					if (knownValue != null) {
						//System.out.println("Produce known value!");
						// The value produced by this instruction is known.
						// Push the known value.
						modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
						produce(knownValue);
						return true;
					}
				}
			} catch (DataflowAnalysisException e) {
				// Ignore...
			}
		}	
		return false;
	}

	@Override
	public void visitACONST_NULL(ACONST_NULL obj) {
		produce(IsNullValue.nullValue());
	}
	@Override
	public void visitNEW(NEW obj) {
		produce(IsNullValue.nonNullValue());
	}

	@Override
	public void visitNEWARRAY(NEWARRAY obj) {
		modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
		produce(IsNullValue.nonNullValue());
	}
	@Override
	public void visitANEWARRAY(ANEWARRAY obj) {
		modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
		produce(IsNullValue.nonNullValue());
	}
	@Override
	public void visitMULTIANEWARRAY(MULTIANEWARRAY obj) {
		modelNormalInstruction(obj, getNumWordsConsumed(obj), 0);
		produce(IsNullValue.nonNullValue());
	}
	@Override
	public void visitLDC(LDC obj) {
		produce(IsNullValue.nonNullValue());
	}

	@Override
	public void visitLDC2_W(LDC2_W obj) {
		produce2(IsNullValue.nonNullValue());
	}

	@Override
	public void visitCHECKCAST(CHECKCAST obj) {
		// Do nothing
	}
	@Override
	public void visitINVOKESTATIC(INVOKESTATIC obj) {
		handleInvoke(obj);
	}
	@Override
	public void visitINVOKESPECIAL(INVOKESPECIAL obj) {
		handleInvoke(obj);
	}
	@Override
	public void visitINVOKEINTERFACE(INVOKEINTERFACE obj) {
		handleInvoke(obj);
	}
	@Override
	public void visitINVOKEVIRTUAL(INVOKEVIRTUAL obj) {
		handleInvoke(obj);
	}

}

// vim:ts=4