Class FindNullDeref

java.lang.Object

edu.umd.cs.findbugs.detect.FindNullDeref

All Implemented Interfaces:

NullDerefAndRedundantComparisonCollector, Detector, Priorities, UseAnnotationDatabase

public class FindNullDeref
extends Object
implements Detector, UseAnnotationDatabase, NullDerefAndRedundantComparisonCollector

A Detector to find instructions where a NullPointerException might be raised. We also look for useless reference comparisons involving null and non-null values.

See Also:

• IsNullValueAnalysis

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	FindNullDeref.CheckCallSitesAndReturnInstructions

Field Summary

Fields

Modifier and Type	Field	Description
private final BugAccumulator	bugAccumulator
private final BugReporter	bugReporter
static final Set<String>	catchTypesForNull
private boolean	checkedDatabases
private static final String	CLASS
private ClassContext	classContext
static final boolean	DEBUG
private static final boolean	DEBUG_NULLARG
private static final boolean	DEBUG_NULLRETURN
private IsNullValueDataflow	invDataflow
private final org.slf4j.Logger	log
private static final boolean	MARK_DOOMED
private org.apache.bcel.classfile.Method	method
private static final String	METHOD_NAME
private NullnessAnnotation	methodAnnotation
private BitSet	previouslyDeadBlocks
private ParameterNullnessPropertyDatabase	unconditionalDerefParamDatabase
private ValueNumberDataflow	vnaDataflow

Fields inherited from interface Priorities

EXP_PRIORITY, HIGH_PRIORITY, IGNORE_PRIORITY, LOW_PRIORITY, NORMAL_PRIORITY

Constructor Summary

Constructors

Constructor	Description
FindNullDeref(BugReporter bugReporter)

Method Summary

Modifier and Type	Method	Description
private void	addParamAnnotations(Location location, BitSet definitelyNullArgSet, BitSet violatedParamSet, WarningPropertySet<? super NullArgumentWarningProperty> propertySet, BugInstance warning)
private void	addPropertiesForDereferenceLocations(WarningPropertySet<WarningProperty> propertySet, Collection<Location> derefLocationSet, boolean isConsistent)
private void	addPropertiesForMethodContainingWarning(WarningPropertySet<WarningProperty> propertySet)
private void	analyzeMethod(ClassContext classContext, org.apache.bcel.classfile.Method method)
(package private) boolean	callToAssertionMethod(Location loc)
static boolean	catchesNull(org.apache.bcel.classfile.ConstantPool constantPool, org.apache.bcel.classfile.Code code, Location location)
private void	checkCallSitesAndReturnInstructions()
private void	checkDatabases()	Check whether the various interprocedural databases we can use exist and are nonempty.
private void	checkNonNullParam(Location location, org.apache.bcel.generic.ConstantPoolGen cpg, TypeDataflow typeDataflow, org.apache.bcel.generic.InvokeInstruction invokeInstruction, BitSet nullArgSet, BitSet definitelyNullArgSet)	We have a method invocation in which a possibly or definitely null parameter is passed.
private void	checkUnconditionallyDereferencedParam(Location location, org.apache.bcel.generic.ConstantPoolGen cpg, TypeDataflow typeDataflow, org.apache.bcel.generic.InvokeInstruction invokeInstruction, BitSet nullArgSet, BitSet definitelyNullArgSet)
private void	decorateWarning(Location location, WarningPropertySet<WarningProperty> propertySet, BugInstance warning)
private void	examineCallSite(Location location, org.apache.bcel.generic.ConstantPoolGen cpg, TypeDataflow typeDataflow)
private void	examinePutfieldInstruction(Location location, org.apache.bcel.generic.PUTFIELD ins, org.apache.bcel.generic.ConstantPoolGen cpg)
private void	examineReturnInstruction(Location location)
private BitSet	findPreviouslyDeadBlocks()	Find set of blocks which were known to be dead before doing the null pointer analysis.
void	foundGuaranteedNullDeref(@NonNull Set<Location> assignedNullLocationSet, @NonNull Set<Location> derefLocationSet, SortedSet<Location> doomedLocations, ValueNumberDataflow vna, ValueNumber refValue, @Nullable BugAnnotation variableAnnotation, NullValueUnconditionalDeref deref, boolean npeIfStatementCovered)	Subclasses should override this method to capture values assigned null (or that become null through a comparison and branch) that are guaranteed to reach a dereference (ignoring implicit exception paths).
void	foundNullDeref(Location location, ValueNumber valueNumber, IsNullValue refValue, ValueNumberFrame vnaFrame)	Deprecated. Use foundNullDeref(Location,ValueNumber,IsNullValue,ValueNumberFrame,boolean) instead
void	foundNullDeref(Location location, ValueNumber valueNumber, IsNullValue refValue, ValueNumberFrame vnaFrame, boolean isConsistent)	Subclasses should override this method to capture locations where a null pointer is dereferenced.
void	foundRedundantNullCheck(Location location, RedundantBranch redundantBranch)	Subclasses should override this method to capture locations where a redundant null comparison is performed.
private String	getDescription(Location loc, ValueNumber refValue)
private NullnessAnnotation	getMethodNullnessAnnotation()	See if the currently-visited method declares a
(package private) BugAnnotation	getVariableAnnotation(Location location)
private boolean	hasManyPreceedingNullTests(int pc)
private boolean	inExplicitCatchNullBlock(Location loc)
private boolean	inIndirectCatchNullBlock(Location loc)
private boolean	isDoomed(Location loc)
boolean	isDuplicated(WarningPropertySet<WarningProperty> propertySet, int pc, boolean isConsistent)
static boolean	isGeneratedCodeInCatchBlock(@NonNull org.apache.bcel.classfile.Method method, int pc)	Java 11+ compiler generates redundant null checks for try-with-resources.
private static boolean	isGeneratedCodeInCatchBlockViaLineNumber(@NonNull org.apache.bcel.classfile.ConstantPool cp, @NonNull org.apache.bcel.classfile.LineNumberTable lineNumberTable, int line, @NonNull org.apache.bcel.generic.InstructionList instructions, @NonNull List<org.apache.bcel.classfile.CodeException> throwables)	Java 11+ compiler generates redundant null checks for try-with-resources.
private boolean	isGoto(org.apache.bcel.generic.Instruction instruction)	Determine whether the given instruction is a goto.
static boolean	isThrower(BasicBlock target)
(package private) int	maxPC(Collection<Location> locs)
(package private) int	minPC(Collection<Location> locs)
void	report()	This method is called after all classes to be visited.
private void	reportNullDeref(WarningPropertySet<WarningProperty> propertySet, Location location, String type, int priority, @Nullable BugAnnotation variable)
private boolean	safeCallToPrimateParseMethod(XMethod calledMethod, Location location)
private boolean	skipIfInsideCatchNull()
private boolean	uniqueLocations(Collection<Location> derefLocationSet)
void	visitClassContext(ClassContext classContext)	Visit the ClassContext for a class which should be analyzed for instances of bug patterns.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

log

private final org.slf4j.Logger log

DEBUG

public static final boolean DEBUG

DEBUG_NULLARG

private static final boolean DEBUG_NULLARG

DEBUG_NULLRETURN

private static final boolean DEBUG_NULLRETURN

MARK_DOOMED

private static final boolean MARK_DOOMED

METHOD_NAME

private static final String METHOD_NAME

CLASS

private static final String CLASS

bugReporter

private final BugReporter bugReporter

bugAccumulator

private final BugAccumulator bugAccumulator

unconditionalDerefParamDatabase

private ParameterNullnessPropertyDatabase unconditionalDerefParamDatabase

checkedDatabases

private boolean checkedDatabases

classContext

private ClassContext classContext

method

private org.apache.bcel.classfile.Method method

invDataflow

private IsNullValueDataflow invDataflow

vnaDataflow

private ValueNumberDataflow vnaDataflow

previouslyDeadBlocks

private BitSet previouslyDeadBlocks

methodAnnotation

private NullnessAnnotation methodAnnotation

catchTypesForNull

@StaticConstant
public static final Set<String> catchTypesForNull

Constructor Details

FindNullDeref

public FindNullDeref(BugReporter bugReporter)

Method Details

visitClassContext

public void visitClassContext(ClassContext classContext)

Description copied from interface: Detector

Visit the ClassContext for a class which should be analyzed for instances of bug patterns.

Specified by:

visitClassContext in interface Detector

Parameters:

classContext - the ClassContext

analyzeMethod

private void analyzeMethod(ClassContext classContext,
 org.apache.bcel.classfile.Method method)
                    throws DataflowAnalysisException,
CFGBuilderException

Throws:

DataflowAnalysisException

CFGBuilderException

findPreviouslyDeadBlocks

private BitSet findPreviouslyDeadBlocks()
                                 throws DataflowAnalysisException,
CFGBuilderException

Find set of blocks which were known to be dead before doing the null pointer analysis.

Returns:

set of previously dead blocks, indexed by block id

Throws:

CFGBuilderException

DataflowAnalysisException

checkDatabases

private void checkDatabases()

Check whether the various interprocedural databases we can use exist and are nonempty.

getMethodNullnessAnnotation

private NullnessAnnotation getMethodNullnessAnnotation()

See if the currently-visited method declares a

checkCallSitesAndReturnInstructions

private void checkCallSitesAndReturnInstructions()

examineCallSite

private void examineCallSite(Location location,
 org.apache.bcel.generic.ConstantPoolGen cpg,
 TypeDataflow typeDataflow)
                      throws DataflowAnalysisException,
CFGBuilderException,
ClassNotFoundException

Throws:

DataflowAnalysisException

CFGBuilderException

ClassNotFoundException

examinePutfieldInstruction

private void examinePutfieldInstruction(Location location,
 org.apache.bcel.generic.PUTFIELD ins,
 org.apache.bcel.generic.ConstantPoolGen cpg)
                                 throws DataflowAnalysisException

Throws:

DataflowAnalysisException

examineReturnInstruction

private void examineReturnInstruction(Location location)
                               throws DataflowAnalysisException,
CFGBuilderException

Throws:

DataflowAnalysisException

CFGBuilderException

hasManyPreceedingNullTests

private boolean hasManyPreceedingNullTests(int pc)

catchesNull

public static boolean catchesNull(org.apache.bcel.classfile.ConstantPool constantPool,
 org.apache.bcel.classfile.Code code,
 Location location)

safeCallToPrimateParseMethod

private boolean safeCallToPrimateParseMethod(XMethod calledMethod,
 Location location)

checkUnconditionallyDereferencedParam

private void checkUnconditionallyDereferencedParam(Location location,
 org.apache.bcel.generic.ConstantPoolGen cpg,
 TypeDataflow typeDataflow,
 org.apache.bcel.generic.InvokeInstruction invokeInstruction,
 BitSet nullArgSet,
 BitSet definitelyNullArgSet)
                                            throws DataflowAnalysisException,
ClassNotFoundException

Throws:

DataflowAnalysisException

ClassNotFoundException

decorateWarning

private void decorateWarning(Location location,
 WarningPropertySet<WarningProperty> propertySet,
 BugInstance warning)

addParamAnnotations

private void addParamAnnotations(Location location,
 BitSet definitelyNullArgSet,
 BitSet violatedParamSet,
 WarningPropertySet<? super NullArgumentWarningProperty> propertySet,
 BugInstance warning)

checkNonNullParam

private void checkNonNullParam(Location location,
 org.apache.bcel.generic.ConstantPoolGen cpg,
 TypeDataflow typeDataflow,
 org.apache.bcel.generic.InvokeInstruction invokeInstruction,
 BitSet nullArgSet,
 BitSet definitelyNullArgSet)

We have a method invocation in which a possibly or definitely null parameter is passed. Check it against the library of nonnull annotations.

Parameters:

location -

cpg -

typeDataflow -

invokeInstruction -

nullArgSet -

definitelyNullArgSet -

report

public void report()

Description copied from interface: Detector

This method is called after all classes to be visited. It should be used by any detectors which accumulate information over all visited classes to generate results.

Specified by:

report in interface Detector

skipIfInsideCatchNull

private boolean skipIfInsideCatchNull()

foundNullDeref

@Deprecated
public void foundNullDeref(Location location,
 ValueNumber valueNumber,
 IsNullValue refValue,
 ValueNumberFrame vnaFrame)

Deprecated.

Use foundNullDeref(Location,ValueNumber,IsNullValue,ValueNumberFrame,boolean) instead

Description copied from interface: NullDerefAndRedundantComparisonCollector

Subclasses should override this method to capture locations where a null pointer is dereferenced.

Specified by:

foundNullDeref in interface NullDerefAndRedundantComparisonCollector

Parameters:

location - the Location of the null dereference

valueNumber - the ValueNumber of the possibly-null value

refValue - the kind of possibly-null value dereferenced

vnaFrame - The ValueNumber Frame at the point where the dereference occurred

foundNullDeref

public void foundNullDeref(Location location,
 ValueNumber valueNumber,
 IsNullValue refValue,
 ValueNumberFrame vnaFrame,
 boolean isConsistent)

Description copied from interface: NullDerefAndRedundantComparisonCollector

Subclasses should override this method to capture locations where a null pointer is dereferenced.

Specified by:

foundNullDeref in interface NullDerefAndRedundantComparisonCollector

Parameters:

location - the Location of the null dereference

valueNumber - the ValueNumber of the possibly-null value

refValue - the kind of possibly-null value dereferenced

vnaFrame - The ValueNumber Frame at the point where the dereference occurred

isConsistent - true if the refValue is identical at all clones of the same instruction

isDuplicated

public boolean isDuplicated(WarningPropertySet<WarningProperty> propertySet,
 int pc,
 boolean isConsistent)

reportNullDeref

private void reportNullDeref(WarningPropertySet<WarningProperty> propertySet,
 Location location,
 String type,
 int priority,
 @Nullable BugAnnotation variable)

isThrower

public static boolean isThrower(BasicBlock target)

foundRedundantNullCheck

public void foundRedundantNullCheck(Location location,
 RedundantBranch redundantBranch)

Description copied from interface: NullDerefAndRedundantComparisonCollector

Subclasses should override this method to capture locations where a redundant null comparison is performed.

Specified by:

foundRedundantNullCheck in interface NullDerefAndRedundantComparisonCollector

Parameters:

location - the Location of the redundant null check

redundantBranch - the RedundantBranch

getVariableAnnotation

BugAnnotation getVariableAnnotation(Location location)

isGoto

private boolean isGoto(org.apache.bcel.generic.Instruction instruction)

Determine whether the given instruction is a goto.

Parameters:

instruction - the instruction

Returns:

true if the instruction is a goto, false otherwise

minPC

int minPC(Collection<Location> locs)

maxPC

int maxPC(Collection<Location> locs)

callToAssertionMethod

boolean callToAssertionMethod(Location loc)

foundGuaranteedNullDeref

public void foundGuaranteedNullDeref(@NonNull Set<Location> assignedNullLocationSet,
 @NonNull Set<Location> derefLocationSet,
 SortedSet<Location> doomedLocations,
 ValueNumberDataflow vna,
 ValueNumber refValue,
 @Nullable BugAnnotation variableAnnotation,
 NullValueUnconditionalDeref deref,
 boolean npeIfStatementCovered)

Description copied from interface: NullDerefAndRedundantComparisonCollector

Subclasses should override this method to capture values assigned null (or that become null through a comparison and branch) that are guaranteed to reach a dereference (ignoring implicit exception paths).

Specified by:

foundGuaranteedNullDeref in interface NullDerefAndRedundantComparisonCollector

Parameters:

assignedNullLocationSet - set of locations where the value becomes null

derefLocationSet - set of locations where dereferences occur

doomedLocations - locations at which the value is doomed

vna - ValueNumberDataflow

refValue - the null value

variableAnnotation - TODO

deref - TODO

npeIfStatementCovered - true if doom location is a statement

addPropertiesForDereferenceLocations

private void addPropertiesForDereferenceLocations(WarningPropertySet<WarningProperty> propertySet,
 Collection<Location> derefLocationSet,
 boolean isConsistent)

uniqueLocations

private boolean uniqueLocations(Collection<Location> derefLocationSet)

addPropertiesForMethodContainingWarning

private void addPropertiesForMethodContainingWarning(WarningPropertySet<WarningProperty> propertySet)

isDoomed

private boolean isDoomed(Location loc)

getDescription

private String getDescription(Location loc,
 ValueNumber refValue)

inExplicitCatchNullBlock

private boolean inExplicitCatchNullBlock(Location loc)

inIndirectCatchNullBlock

private boolean inIndirectCatchNullBlock(Location loc)

isGeneratedCodeInCatchBlock

public static boolean isGeneratedCodeInCatchBlock(@NonNull org.apache.bcel.classfile.Method method,
 int pc)

Java 11+ compiler generates redundant null checks for try-with-resources. This method detects the ifnull bytecode generated by javac, to help the detector to avoid to report needless RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE bug.

Parameters:

method - the method

pc - the program counter

Returns:

true if the pc specifies redundant null check generated by javac

See Also:

• false positive RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE on try-with-resources
• false positive RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE on try-with-resources

isGeneratedCodeInCatchBlockViaLineNumber

private static boolean isGeneratedCodeInCatchBlockViaLineNumber(@NonNull org.apache.bcel.classfile.ConstantPool cp,
 @NonNull org.apache.bcel.classfile.LineNumberTable lineNumberTable,
 int line,
 @NonNull org.apache.bcel.generic.InstructionList instructions,
 @NonNull List<org.apache.bcel.classfile.CodeException> throwables)

Java 11+ compiler generates redundant null checks for try-with-resources. This method tries to distinguish such code from manually written code by analysing null numbers.

Parameters:

cp - the constant pool

lineNumberTable - the table with the line numbers

line - the line which belongs to the program counter

instructions - the list of instructions

throwables - the list of Throwables in this method

Returns:

true if the pc specifies redundant null check generated by javac