Package edu.umd.cs.findbugs.detect

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.

Author:

David Hovemeyer, William Pugh

See Also:

• IsNullValueAnalysis

Field Summary

Fields

Modifier and Type	Field	Description
static final Set<String>	catchTypesForNull
static final boolean	DEBUG

Fields inherited from interface edu.umd.cs.findbugs.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
static boolean	catchesNull(org.apache.bcel.classfile.ConstantPool constantPool, org.apache.bcel.classfile.Code code, Location location)
void	foundGuaranteedNullDeref(Set<Location> assignedNullLocationSet, Set<Location> derefLocationSet, SortedSet<Location> doomedLocations, ValueNumberDataflow vna, ValueNumber refValue, 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.
boolean	isDuplicated(WarningPropertySet<WarningProperty> propertySet, int pc, boolean isConsistent)
static boolean	isGeneratedCodeInCatchBlock(org.apache.bcel.classfile.Method method, int pc)	Java 11+ compiler generates redundant null checks for try-with-resources.
static boolean	isThrower(BasicBlock target)
void	report()	This method is called after all classes to be visited.
void	visitClassContext(ClassContext classContext)	Visit the ClassContext for a class which should be analyzed for instances of bug patterns.

Methods inherited from class java.lang.Object

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

Field Details

DEBUG

public static final boolean DEBUG

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

catchesNull

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

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

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)

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

foundGuaranteedNullDeref

public void foundGuaranteedNullDeref(@Nonnull
 Set<Location> assignedNullLocationSet,
 @Nonnull
 Set<Location> derefLocationSet,
 SortedSet<Location> doomedLocations,
 ValueNumberDataflow vna,
 ValueNumber refValue,
 @CheckForNull
 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

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