edu.umd.cs.findbugs.ba.npe2

Class DefinitelyNullSetAnalysis

java.lang.Object

edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis<DefinitelyNullSet>

edu.umd.cs.findbugs.ba.npe2.DefinitelyNullSetAnalysis

All Implemented Interfaces:

DataflowAnalysis<DefinitelyNullSet>

public class DefinitelyNullSetAnalysis
extends ForwardDataflowAnalysis<DefinitelyNullSet>

A simple null-pointer analysis that keeps track of which value numbers are definitely known to be null.

Author:

David Hovemeyer

Constructor Summary

Constructors

Constructor and Description
DefinitelyNullSetAnalysis(DepthFirstSearch dfs, ValueNumberDataflow vnaDataflow, CompactLocationNumbering compactLocationNumbering) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
void	copy(DefinitelyNullSet source, DefinitelyNullSet dest) Copy dataflow facts.
DefinitelyNullSet	createFact() Create empty (uninitialized) dataflow facts for one program point.
void	edgeTransfer(Edge edge, DefinitelyNullSet fact) Edge transfer function.
void	initEntryFact(DefinitelyNullSet result) Initialize the "entry" fact for the graph.
boolean	isFactValid(DefinitelyNullSet fact) Determine whether the given fact is valid (neither top nor bottom).
boolean	isTop(DefinitelyNullSet fact) Is the given fact the top value.
void	makeFactTop(DefinitelyNullSet fact) Make given fact the top value.
void	meetInto(DefinitelyNullSet fact, Edge edge, DefinitelyNullSet result) Meet a dataflow fact associated with an incoming edge into another fact.
boolean	same(DefinitelyNullSet fact1, DefinitelyNullSet fact2) Are given dataflow facts the same?
void	transferInstruction(org.apache.bcel.generic.InstructionHandle handle, BasicBlock basicBlock, DefinitelyNullSet fact) Transfer function for a single instruction.

Methods inherited from class edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis

getBlockOrder, getDepthFirstSearch, isForwards

Methods inherited from class edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis

getFactAfterLocation, getFactAtLocation, transfer

Methods inherited from class edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis

factToString, finishIteration, getFactOnEdge, getLastUpdateTimestamp, getResultFact, getStartFact, resultFactIterator, setLastUpdateTimestamp, startIteration

Methods inherited from class java.lang.Object

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

Constructor Detail

DefinitelyNullSetAnalysis

public DefinitelyNullSetAnalysis(DepthFirstSearch dfs,
                         ValueNumberDataflow vnaDataflow,
                         CompactLocationNumbering compactLocationNumbering)

Constructor.

Parameters:

dfs - DepthFirstSearch for the method

vnaDataflow - value number dataflow for the method

compactLocationNumbering - CompactLocationNumbering for the method

Method Detail

isFactValid

public boolean isFactValid(DefinitelyNullSet fact)

Description copied from class: AbstractDataflowAnalysis

Determine whether the given fact is valid (neither top nor bottom).

Specified by:

isFactValid in class AbstractDataflowAnalysis<DefinitelyNullSet>

transferInstruction

public void transferInstruction(org.apache.bcel.generic.InstructionHandle handle,
                       BasicBlock basicBlock,
                       DefinitelyNullSet fact)
                         throws DataflowAnalysisException

Description copied from class: AbstractDataflowAnalysis

Transfer function for a single instruction.

Specified by:

transferInstruction in class AbstractDataflowAnalysis<DefinitelyNullSet>

Parameters:

handle - the instruction

basicBlock - the BasicBlock containing the instruction; needed to disambiguate instructions in inlined JSR subroutines

fact - which should be modified based on the instruction

Throws:

DataflowAnalysisException

edgeTransfer

public void edgeTransfer(Edge edge,
                DefinitelyNullSet fact)
                  throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Edge transfer function. Modify the given fact that is true on the (logical) edge source to modify it so that it is true at the (logical) edge target.

A do-nothing implementation is legal, and appropriate for analyses where branches are not significant.

Specified by:

edgeTransfer in interface DataflowAnalysis<DefinitelyNullSet>

Overrides:

edgeTransfer in class BasicAbstractDataflowAnalysis<DefinitelyNullSet>

Parameters:

edge - the Edge

fact - a dataflow fact

Throws:

DataflowAnalysisException

copy

public void copy(DefinitelyNullSet source,
        DefinitelyNullSet dest)

Description copied from interface: DataflowAnalysis

Copy dataflow facts.

createFact

public DefinitelyNullSet createFact()

Description copied from interface: DataflowAnalysis

Create empty (uninitialized) dataflow facts for one program point. A valid value will be copied into it before it is used.

initEntryFact

public void initEntryFact(DefinitelyNullSet result)
                   throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Initialize the "entry" fact for the graph.

Throws:

DataflowAnalysisException

makeFactTop

public void makeFactTop(DefinitelyNullSet fact)

Description copied from interface: DataflowAnalysis

Make given fact the top value.

isTop

public boolean isTop(DefinitelyNullSet fact)

Description copied from interface: DataflowAnalysis

Is the given fact the top value.

meetInto

public void meetInto(DefinitelyNullSet fact,
            Edge edge,
            DefinitelyNullSet result)
              throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Meet a dataflow fact associated with an incoming edge into another fact. This is used to determine the start fact for a basic block.

Parameters:

fact - the predecessor fact (incoming edge)

edge - the edge from the predecessor

result - the result fact

Throws:

DataflowAnalysisException

same

public boolean same(DefinitelyNullSet fact1,
           DefinitelyNullSet fact2)

Description copied from interface: DataflowAnalysis

Are given dataflow facts the same?