edu.umd.cs.findbugs.ba.npe

Class ReturnPathTypeAnalysis

java.lang.Object

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

edu.umd.cs.findbugs.ba.npe.ReturnPathTypeAnalysis

All Implemented Interfaces:

DataflowAnalysis<ReturnPathType>

public class ReturnPathTypeAnalysis
extends BasicAbstractDataflowAnalysis<ReturnPathType>

A dataflow analysis to determine, at each location in a method's CFG, whether or not it is possible to return normally at that location.

Author:

David Hovemeyer

Constructor Summary

Constructors

Constructor and Description
ReturnPathTypeAnalysis(CFG cfg, ReverseDepthFirstSearch rdfs, DepthFirstSearch dfs) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
void	copy(ReturnPathType source, ReturnPathType dest) Copy dataflow facts.
ReturnPathType	createFact() Create empty (uninitialized) dataflow facts for one program point.
void	edgeTransfer(Edge edge, ReturnPathType fact) Edge transfer function.
void	finishIteration() Called after finishing an iteration of analysis.
BlockOrder	getBlockOrder(CFG cfg) Return the BlockOrder specifying the order in which BasicBlocks should be visited in the main dataflow loop.
int	getLastUpdateTimestamp(ReturnPathType fact)
void	initEntryFact(ReturnPathType result) Initialize the "entry" fact for the graph.
boolean	isForwards() Returns true if the analysis is forwards, false if backwards.
boolean	isTop(ReturnPathType fact) Is the given fact the top value.
void	makeFactTop(ReturnPathType fact) Make given fact the top value.
void	meetInto(ReturnPathType fact, Edge edge, ReturnPathType result) Meet a dataflow fact associated with an incoming edge into another fact.
boolean	same(ReturnPathType fact1, ReturnPathType fact2) Are given dataflow facts the same?
void	setLastUpdateTimestamp(ReturnPathType fact, int timestamp)
void	startIteration() Called before beginning an iteration of analysis.
void	transfer(BasicBlock basicBlock, org.apache.bcel.generic.InstructionHandle end, ReturnPathType start, ReturnPathType result) Transfer function for the analysis.

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

factToString, getFactAfterLocation, getFactAtLocation, getFactOnEdge, getResultFact, getStartFact, resultFactIterator

Methods inherited from class java.lang.Object

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

Constructor Detail

ReturnPathTypeAnalysis

public ReturnPathTypeAnalysis(CFG cfg,
                      ReverseDepthFirstSearch rdfs,
                      DepthFirstSearch dfs)

Constructor.

Parameters:

cfg - the method's CFG

rdfs - a ReverseDepthFirstSearch on the method's CFG

dfs - a DepthFirstSearch on the method's CFG

Method Detail

copy

public void copy(ReturnPathType source,
        ReturnPathType dest)

Description copied from interface: DataflowAnalysis

Copy dataflow facts.

createFact

public ReturnPathType 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.

edgeTransfer

public void edgeTransfer(Edge edge,
                ReturnPathType fact)

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<ReturnPathType>

Overrides:

edgeTransfer in class BasicAbstractDataflowAnalysis<ReturnPathType>

Parameters:

edge - the Edge

fact - a dataflow fact

finishIteration

public void finishIteration()

Description copied from interface: DataflowAnalysis

Called after finishing an iteration of analysis.

Specified by:

finishIteration in interface DataflowAnalysis<ReturnPathType>

Overrides:

finishIteration in class BasicAbstractDataflowAnalysis<ReturnPathType>

getBlockOrder

public BlockOrder getBlockOrder(CFG cfg)

Description copied from interface: DataflowAnalysis

Return the BlockOrder specifying the order in which BasicBlocks should be visited in the main dataflow loop.

Parameters:

cfg - the CFG upon which we're performing dataflow analysis

getLastUpdateTimestamp

public int getLastUpdateTimestamp(ReturnPathType fact)

Specified by:

getLastUpdateTimestamp in interface DataflowAnalysis<ReturnPathType>

Overrides:

getLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<ReturnPathType>

initEntryFact

public void initEntryFact(ReturnPathType result)
                   throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Initialize the "entry" fact for the graph.

Throws:

DataflowAnalysisException

isForwards

public boolean isForwards()

Description copied from interface: DataflowAnalysis

Returns true if the analysis is forwards, false if backwards.

isTop

public boolean isTop(ReturnPathType fact)

Description copied from interface: DataflowAnalysis

Is the given fact the top value.

makeFactTop

public void makeFactTop(ReturnPathType fact)

Description copied from interface: DataflowAnalysis

Make given fact the top value.

meetInto

public void meetInto(ReturnPathType fact,
            Edge edge,
            ReturnPathType 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(ReturnPathType fact1,
           ReturnPathType fact2)

Description copied from interface: DataflowAnalysis

Are given dataflow facts the same?

setLastUpdateTimestamp

public void setLastUpdateTimestamp(ReturnPathType fact,
                          int timestamp)

Specified by:

setLastUpdateTimestamp in interface DataflowAnalysis<ReturnPathType>

Overrides:

setLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<ReturnPathType>

startIteration

public void startIteration()

Description copied from interface: DataflowAnalysis

Called before beginning an iteration of analysis. Each iteration visits every basic block in the CFG.

Specified by:

startIteration in interface DataflowAnalysis<ReturnPathType>

Overrides:

startIteration in class BasicAbstractDataflowAnalysis<ReturnPathType>

transfer

public void transfer(BasicBlock basicBlock,
            org.apache.bcel.generic.InstructionHandle end,
            ReturnPathType start,
            ReturnPathType result)
              throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Transfer function for the analysis. Taking dataflow facts at start (which might be either the entry or exit of the block, depending on whether the analysis is forwards or backwards), modify result to be the facts at the other end of the block.

Parameters:

basicBlock - the basic block

end - if nonnull, stop before considering this instruction; otherwise, consider all of the instructions in the basic block

start - dataflow facts at beginning of block (if forward analysis) or end of block (if backwards analysis)

result - resulting dataflow facts at other end of block

Throws:

DataflowAnalysisException