jif.visit

Class NotNullChecker

java.lang.Object

polyglot.visit.NodeVisitor

polyglot.visit.HaltingVisitor

polyglot.visit.ErrorHandlingVisitor

polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

jif.visit.NotNullChecker

All Implemented Interfaces:

java.lang.Cloneable, polyglot.util.Copy<polyglot.visit.NodeVisitor>

public class NotNullChecker
extends polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

Visitor which determines at which program points local variables and final fields of this class cannot be null, and thus field access and method calls to them cannot produce NullPointerExceptions. This information is then stored in the appropriate delegates.

Nested Class Summary

Nested classes/interfaces inherited from class polyglot.visit.DataFlow

polyglot.visit.DataFlow.BoolItem<FlowItem extends polyglot.visit.DataFlow.Item>, polyglot.visit.DataFlow.ConditionNavigator<FlowItem extends polyglot.visit.DataFlow.Item>, polyglot.visit.DataFlow.FlowGraphSource<FlowItem extends polyglot.visit.DataFlow.Item>, polyglot.visit.DataFlow.Frame<FlowItem extends polyglot.visit.DataFlow.Item>, polyglot.visit.DataFlow.Item

Nested classes/interfaces inherited from interface polyglot.util.Copy

polyglot.util.Copy.Util

Field Summary

Fields inherited from class polyglot.visit.DataFlow

dataflowOnEntry, detectBackEdges, flowCounter, flowgraphStack, forward, postordering

Fields inherited from class polyglot.visit.ErrorHandlingVisitor

error, job, nf, ts

Fields inherited from class polyglot.visit.HaltingVisitor

bypass, bypassParent

Constructor Summary

Constructors

Constructor and Description
NotNullChecker(polyglot.frontend.Job job)
NotNullChecker(polyglot.frontend.Job job, polyglot.types.TypeSystem ts, polyglot.ast.NodeFactory nf)

Method Summary

Modifier and Type	Method and Description
polyglot.visit.NodeVisitor	begin()
protected void	check(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph, polyglot.ast.Term n, boolean entry, jif.visit.NotNullChecker.DataFlowItem inItem, java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem> outItems) "Check" the nodes of the graph for the not null analysis.
protected jif.visit.NotNullChecker.DataFlowItem	confluence(java.util.List<jif.visit.NotNullChecker.DataFlowItem> items, polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer, polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph) The confluence operator is intersection: a variable is not null only if it is not null on all paths flowing in.
protected jif.visit.NotNullChecker.DataFlowItem	createInitialItem(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph, polyglot.ast.Term node, boolean entry) Create an initial Item for the dataflow analysis.
jif.visit.NotNullChecker.DataFlowItem	createItem(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph, polyglot.ast.Term n)
protected java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem>	flow(java.util.List<jif.visit.NotNullChecker.DataFlowItem> inItems, java.util.List<polyglot.visit.FlowGraph.EdgeKey> inItemKeys, polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph, polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer)
java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem>	flow(jif.visit.NotNullChecker.DataFlowItem trueItem, jif.visit.NotNullChecker.DataFlowItem falseItem, jif.visit.NotNullChecker.DataFlowItem otherItem, polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph, polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer) If a local variable is initialized with a non-null expression, then the variable is not null.

Methods inherited from class polyglot.visit.DataFlow

check, confluence, constructItemsFromCondition, createCFGBuilder, createFrame, createInitialItem, currentFlowGraph, dataflow, dataflow, dataflow, dumpFlowGraph, enterCall, filterItems, filterItemsExceptionSubclass, filterItemsNonError, filterItemsNonException, findSCCs, flow, flow, flow, flowBooleanConditions, flowToBooleanFlow, hasTrueFalseBranches, initGraph, initGraph, itemsToMap, itemToMap, lang, leave, leaveCall, post, safeConfluence, safeConfluence, safeConfluence

Methods inherited from class polyglot.visit.ErrorHandlingVisitor

catchErrors, enter, enterCall, enterError, errorQueue, hasErrors, job, leaveCall, leaveCall, nodeFactory, typeSystem

Methods inherited from class polyglot.visit.HaltingVisitor

bypass, bypass, bypassChildren, override, visitChildren

Methods inherited from class polyglot.visit.NodeVisitor

copy, enter, finish, finish, leave, override, toString, visitEdge, visitEdgeNoOverride

Methods inherited from class java.lang.Object

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

Constructor Detail

NotNullChecker

public NotNullChecker(polyglot.frontend.Job job,
                      polyglot.types.TypeSystem ts,
                      polyglot.ast.NodeFactory nf)

NotNullChecker

public NotNullChecker(polyglot.frontend.Job job)

Method Detail

begin

public polyglot.visit.NodeVisitor begin()

Overrides:

begin in class polyglot.visit.ErrorHandlingVisitor

createItem

public jif.visit.NotNullChecker.DataFlowItem createItem(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph,
                                                        polyglot.ast.Term n)

createInitialItem

protected jif.visit.NotNullChecker.DataFlowItem createInitialItem(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph,
                                                                  polyglot.ast.Term node,
                                                                  boolean entry)

Create an initial Item for the dataflow analysis. By default, the set of not null variables is empty.

Specified by:

createInitialItem in class polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

flow

protected java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem> flow(java.util.List<jif.visit.NotNullChecker.DataFlowItem> inItems,
                                                                                                     java.util.List<polyglot.visit.FlowGraph.EdgeKey> inItemKeys,
                                                                                                     polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph,
                                                                                                     polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer)

Overrides:

flow in class polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

flow

public java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem> flow(jif.visit.NotNullChecker.DataFlowItem trueItem,
                                                                                                  jif.visit.NotNullChecker.DataFlowItem falseItem,
                                                                                                  jif.visit.NotNullChecker.DataFlowItem otherItem,
                                                                                                  polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph,
                                                                                                  polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer)

If a local variable is initialized with a non-null expression, then the variable is not null. If a local variable is assigned non-null expression then the variable is not null; if a local variable is assigned a possibly null expression, then the local variable is possibly null.

Overrides:

flow in class polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

confluence

protected jif.visit.NotNullChecker.DataFlowItem confluence(java.util.List<jif.visit.NotNullChecker.DataFlowItem> items,
                                                           polyglot.visit.FlowGraph.Peer<jif.visit.NotNullChecker.DataFlowItem> peer,
                                                           polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph)

The confluence operator is intersection: a variable is not null only if it is not null on all paths flowing in.

Specified by:

confluence in class polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>

check

protected void check(polyglot.visit.FlowGraph<jif.visit.NotNullChecker.DataFlowItem> graph,
                     polyglot.ast.Term n,
                     boolean entry,
                     jif.visit.NotNullChecker.DataFlowItem inItem,
                     java.util.Map<polyglot.visit.FlowGraph.EdgeKey,jif.visit.NotNullChecker.DataFlowItem> outItems)

"Check" the nodes of the graph for the not null analysis. This actually consists of setting various "not null" flags in the Jif extensions to nodes, so that their exceptionCheck methods can decide whether to suppress the NullPointerExceptions that they would otherwise declare would be thrown.

Specified by:

check in class polyglot.visit.DataFlow<jif.visit.NotNullChecker.DataFlowItem>