checkers.flow
Class Flow

java.lang.Object
  com.sun.source.util.TreeScanner<R,P>
      com.sun.source.util.TreePathScanner<Void,Void>
          checkers.flow.Flow

All Implemented Interfaces:

TreeVisitor<Void,Void>

public class Flow
extends TreePathScanner<Void,Void>

Provides a generalized flow-sensitive qualifier inference for the checkers framework.

This implementation is based largely on javac's dataflow analysis module, which may be found in com.sun.tools.javac.comp.Flow from 13 Sep 2007. It differs from that class in two ways:

1. It performs a GEN-KILL analysis for qualifiers that is similar to the initialization/uninitialization analysis in javac's Flow. It does not perform exception analysis, and performs liveness analysis only to the extent required for the GEN-KILL analysis.
2. Whenever possible, this implementation prefers the use of classes in the public API (BitSet, the Compiler Tree API) over those in com.sun.tools.javac (for these reasons, examining a diff against that class would not be particularly enlightening).

As in javac's Flow class, methods named "visit*" perform analysis for a particular type of tree node, while methods named "scan*" perform the analysis for a general, higher-level class of structural element. Typically "visit*" methods delegate to "scan*" methods. As an example, visitIf(com.sun.source.tree.IfTree, java.lang.Void), visitWhileLoop(com.sun.source.tree.WhileLoopTree, java.lang.Void), visitAssert(com.sun.source.tree.AssertTree, java.lang.Void), and visitConditionalExpression(com.sun.source.tree.ConditionalExpressionTree, java.lang.Void) all use scanCond(com.sun.source.tree.Tree) for analyzing conditions and handling branching.

A separate instance of the analysis must be created for each compilation unit.

Field Summary

Modifier and Type	Field and Description
protected QualifierHierarchy	annoRelations The hierarchy for the type qualifiers that this class infers.
protected GenKillBits<AnnotationMirror>	annos Tracks the annotated state of each variable during flow.
protected GenKillBits<AnnotationMirror>	annosWhenFalse Tracks the annotated state of each variable in a false branch.
protected GenKillBits<AnnotationMirror>	annosWhenTrue Tracks the annotated state of each variable in a true branch.
protected Set<AnnotationMirror>	annotations The annotations (qualifiers) to infer.
protected AnnotatedTypes	atypes Utility class for operations on annotated types.
protected SourceChecker	checker The checker to which this instance belongs.
protected Elements	elements Utilities for Elements.
protected ProcessingEnvironment	env The processing environment to use.
protected AnnotatedTypeFactory	factory Utility class for determining annotated types.
protected Map<Tree,AnnotationMirror>	flowResults Stores the results of the analysis (source location to qualifier).
protected CompilationUnitTree	root The file that's being analyzed.
protected List<VariableElement>	vars Maps variables to a bit index.

Constructor and Description

Flow(BaseTypeChecker checker, CompilationUnitTree root, Set<AnnotationMirror> annotations, AnnotatedTypeFactory factory)
Creates a new analysis.

Method Summary

Modifier and Type	Method and Description
protected static boolean	containsKey(Tree tree, Collection<String> keys)
protected void	merge() Merge the bitset after a conditional branch.
protected void	popLastLevel()
protected void	pushNewLevel()
protected void	recordBits(TreePath path) Record the value of the annotation bit for the given usage of a variable, so that a type-checker may use its value after the analysis has finished.
Void	scan(Tree tree, Void p)
protected void	scanCond(Tree tree) Called whenever a conditional expression is scanned.
protected void	scanDef(Tree tree) Called whenever a definition is scanned.
protected void	scanExpr(ExpressionTree tree) Called whenever an expression is scanned.
protected void	scanStat(StatementTree tree) Called whenever a statement is scanned.
protected void	scanStats(List<? extends StatementTree> trees) Called whenever a block of statements is scanned.
void	setDebug(PrintStream debug) Sets the PrintStream for printing debug messages, such as System.out or System.err, or null if no debugging output should be emitted.
protected void	split() Split the bitset before a conditional branch.
AnnotationMirror	test(Tree tree) Determines the inference result for tree.
Void	visitAnnotation(AnnotationTree tree, Void p)
Void	visitAssert(AssertTree node, Void p)
Void	visitAssignment(AssignmentTree node, Void p)
Void	visitBlock(BlockTree node, Void p)
Void	visitBreak(BreakTree node, Void p)
Void	visitClass(ClassTree node, Void p)
Void	visitCompoundAssignment(CompoundAssignmentTree node, Void p)
Void	visitConditionalExpression(ConditionalExpressionTree node, Void p)
Void	visitContinue(ContinueTree node, Void p)
Void	visitDoWhileLoop(DoWhileLoopTree node, Void p)
Void	visitEnhancedForLoop(EnhancedForLoopTree node, Void p)
Void	visitForLoop(ForLoopTree node, Void p)
Void	visitIdentifier(IdentifierTree node, Void p)
Void	visitIf(IfTree node, Void p)
Void	visitImport(ImportTree tree, Void p)
Void	visitMemberSelect(MemberSelectTree node, Void p)
Void	visitMethod(MethodTree node, Void p)
Void	visitMethodInvocation(MethodInvocationTree node, Void p)
Void	visitReturn(ReturnTree node, Void p)
Void	visitThrow(ThrowTree node, Void p)
Void	visitTry(TryTree node, Void p)
Void	visitTypeCast(TypeCastTree node, Void p)
Void	visitVariable(VariableTree node, Void p)
Void	visitWhileLoop(WhileLoopTree node, Void p)

Methods inherited from class com.sun.source.util.TreePathScanner

getCurrentPath, scan

Methods inherited from class com.sun.source.util.TreeScanner

reduce, scan, visitAnnotatedType, visitArrayAccess, visitArrayType, visitBinary, visitCase, visitCatch, visitCompilationUnit, visitEmptyStatement, visitErroneous, visitExpressionStatement, visitInstanceOf, visitLabeledStatement, visitLiteral, visitModifiers, visitNewArray, visitNewClass, visitOther, visitParameterizedType, visitParenthesized, visitPrimitiveType, visitSwitch, visitSynchronized, visitTypeParameter, visitUnary, visitWildcard

Methods inherited from class java.lang.Object

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

Field Detail

checker

protected final SourceChecker checker

The checker to which this instance belongs.

env

protected final ProcessingEnvironment env

The processing environment to use.

root

protected final CompilationUnitTree root

The file that's being analyzed.

annotations

protected final Set<AnnotationMirror> annotations

The annotations (qualifiers) to infer. The relationship among them is determined using BaseTypeChecker.getQualifierHierarchy(). By consulting the hierarchy, the analysis will only infer a qualifier on a type if it is more restrictive (i.e. a subtype) than the existing qualifier for that type.

factory

protected final AnnotatedTypeFactory factory

Utility class for determining annotated types.

atypes

protected final AnnotatedTypes atypes

Utility class for operations on annotated types.

vars

protected final List<VariableElement> vars

Maps variables to a bit index. This index is also used as the bit index to determine a variable's annotatedness using annos/annosWhenTrue/annosWhenFalse.

flowResults

protected final Map<Tree,AnnotationMirror> flowResults

Stores the results of the analysis (source location to qualifier).

annos

protected GenKillBits<AnnotationMirror> annos

Tracks the annotated state of each variable during flow. Bit indices correspond exactly to indices in vars. This field is set to null immediately after splitting for a branch, and is set to some combination (usually boolean "and") of annosWhenTrue and annosWhenFalse after merging. Since it is used when visiting the true and false branches, however, it may be non-null concurrently with annosWhenTrue and annosWhenFalse.

annosWhenTrue

protected GenKillBits<AnnotationMirror> annosWhenTrue

Tracks the annotated state of each variable in a true branch. As in javac's Flow, saving/restoring via local variables handles nested branches. Bit indices correspond exactly to indices in vars. This field is copied from annos when splitting for a branch and is set to null immediately after merging.

See Also:

annos

annosWhenFalse

protected GenKillBits<AnnotationMirror> annosWhenFalse

Tracks the annotated state of each variable in a false branch. As in javac's Flow, saving/restoring via local variables handles nested branches. Bit indices correspond exactly to indices in vars. This field is copied from annos when splitting for a branch and is set to null immediately after merging.

See Also:

annos

annoRelations

protected final QualifierHierarchy annoRelations

The hierarchy for the type qualifiers that this class infers.

elements

protected final Elements elements

Utilities for Elements.

Constructor Detail

Flow

public Flow(BaseTypeChecker checker,
            CompilationUnitTree root,
            Set<AnnotationMirror> annotations,
            AnnotatedTypeFactory factory)

Creates a new analysis. The analysis will use the given AnnotatedTypeFactory to obtain annotated types.

Parameters:

checker - the current checker

root - the compilation unit that will be scanned

annotations - the annotations to track

factory - the factory class that will be used to get annotated types, or null if the default factory should be used

Method Detail

setDebug

public void setDebug(PrintStream debug)

Sets the PrintStream for printing debug messages, such as System.out or System.err, or null if no debugging output should be emitted.

scan

public Void scan(Tree tree,
                 Void p)

Overrides:

scan in class TreePathScanner<Void,Void>

test

public AnnotationMirror test(Tree tree)

Determines the inference result for tree.

Parameters:

tree - the tree to test

Returns:

the annotation inferred for a tree, or null if no annotation was inferred for that tree

split

protected void split()

Split the bitset before a conditional branch.

merge

protected void merge()

Merge the bitset after a conditional branch.

recordBits

protected void recordBits(TreePath path)

Record the value of the annotation bit for the given usage of a variable, so that a type-checker may use its value after the analysis has finished.

Parameters:

path -

scanDef

protected void scanDef(Tree tree)

Called whenever a definition is scanned.

Parameters:

tree - the definition being scanned

scanStat

protected void scanStat(StatementTree tree)

Called whenever a statement is scanned.

Parameters:

tree - the statement being scanned

scanStats

protected void scanStats(List<? extends StatementTree> trees)

Called whenever a block of statements is scanned.

Parameters:

trees - the statements being scanned

scanCond

protected void scanCond(Tree tree)

Called whenever a conditional expression is scanned.

Parameters:

tree - the condition being scanned

scanExpr

protected void scanExpr(ExpressionTree tree)

Called whenever an expression is scanned.

Parameters:

tree - the expression being scanned

visitClass

public Void visitClass(ClassTree node,
                       Void p)

Specified by:

visitClass in interface TreeVisitor<Void,Void>

Overrides:

visitClass in class TreeScanner<Void,Void>

visitImport

public Void visitImport(ImportTree tree,
                        Void p)

Specified by:

visitImport in interface TreeVisitor<Void,Void>

Overrides:

visitImport in class TreeScanner<Void,Void>

visitTypeCast

public Void visitTypeCast(TypeCastTree node,
                          Void p)

Specified by:

visitTypeCast in interface TreeVisitor<Void,Void>

Overrides:

visitTypeCast in class TreeScanner<Void,Void>

visitAnnotation

public Void visitAnnotation(AnnotationTree tree,
                            Void p)

Specified by:

visitAnnotation in interface TreeVisitor<Void,Void>

Overrides:

visitAnnotation in class TreeScanner<Void,Void>

visitIdentifier

public Void visitIdentifier(IdentifierTree node,
                            Void p)

Specified by:

visitIdentifier in interface TreeVisitor<Void,Void>

Overrides:

visitIdentifier in class TreeScanner<Void,Void>

visitMemberSelect

public Void visitMemberSelect(MemberSelectTree node,
                              Void p)

Specified by:

visitMemberSelect in interface TreeVisitor<Void,Void>

Overrides:

visitMemberSelect in class TreeScanner<Void,Void>

visitVariable

public Void visitVariable(VariableTree node,
                          Void p)

Specified by:

visitVariable in interface TreeVisitor<Void,Void>

Overrides:

visitVariable in class TreeScanner<Void,Void>

visitAssignment

public Void visitAssignment(AssignmentTree node,
                            Void p)

Specified by:

visitAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitAssignment in class TreeScanner<Void,Void>

visitCompoundAssignment

public Void visitCompoundAssignment(CompoundAssignmentTree node,
                                    Void p)

Specified by:

visitCompoundAssignment in interface TreeVisitor<Void,Void>

Overrides:

visitCompoundAssignment in class TreeScanner<Void,Void>

visitEnhancedForLoop

public Void visitEnhancedForLoop(EnhancedForLoopTree node,
                                 Void p)

Specified by:

visitEnhancedForLoop in interface TreeVisitor<Void,Void>

Overrides:

visitEnhancedForLoop in class TreeScanner<Void,Void>

containsKey

protected static boolean containsKey(Tree tree,
                                     Collection<String> keys)

pushNewLevel

protected void pushNewLevel()

popLastLevel

protected void popLastLevel()

visitAssert

public Void visitAssert(AssertTree node,
                        Void p)

Specified by:

visitAssert in interface TreeVisitor<Void,Void>

Overrides:

visitAssert in class TreeScanner<Void,Void>

visitIf

public Void visitIf(IfTree node,
                    Void p)

Specified by:

visitIf in interface TreeVisitor<Void,Void>

Overrides:

visitIf in class TreeScanner<Void,Void>

visitConditionalExpression

public Void visitConditionalExpression(ConditionalExpressionTree node,
                                       Void p)

Specified by:

visitConditionalExpression in interface TreeVisitor<Void,Void>

Overrides:

visitConditionalExpression in class TreeScanner<Void,Void>

visitWhileLoop

public Void visitWhileLoop(WhileLoopTree node,
                           Void p)

Specified by:

visitWhileLoop in interface TreeVisitor<Void,Void>

Overrides:

visitWhileLoop in class TreeScanner<Void,Void>

visitDoWhileLoop

public Void visitDoWhileLoop(DoWhileLoopTree node,
                             Void p)

Specified by:

visitDoWhileLoop in interface TreeVisitor<Void,Void>

Overrides:

visitDoWhileLoop in class TreeScanner<Void,Void>

visitForLoop

public Void visitForLoop(ForLoopTree node,
                         Void p)

Specified by:

visitForLoop in interface TreeVisitor<Void,Void>

Overrides:

visitForLoop in class TreeScanner<Void,Void>

visitBreak

public Void visitBreak(BreakTree node,
                       Void p)

Specified by:

visitBreak in interface TreeVisitor<Void,Void>

Overrides:

visitBreak in class TreeScanner<Void,Void>

visitContinue

public Void visitContinue(ContinueTree node,
                          Void p)

Specified by:

visitContinue in interface TreeVisitor<Void,Void>

Overrides:

visitContinue in class TreeScanner<Void,Void>

visitReturn

public Void visitReturn(ReturnTree node,
                        Void p)

Specified by:

visitReturn in interface TreeVisitor<Void,Void>

Overrides:

visitReturn in class TreeScanner<Void,Void>

visitThrow

public Void visitThrow(ThrowTree node,
                       Void p)

Specified by:

visitThrow in interface TreeVisitor<Void,Void>

Overrides:

visitThrow in class TreeScanner<Void,Void>

visitTry

public Void visitTry(TryTree node,
                     Void p)

Specified by:

visitTry in interface TreeVisitor<Void,Void>

Overrides:

visitTry in class TreeScanner<Void,Void>

visitMethodInvocation

public Void visitMethodInvocation(MethodInvocationTree node,
                                  Void p)

Specified by:

visitMethodInvocation in interface TreeVisitor<Void,Void>

Overrides:

visitMethodInvocation in class TreeScanner<Void,Void>

visitBlock

public Void visitBlock(BlockTree node,
                       Void p)

Specified by:

visitBlock in interface TreeVisitor<Void,Void>

Overrides:

visitBlock in class TreeScanner<Void,Void>

visitMethod

public Void visitMethod(MethodTree node,
                        Void p)

Specified by:

visitMethod in interface TreeVisitor<Void,Void>

Overrides:

visitMethod in class TreeScanner<Void,Void>