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/*
* Copyright 2009 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.jjs.impl.gflow.cfg;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JArrayRef;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JBinaryOperator;
import com.google.gwt.dev.jjs.ast.JBlock;
import com.google.gwt.dev.jjs.ast.JBreakStatement;
import com.google.gwt.dev.jjs.ast.JCaseStatement;
import com.google.gwt.dev.jjs.ast.JCastOperation;
import com.google.gwt.dev.jjs.ast.JClassType;
import com.google.gwt.dev.jjs.ast.JConditional;
import com.google.gwt.dev.jjs.ast.JContinueStatement;
import com.google.gwt.dev.jjs.ast.JDeclarationStatement;
import com.google.gwt.dev.jjs.ast.JDeclaredType;
import com.google.gwt.dev.jjs.ast.JDoStatement;
import com.google.gwt.dev.jjs.ast.JExpression;
import com.google.gwt.dev.jjs.ast.JExpressionStatement;
import com.google.gwt.dev.jjs.ast.JFieldRef;
import com.google.gwt.dev.jjs.ast.JForStatement;
import com.google.gwt.dev.jjs.ast.JIfStatement;
import com.google.gwt.dev.jjs.ast.JLabeledStatement;
import com.google.gwt.dev.jjs.ast.JMethodCall;
import com.google.gwt.dev.jjs.ast.JNode;
import com.google.gwt.dev.jjs.ast.JProgram;
import com.google.gwt.dev.jjs.ast.JReboundEntryPoint;
import com.google.gwt.dev.jjs.ast.JReturnStatement;
import com.google.gwt.dev.jjs.ast.JStatement;
import com.google.gwt.dev.jjs.ast.JSwitchStatement;
import com.google.gwt.dev.jjs.ast.JThrowStatement;
import com.google.gwt.dev.jjs.ast.JTryStatement;
import com.google.gwt.dev.jjs.ast.JType;
import com.google.gwt.dev.jjs.ast.JTypeOracle;
import com.google.gwt.dev.jjs.ast.JUnaryOperation;
import com.google.gwt.dev.jjs.ast.JVariableRef;
import com.google.gwt.dev.jjs.ast.JVisitor;
import com.google.gwt.dev.jjs.ast.JWhileStatement;
import com.google.gwt.dev.jjs.ast.js.JDebuggerStatement;
import com.google.gwt.thirdparty.guava.common.base.Preconditions;
import java.util.ArrayList;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* Builder for CFG graph.
*
* Resulting CFG graph contains as much information as needed by current
* analysis set. The amount of detail in call graph can be shrink or extend over
* time. Current CfgNode inheritance tree gives an accurate understanding of
* current detail level.
*
* To build an accurate representation of control flow graph in the presence of
* exceptions, we maintain all possible exit reason from statement. (This is
* called completion in JLS. We use exit name in code for brevity).
*
* CfgBuilder also tries to assign cfg node parents to correspond to AST tree
* structure. This is not always correct (yet). But it is always guaranteed that
* you will always meet a cfg node corresponding to containing statements when
* traversing cfg node parents.
*
* Every statement always has the corresponding node in cfg graph.
*
* TODO: such nodes as if, etc, should be parent of their expressions.
*/
public class CfgBuilder {
/**
* Visitor class which does all cfg building.
*/
private static class BuilderVisitor extends JVisitor {
/**
* Representation of possible exits from statement. Emulates algebraic data
* type to save memory.
*/
private static class Exit {
private enum Reason {
/**
* Exit with a break statement.
*/
BREAK,
/**
* Exit with case else.
*/
CASE_ELSE,
/**
* Exit with case then.
*/
CASE_THEN,
/**
* Exit with continue statement.
*/
CONTINUE,
/**
* Normal exit from statement.
*/
NORMAL,
/**
* Exit with return statement.
*/
RETURN,
/**
* Exit with exception throwing.
*/
THROW
}
private static Exit createBreak(CfgNode node, String label) {
return new Exit(Reason.BREAK, node, null, label, null);
}
private static Exit createCaseElse(CfgNode node) {
return new Exit(Reason.CASE_ELSE, node, null, null,
CfgConditionalNode.ELSE);
}
private static Exit createCaseThen(CfgNode node) {
return new Exit(Reason.CASE_THEN, node, null, null,
CfgConditionalNode.THEN);
}
private static Exit createContinue(CfgNode node, String label) {
return new Exit(Reason.CONTINUE, node, null, label, null);
}
private static Exit createNormal(CfgNode node, String role) {
return new Exit(Reason.NORMAL, node, null, null, role);
}
private static Exit createReturn(CfgNode node) {
return new Exit(Reason.RETURN, node, null, null, null);
}
private static Exit createThrow(CfgNode node,
JType exceptionType, String role) {
return new Exit(Reason.THROW, node, exceptionType, null, role);
}
/**
* Exception type for THROW exit.
*/
private final JType exceptionType;
/**
* Break/continue target label. Null if label wasn't set.
*/
private final String label;
/**
* Cfg node which generated this exit.
*/
private final CfgNode node;
/**
* Exit reason.
*/
private final Reason reason;
/**
* Role for all cfg edges generated from this exit.
*/
private final String role;
private Exit(Reason reason, CfgNode source,
JType exceptionType, String label, String role) {
if (source == null) {
throw new IllegalArgumentException();
}
this.reason = reason;
this.node = source;
this.exceptionType = exceptionType;
this.label = label;
this.role = role;
}
public JType getExceptionType() {
if (!isThrow()) {
throw new IllegalArgumentException();
}
return exceptionType;
}
public String getLabel() {
if (!isContinue() && !isBreak()) {
throw new IllegalArgumentException();
}
return label;
}
public CfgNode getNode() {
return node;
}
public boolean isBreak() {
return reason == Reason.BREAK;
}
public boolean isContinue() {
return reason == Reason.CONTINUE;
}
public boolean isNormal() {
return reason == Reason.NORMAL;
}
public boolean isThrow() {
return reason == Reason.THROW;
}
@Override
public String toString() {
return reason.toString();
}
}
/**
* All exits at this point of interpretation tabulated by their reason.
*/
private final EnumMap> currentExitsByReason =
new EnumMap>(Exit.Reason.class);
/**
* Artificial cfg end node.
*/
private final CfgEndNode endNode = new CfgEndNode();
/**
* Resulting graph.
*/
private final Cfg graph = new Cfg();
/**
* Map from statement to its label.
*/
private final Map labels =
new HashMap();
/**
* All nodes in the graph.
*/
private final List> nodes = new ArrayList>();
/**
* Parent for newly created cfg nodes.
*/
private CfgNode parent = null;
private final JProgram program;
private JSwitchStatement switchStatement;
private final JTypeOracle typeOracle;
public BuilderVisitor(JProgram program) {
this.program = program;
this.typeOracle = program.typeOracle;
for (Exit.Reason reason : Exit.Reason.values()) {
this.currentExitsByReason.put(reason, new ArrayList());
}
}
/**
* Build cfg for codeblock. Resulting graph will have one incoming edge
* and no outgoing edges.
*/
public Cfg build(JBlock codeBlock) {
CfgEdge methodIn = new CfgEdge();
graph.addGraphInEdge(methodIn);
accept(codeBlock);
graph.addIn(nodes.get(0), methodIn);
addNode(endNode);
// Wire all remaining exits to end node.
for (Exit.Reason reason : Exit.Reason.values()) {
switch (reason) {
case CONTINUE:
case BREAK:
case CASE_ELSE:
case CASE_THEN:
if (!currentExitsByReason.get(reason).isEmpty()) {
// This shouldn't happen.
throw new IllegalArgumentException("Unhandled exit: " + reason);
}
break;
case NORMAL:
case RETURN:
case THROW: {
for (Exit exit : currentExitsByReason.get(reason)) {
addEdge(exit, endNode);
}
break;
}
}
}
return graph;
}
/**
* Build cfg for codeblock. Resulting graph will have one incoming edge
* and no outgoing edges.
*/
public Cfg build(JExpression expression) {
accept(expression);
addNode(endNode);
for (Exit.Reason reason : Exit.Reason.values()) {
Preconditions.checkArgument(currentExitsByReason.get(reason).isEmpty(),
"Unhandled exits %s", reason);
}
return graph;
}
@Override
public boolean visit(JBinaryOperation x, Context ctx) {
if (x.isAssignment()) {
// Generate writes.
accept(x.getRhs());
acceptExpressionSubreads(x.getLhs());
if (x.getOp() == JBinaryOperator.ASG) {
addNode(new CfgWriteNode(parent, x, x.getLhs(), x.getRhs()));
} else {
addNode(new CfgReadWriteNode(parent, x, x.getLhs(), null));
}
return false;
} else if (x.getOp() == JBinaryOperator.AND
|| x.getOp() == JBinaryOperator.OR) {
// generate conditionals.
accept(x.getLhs());
CfgBinaryConditionalOperationNode node =
pushNode(new CfgBinaryConditionalOperationNode(parent, x));
if (x.getOp() == JBinaryOperator.AND) {
addNormalExit(node, CfgConditionalNode.THEN);
accept(x.getRhs());
List thenExits = removeNormalExits();
addNormalExit(node, CfgConditionalNode.ELSE);
addExits(thenExits);
} else {
addNormalExit(node, CfgConditionalNode.ELSE);
accept(x.getRhs());
List elseExits = removeNormalExits();
addNormalExit(node, CfgConditionalNode.THEN);
addExits(elseExits);
}
popNode();
return false;
}
return true;
}
@Override
public boolean visit(JBlock x, Context ctx) {
pushNode(new CfgBlockNode(parent, x));
accept(x.getStatements());
popNode();
return false;
}
@Override
public boolean visit(JBreakStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
String label = null;
if (x.getLabel() != null) {
label = x.getLabel().getName();
}
CfgBreakNode node = addNode(new CfgBreakNode(parent, x));
addExit(Exit.createBreak(node, label));
popNode();
return false;
}
@Override
public boolean visit(JCaseStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
if (x.getExpr() != null) {
// case label
JExpression condition = new JBinaryOperation(x.getSourceInfo(),
program.getTypePrimitiveBoolean(),
JBinaryOperator.EQ, switchStatement.getExpr(), x.getExpr());
CfgCaseNode node = addNode(new CfgCaseNode(parent, x, condition));
addExit(Exit.createCaseThen(node));
addExit(Exit.createCaseElse(node));
} else {
// default label
}
popNode();
return false;
}
/**
* Each cast operation generates optional throw.
* Fixes http://code.google.com/p/google-web-toolkit/issues/detail?id=5739
*/
@Override
public boolean visit(JCastOperation x, Context ctx) {
accept(x.getExpr());
CfgOptionalThrowNode node = addNode(new CfgOptionalThrowNode(parent, x));
addNormalExit(node, CfgOptionalThrowNode.NO_THROW);
JDeclaredType runtimeExceptionType =
program.getFromTypeMap("java.lang.RuntimeException");
if (runtimeExceptionType != null) {
addExit(Exit.createThrow(node, runtimeExceptionType,
CfgOptionalThrowNode.RUNTIME_EXCEPTION));
}
addNode(new CfgCastOperationNode(parent, x));
return false;
}
@Override
public boolean visit(JConditional x, Context ctx) {
accept(x.getIfTest());
CfgConditionalExpressionNode node =
pushNode(new CfgConditionalExpressionNode(parent, x));
addNormalExit(node, CfgConditionalNode.THEN);
accept(x.getThenExpr());
List thenExits = removeNormalExits();
addNormalExit(node, CfgConditionalNode.ELSE);
accept(x.getElseExpr());
addExits(thenExits);
popNode();
return false;
}
@Override
public boolean visit(JContinueStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
String label = null;
if (x.getLabel() != null) {
label = x.getLabel().getName();
}
CfgContinueNode node = addNode(new CfgContinueNode(parent, x));
addExit(Exit.createContinue(node, label));
popNode();
return false;
}
@Override
public boolean visit(JDebuggerStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
popNode();
return false;
}
@Override
public boolean visit(JDeclarationStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
if (x.getInitializer() != null) {
accept(x.getInitializer());
addNode(new CfgWriteNode(parent, x, x.getVariableRef(),
x.getInitializer()));
}
popNode();
return false;
}
@Override
public boolean visit(JDoStatement x, Context ctx) {
List unlabeledExits = removeUnlabeledExits();
pushNode(new CfgStatementNode(parent, x));
int pos = nodes.size();
if (x.getBody() != null) {
accept(x.getBody());
}
if (x.getTestExpr() != null) {
accept(x.getTestExpr());
}
CfgDoNode node = addNode(new CfgDoNode(parent, x));
addEdge(node, nodes.get(pos), new CfgEdge(CfgConditionalNode.THEN));
String label = labels.get(x);
addContinueEdges(nodes.get(pos), label);
addBreakExits(label);
addNormalExit(node, CfgConditionalNode.ELSE);
popNode();
addExits(unlabeledExits);
return false;
}
@Override
public boolean visit(JExpressionStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
accept(x.getExpr());
popNode();
return false;
}
@Override
public boolean visit(JForStatement x, Context ctx) {
List unlabeledExits = removeUnlabeledExits();
pushNode(new CfgStatementNode(parent, x));
accept(x.getInitializers());
CfgForNode cond = null;
int testPos = nodes.size();
if (x.getCondition() != null) {
accept(x.getCondition());
cond = addNode(new CfgForNode(parent, x));
addNormalExit(cond, CfgConditionalNode.THEN);
}
if (x.getBody() != null) {
accept(x.getBody());
}
int incrementsPos = nodes.size();
if (x.getIncrements() != null) {
accept(x.getIncrements());
}
List thenExits = removeNormalExits();
for (Exit e : thenExits) {
addEdge(e, nodes.get(testPos));
}
String label = labels.get(x);
// If there's no increments, continue goes straight to test.
int continuePos = incrementsPos != nodes.size() ? incrementsPos : testPos;
addContinueEdges(nodes.get(continuePos), label);
addBreakExits(label);
if (cond != null) {
addNormalExit(cond, CfgConditionalNode.ELSE);
}
popNode();
addExits(unlabeledExits);
return false;
}
@Override
public boolean visit(JIfStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
accept(x.getIfExpr());
CfgIfNode node = addNode(new CfgIfNode(parent, x));
addNormalExit(node, CfgConditionalNode.THEN);
if (x.getThenStmt() != null) {
accept(x.getThenStmt());
}
List thenExits = removeNormalExits();
addNormalExit(node, CfgConditionalNode.ELSE);
if (x.getElseStmt() != null) {
accept(x.getElseStmt());
}
addExits(thenExits);
popNode();
return false;
}
@Override
public boolean visit(JLabeledStatement x, Context ctx) {
String label = x.getLabel().getName();
labels.put(x.getBody(), label);
accept(x.getBody());
addBreakExits(label);
return false;
}
/**
* Each method call generates optional throw.
*/
@Override
public boolean visit(JMethodCall x, Context ctx) {
// TODO: join optthrow + call
if (x.getInstance() != null) {
// TODO: add optional NPE exception
accept(x.getInstance());
}
accept(x.getArgs());
CfgOptionalThrowNode node = addNode(new CfgOptionalThrowNode(parent, x));
addNormalExit(node, CfgOptionalThrowNode.NO_THROW);
for (JClassType exceptionType : x.getTarget().getThrownExceptions()) {
addExit(Exit.createThrow(node, exceptionType, null));
}
JDeclaredType runtimeExceptionType =
program.getFromTypeMap("java.lang.RuntimeException");
if (runtimeExceptionType != null) {
addExit(Exit.createThrow(node, runtimeExceptionType,
CfgOptionalThrowNode.RUNTIME_EXCEPTION));
}
JDeclaredType errorExceptionType =
program.getFromTypeMap("java.lang.Error");
if (errorExceptionType != null) {
addExit(Exit.createThrow(node, errorExceptionType,
CfgOptionalThrowNode.ERROR));
}
addNode(new CfgMethodCallNode(parent, x));
return false;
}
@Override
public boolean visit(JReboundEntryPoint x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
accept(x.getEntryCalls());
popNode();
return false;
}
@Override
public boolean visit(JReturnStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
if (x.getExpr() != null) {
accept(x.getExpr());
}
CfgReturnNode node = addNode(new CfgReturnNode(parent, x));
addExit(Exit.createReturn(node));
popNode();
return false;
}
@Override
public boolean visit(JStatement x, Context ctx) {
// The statement isn't supported.
throw new UnsupportedNodeException(x.getClass().toString());
}
@Override
public boolean visit(JSwitchStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
accept(x.getExpr());
JSwitchStatement oldSwitchStatement = switchStatement;
// We don't want to mess with other case exits here
List oldCaseElseExits = removeExits(Exit.Reason.CASE_ELSE);
List oldCaseThenExits = removeExits(Exit.Reason.CASE_THEN);
List oldBreakExits = removeUnlabeledBreaks();
switchStatement = x;
// Goto to the first non-default node.
CfgSwitchGotoNode gotoNode = addNode(new CfgSwitchGotoNode(parent, x));
Exit gotoExit = Exit.createNormal(gotoNode, null);
int defaultPos = -1;
List breakExits = new ArrayList();
List fallThroughExits = new ArrayList();
List statements = x.getBody().getStatements();
for (JStatement s : statements) {
if (s instanceof JCaseStatement) {
if (((JCaseStatement) s).getExpr() != null) {
// case label
fallThroughExits.addAll(removeExits(Exit.Reason.NORMAL));
if (gotoExit != null) {
// This is first non-default case.
addExit(gotoExit);
gotoExit = null;
}
List elseExits = removeExits(Exit.Reason.CASE_ELSE);
for (Exit e : elseExits) {
addNormalExit(e.getNode(), e.role);
}
} else {
// default label
defaultPos = nodes.size();
}
} else {
List thenExits = removeExits(Exit.Reason.CASE_THEN);
for (Exit e : thenExits) {
addNormalExit(e.getNode(), e.role);
}
if (!fallThroughExits.isEmpty()) {
for (Exit e : fallThroughExits) {
addExit(e);
}
fallThroughExits.clear();
}
}
accept(s);
breakExits.addAll(removeUnlabeledBreaks());
}
if (gotoExit != null) {
// Happens when there are no case statements.
if (defaultPos >= 0) {
addEdge(gotoExit, nodes.get(defaultPos));
} else {
addExit(gotoExit);
}
gotoExit = null;
}
List thenExits = removeExits(Exit.Reason.CASE_THEN);
for (Exit e : thenExits) {
addNormalExit(e.getNode(), e.role);
}
List elseExits = removeExits(Exit.Reason.CASE_ELSE);
if (defaultPos >= 0) {
for (Exit e : elseExits) {
addEdge(e, nodes.get(defaultPos));
}
} else {
for (Exit e : elseExits) {
addExit(Exit.createNormal(e.getNode(), e.role));
}
}
for (Exit e : breakExits) {
addNormalExit(e.getNode(), e.role);
}
switchStatement = oldSwitchStatement;
addExits(oldCaseElseExits);
addExits(oldCaseThenExits);
addExits(oldBreakExits);
popNode();
return false;
}
@Override
public boolean visit(JThrowStatement x, Context ctx) {
pushNode(new CfgStatementNode(parent, x));
accept(x.getExpr());
CfgThrowNode node = addNode(new CfgThrowNode(parent, x));
addExit(Exit.createThrow(node, x.getExpr().getType(), null));
popNode();
return false;
}
@Override
public boolean visit(JTryStatement x, Context ctx) {
pushNode(new CfgTryNode(parent, x));
accept(x.getTryBlock());
// Process all blocks and determine their exits
List tryBlockExits = removeCurrentExits();
List catchBlockPos = new ArrayList();
List> catchExits = new ArrayList>();
for (JTryStatement.CatchClause clause : x.getCatchClauses()) {
JBlock b = clause.getBlock();
catchBlockPos.add(nodes.size());
accept(b);
catchExits.add(removeCurrentExits());
}
int finallyPos = nodes.size();
if (x.getFinallyBlock() != null) {
accept(x.getFinallyBlock());
}
List finallyExits = removeCurrentExits();
// Actual work goes here. We are citing JLS to make it easier to follow.
// We prefer to have duplicated code for finally block handling just
// to make it easier to follow.
// A try statement without a finally block is executed by first executing
// the try block. Then there is a choice:
if (x.getFinallyBlock() == null) {
// If execution of the try block completes normally, then no further
// action is taken and the try statement completes normally.
addExits(removeNormalExits(tryBlockExits));
nextExit : for (Exit e : tryBlockExits) {
if (e.isThrow()) {
// If execution of the try block completes abruptly because of a
// throw of a value V, then there is a choice:
nextCatchBlock : for (int i = 0; i < x.getCatchClauses().size(); ++i) {
// If the run-time type of V is assignable (�5.2) to the
// Parameter of any catch clause of the try statement, then
// the first (leftmost) such catch clause is selected.
// TODO(rluble): we are safely overapproximating the exception
// caught in this block by the type of the exception variable.
// We could do better in multiexceptions.
JClassType catchType =
(JClassType) x.getCatchClauses().get(i).getArg().getType();
JType exceptionType = e.getExceptionType();
boolean canCatch = false;
boolean fullCatch = false;
// It's not that simple in static analysis though.
if (typeOracle.canTriviallyCast(exceptionType, catchType)) {
// Catch clause fully covers exception type. We'll land
// here for sure.
canCatch = true;
// Safe approximation. If it is a multi exception with only one
// exception declared in the clause then the variable is of the
// the same type as the exception declared and the approximation
// is exact hence and this is a full catch.
fullCatch = x.getCatchClauses().get(i).getTypes().size() == 1 &&
x.getCatchClauses().get(i).getTypes().get(0) == catchType;
} else if (typeOracle.canTriviallyCast(catchType, exceptionType)) {
// We can land here if we throw some subclass of
// exceptionType
canCatch = true;
fullCatch = false;
}
if (canCatch) {
addEdge(e, nodes.get(catchBlockPos.get(i)));
if (fullCatch) {
continue nextExit;
}
continue nextCatchBlock;
}
}
// If the run-time type of V is not assignable to the parameter of
// any catch clause of the try statement, then the try statement
// completes abruptly because of a throw of the value V.
addExit(e);
} else {
// If execution of the try block completes abruptly for any other
// reason, then the try statement completes abruptly for the same
// reason.
addExit(e);
}
}
// Continuing catch case here:
// If that block completes normally, then the try statement
// completes normally; if that block completes abruptly for any reason,
// then the try statement completes abruptly for the same reason.
for (List exits : catchExits) {
addExits(exits);
}
} else {
// A try statement with a finally block is executed by first
// executing the try block. Then there is a choice:
// If execution of the try block completes normally, then the finally
// block is executed,
CfgNode finallyNode = nodes.get(finallyPos);
for (Exit e : removeNormalExits(tryBlockExits)) {
addEdge(e, finallyNode);
}
// and then there is a choice: If the finally block completes normally,
// then the try statement completes normally.
// If the finally block completes abruptly for reason S, then the
// try statement completes abruptly for reason S.
addExits(finallyExits);
nextExit : for (Exit e : tryBlockExits) {
if (e.isThrow()) {
// If execution of the try block completes abruptly because of a
// throw of a value V, then there is a choice:
nextCatchBlock : for (int i = 0; i < x.getCatchClauses().size(); ++i) {
// If the run-time type of V is assignable to the parameter of any
// catch clause of the try statement, then the first
// (leftmost) such catch clause is selected.
// TODO(rluble): we are safely overapproximating the exception
// caught in this block by the type of the exception variable.
// We could do better in multiexceptions.
JClassType catchType =
(JClassType) x.getCatchClauses().get(i).getArg().getType();
JType exceptionType = e.getExceptionType();
boolean canCatch = false;
boolean fullCatch = false;
// It's not that simple in static analysis though.
if (typeOracle.canTriviallyCast(exceptionType, catchType)) {
// Catch clause fully covers exception type. We'll land
// here for sure.
canCatch = true;
// Safe approximation. If it is a multi exception with only one
// exception declared in the clause then the variable is of the
// the same type as the exception declared and the approximation
// is exact hence and this is a full catch.
fullCatch = x.getCatchClauses().get(i).getTypes().size() == 1 &&
x.getCatchClauses().get(i).getTypes().get(0) == catchType;
} else if (typeOracle.canTriviallyCast(catchType, exceptionType)) {
// We can land here if we throw some subclass of
// exceptionType
canCatch = true;
fullCatch = false;
}
if (canCatch) {
addEdge(e, nodes.get(catchBlockPos.get(i)));
if (fullCatch) {
continue nextExit;
}
continue nextCatchBlock;
}
}
// If the run-time type of V is not assignable to the parameter of
// any catch clause of the try statement, then the finally block is
// executed.
addEdge(e, finallyNode);
// Then there is a choice:
for (Exit finallyExit : finallyExits) {
if (finallyExit.isNormal()) {
// If the finally block completes normally, then the try
// statement completes abruptly because of a throw of the
// value V.
addExit(new Exit(e.reason, finallyExit.node, e.exceptionType,
e.label, e.role));
} else {
// If the finally block completes abruptly for reason S, then
// the try statement completes abruptly for reason S
// (and reason R is discarded).
// This is already covered earlier:
// addExits(finallyExits)
}
}
} else {
// If execution of the try block completes abruptly for any other
// reason R, then the finally block is executed.
addEdge(e, finallyNode);
// Then there is a choice:
for (Exit finallyExit : finallyExits) {
if (finallyExit.isNormal()) {
// If the finally block completes normally, then the try
// statement completes abruptly for reason R.
addExit(new Exit(e.reason, finallyExit.node, e.exceptionType,
e.label, e.role));
} else {
// If the finally block completes abruptly for reason S, then
// the try statement completes abruptly for reason S
// (and reason R is discarded).
// This is already covered earlier:
// addExits(finallyExits)
}
}
}
}
// Continuing catch case here:
// If that block completes normally, then the try statement
// completes normally; if that block completes abruptly for any reason,
// then the try statement completes abruptly for the same reason.
for (List exits : catchExits) {
for (Exit e : exits) {
// If the catch block completes normally or abruptly, then the finally block is
// executed.
addEdge(e, finallyNode);
if (!e.isNormal()) {
// If the catch block completes abruptly for reason R there is a choice:
for (Exit finallyExit : finallyExits) {
if (finallyExit.isNormal()) {
// If the finally block completes normally, then the try
// statement completes abruptly for reason R.
addExit(new Exit(e.reason, finallyExit.node, e.exceptionType,
e.label, e.role));
} else {
// If the finally block completes abruptly for reason S, then
// the try statement completes abruptly for reason S
// (and reason R is discarded).
// This is already covered earlier:
// addExits(finallyExits)
}
}
}
}
}
}
popNode();
return false;
}
@Override
public boolean visit(JUnaryOperation x, Context ctx) {
if (x.getOp().isModifying()) {
acceptExpressionSubreads(x.getArg());
addNode(new CfgReadWriteNode(parent, x, x.getArg(), null));
return false;
}
// read will be added by normal flow
return true;
}
@Override
public boolean visit(JVariableRef x, Context ctx) {
// TODO: add NPE exceptions for field references.
addNode(new CfgReadNode(parent, x));
return true;
}
@Override
public boolean visit(JWhileStatement x, Context ctx) {
List unlabeledExits = removeUnlabeledExits();
pushNode(new CfgStatementNode(parent, x));
int pos = nodes.size();
accept(x.getTestExpr());
CfgWhileNode node = addNode(new CfgWhileNode(parent, x));
addNormalExit(node, CfgConditionalNode.THEN);
if (x.getBody() != null) {
accept(x.getBody());
}
List thenExits = removeNormalExits();
for (Exit e : thenExits) {
addEdge(e, nodes.get(pos));
}
String label = labels.get(x);
addContinueEdges(nodes.get(pos), label);
addBreakExits(label);
addNormalExit(node, CfgConditionalNode.ELSE);
popNode();
addExits(unlabeledExits);
return false;
}
/**
* Detect all reads which are performed before evaluating expression.
*/
private void acceptExpressionSubreads(JExpression expression) {
if (expression instanceof JFieldRef) {
JExpression instance = ((JFieldRef) expression).getInstance();
if (instance != null) {
accept(instance);
}
} else if (expression instanceof JArrayRef) {
JArrayRef arrayRef = (JArrayRef) expression;
accept(arrayRef.getInstance());
accept(arrayRef.getIndexExpr());
} else if (!(expression instanceof JVariableRef)) {
throw new IllegalArgumentException("Unexpected lhs: " + expression);
}
}
/**
* Transform all break exits into normal exits, thus making sure that
* next node will get edges from them.
*/
private void addBreakExits(String label) {
List exits = removeLoopExits(Exit.Reason.BREAK, label);
for (Exit e : exits) {
addNormalExit(e.getNode());
}
}
/**
* Transform all continue exits into normal exits, thus making sure that
* next node will get edges from them.
*/
private void addContinueEdges(CfgNode node, String label) {
List continueExits = removeLoopExits(Exit.Reason.CONTINUE, label);
for (Exit e : continueExits) {
addEdge(e, node);
}
}
private CfgEdge addEdge(CfgNode from, CfgNode to, CfgEdge edge) {
graph.addOut(from, edge);
graph.addIn(to, edge);
return edge;
}
private CfgEdge addEdge(Exit e, CfgNode to) {
CfgEdge edge = new CfgEdge(e.role);
return addEdge(e.node, to, edge);
}
private void addExit(Exit exit) {
currentExitsByReason.get(exit.reason).add(exit);
}
private void addExits(List exits) {
for (Exit exit : exits) {
currentExitsByReason.get(exit.reason).add(exit);
}
}
/**
* Add new node to cfg. Wire all current normal exits to it.
*/
private > N addNode(N node) {
nodes.add(node);
graph.addNode(node);
ArrayList normalExits =
currentExitsByReason.put(Exit.Reason.NORMAL, new ArrayList());
for (Exit exit : normalExits) {
addEdge(exit, node);
}
// Simplify all the code, add normal exit for CfgSimplNode automatically.
if (node instanceof CfgSimpleNode) {
addNormalExit(node);
}
return node;
}
private void addNormalExit(CfgNode node) {
addNormalExit(node, null);
}
private void addNormalExit(CfgNode node, String role) {
addExit(Exit.createNormal(node, role));
}
private void popNode() {
parent = parent.getParent();
}
private > N pushNode(N node) {
addNode(node);
parent = node;
return node;
}
private List removeCurrentExits() {
ArrayList result = new ArrayList();
for (Exit.Reason reason : Exit.Reason.values()) {
result.addAll(currentExitsByReason.put(reason, new ArrayList()));
}
return result;
}
private List removeExits(Exit.Reason reason) {
return currentExitsByReason.put(reason, new ArrayList());
}
private List removeExits(List exits, Exit.Reason reason) {
List result = new ArrayList();
for (Iterator i = exits.iterator(); i.hasNext();) {
Exit exit = i.next();
if (exit.reason == reason) {
i.remove();
result.add(exit);
}
}
return result;
}
/**
* Remove all loop exits to specified label.
*/
private List removeLoopExits(Exit.Reason reason, String label) {
ArrayList removedExits = new ArrayList();
ArrayList remainingExits = new ArrayList();
for (Exit exit : currentExitsByReason.get(reason)) {
if (exit.getLabel() == null || exit.getLabel().equals(label)) {
removedExits.add(exit);
} else {
remainingExits.add(exit);
}
}
currentExitsByReason.put(reason, remainingExits);
return removedExits;
}
/**
* Remove all normal exits from current exit list.
*/
private List removeNormalExits() {
return currentExitsByReason.put(Exit.Reason.NORMAL, new ArrayList());
}
private List removeNormalExits(List exits) {
return removeExits(exits, Exit.Reason.NORMAL);
}
private List removeUnlabeledBreaks() {
List breakExits = removeExits(Exit.Reason.BREAK);
List labeledBreaks = new ArrayList();
for (Iterator i = breakExits.iterator(); i.hasNext();) {
Exit exit = i.next();
if (exit.getLabel() != null) {
i.remove();
labeledBreaks.add(exit);
}
}
addExits(labeledBreaks);
return breakExits;
}
private List removeUnlabeledExits() {
List unlabeledExits = new ArrayList();
Exit.Reason reasons[] = { Exit.Reason.BREAK, Exit.Reason.CONTINUE };
for (Exit.Reason reason : reasons) {
for (Iterator i = currentExitsByReason.get(reason).iterator(); i.hasNext();) {
Exit exit = i.next();
if (exit.getLabel() == null) {
i.remove();
unlabeledExits.add(exit);
}
}
}
return unlabeledExits;
}
}
private static class CfgCastOperationNode extends CfgSimpleNode {
public CfgCastOperationNode(CfgNode parent, JNode jNode) {
super(parent, jNode);
}
@Override
public void accept(CfgVisitor visitor) {
visitor.visitSimpleNode(this);
}
@Override
protected CfgNode cloneImpl() {
return new CfgCastOperationNode(getParent(), getJNode());
}
}
/**
* Special exception which is thrown when we encounter some syntactic
* construction which is not yet supported by CfgBuilder.
*/
private static class UnsupportedNodeException extends RuntimeException {
public UnsupportedNodeException(String message) {
super(message);
}
}
/**
* Build Cfg for code block.
*/
public static Cfg build(JProgram program, JBlock codeblock) {
return new BuilderVisitor(program).build(codeblock);
}
public static Cfg buildExpressionCfg(JProgram program, JExpression value) {
return new BuilderVisitor(program).build(value);
}
}
