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Eclipse Compiler for Java(TM)
/*******************************************************************************
* Copyright (c) 2000, 2021 IBM Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* IBM Corporation - initial API and implementation
* Stephan Herrmann - Contributions for
* bug 319201 - [null] no warning when unboxing SingleNameReference causes NPE
* bug 349326 - [1.7] new warning for missing try-with-resources
* bug 345305 - [compiler][null] Compiler misidentifies a case of "variable can only be null"
* bug 403147 - [compiler][null] FUP of bug 400761: consolidate interaction between unboxing, NPE, and deferred checking
* Bug 415790 - [compiler][resource]Incorrect potential resource leak warning in for loop with close in try/catch
*******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;
import org.eclipse.jdt.internal.compiler.ASTVisitor;
import org.eclipse.jdt.internal.compiler.impl.*;
import org.eclipse.jdt.internal.compiler.classfmt.ClassFileConstants;
import org.eclipse.jdt.internal.compiler.codegen.*;
import org.eclipse.jdt.internal.compiler.flow.*;
import org.eclipse.jdt.internal.compiler.lookup.*;
public class WhileStatement extends Statement {
public Expression condition;
public Statement action;
private BranchLabel breakLabel, continueLabel;
int preCondInitStateIndex = -1;
int condIfTrueInitStateIndex = -1;
int mergedInitStateIndex = -1;
public WhileStatement(Expression condition, Statement action, int s, int e) {
this.condition = condition;
this.action = action;
// remember useful empty statement
if (action instanceof EmptyStatement) action.bits |= IsUsefulEmptyStatement;
this.sourceStart = s;
this.sourceEnd = e;
}
@Override
public FlowInfo analyseCode(BlockScope currentScope, FlowContext flowContext, FlowInfo flowInfo) {
this.breakLabel = new BranchLabel();
this.continueLabel = new BranchLabel();
int initialComplaintLevel = (flowInfo.reachMode() & FlowInfo.UNREACHABLE) != 0 ? Statement.COMPLAINED_FAKE_REACHABLE : Statement.NOT_COMPLAINED;
Constant cst = this.condition.constant;
boolean isConditionTrue = cst != Constant.NotAConstant && cst.booleanValue() == true;
boolean isConditionFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;
cst = this.condition.optimizedBooleanConstant();
boolean isConditionOptimizedTrue = cst != Constant.NotAConstant && cst.booleanValue() == true;
boolean isConditionOptimizedFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;
this.preCondInitStateIndex = currentScope.methodScope().recordInitializationStates(flowInfo);
LoopingFlowContext condLoopContext;
FlowInfo condInfo = flowInfo.nullInfoLessUnconditionalCopy();
// we need to collect the contribution to nulls of the coming paths through the
// loop, be they falling through normally or branched to break, continue labels
// or catch blocks
condInfo = this.condition.analyseCode(
currentScope,
(condLoopContext =
new LoopingFlowContext(flowContext, flowInfo, this, null,
null, currentScope, true)),
condInfo);
this.condition.checkNPEbyUnboxing(currentScope, flowContext, flowInfo);
LoopingFlowContext loopingContext;
FlowInfo actionInfo;
FlowInfo exitBranch;
if (this.action == null
|| (this.action.isEmptyBlock() && currentScope.compilerOptions().complianceLevel <= ClassFileConstants.JDK1_3)) {
condLoopContext.complainOnDeferredFinalChecks(currentScope,
condInfo);
condLoopContext.complainOnDeferredNullChecks(currentScope,
condInfo.unconditionalInits());
if (isConditionTrue) {
return FlowInfo.DEAD_END;
} else {
FlowInfo mergedInfo = flowInfo.copy().addInitializationsFrom(condInfo.initsWhenFalse());
if (isConditionOptimizedTrue){
mergedInfo.setReachMode(FlowInfo.UNREACHABLE_OR_DEAD);
}
this.mergedInitStateIndex =
currentScope.methodScope().recordInitializationStates(mergedInfo);
return mergedInfo;
}
} else {
// in case the condition was inlined to false, record the fact that there is no way to reach any
// statement inside the looping action
loopingContext =
new LoopingFlowContext(
flowContext,
flowInfo,
this,
this.breakLabel,
this.continueLabel,
currentScope,
true);
loopingContext.copyNullCheckedFieldsFrom(condLoopContext);
if (isConditionFalse) {
actionInfo = FlowInfo.DEAD_END;
} else {
actionInfo = condInfo.initsWhenTrue().copy();
if (isConditionOptimizedFalse){
actionInfo.setReachMode(FlowInfo.UNREACHABLE_OR_DEAD);
}
}
// for computing local var attributes
this.condIfTrueInitStateIndex =
currentScope.methodScope().recordInitializationStates(
condInfo.initsWhenTrue());
if (this.action.complainIfUnreachable(actionInfo, currentScope, initialComplaintLevel, true) < Statement.COMPLAINED_UNREACHABLE) {
this.condition.updateFlowOnBooleanResult(actionInfo, true);
actionInfo = this.action.analyseCode(currentScope, loopingContext, actionInfo);
}
// code generation can be optimized when no need to continue in the loop
exitBranch = flowInfo.copy();
// need to start over from flowInfo so as to get null inits
int combinedTagBits = actionInfo.tagBits & loopingContext.initsOnContinue.tagBits;
if ((combinedTagBits & FlowInfo.UNREACHABLE) != 0) {
if ((combinedTagBits & FlowInfo.UNREACHABLE_OR_DEAD) != 0)
this.continueLabel = null;
exitBranch.addInitializationsFrom(condInfo.initsWhenFalse());
actionInfo = actionInfo.mergedWith(loopingContext.initsOnContinue.unconditionalInits());
condLoopContext.complainOnDeferredNullChecks(currentScope,
actionInfo, false);
loopingContext.complainOnDeferredNullChecks(currentScope,
actionInfo, false);
} else {
condLoopContext.complainOnDeferredFinalChecks(currentScope,
condInfo);
actionInfo = actionInfo.mergedWith(loopingContext.initsOnContinue.unconditionalInits());
condLoopContext.complainOnDeferredNullChecks(currentScope,
actionInfo);
loopingContext.complainOnDeferredFinalChecks(currentScope,
actionInfo);
loopingContext.complainOnDeferredNullChecks(currentScope,
actionInfo);
exitBranch.
addPotentialInitializationsFrom(
actionInfo.unconditionalInits()).
addInitializationsFrom(condInfo.initsWhenFalse());
}
if (loopingContext.hasEscapingExceptions()) { // https://bugs.eclipse.org/bugs/show_bug.cgi?id=321926
FlowInfo loopbackFlowInfo = flowInfo.copy();
if (this.continueLabel != null) { // we do get to the bottom
// loopback | (loopback + action):
loopbackFlowInfo = loopbackFlowInfo.mergedWith(loopbackFlowInfo.unconditionalCopy().addNullInfoFrom(actionInfo).unconditionalInits());
}
loopingContext.simulateThrowAfterLoopBack(loopbackFlowInfo);
}
}
// end of loop
FlowInfo mergedInfo = FlowInfo.mergedOptimizedBranches(
(loopingContext.initsOnBreak.tagBits &
FlowInfo.UNREACHABLE) != 0 ?
loopingContext.initsOnBreak :
flowInfo.addInitializationsFrom(loopingContext.initsOnBreak), // recover upstream null info
isConditionOptimizedTrue,
exitBranch,
isConditionOptimizedFalse,
!isConditionTrue /*while(true); unreachable(); */);
this.mergedInitStateIndex = currentScope.methodScope().recordInitializationStates(mergedInfo);
this.condition.updateFlowOnBooleanResult(mergedInfo, false);
return mergedInfo;
}
/**
* While code generation
*
* @param currentScope org.eclipse.jdt.internal.compiler.lookup.BlockScope
* @param codeStream org.eclipse.jdt.internal.compiler.codegen.CodeStream
*/
@Override
public void generateCode(BlockScope currentScope, CodeStream codeStream) {
if ((this.bits & IsReachable) == 0) {
return;
}
if (containsPatternVariable()) {
this.condition.addPatternVariables(currentScope, codeStream);
}
int pc = codeStream.position;
Constant cst = this.condition.optimizedBooleanConstant();
boolean isConditionOptimizedFalse = cst != Constant.NotAConstant && cst.booleanValue() == false;
if (isConditionOptimizedFalse) {
this.condition.generateCode(currentScope, codeStream, false);
// May loose some local variable initializations : affecting the local variable attributes
if (this.mergedInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
}
codeStream.recordPositionsFrom(pc, this.sourceStart);
return;
}
this.breakLabel.initialize(codeStream);
// generate condition
if (this.continueLabel == null) {
// no need to reverse condition
if (this.condition.constant == Constant.NotAConstant) {
this.condition.generateOptimizedBoolean(
currentScope,
codeStream,
null,
this.breakLabel,
true);
}
} else {
this.continueLabel.initialize(codeStream);
if (!(((this.condition.constant != Constant.NotAConstant)
&& (this.condition.constant.booleanValue() == true))
|| (this.action == null)
|| this.action.isEmptyBlock())) {
int jumpPC = codeStream.position;
codeStream.goto_(this.continueLabel);
codeStream.recordPositionsFrom(jumpPC, this.condition.sourceStart);
}
}
// generate the action
BranchLabel actionLabel = new BranchLabel(codeStream);
if (this.action != null) {
actionLabel.tagBits |= BranchLabel.USED;
// Required to fix 1PR0XVS: LFRE:WINNT - Compiler: variable table for method appears incorrect
if (this.condIfTrueInitStateIndex != -1) {
// insert all locals initialized inside the condition into the action generated prior to the condition
codeStream.addDefinitelyAssignedVariables(
currentScope,
this.condIfTrueInitStateIndex);
}
actionLabel.place();
this.action.generateCode(currentScope, codeStream);
// May loose some local variable initializations : affecting the local variable attributes
if (this.preCondInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.preCondInitStateIndex);
}
} else {
actionLabel.place();
}
// output condition and branch back to the beginning of the repeated action
if (this.continueLabel != null) {
this.continueLabel.place();
this.condition.generateOptimizedBoolean(
currentScope,
codeStream,
actionLabel,
null,
true);
}
// May loose some local variable initializations : affecting the local variable attributes
if (this.mergedInitStateIndex != -1) {
codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedInitStateIndex);
}
this.breakLabel.place();
codeStream.recordPositionsFrom(pc, this.sourceStart);
}
@Override
public void resolve(BlockScope scope) {
TypeBinding type = this.condition.resolveTypeExpecting(scope, TypeBinding.BOOLEAN);
this.condition.computeConversion(scope, type, type);
if (this.action != null) {
this.action.resolveWithBindings(this.condition.bindingsWhenTrue(), scope);
}
}
@Override
public boolean containsPatternVariable() {
return this.condition.containsPatternVariable();
}
@Override
public StringBuilder printStatement(int tab, StringBuilder output) {
printIndent(tab, output).append("while ("); //$NON-NLS-1$
this.condition.printExpression(0, output).append(')');
if (this.action == null)
output.append(';');
else
this.action.printStatement(tab + 1, output);
return output;
}
@Override
public void traverse(
ASTVisitor visitor,
BlockScope blockScope) {
if (visitor.visit(this, blockScope)) {
this.condition.traverse(visitor, blockScope);
if (this.action != null)
this.action.traverse(visitor, blockScope);
}
visitor.endVisit(this, blockScope);
}
@Override
public LocalVariableBinding[] bindingsWhenComplete() {
return this.condition.containsPatternVariable() && this.action != null && !this.action.breaksOut(null) ?
this.condition.bindingsWhenFalse() : NO_VARIABLES;
}
@Override
public boolean doesNotCompleteNormally() {
Constant cst = this.condition.constant;
boolean isConditionTrue = cst == null || cst != Constant.NotAConstant && cst.booleanValue() == true;
cst = this.condition.optimizedBooleanConstant();
boolean isConditionOptimizedTrue = cst == null ? true : cst != Constant.NotAConstant && cst.booleanValue() == true;
return (isConditionTrue || isConditionOptimizedTrue) && (this.action == null || !this.action.breaksOut(null));
}
@Override
public boolean completesByContinue() {
return this.action.continuesAtOuterLabel();
}
@Override
public boolean canCompleteNormally() {
Constant cst = this.condition.constant;
boolean isConditionTrue = cst == null || cst != Constant.NotAConstant && cst.booleanValue() == true;
cst = this.condition.optimizedBooleanConstant();
boolean isConditionOptimizedTrue = cst == null ? true : cst != Constant.NotAConstant && cst.booleanValue() == true;
if (!(isConditionTrue || isConditionOptimizedTrue))
return true;
return this.action != null && this.action.breaksOut(null);
}
@Override
public boolean continueCompletes() {
return this.action.continuesAtOuterLabel();
}
}