Copyright (c) 2000, 2011, 2015 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
    Carmi Grushko - Bug 465048 - Binding is null for class literals in synchronized blocks
/*******************************************************************************
 * Copyright (c) 2000, 2011, 2015 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
 *     Carmi Grushko - Bug 465048 - Binding is null for class literals in synchronized blocks
 *******************************************************************************/
package org.eclipse.jdt.internal.compiler.ast;

import org.eclipse.jdt.internal.compiler.ASTVisitor;
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.impl.Constant;
import org.eclipse.jdt.internal.compiler.lookup.*;

public class SynchronizedStatement extends SubRoutineStatement {

	public Expression expression;
	public Block block;
	public BlockScope scope;
	public LocalVariableBinding synchroVariable;
	static final char[] SecretLocalDeclarationName = " syncValue".toCharArray(); //$NON-NLS-1$

	// for local variables table attributes
	int preSynchronizedInitStateIndex = -1;
	int mergedSynchronizedInitStateIndex = -1;

public SynchronizedStatement(
	Expression expression,
	Block statement,
	int s,
	int e) {

	this.expression = expression;
	this.block = statement;
	this.sourceEnd = e;
	this.sourceStart = s;
}

@Override
public FlowInfo analyseCode(
	BlockScope currentScope,
	FlowContext flowContext,
	FlowInfo flowInfo) {

	this.preSynchronizedInitStateIndex =
		currentScope.methodScope().recordInitializationStates(flowInfo);
    // TODO (philippe) shouldn't it be protected by a check whether reachable statement ?

	// mark the synthetic variable as being used
	this.synchroVariable.useFlag = LocalVariableBinding.USED;

	// simple propagation to subnodes
	FlowInfo expressionFlowInfo = this.expression.analyseCode(this.scope, flowContext, flowInfo);

	this.expression.checkNPE(currentScope, flowContext, expressionFlowInfo, 1);

	flowInfo =
		this.block.analyseCode(
			this.scope,
			new InsideSubRoutineFlowContext(flowContext, this),
			expressionFlowInfo);

	this.mergedSynchronizedInitStateIndex =
		currentScope.methodScope().recordInitializationStates(flowInfo);

	// optimizing code gen
	if ((flowInfo.tagBits & FlowInfo.UNREACHABLE_OR_DEAD) != 0) {
		this.bits |= ASTNode.BlockExit;
	}

	return flowInfo;
}

@Override
public boolean isSubRoutineEscaping() {
	return false;
}

Synchronized statement code generation
Params:
currentScope – org.eclipse.jdt.internal.compiler.lookup.BlockScope
codeStream – org.eclipse.jdt.internal.compiler.codegen.CodeStream/**
 * Synchronized statement 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;
	}
	// in case the labels needs to be reinitialized
	// when the code generation is restarted in wide mode
	this.anyExceptionLabel = null;

	int pc = codeStream.position;

	// generate the synchronization expression
	this.expression.generateCode(this.scope, codeStream, true);
	if (this.block.isEmptyBlock()) {
		switch(this.synchroVariable.type.id) {
			case TypeIds.T_long :
			case TypeIds.T_double :
				codeStream.dup2();
				break;
			default :
				codeStream.dup();
				break;
		}		
		// only take the lock
		codeStream.monitorenter();
		codeStream.monitorexit();
		if (this.scope != currentScope) {
			codeStream.exitUserScope(this.scope);
		}
	} else {
		// enter the monitor
		codeStream.store(this.synchroVariable, true);
		codeStream.addVariable(this.synchroVariable);
		codeStream.monitorenter();

		// generate  the body of the synchronized block
		enterAnyExceptionHandler(codeStream);
		this.block.generateCode(this.scope, codeStream);
		if (this.scope != currentScope) {
			// close all locals defined in the synchronized block except the secret local
			codeStream.exitUserScope(this.scope, this.synchroVariable);
		}

		BranchLabel endLabel = new BranchLabel(codeStream);
		if ((this.bits & ASTNode.BlockExit) == 0) {
			codeStream.load(this.synchroVariable);
			codeStream.monitorexit();
			exitAnyExceptionHandler();
			codeStream.goto_(endLabel);
			enterAnyExceptionHandler(codeStream);
		}
		// generate the body of the exception handler
		codeStream.pushExceptionOnStack(this.scope.getJavaLangThrowable());
		if (this.preSynchronizedInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.preSynchronizedInitStateIndex);
		}
		placeAllAnyExceptionHandler();
		codeStream.load(this.synchroVariable);
		codeStream.monitorexit();
		exitAnyExceptionHandler();
		codeStream.athrow();
		// May loose some local variable initializations : affecting the local variable attributes
		if (this.mergedSynchronizedInitStateIndex != -1) {
			codeStream.removeNotDefinitelyAssignedVariables(currentScope, this.mergedSynchronizedInitStateIndex);
			codeStream.addDefinitelyAssignedVariables(currentScope, this.mergedSynchronizedInitStateIndex);
		}
		if (this.scope != currentScope) {
			codeStream.removeVariable(this.synchroVariable);
		}
		if ((this.bits & ASTNode.BlockExit) == 0) {
			endLabel.place();
		}
	}
	codeStream.recordPositionsFrom(pc, this.sourceStart);
}

See Also:
generateSubRoutineInvocation.generateSubRoutineInvocation(BlockScope, CodeStream, Object, int, LocalVariableBinding)/**
 * @see SubRoutineStatement#generateSubRoutineInvocation(BlockScope, CodeStream, Object, int, LocalVariableBinding)
 */
@Override
public boolean generateSubRoutineInvocation(BlockScope currentScope, CodeStream codeStream, Object targetLocation, int stateIndex, LocalVariableBinding secretLocal) {
	codeStream.load(this.synchroVariable);
	codeStream.monitorexit();
	exitAnyExceptionHandler();
	return false;
}

@Override
public void resolve(BlockScope upperScope) {
	// special scope for secret locals optimization.
	this.scope = new BlockScope(upperScope);
	TypeBinding type = this.expression.resolveType(this.scope);
	if (type != null) {
		switch (type.id) {
			case T_boolean :
			case T_char :
			case T_float :
			case T_double :
			case T_byte :
			case T_short :
			case T_int :
			case T_long :
				this.scope.problemReporter().invalidTypeToSynchronize(this.expression, type);
				break;
			case T_void :
				this.scope.problemReporter().illegalVoidExpression(this.expression);
				break;
			case T_null :
				this.scope.problemReporter().invalidNullToSynchronize(this.expression);
				break;
			}
			//continue even on errors in order to have the TC done into the statements
			this.synchroVariable = new LocalVariableBinding(SecretLocalDeclarationName, type, ClassFileConstants.AccDefault, false);
			this.scope.addLocalVariable(this.synchroVariable);
			this.synchroVariable.setConstant(Constant.NotAConstant); // not inlinable
			this.expression.computeConversion(this.scope, type, type);
	}
	this.block.resolveUsing(this.scope);
}

@Override
public StringBuffer printStatement(int indent, StringBuffer output) {
	printIndent(indent, output);
	output.append("synchronized ("); //$NON-NLS-1$
	this.expression.printExpression(0, output).append(')');
	output.append('\n');
	return this.block.printStatement(indent + 1, output);
}

@Override
public void traverse(ASTVisitor visitor, BlockScope blockScope) {
	if (visitor.visit(this, blockScope)) {
		this.expression.traverse(visitor, this.scope);
		this.block.traverse(visitor, this.scope);
	}
	visitor.endVisit(this, blockScope);
}

@Override
public boolean doesNotCompleteNormally() {
	return this.block.doesNotCompleteNormally();
}
@Override
public boolean completesByContinue() {
	return this.block.completesByContinue();
}
}