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added check to detect the double-checked locking idiom, rfe #709333

This commit is contained in:
Lars Kühne 2003-03-29 17:34:12 +00:00
parent ba1663fc94
commit 8f965910b0
10 changed files with 179 additions and 0 deletions
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49
docs/config_misc.html
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@ -70,6 +70,9 @@
<li>
<a href="#FinalParameters">FinalParameters</a>
</li>
<li>
<a href="#DoubleCheckedLocking">DoubleCheckedLocking</a>
</li>
</ul>
</td>
<!--Content-->
@ -787,6 +790,52 @@ public class StringUtils // not final to allow subclassing
<a href="config.html#treewalker">TreeWalker</a>
</p>
<!-- --> <a name="DoubleCheckedLocking"></a> <h2>DoubleCheckedLocking</h2> <h4>Description</h4>
<p class="body">
The &quot;double-checked locking&quot; idiom (DCL) tries to avoid the runtime cost
of synchronization. An example that uses the DCL idiom is this:
</p>
<pre class="body">
public class MySingleton
{
private theInstance = null;
private MySingleton() {}
public MySingleton getInstance() {
if ( theInstance == null ) { // synchronize only if necessary
synchronized( MySingleton.class ) {
if ( s_singleton == null ) {
theInstance = new MySingleton();
}
}
}
}
}
</pre>
<p class="body">
The problem with the DCL idiom in Java is that it just does not work correctly.
Using it introduces bugs that are extremely hard to track down and reproduce.
The <a href="http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html">
&quot;Double-Checked Locking is Broken&quot; Declaration</a> has an in depth explanation
of the exact problem which has to do with the semantics of the Java memory model.
</p>
<h4>Examples</h4>
<p class="body">
To configure the check:
</p>
<pre class="body">
&lt;module name=&quot;DoubleCheckedLocking&quot;/&gt;
</pre>
<h4>Package</h4>
<p class="body">
com.puppycrawl.tools.checkstyle.checks
</p>
<h4>Parent Module</h4>
<p class="body">
<a href="config.html#treewalker">TreeWalker</a>
</p>
</td>
</tr>
</table>

3
docs/releasenotes.html
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@ -76,6 +76,9 @@
[Bloch, Effective Java], Item 17 &quot;Use interfaces only to define
types&quot;).</li>
<li class="body">Added check to detect the double-checked locking
idiom (module DoubleCheckedLocking, request 709333).</li>
<li class="body">Added check to enforce C style (char c[]) or Java
style (char[] c) for array type declaration (module ArrayTypeStyle,
request 493380).</li>

93
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/DoubleCheckedLockingCheck.java Normal file
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@ -0,0 +1,93 @@
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2002 Oliver Burn
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks;
import antlr.collections.AST;
import com.puppycrawl.tools.checkstyle.api.Check;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* Detect the double-checked locking idiom, a technique that tries to avoid
* synchronization overhead but is incorrect because of subtle artifacts of
* the java memory model.
*
* See <a href=
* "http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html"
* >The &quot;Double-Checked Locking is Broken&quot; Declaration</a>
* for a more in depth explanation.
*
* @author Lars K&uuml;hne
*/
public class DoubleCheckedLockingCheck extends Check
{
/** @see Check */
public int[] getDefaultTokens()
{
return new int[]{TokenTypes.LITERAL_IF};
}
/** @see Check */
public void visitToken(DetailAST aAST)
{
DetailAST synchronizedAST =
getLowestParent(aAST, TokenTypes.LITERAL_SYNCHRONIZED);
if (synchronizedAST == null) {
return;
}
DetailAST ifAST =
getLowestParent(synchronizedAST, TokenTypes.LITERAL_IF);
if (ifAST == null) {
return;
}
if (getIfCondition(aAST).equalsTree(getIfCondition(ifAST))) {
log(aAST.getLineNo(), aAST.getColumnNo(),
"doublechecked.locking.avoid");
}
}
/**
* returns the condition of an if statement.
* @param aIfAST the LITERAL_IF AST
* @return the AST that represents the condition of the if statement
*/
private AST getIfCondition(DetailAST aIfAST)
{
return aIfAST.getFirstChild().getNextSibling();
}
/**
* searches towards the root of the AST for a specific AST type.
* @param aAST the starting node for searching (inclusive)
* @param aTokenType the token type to search for
* @return the first token of type aTokenTye or null if no such token exists
*/
private DetailAST getLowestParent(DetailAST aAST, int aTokenType)
{
DetailAST synchronizedParent = aAST;
while (synchronizedParent != null
&& synchronizedParent.getType() != aTokenType)
{
synchronizedParent = synchronizedParent.getParent();
}
return synchronizedParent;
}
}

2
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages.properties
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@ -72,3 +72,5 @@ translation.missingKey=Key ''{0}'' missing.
simplify.expression=Expression can be simplified.
simplify.boolreturn=Conditional logic can be removed.
doublechecked.locking.avoid=The double-checked locking idiom is broken and should be avoided.

2
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages_de.properties
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@ -73,3 +73,5 @@ translation.missingKey=
simplify.expression=Der Ausdruck kann vereinfacht werden.
simplify.boolreturn=Die Verzweigung sollte entfernt werden.
doublechecked.locking.avoid=Das ''double-checked locking'' Idiom sollte vermieden werden.

2
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages_fi.properties
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@ -72,3 +72,5 @@ translation.missingKey=Käännösavain ''{0}'' puuttuu.
simplify.expression=Ilmaisua voisi yksinkertaistaa.
simplify.boolreturn=Konditionaalilogiikan voisi poistaa.
doublechecked.locking.avoid=The double-checked locking idiom is broken and should be avoided.

2
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages_fr.properties
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@ -72,3 +72,5 @@ translation.missingKey=Clef ''{0}'' manquante.
simplify.expression=L'expression peut-être simplifiée.
simplify.boolreturn=Supprimez la logique conditionnelle.
doublechecked.locking.avoid=The double-checked locking idiom is broken and should be avoided.

2
src/checkstyle/com/puppycrawl/tools/checkstyle/checks/messages_pt.properties
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@ -72,3 +72,5 @@ translation.missingKey=Falta a chave ''{0}''.
simplify.expression=Expressão pode ser simplicada.
simplify.boolreturn=A lógica condicional deve ser removida.
doublechecked.locking.avoid=The double-checked locking idiom is broken and should be avoided.

2
src/tests/com/puppycrawl/tools/checkstyle/AllTests.java
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@ -55,6 +55,7 @@ import com.puppycrawl.tools.checkstyle.checks.UpperEllCheckTest;
import com.puppycrawl.tools.checkstyle.checks.VisibilityModifierCheckTest;
import com.puppycrawl.tools.checkstyle.checks.WhitespaceAfterCheckTest;
import com.puppycrawl.tools.checkstyle.checks.WhitespaceAroundTest;
import com.puppycrawl.tools.checkstyle.checks.DoubleCheckedLockingCheckTest;
import junit.framework.Test;
import junit.framework.TestSuite;
@ -78,6 +79,7 @@ public class AllTests {
suite.addTest(new TestSuite(AvoidStarImportTest.class));
suite.addTest(new TestSuite(ConfigurationLoaderTest.class));
suite.addTest(new TestSuite(ConstantNameCheckTest.class));
suite.addTest(new TestSuite(DoubleCheckedLockingCheckTest.class));
suite.addTest(new TestSuite(EmptyBlockCheckTest.class));
suite.addTest(new TestSuite(EmptyForIteratorPadCheckTest.class));
suite.addTest(new TestSuite(EqualsHashCodeCheckTest.class));

22
src/tests/com/puppycrawl/tools/checkstyle/checks/DoubleCheckedLockingCheckTest.java Normal file
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@ -0,0 +1,22 @@
package com.puppycrawl.tools.checkstyle.checks;
import com.puppycrawl.tools.checkstyle.BaseCheckTestCase;
import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
/**
* @author lkuehne
*/
public class DoubleCheckedLockingCheckTest
extends BaseCheckTestCase
{
public void testIt() throws Exception
{
final DefaultConfiguration checkConfig =
createCheckConfig(DoubleCheckedLockingCheck.class);
final String[] expected = {
"34:17: The double-checked locking idiom is broken and should be avoided.",
};
verify(checkConfig, getPath("InputDoubleCheckedLocking.java"), expected);
}
}