edu.umd.cs.findbugs.detect
Class BCPDoubleCheck

java.lang.Object
  edu.umd.cs.findbugs.ByteCodePatternDetector
      edu.umd.cs.findbugs.detect.BCPDoubleCheck

All Implemented Interfaces:

Detector

public class BCPDoubleCheck
extends ByteCodePatternDetector

A bug detector that uses a ByteCodePattern to find instances of the double check idiom. This class serves as a good example of how ByteCodePatterns can be used to simplify the task of implementing Detectors.

Author:

David Hovemeyer

See Also:

ByteCodePattern

Field Summary

private BugReporter	bugReporter
private static int	CREATE_OBJ_WILD Maximum number of "wildcard" instructions to accept for object creation in the doublecheck.
private static int	MAX_WILD Default maximum number of "wildcard" instructions to accept between explicit pattern instructions.
private static ByteCodePattern	pattern The doublecheck pattern.

Fields inherited from interface edu.umd.cs.findbugs.Detector

EXP_PRIORITY, HIGH_PRIORITY, LOW_PRIORITY, NORMAL_PRIORITY

Constructor Summary

BCPDoubleCheck(BugReporter bugReporter)
Constructor.

Method Summary

ByteCodePattern	getPattern() Get the ByteCodePattern for this detector.
boolean	prescreen(org.apache.bcel.classfile.Method method, ClassContext classContext) Prescreen a method.
void	reportMatch(ClassContext classContext, org.apache.bcel.classfile.Method method, ByteCodePatternMatch match) Called to report an instance of the ByteCodePattern.

Methods inherited from class edu.umd.cs.findbugs.ByteCodePatternDetector

getAnalysisContext, report, setAnalysisContext, visitClassContext

Methods inherited from class java.lang.Object

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

Field Detail

bugReporter

private BugReporter bugReporter

MAX_WILD

private static final int MAX_WILD

Default maximum number of "wildcard" instructions to accept between explicit pattern instructions.

See Also:

Constant Field Values

CREATE_OBJ_WILD

private static final int CREATE_OBJ_WILD

Maximum number of "wildcard" instructions to accept for object creation in the doublecheck. This needs to be a lot higher than MAX_WILD.

See Also:

Constant Field Values

pattern

private static final ByteCodePattern pattern

The doublecheck pattern. The variable "h" represents the field. "x" and "y" are local values resulting from loading the field.

Constructor Detail

BCPDoubleCheck

public BCPDoubleCheck(BugReporter bugReporter)

Constructor.

Parameters:

bugReporter -

Method Detail

getPattern

public ByteCodePattern getPattern()

Description copied from class: ByteCodePatternDetector

Get the ByteCodePattern for this detector.

Specified by:

getPattern in class ByteCodePatternDetector

prescreen

public boolean prescreen(org.apache.bcel.classfile.Method method,
                         ClassContext classContext)

Description copied from class: ByteCodePatternDetector

Prescreen a method. It is a valid, but dumb, implementation simply to return true unconditionally. A better implementation is to call ClassContext.getBytecodeSet() to check whether the method actually contains the bytecode instructions that the pattern will look for. The theory is that checking the bytecode set is very fast, while building the MethodGen, CFG, ValueNumberAnalysis, etc. objects required to match ByteCodePatterns is slow, and the bytecode pattern matching algorithm is also not particularly fast.

As a datapoint, prescreening speeds up the BCPDoubleCheck detector by a factor of 5 with no loss of generality and only a dozen or so extra lines of code.

Specified by:

prescreen in class ByteCodePatternDetector

Parameters:

method - the method

classContext - the ClassContext for the method

Returns:

true if the method should be analyzed for instances of the ByteCodePattern

reportMatch

public void reportMatch(ClassContext classContext,
                        org.apache.bcel.classfile.Method method,
                        ByteCodePatternMatch match)

Description copied from class: ByteCodePatternDetector

Called to report an instance of the ByteCodePattern.

Specified by:

reportMatch in class ByteCodePatternDetector

Parameters:

classContext - the ClassContext for the analyzed class

method - the method to instance appears in

match - the ByteCodePatternMatch object representing the match of the ByteCodePattern against actual instructions in the method