Description David Biesack 2006-12-20 14:39:46 EST

Build ID: M20060921-0945

Steps To Reproduce:

1. Create a PDE project
2. Set an exception breakpoint on ArrayIndexOutOfBoundsException
3. Launch the plugin it in Debug mode
4. In the debug session workspace, open a Java project and open a Java source file
5. Modify/save the source, causing the JDT compiler to run.

The compiler halts in org.eclipse.jdt.internal.compiler.parser.Scanner. 

This same breakpoint is hit many times. The exception occurs over 24 times per keystroke or file save. It appears to occur less often in 3.3M4.


More information:
This makes it difficult to track down ArrayIndexOutOfBoundsException when developing a plugin,
because the scanner throws it so often. (I cannot filter on the exception being thrown in org.eclipse.jdt.internal.compiler.parser.Scanner because that package/class is not available when I try to add an exclusion filter to the exception breakpoint.)

Scanner.java does:

			do {
				unicodePtr = this.withoutUnicodePtr;
				offset = this.currentPosition;
				this.startPosition = this.currentPosition;
				try {
					checkIfUnicode = ((this.currentCharacter = this.source[this.currentPosition++]) == '\\')
						&& (this.source[this.currentPosition] == 'u');
				} catch(IndexOutOfBoundsException e) {
					if (this.tokenizeWhiteSpace && (whiteStart != this.currentPosition - 1)) {
						// reposition scanner in case we are interested by spaces as tokens
						this.currentPosition--;
						this.startPosition = whiteStart;
						return TokenNameWHITESPACE;
					}
					if (this.currentPosition > this.eofPosition)
						return TokenNameEOF;
				}
				if (this.currentPosition > this.eofPosition)
					return TokenNameEOF;


Before testing for a "\u" sequence or incrementing this.currentPosition, it should test bounds with:

  if (this.currentPosition > this.eofPosition)
    return TokenNameEOF;

After seeing a '\\', it should set currentCharacter but
also test that (currentPosition+1) < eofPosition again before autoincrementing currentPosition, to avoid the exception.

Here is a traceback

Thread [org.eclipse.jdt.internal.ui.text.JavaReconciler] (Suspended (exception ArrayIndexOutOfBoundsException))	
	CommentRecorderScanner(Scanner).getNextToken() line: 857	
	SourceElementParser(Parser).parse() line: 8801	
	SourceElementParser(Parser).parse(ICompilationUnit, CompilationResult, int, int) line: 9062	
	SourceElementParser(Parser).parse(ICompilationUnit, CompilationResult) line: 9019	
	SourceElementParser.parseCompilationUnit(ICompilationUnit, boolean) line: 1518	
	CompilationUnit.buildStructure(OpenableElementInfo, IProgressMonitor, Map, IResource) line: 134	
	CompilationUnit(Openable).generateInfos(Object, HashMap, IProgressMonitor) line: 229	
	CompilationUnit(JavaElement).openWhenClosed(Object, IProgressMonitor) line: 505	
	CompilationUnit.makeConsistent(int, boolean, boolean, HashMap, IProgressMonitor) line: 992	
	ReconcileWorkingCopyOperation.makeConsistent(CompilationUnit, IProblemRequestor) line: 132	
	ReconcileWorkingCopyOperation.executeOperation() line: 72	
	ReconcileWorkingCopyOperation(JavaModelOperation).run(IProgressMonitor) line: 720	
	ReconcileWorkingCopyOperation(JavaModelOperation).runOperation(IProgressMonitor) line: 779	
	CompilationUnit.reconcile(int, boolean, boolean, WorkingCopyOwner, IProgressMonitor) line: 1122	
	JavaReconcilingStrategy$1.run() line: 97	
	SafeRunner.run(ISafeRunnable) line: 37	
	JavaReconcilingStrategy.reconcile(boolean) line: 82	
	JavaReconcilingStrategy.reconcile(IRegion) line: 145	
	JavaCompositeReconcilingStrategy(CompositeReconcilingStrategy).reconcile(IRegion) line: 86	
	JavaCompositeReconcilingStrategy.reconcile(IRegion) line: 94	
	JavaReconciler(MonoReconciler).process(DirtyRegion) line: 75	
	JavaReconciler.process(DirtyRegion) line: 342	
	AbstractReconciler$BackgroundThread.run() line: 204