= The AspectJ^TM^ Problem Diagnosis Guide

:doctype: book

_by the AspectJ Team_

_Copyright (c) 2006 IBM Corporation and others. 2006 Contributors. All rights reserved._

This guide describes how to configure the AspectJ compiler/weaver to provide
information for diagnosing problems in the input programs, the
compiler/weaver or its configuration.

The AspectJ compiler and weaver can provide lots of information for diagnosing
problems in building AspectJ programs. For problems in the input program,
there are a number of default warning and error messages, as well as many
configurable "lint" messages, all of which can be emitted normally,
logged using standard facilities, or intercepted programmatically.
These are discussed in xref:messages.adoc#messages[Messages]. Since most errors
relate to writing pointcuts incorrectly, there is a section on
xref:pointcuts.adoc#pointcuts[Debugging Pointcuts].

For problems with the compiler/weaver itself there are three facilities
that enable the AspectJ developers to resolve bugs even when it is
too hard to deliver a reproducible test case:

* xref:trace.adoc#trace[Tracing] can be enabled to track progress up to the time of a failure;
* xref:ajcore.adoc#ajcore[AspectJ Core Files] can give a relatively complete picture of the state of
  the world at the time of a failure; and
* xref:ltwdump.adoc#ltwdump[Dumping classes during load-time weaving] is a way to capture both input and output classes during load-time weaving.

This guide describes how to configure messages to get the right information
and how to configure traces, dumps, and core files. Although the compiler/weaver
operates in roughly three modes (from the command-line, embedded in an IDE,
and enabled as load-time weaving), the principles are basically the same for
all modes. The differences lie in how to set up diagnostics and what
information is likely to be relevant.

**Table of Contents**

* xref:messages.adoc[Messages]
* xref:pointcuts.adoc[Debugging Pointcuts]
* xref:trace.adoc[Tracing]
* xref:ajcore.adoc[AspectJ Core Files]
* xref:ltwdump.adoc[Dumping classes during load-time weaving]