The class StdStreams in the package org.deepjava.host defines three output streams.

• log: is used for normal logging (e.g. successful compilation)
• vrb: for debugging purposes
• err: for errors

For development assertions should be extensively used. Make sure that they are enabled in eclipse with -ea as argument for the VM.

Debug output is very convenient during the development process. For efficiency reasons we use the following scheme: Every class has a constant debug of type boolean. If debug == true the compiler inserts write statements to StdStreams.vrb. To enable debug output you have to edit the source code (switch on debug). In the productive code their is no runtime penalty.

The class org.deepjava.host.ErrorReporter is used for reporting errors. Each error increments nofErrors. The launcher checks this variable and stops if necessary.

The ErrorReporter needs the file ErrorMsg.txt in the folder rsc. This text file contains error numbers, descriptions and possible solution. The methods error(int errNr) and error(int errNr, String additonalInfo) access ErrorMsg.txt.

Further, there is a method error(String errMsg). It allows for outputting a message without error number.

The launcher checks if no error occured before starting the next step. However, what happens if there is an error within a step (e.g. while allocating registers) and it's not possible to complete this step? We do not want to check for nofErrors within each step.
Every method should call the error reporter in case of an error and at the same time it should return a useable value (e.g. register 0 or node 0). If necessary special objects should be created for this purpose.
Use assertions whenever possible. They will be switched of in the productive code but can be enabled during the development process.