Debug linked Java method

Question

I have some issues with debugging Java code. I have a Rascal module from where I am calling a linked Java method. This Java method contains a couple of System.err.println statements like suggested here: https://github.com/usethesource/rascal/wiki/Error-Reporting. But where are they shown? When I execute the Rascal code from the Rascal debug console and call the linked Java method the messages are not shown. I even flush System.err directly after printing, but no luck. What am I doing wrong here?

Regards, Nico

score 2 · Accepted Answer · answered Apr 05 '16 at 14:37

System.err is hard because Eclipse will hide it if you did not start Eclipse from a commandline console. So you should use evaluator.getStdErr() as suggested on https://github.com/usethesource/rascal/wiki/Error-Reporting.

First extend your Rascal function header to give access to the evaluator context:

@reflect{need access to stderr}
@javaClass{path.to.MyClass}
java int myFunction(int myParam);

Then change your interface in Java accordingly and retrieve a reference to the error stream:

public class MyClass {
   public IValue myFunction(IInteger myParam, IEvaluatorContext ctx) {
      ctx.getStdErr().println("Hello Rascal!");
   }
}

Debug linked Java method

1 Answers1