DSF GDB extract data about stack frames

Question

I develop a plugin to visualization C/C++ programs during debug in Eclipse. I try to use DSF (Debugger Services Framework). I studied a lot of documentation about DSF, but I ran into problem with understanding, how to work with DSF contexts.

For beggining I open project org.eclipse.cdt.examples.dsf.gdb and start to modify it. My goal is on each debug step extract information about all stack frames (activation records), local variables, variables in heap, and global/static variables.

What I've done. I subclass service MIStack and add in its constructor event listener.

package org.eclipse.cdt.examples.dsf.gdb.service;

import org.eclipse.cdt.dsf.mi.service.MIStack;
import org.eclipse.cdt.dsf.service.DsfSession;
import org.eclipse.cdt.example.dsf.gdb.listener.Listener;

public class NewlMIStack extends MIStack {

    public NewMIStack(DsfSession session) {
        super(session);
        getSession().addServiceEventListener(new Listener(), null);
    }
}

By this way I realy can handle each event when user hit button "next step", "step forward", etc. In order to do it I use the following method from my class Listener:

@DsfServiceEventHandler
public void eventDispatched(MISteppingRangeEvent e) {

    MIFrame frame = e.getFrame();
    System.out.println(frame.getFullname()); // Same as getFile()
    System.out.println("Function: " + frame.getFunction());
    System.out.println("File: " + frame.getFile());
    System.out.println("Frame level: " + frame.getLevel()); // Always equals zero
    System.out.println("Line: " + frame.getLine());
    System.out.println("Address: " + frame.getAddress());

    MIArg[] args = frame.getArgs();
    if (args.length > 0) {
        System.out.println("Arguments:");
        for (MIArg arg : args) {
            System.out.println("Name: " + arg.getName());
            System.out.println("Value: " + arg.getValue());
        }
    }
}

The problem is that it is only a little part of information that I need to extract. As I understood, other part of information (such as state of variables, types of variables, etc.) I can extract using service IExpression, and may be GDBMemory. But I don't understand how to use these services. May I some how invoke their methods from my method eventDispatched?

Also I tried to add in my event hanle method the following code:

IExpressionDMContext expressionDMC = DMContexts.getAncestorOfType(e.getDMContext(), IExpressionDMContext.class); 
// getAncestorOfType always returns null

IExpressions expressionService = getServicesTracker().getService(IExpressions.class);
DataRequestMonitor<IExpressionDMData> drm = new DataRequestMonitor<>(getExecutor(), null);
expressionService.getExpressionData(expressionDMC, drm);  

But due to I can't fully understand hot to work with contexts, this code didn't help me to solve my problem.

I really put in a lot of time to solve this problem, sadly without success, so I will very glad to see any comments!

Answer 1

May I some how invoke their methods from my method eventDispatched?

I cannot help much about the details of your implementation, but I can try to help for the following point:

But due to I can't fully understand hot to work with contexts,

I am myself trying to understand how to work with GDB contexts from the CDT DSF session. I need to read data from a different physical memory in each thread, so I need to switch the thread context to switch the memory space. What I found is the following implementation for the MI session of the DSF, and it seems to provide what we both need. MIProcesses.java on github

It is pretty hard to find a good documentation about usage! Please tell me if you have found any.

PS: I am new to SO so I don't exactly know if this is correct as an answer.