Why Eclipse Debugger does not stop on scoped exception breakpoint (how to stop on handled exception)

Question

I am using Eclipse Luna (tested also in Kepler so not version specific). Run on JDK 1.8_40. I would like to find places with "eaten" exceptions - e.g. inproperly handled with try/catch block.

Example code below. When I am setting Exception breakpoint as on picture e.printStackTrace() does not stop with exception.

How to make this work or any workaround / alternative ? It is handy to find out what your code is catching, and not see all the libraries code exception handling.

NOTE: Of course if we remove scope it will improperly stop in BigDecimal. where exception is raised, and also on any other exception during main() execution - in this case some ClassNotFoundException s

Common sense says it is a caught location, scope matches and Exception type also (subtype).

the API description says that it should work correctly (for each throw find a related catch): http://docs.oracle.com/javase/8/docs/jdk/api/jpda/jdi/com/sun/jdi/event/ExceptionEvent.html#catchLocation--

I can see this may be something related to Java Debugging interface itself as per long long time ago since java 1.4 - but not sure how many events are eaten when:

https://bugs.openjdk.java.net/browse/JDK-4515254

package test.me;

import java.math.BigDecimal;

public class EatExceptionBreakpoint {

  public static void main(String[] args) {
    try {
        new BigDecimal("10 "); // how to make Exception Breakpoint to stop ?
    } catch (Exception e) {
        e.printStackTrace();
    }

    new BigDecimal("20 ");
  }
}

Answer 1

After debugging Eclipse I understood that "scope" filters should match throwing location (in this case java.math.BigDecimal) and not the catch location.

This is the original JVM debugger filtering on "scope", however JVM limits filter to one item (class or package), while Eclipse can process multiple items.

The code that does the filtering in Eclipse is in class

org.eclipse.jdt.internal.debug.core.breakpoints.JavaExceptionBreakpoint

The JAR containing this class can be updated - so "uncaught exceptions" will relate scope to throw location, while "caught exceptions" relate scope to catch location [I find this behaviour most useful]

The below change does this - maybe somebody will ever implement in Eclipse:

public boolean handleBreakpointEvent(Event event, JDIThread thread, boolean suspendVote)
    ...
    Location location = ((ExceptionEvent)event).catchLocation();
    if (location == null) {
           location = ((ExceptionEvent)event).location();
    }