Re: Problems debugging shared object code called from Java JNI

From: Wiseguy (noone_at_all.com)
Date: 12/02/04

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    Date: 2 Dec 2004 00:50:48 -0600

    Exits Funnel <exitsfunnel@noyahoospam.com> mumbled in news:khurd.464
    $wk4.54@fe12.lga:

    > Hello,
    >
    > I'm currently working a project which comprises a Java API layer and a
    > native C++ piece (which I'll call the driver). Only the java API is
    > exposed to our clients. Internally, the java makes calls to the C++
    > through JNI. We port the native stuff to several platforms including
    > RedHat linux on which we generate from it a shared object. I'm trying
    > to figure out how to use gdb to debug the driver but having no luck.
    I
    > want to be able to set a breakpoint in one of the native source files
    > and then launch the java process on some java test code which results
    in
    > calls into the shared object - thereby letting me do source level
    > debugging in the shared object. Just to be clear, I'm not trying to
    > debug the java code, just the shared object. I can do this in the
    > developer studio on Windows so I'd be surprised if I couldn't do it
    with
    > gdb but I can't figure it out.
    >
    > I've tried this:
    >
    > gdb --args java MyTest
    >
    > run
    >
    > but gdb complains about 'no debugging symbols found' and also that it
    > 'Cannot find user-level thread for LWP 4494: generic error.'
    >
    > Does anyone have any suggestions. Thanks in advance for any help.
    >
    > -exits
    >

    I'm kind of shooting in the dark here because I've never done it myself,
    but IIRC you can attach gdb to a running process. Maybe put some kind
    of an explicit wait at the point where JNI takes over and then run gdb
    as a separate task. Use gdb to attach to the process of the running
    thread that will go JNI after the wait passes.

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