Subj : Re: Problems debugging shared object code called from Java JNI
To   : comp.os.linux.development,comp.os.linux
From : Wiseguy
Date : Thu Dec 02 2004 12:50 am

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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