Re: jni fixlet

[David Daney <ddaney at avtrex dot com>]

Marco Trudel wrote:
> David Daney wrote:
> > Marco Trudel wrote:
> > > Attached a jni fixlet.
> > >
> > >
> > > 2007-02-01 Marco Trudel <mtrudel@gmx.ch>
> > >
> > > * jni.cc (_Jv_JNI_DeleteWeakGlobalRef): Check for NULL objects.
> > >
> > >
> > > Question? Comments?
> >
> > What was the undesirable behavior you observed that this patch fixes?
>
> A compiled application crashed with "Aborted". A native lib called 
> "_Jv_JNI_DeleteWeakGlobalRef" with a null obj what in the end causes a 
> segmentation fault in unmark_for_gc:
>     jint val = refcount->intValue() - 1; (refcount null)
>
>
> > How did you test it?
>
> I played a little with gdb, saw the segfault, added a check, compiled my 
> app again and was happy that it worked.
> Ah, and I then ran the library I use which does this null call in a Sun 
> JVM to ensure that there _Jv_JNI_DeleteWeakGlobalRef is also called with 
> NULL. It is...

Usually you whould run the libgcj testsuite before and after the change. 
 That would show that the patch does not affect any existing test 
cases.  Optionally you could add a test case for this.

It looks safe, but you can never tell until you run the tests.

David Daney