Re: gnu.gcj.runtime.StackTrace.findCallerClass()

[Andrew Haley <aph at redhat dot com>]

Mohan Embar writes:
 > Hi Andrew,
 > 
 > > > - know that you have to deal with both cases, and now be required to
 > > > introduce #ifdef HAVE_BACKTRACE in the caller's code too because there's
 > > > no other way to effectively deal with this.
 > > > 
 > > > Even in the current case, the caller is always catching the
 > > > ArrayIndexOutOfBoundsException and never letting it trickle up
 > > > to a higher level.
 > >
 > >But that's wrong -- the caller shouldn't do that.  The only reasonable
 > >thing to do if a caller isn't found in the stack is stop the entire
 > >JVM with a RuntimeError.  Something has gone badly wrong.
 > 
 > Okay. But what is the caller supposed to do if HAVE_BACKTRACE
 > is not set?

If HAVE_BACKTRACE is not set, we don't search but return null.

 > If we terminate the JVM if HAVE_BACKTRACE is set,
 > can't we call exit() instead of returning null if HAVE_BACKTRACE
 > is not set?

An example is worth a thousand words:

  caller = findCallerClass(1);
  caller_loader = caller ? caller->getClassLoaderInternal() : NULL;
  if (caller_loader != NULL && ! caller_loader->isAncestorOf(loader))
    s->checkPermission (new RuntimePermission (JvNewStringLatin1 ("getClassLoader")));

When we get round to implementing proper Java security we'll have to
close this loophole.  But not yet.

Andrew.