UnsatisfiedLinkError and stracktraces

[Christian Thalinger]

On Fri, 2007-10-05 at 13:30 -0700, Tom Rodriguez wrote:
> > 1. Is there somewhere a specification of what methods need to be in the
> > stacktrace?  Would it also be OK to print something like this:
> > 
> > java.lang.UnsatisfiedLinkError: nsub
> >         at java.lang.Throwable.fillInStackTrace(Native Method)
> >         at java.lang.Throwable.<init>(Throwable.java:214)
> >         at java.lang.Error.<init>(Error.java:67)
> >         at java.lang.LinkageError.<init>(LinkageError.java:54)
> >         at java.lang.UnsatisfiedLinkError.<init>(UnsatisfiedLinkError.java:53)
> >         at extest.nsub(Native Method)
> >         at extest.main(extest.java:336)
> 
> I don't think there's a specification of what should be in a stack trace other 
> than the vague language that they are precise.  The standard logic we use for 
> recording stack traces skips the exception constructor frames since they're 
> really just noise.  I think some printing functions for chained exceptions will 
> only dump a few frames of the stack trace and wasting five of them may make 
> those printouts less useful.  With the Throwable.getStackTrace API it's possible 
> to programmatically inspect trace information which could conceivably expose 
> differences between implementations but that seems like stretch.

Yes, I agree they are just noise.  I only showed this example to make my
point clear.

> 
> > 2. What is the reason the failing native method is in the stacktrace?
> > Actually it isn't called.  I guess it's something about the way native
> > methods are called in HotSpot (e.g. native stubs).  Would this be OK
> > too:
> > 
> > java.lang.UnsatisfiedLinkError: extest.nsub()V
> >         at extest.main(extest.java:336)
> 
> I believe that at the point we throw it we've already pushed a frame for the 
> native method so we could start invoking it and then we discover that we can't 
> link it which is why it shows up in the call stack.  I can't think of any reason 
> why one would be preferred over the other.

So we could simply leave the native one out.

- twisti