Re: Reminder: Illegal Package-Private Accesses in libgcj

[Bryce McKinlay <bryce at mckinlay dot net dot nz>]

On Nov 4, 2003, at 11:01 AM, Andrew Haley wrote:

> Bryce McKinlay writes:
> > On Nov 4, 2003, at 12:25 AM, Andrew Haley wrote:
> >
> > > Bryce McKinlay writes:
> > > > If there are targets that will never support the unwinder (are
> > > > there?), then it might make sense to allow platforms to define some
> > > > platform-specific unwinding functions, but ideally, by far the
> > > > cleanest and most efficient solution is to get the libgcc DWARF2
> > > > unwinder working.
> > >
> > > Efficient?  I don't think so.  The glibc backtrace() function simply
> > > walks a linked list, and there's no more efficient way to do it than
> > > that.  The DWARF unwinder is a couple of orders of magnitude slower.
> >
> > OK, but how do you get the java.lang.Class object from the IP value
> > which backtrace() gives you?
>
> We look it up in a hash table.  We sure don't call external programs!

But you can't map a backtrace IP directly to a Class in the hashtable, 
you have to find the function entry point first. I don't know of a way 
to do that apart from using _Unwind_FindEnclosingFunction.

Regards

Bryce.