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Re: c++ debugging hosed

On Mon, 26 Nov 2001, Daniel Jacobowitz wrote:

> On Sun, Nov 25, 2001 at 03:29:08PM -0500, Daniel Berlin wrote:
> >
> >
> > On Sun, 25 Nov 2001, Benjamin Kosnik wrote:
> >
> > >
> > > > No, it's relevant to STABS, too.
> > > > It's due to not properly searching virtual baseclasses.
> > > > I might still have the changes to do that somewhere, if someone wants
> > > > them.
> > >
> > > This has been broken for some time now. I'd appreciate it if it got
> > > fixed, so that C++ could be debugged properly.
> > I'm sure a lot of people would.
> > Unfortunately, it appears I don't have the code i had worked up to
> > abstract out the base class offset finding anymore.
> > What's happening is that GDB wants to know the baseclass offset, and
> > the routine it uses is tuned to either gnu-v2 or hp aCC (it checks
> > for something only hp's debug readers fill in, and if it doesn't find
> > it, it assumes gnu-v2), and the gnu-v2 code either returns the wrong
> > value (weird errors occur), or -1, which gives you "virtual baseclass
> > botch"/attempts to deref int values as pointers.
> >
> > baseclass_offset needs to be abstracted into the cp abi model, and all
> > existing uses need to use it.
> Could you clarify what symptom this fix you're discussing is supposed
> to solve?
Not being able to print subobjects, etc.
>   I thought it was the one I was working on, but
> baseclass_offset actually does nothing ABI specific at all.
This would be incorrect for virtual base classes
Look at it again.
Also notice we call find_rt_base_offset for the HP ABI.
The reason is that baseclass offsets are *always* abi specific.

> Meanwhile the problem that was most annoying me wasn't even covered by
> the testsuite.  Patch and tests coming up in the next hour.
> --
> Daniel Jacobowitz                           Carnegie Mellon University
> MontaVista Software                         Debian GNU/Linux Developer

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