Re: crasher in C++ ABI code

[Michael Snyder <msnyder@redhat.com>]

Daniel Jacobowitz wrote:
> 
> On Thu, Sep 12, 2002 at 05:23:16PM -0700, Michael Snyder wrote:
> > Attention, all you c++_abi_savvy folk...
> >
> > I found a crasher bug while running the gdb testsuite on a COFF
> > toolchain.  TYPE_VPTR_FIELDNO returned -1; I haven't looked into
> > this mechanism, but I assume that's a mistake.  When it was applied
> > via value_field, of course it yielded a garbage value.
> >
> > So looking at coffread.c, I see that there are no references
> > to vptr_fieldno nor vptr_basetype -- these fields are never
> > initialized.
> 
> They're initialized in alloc_type to -1... and further by stabs and
> dwarf2.
> 
> > I'm just wondering where to go from here.  Is it possible to
> > obtain these values from COFF?  If not, perhaps their access
> > methods should check for an invalid value?
> 
> COFF is not the issue.  coffread is just like elfread; it's an object
> file reader.  The question is where your debug information comes from.
> Mdebug?  Stabs?  DWARF-2?  If it's real mdebug instead of
> stabs-in-mdebug, you're squat out of luck for C++.
> 
> Also, TYPE_VPTR_FIELDNO is often -1 by design; see
> fill_in_vptr_fieldno and the comment above it.
> 
>  -  Is fill_in_vptr_fieldno getting called?
>  -  If it were called would it succeed?
>  -  Probably its return value needs to be checked somewhere.

Yes, I've found it, I'm about to submit a patch.