Re: C++ demangling of 64-bit symbols on ppc64

[Maynard Johnson <maynardj at us dot ibm dot com>]

Ian Lance Taylor wrote:

> Maynard Johnson <maynardj@us.ibm.com> writes:
>
>  
>
> > As the de facto maintainer of the ppc64 bits of oprofile, I was
> > recently asked to look into an oprofile bug where it was incorrectly
> > demangling 64-bit symbols.  The oprofile code uses the libiberty
> > function, cplus_demangle(), but is not getting back the right answer
> > for ppc64 64-bit symbols.  This appears to be more fallout from the
> > change (made a couple years ago or so) to the opd for ppc64, where the
> > leading "." was removed from 64-bit symbols.
> >
> > I hacked around the problem in my private oprofile src tree, but I'm
> > thinking this issue should be solved at its source.  I'm seeing this
> > problem on a SLES 10 system with binutils version 2.16.91.  Has this
> > possibly been resolved in a more recent binutils version or in CVS?
> >    
>
> Can you give an example of a symbol which the demangler is not
> handling correctly?
>  
Below is the testcase provided to me by the person who reported it:

==========

void doit(char *str)
{
       while (1)
               ;
}

char *blah;
int main()
{
       doit(blah);
}

When built as 32bit:

# g++ -O2 test.c -o test

opreport -l gives:

42345    89.6627  test                     doit(char*)

However when built as 64bit:

# g++ -m64 -O2 test.c -o test

opreport -l gives:

6513     93.7392  test                     ._Z4doitPc

=================

Regards,
-Maynard

> Ian
>