[Crash-utility] [PATCH] Fix compile warnings

[Dave Anderson]

Bernhard Walle wrote:

> Hi,
>
> * Dave Anderson <anderson at redhat.com> [2007-01-17 21:10]:
> > Bernhard Walle wrote:
> > > >
> > > > This patch makes me a litte nervous.  I see that gdb 6.5 does this:
> > > >
> > > >           else if (*augmentation == 'P')
> > > >             {
> > > >               /* Skip.  Avoid indirection since we throw away the result.  */
> > > >               gdb_byte encoding = (*buf++) & ~DW_EH_PE_indirect;
> > > >               read_encoded_value (unit, encoding, buf, &bytes_read);
> > > >               buf += bytes_read;
> > > >               augmentation++;
> > > >             }
> > > >
> > > > Are they equivalent?
> > >
> > > Of course not. :) After thinking a bit I think the correct fix would
> > > be:
> > >
> > >         buf += size_of_encoded_value(*buf);
> > >         buf++;
> > >
> > > Do you aggree?
> >
> > I can't say with any confidence.  I was trying to correlate the difference
> > between the way it's done in gdb-6.5 vs 6.1, and got lost doing so...
>
> Yes, but 6.5 basically does:
>
>     gdb_byte tmp = *buf++;
>     buf += size_of_encoded_value(tmp);
>
> which should be equivalent to
>
>     buf += size_of_encoded_value(*buf);
>     buf++;
>
> Of course, read_encoded_value() does more than just calling
> size_of_encoded_value(), but anyway.
>
> > Just curious -- how do you manage to get crash to run through that
> > code path?  (I put an exit() there, but can't seem to get there...)
>
> I didn't. I just wrote a small C program which has the same problem.
> (Increasing that pointer in the same operation.)
>
> Probably that code path will be never hit at all. ;)
>

Ok then, I trust your "equivalency" explanation, and since in all
probability the code path won't be hit, it should be safe.
In fact, I don't believe that any of the other patches that you
sent will ever be exercised by crash either?  But, if they make
your compiler happy, that's fine with me...

>
> BTW: Is it planned to upgrade crash to use GDB 6.6 or some higher
> version?
>

Only when and if it becomes absolutely necessary.  Every time I've
done an upgrade, it's been a nightmare.  The hooks that are there to
make back-door entries into the gdb code for the crash utility's purposes
never seem to port cleanly.  And after the upgrades, there have always
been new issues that have cropped up  -- in fact there was a time where
I had to revert back to gdb-6.0 from gdb-6.1.

And given that the gdb module is only utilized as "gdb vmlinux", as
long as gdb-6.1 is capable of returning structure sizes, member offsets,
code disassembly, etc., then there's no compelling need to upgrade it.
And if there are, the first line of defense would be to patch the current
version than make a wholesale upgrade.

Thanks,
  Dave