Re: [PATCH 4/8] gdb/s390: Fill gen_return_address hook.

[Pedro Alves <palves at redhat dot com>]

On 03/11/2016 06:16 PM, Eli Zaretskii wrote:
> > Cc: Eli Zaretskii <eliz@gnu.org>,
> >          Marcin KoÅcielnicki
> >   <koriakin@0x04.net>,
> >          gdb-patches@sourceware.org
> > From: Pedro Alves <palves@redhat.com>
> > Date: Fri, 11 Mar 2016 17:02:19 +0000
> >
> > >    @item $_ret
> > >    Collect the return address.  This is helpful if you want to see more
> > > -of a backtrace.
> > > +of a backtrace.  Note that the return address can not always be
> > > +determined reliably, and a wrong address may be collected instead.
> > > +The reliability is usually higher for tracepoints at function entry.
> >
> > Hmm, this reads a bit as if the backtrace will be incorrect/bogus
> > later on, which is not true.
> >
> > How about a merge of your suggestion with Marcin's previous reply,
> > and some extras on top:
> >
> > @item $_ret
> > Collect the set of memory addresses and/or registers necessary to compute
> > the frame's return address.  This is helpful if you want to see
> > more of a backtrace.
> >
> > @emph{Note:} The necessary set can not always be reliability determined up
> > front, and the wrong address / registers may end up collected instead.
> > The reliability is usually higher for tracepoints at function entry.
> > When this happens, backtracing will stop because the return address
> > is found unavailable (unless another collect rule happened to match it).
>
> Maybe it's me, but I don't see the significant difference between
> these two versions.

I think the original version can be misinterpreted as if the
backtrace will show the wrong caller when the wrong address
is collected.  This version clarifies that it won't.

> (And there's a typo in the second one:
> "reliability" should be "reliably".)

Whoops.

Thanks,
Pedro Alves