RE: [PATCH v3 2/3] stack: check frame_unwind_caller_id

Metzger, Markus T
2016-07-22T07:53:29Z

> -----Original Message-----
> From: Yao Qi [mailto:qiyaoltc@gmail.com]
> Sent: Thursday, July 21, 2016 6:36 PM
> To: Metzger, Markus T <markus.t.metzger@intel.com>
> Cc: Pedro Alves <palves@redhat.com>; gdb-patches@sourceware.org
> Subject: Re: [PATCH v3 2/3] stack: check frame_unwind_caller_id

Hi Yao,

> On Thu, Feb 11, 2016 at 4:14 PM, Markus Metzger
> <markus.t.metzger@intel.com> wrote:
> > diff --git a/gdb/stack.c b/gdb/stack.c
> > index 89879f3..6e3acc7 100644
> > --- a/gdb/stack.c
> > +++ b/gdb/stack.c
> > @@ -1509,27 +1509,32 @@ frame_info (char *addr_exp, int from_tty)
> > wrap_here (" ");
> > printf_filtered ("saved %s = ", pc_regname);
> >
> > - TRY
> > - {
> > - caller_pc = frame_unwind_caller_pc (fi);
> > - caller_pc_p = 1;
> > - }
> > - CATCH (ex, RETURN_MASK_ERROR)
> > + if (!frame_id_p (frame_unwind_caller_id (fi)))
> > + val_print_unavailable (gdb_stdout);
> > + else
>
> This patch causes a fail
>
> FAIL: gdb.dwarf2/dw2-undefined-ret-addr.exp: info frame
>
> because part of the output "info frame" is changed from "saved rip =
> <not saved>"
> to "saved rip = <unavailable>". The regression is caught by buildbot too
> https://sourceware.org/ml/gdb-testers/2016-q1/msg05292.html
> Could you take a look?
>
> Note that Jan posted a patch
> https://sourceware.org/ml/gdb-patches/2016-04/msg00181.html
> fixing test case, but I think the test case itself is valid. Also in the commit
> log of adding gdb.dwarf2/dw2-undefined-ret-addr.exp, it is intended to match
> "<not saved>" in the test.

I found a comment in value.c:333 that suggests GDB uses optimized-out for
registers that are not stored in the frame. Since the patch is handling the case
of an invalid frame-id I guess I should have used val_print_not_saved instead
of val_print_unavailable.

Let me revert Jan's fix and see if changing it to val_print_not_saved causes other
regressions.

regards,
Markus.
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