Re: [RFA] use frame IDs to detect function calls while stepping

[Joel Brobecker <brobecker@gnat.com>]

> >>> > +      if (IN_SOLIB_CALL_TRAMPOLINE (stop_pc, ecs->stop_func_name))
> >>> > +        {
> >>> > +          /* We landed in a shared library call trampoline, so it
> >>> > +             is a subroutine call.  */
> >>> > +          handle_step_into_function (ecs);
> >>> > +          return;
> >>> > +        }
> >>>
> >>>
> >>>I am not sure I understand why the case above is not covered by the
> >>>test below.  Is this to fix regression #1? I.e multiple frames? 
> >
> >
> >Hmmm, good question...
> >
> >Although it does fix regression #2, it is not the only reason why we
> >added this test. It was also based on logic (see "After ... here is
> >what we found", in my previous message).
> >
> >I should admit that in the case at hand (regression #2), the unwinder
> >is having a hard time unwinding out of this code, and causes the
> >frame ID check to fail. I don't remember seeing several levels of
> >function call.
> >
> >However, I still thought that this test was necessary because we could
> >just as well have reached this trampoline one or more levels of function
> >call down, just as we end up stepping into undebuggable code in
> >regression #1.
> 
> I'd not noticed this issue.  Hmm, if GDB's single stepping then the 
> second test should cover this case.  It's when GDB is free running that 
> we might find ourselves stopped IN_SOLIB_CALL_TRAMPOLINE.  If it is the 
> latter case then I'm not sure that silently single stepping away from 
> where the program stopped is being helpful.
> 
> Can you try the testsuite without that check?  If the results are ok 
> then (with other changes) commit it.  If its not we need to re-think 
> whats happening :-(  Yes, this will mean it goes into 6.1.

Yes, there is a regression (regression #2 in my previous message) if
we leave that test out. It's been a while since I posted that patch,
so I don't remember the details anymore :-/. I'll dig again later today.

I did rerun the testsuite without it to double-check that my
recollection was right. And I also ran the testsuite with the frame_id
patch you recently posted, hoping that it might solve the extra
regression. Unfortunately, I am sorry to report that it actually
introduced another 5 or 6 regressions...

On the other hand, as soon as I add the check back, we're down to
zero regression (that is, with your frame_id patch as well).

More details later today about the failing test when the test above
is removed.

-- 
Joel