[RFA] enable software single step on alpha-osf

[Andrew Cagney]

> Following Andrew's suggestion, here is a revised patch to provide
> software single stepping on alpha-osf1, plus fix all the quirks that
> appeared after the switch.
> 
> I know the alpha-osf1-tdep.c change is approved, but since I haven't
> committed it yet, I am including it in this patch for completeness.
> 
> No regression on alpha-osf1 (SW single step enabled) and on x86-linux
> (sw single step disabled):

Yep, testing x68 linux is a good idea.

> 2002-07-18  Joel Brobecker  <brobecker@gnat.com>
> 
>         * alpha-osf1-tdep.c (alpha_osf1_init_abi): Unfortunately,
>         procfs appears to be broken when debugging on multi-processor
>         machines. So enable software single stepping in order to avoid
>         using the procfs interface to do next/step operations, using
>         internal breakpoints instead.
> 
>         * infrun.c (handle_inferior_event): Readjust the stop_pc by
>         DECR_PC_AFTER_BREAK when hitting a single step breakpoint, to
>         make this pc address equal to the value it would have if the
>         system stepping capability was used. Also set a new flag used
>         to ensure that we don't readjust the PC one more time later.
> 
>         * breakpoint.c (bpstat_stop_status): Do not adjust the PC
>         address by DECR_PC_AFTER_BREAK when software single step is
>         in use for this architecture, as this has already been taken
>         care of in handle_inferior_event().
> 

Yes and thanks.  Finally something in wfi that I understand!

Andrew