Re: GDB single-step fails on alpha (Re: CVS commit: src/share/mk)

[Rin Okuyama <rokuyama%rk.phys.keio.ac.jp@localhost>]

On 2016/12/06 22:29, Kamil Rytarowski wrote:
> I consider PT_STEP feature as desired with the goal to be independent
> from the GNU toolchain and without need to reimplement basic features in
> per-platform basis in a custom debugger.

I agree. I feel that it is not so difficult to implement PT_STEP for
alpha based on software single stepping. We already have it for mips
(not currently enabled), and I wrote it for powerpc/ibm4xx (cf.
port-evbppc/24096).

However, before proceeding further, we need to discuss undocumented
details related to PT_STEP; What should we do when a process steps into
a RAS? How about the case where PT_STEP is used against a process which
is already in single stepping? And so on...

> I was trying to find users of FIX_SSTEP() in the NetBSD CVS history (git
> log -p|grep) and I couldn't find any users till BSD4.4-lite2 -- it's a
> dead macro since then, older code is partially removed and I couldn't
> find users back in 1994 year. The alpha port could be the first user!

For mips and powerpc/ibm4xx, we do not need it; the trap handler takes
care of them. But there might be some reasons to do so. We should
carefully examine if we decide to implement it.

Thanks,
Rin