Re: Cannot execute this command without a live selected thread.

[Pedro Alves <palves@redhat.com>]

On 10/24/2014 09:38 PM, Doug Evans wrote:
> Pedro Alves writes:
>  > > Not all targets use ptid.lwp.
>  > 
>  > All process_stratum targets do.
> 
> windows-nat.c doesn't
> (at least I remember seeing all calls to ptid_build there
> passing 0 for lwp).
> Could be missing something of course.

Eh, I was quite sure I once wrote a patch for that, and
I thought I had pushed it, but I can't find it now.

Ah, back in 2008 I went through all targets migrating
away from storing the thread in ptid_t.pid.

commit 2dc38344f418c9abe65755308ef6db836a61103a
Author:     Pedro Alves <palves@redhat.com>

        Use ptid_t.tid to store thread ids instead of ptid_t.pid.

        * win32-nat.c (win32_add_thread): Change thread argument type to

etc.  That made way for the multi-process support in the core
being able to rely on ptid_t.pid.

It was much later (years) that I realized that ptid.lwpid would
be a better field.

Anyway, should be a trivial change.  Nothing outside the target
should be looking at ptid.lwpid vs ptid.tid.  I fixed gnu-nat.c
and remote.c recently, but I now see that nto-procfs.c, remote-sim.c
and darwin-nat.c still haven't been given the treatment.
I got confused with wishful thinking.  :-P

> 
>  >     I believe that on the GDB side too, it's best that we standardize on
>  >     process_stratum targets using the ptid.lwp field to store thread ids
>  >     anyway.  The idea being leave the ptid.tid field free for any
>  >     thread_stratum target that might want to sit on top.
> 
> The language in the comment in ptid.h waffles a bit:
> 
>    process_stratum targets that handle threading themselves should
>    prefer using the ptid.lwp field, leaving the ptid.tid field for any
>    thread_stratum target that might want to sit on top.
> 
> Can we make this more of a rule than just a "should prefer"?
> [and fix targets to follow]

Sure, guess I didn't use a stronger word at the time because
I hadn't yet forgotten that the all-targets conversion wasn't
finished.  :-)

Thanks,
Pedro Alves