[RFA] fix crasher on detach command

[Michael Snyder]

Pedro Alves wrote:
> On Monday 07 June 2010 19:31:26, Michael Snyder wrote:
>> Pedro Alves wrote:
>>> On Monday 07 June 2010 19:11:02, Michael Snyder wrote:
>>>> Hi,
>>>>
>>>> The circumstances are, detach from a remote target that doesn't have
>>>> threads.  Remote.c leaves the PID arbitrarily as "42000", and
>>>> target_detach calls remove_breakpoints_pid, which crashes because
>>>> find_inferior_pid returns NULL.
>>> It shouldn't matter that the PID is arbitrary; there should be an
>>> inferior with that PID in the inferior list.  This probably means
>>> that the inferior got its PID cleared to 0 already when you get here?
>>> How?
>> It was a bad connect, which aborted part way through.
>> So yes, we're in an inconsistent internal state.
> 
> Then we need to fix that, instead of adding workarounds in other
> areas.

I'm not sure how feasible that is.  At this point I've had to use a
^C^C to get out of a failing attach (target remote), and I'm hoping to
use the "detach" to cancel out any remaining inconsistent state.
The ^C^C handler can't necessarily do it by itself, 'cause from its
point of view, you don't really know what state you're in or what
state you want to be in.