Re: [PATCH 02/23] Don't rely on inferior_ptid in record_full_wait

[Tom Tromey <tom@tromey.com>]

Simon> I don't know if this makes sense: you tell the core of GDB that some
Simon> process was signalled (terminated by a signal), but you don't tell
Simon> what process it is.  I am not sure what the core of GDB can do with
Simon> this information.

Simon> The contract that the `wait` implementations must respect is not
Simon> very well documented I believe, so it's not clear which value is
Simon> valid with which event.

Yeah.  I think it would be good to fix this.

The reason I had it return minus_one_ptid is this text in
target/target.h:

     Return pid of child, or -1 in case of error;
   store status through argument pointer STATUS.

remote_target::wait does this as well, though perhaps not with this
target waitkind, e.g.:

	  status->kind = TARGET_WAITKIND_NO_RESUMED;
	  return minus_one_ptid;

or

  if (status->kind == TARGET_WAITKIND_NO_RESUMED)
    return minus_one_ptid;

... though not all returns set the kind.

Simon> Note that this waitpid call is blocking (and there's no async stuff in
Simon> inf-ptrace.c), so I presume that this is only used in sync targets.

Yeah.  I found this because I was wondering what it would take to
convert the remaining sync targets, and have only target-async left.

I suspect the inf-ptrace targets can be converted by just lifting the
Linux code into in inf_ptrace_target.  This comment in nbsd-nat.c is
worrying though:

      /* The common code passes WNOHANG that leads to crashes, overwrite it.  */

Other targets require a little more research.  For Windows, Darwin, and
remote-sim, I thought perhaps we could put some of the current
resume/wait code into a separate thread.  (Though in the case of the
sim, I think it would be better to move the sims to using the remote
protocol.)

Simon> Perhaps we could return TARGET_WAITKIND_NO_RESUMED in both cases?

remote.c does this in at least one case, though apparently not in all.

Tom