Re: [pushed 07/28] Windows gdb: Simplify windows_nat_target::wait

[Hannes Domani <ssbssa@yahoo.de>]

 I initially missed these commits, because I was once again unsubscribed
from gdb-patches (because of bounces) when these emails where sent.
I only noticed in the GNU weekly news mention of many Windows
improvements which I didn't remember, so I checked again.


On 4/24/26 22:44, Pedro Alves wrote:
> The logic in windows_nat_target::wait, where we decide what to do
> depending on the result from get_windows_debug_event is harder to
> grasp than it looks.
>
> It is not easy to tell what should happen when in async mode
> get_windows_debug_event returns that there's no event to process.
>
> And then, if get_windows_debug_event returns null_ptid /
> TARGET_WAITKIND_SPURIOUS, then we need to issue a ContinueDebugEvent.
>
> There's also this comment in windows_nat_target::wait, which we're not
> really implementing today:
>
> ~~~~
>   /* We loop when we get a non-standard exception rather than return
>      with a SPURIOUS because resume can try and step or modify things,
>      which needs a current_thread->h.  But some of these exceptions mark
>      the birth or death of threads, which mean that the current thread
>      isn't necessarily what you think it is.  */
> ~~~~
>
> This patch changes things a bit so that the code is more obvious:
>
>  - look at the status kind, instead of ptid_t.
>
>  - add an explicit early return case for no-event.
>
>  - add an explicit case for TARGET_WAITKIND_SPURIOUS.
>
>  - with those, we no longer need to handle the case of find_thread not
>    finding a thread, so we can drop one indentation level.
>
> Approved-By: Tom Tromey <tom@tromey.com>
> Change-Id: I76c41762e1f893a7ff23465856ccf6a44af1f0e7
> commit-id:aff7fc4a
> ---
>  gdb/windows-nat.c | 39 +++++++++++++++++++++++++--------------
>  1 file changed, 25 insertions(+), 14 deletions(-)
>
> diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
> index 2dd372ae7b2..30b07221b62 100644
> --- a/gdb/windows-nat.c
> +++ b/gdb/windows-nat.c
> @@ -1139,7 +1139,10 @@ windows_nat_target::get_windows_debug_event
>      }
>  
>    if (thread_id == 0)
> -    return null_ptid;
> +    {
> +      ourstatus->set_ignore ();
> +      return null_ptid;
> +    }
>    return ptid_t (windows_process->current_event.dwProcessId, thread_id, 0);
>  }
>  
> @@ -1160,25 +1163,33 @@ windows_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
>      {
>        ptid_t result = get_windows_debug_event (pid, ourstatus, options);
>  
> -      if (result != null_ptid)
> +      if ((options & TARGET_WNOHANG) != 0
> +      && ourstatus->kind () == TARGET_WAITKIND_IGNORE)
> +    return result;
> +
> +      if (ourstatus->kind () == TARGET_WAITKIND_SPURIOUS)
> +    {
> +      CHECK (windows_continue (DBG_CONTINUE,
> +                   windows_process->desired_stop_thread_id, 0));
> +    }
> +      else if (ourstatus->kind () != TARGET_WAITKIND_IGNORE)
>      {
>        if (ourstatus->kind () != TARGET_WAITKIND_EXITED
> -          && ourstatus->kind () !=  TARGET_WAITKIND_SIGNALLED)
> +          && ourstatus->kind () != TARGET_WAITKIND_SIGNALLED)
>          {
>            windows_thread_info *th = windows_process->find_thread (result);
>  
> -          if (th != nullptr)
> +          th->stopped_at_software_breakpoint = false;
> +          if (windows_process->current_event.dwDebugEventCode
> +          == EXCEPTION_DEBUG_EVENT
> +          && ((windows_process->current_event.u.Exception.ExceptionRecord.ExceptionCode
> +               == EXCEPTION_BREAKPOINT)
> +              || (windows_process->current_event.u.Exception.ExceptionRecord.ExceptionCode
> +              == STATUS_WX86_BREAKPOINT))
> +          && windows_process->windows_initialization_done)
>          {
> -          th->stopped_at_software_breakpoint = false;
> -          if (windows_process->current_event.dwDebugEventCode
> -              == EXCEPTION_DEBUG_EVENT
> -              && is_sw_breakpoint (&windows_process->current_event
> -                       .u.Exception.ExceptionRecord)
> -              && windows_process->windows_initialization_done)
> -            {
> -              th->stopped_at_software_breakpoint = true;
> -              th->pc_adjusted = false;
> -            }
> +          th->stopped_at_software_breakpoint = true;
> +          th->pc_adjusted = false;
>          }
>          }
>  

This reverted the is_sw_breakpoint change done for aarch64 support.


Hannes