[RFA] Fix GDB build failure on Windows

  Hello,

A recent enhancement to use thread_info and inferior pointers more
throughout accidently broke the build in windows-nat.c.  This patch
fixes it by completing the transition for the couple of spots that
were missed.

gdb/ChangeLog:

        * windows-nat.c (windows_delete_thread): Make parameter ptid
        a constant reference.  Fix call to delete_thread.  Log a
        DEBUG_EVENTS message if the thread_info corresponding to
        the given ptid_t could not be found.
        (windows_nat_target::detach): Fix call to detach_inferior.

Tested on x86-windows and x86_64-windows, using AdaCore's testsuite.
OK to apply?

Thanks,
  

Hi Joel,

I had already pushed a patch to fix this:
<https://sourceware.org/ml/gdb-patches/2018-06/msg00583.html> 
which just restores the old behavior, but I'm fine with your
patch too.

Thanks,
Pedro Alves

On 06/25/2018 07:27 PM, Joel Brobecker wrote:
> ---
>  gdb/windows-nat.c | 25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
> index 63a7800..620e25c 100644
> --- a/gdb/windows-nat.c
> +++ b/gdb/windows-nat.c
> @@ -479,7 +479,7 @@ windows_init_thread_list (void)
>  
>  /* Delete a thread from the list of threads.  */
>  static void
> -windows_delete_thread (ptid_t ptid, DWORD exit_code)
> +windows_delete_thread (const ptid_t &ptid, DWORD exit_code)
>  {
>    windows_thread_info *th;
>    DWORD id;
> @@ -493,7 +493,26 @@ windows_delete_thread (ptid_t ptid, DWORD exit_code)
>    else if (print_thread_events && id != main_thread_id)
>      printf_unfiltered (_("[%s exited with code %u]\n"),
>  		       target_pid_to_str (ptid), (unsigned) exit_code);
> -  delete_thread (ptid);
> +
> +  thread_info *tp = find_thread_ptid (ptid);
> +  if (tp != NULL)
> +    delete_thread (tp);
> +  else
> +    {
> +      /* Something unexpected happened: We are trying to delete
> +	 a thread that the core layer apparently does not know about.
> +	 This should never happen, and thus we want to be able to
> +	 report this discrepancy should it actually happen and have
> +	 unanticipated side-effects; but since we were trying to
> +	 delete the thread anyway, it's quite possible that this
> +	 issue has no actual consequence in terms of the overall
> +	 behavior.  So, instead of unnecessarily worrying the user
> +	 with a warning or internal-error, just log a DEBUG_EVENTS
> +	 event.  */
> +      DEBUG_EVENTS (("gdb: windows_delete_thread cannot find thread"
> +		     " for ptid (pid=%d, tid=%ld)\n",
> +		     ptid.pid(), ptid.tid()));
> +    }
>  
>    for (th = &thread_head;
>         th->next != NULL && th->next->id != id;
> @@ -2000,7 +2019,7 @@ windows_nat_target::detach (inferior *inf, int from_tty)
>  
>    x86_cleanup_dregs ();
>    inferior_ptid = null_ptid;
> -  detach_inferior (current_event.dwProcessId);
> +  detach_inferior (current_inferior ());
>  
>    maybe_unpush_target ();
>  }
  

Hi Pedro,

> I had already pushed a patch to fix this:
> <https://sourceware.org/ml/gdb-patches/2018-06/msg00583.html> 
> which just restores the old behavior, but I'm fine with your
> patch too.

Thanks for doing that. I looked at your patch, and it looks good
to me. In fact, the second half looks better, as far as I can tell.
So I'm withdrawing this patch.