Windows gdb: Simplify windows_nat_target::wait

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.

Change-Id: I76c41762e1f893a7ff23465856ccf6a44af1f0e7

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 8e0abe9403f7035c33da8802e61c9c4ada88c939..f1ec8837e8273582004b4f09f443798151fb065a 100644 (file)
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -1665,7 +1665,10 @@ 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);
 }
 
@@ -1686,27 +1689,33 @@ 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
-                     && ((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 = true;
-                     th->pc_adjusted = false;
-                   }
+                 th->stopped_at_software_breakpoint = true;
+                 th->pc_adjusted = false;
                }
            }