[newlib-cygwin] Cygwin: timerfd: add a sleep when being debugged

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=639645a2fd753f29ed9693b7c34f015c01de1741

commit 639645a2fd753f29ed9693b7c34f015c01de1741
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Tue Feb 26 10:46:05 2019 +0100

    Cygwin: timerfd: add a sleep when being debugged
    
    A sleep is required on Windows 10 64 bit only before calling
    RegisterClassW in the timerfd thread, and only when running
    under strace.  One of the child processes inheriting the timerfd
    descriptor will get a STATUS_FLOAT_INEXACT_RESULT exception inside
    of msvcrt.dll.  It's apparently some timing problem.  It occurs
    in 4 out of 5 runs under strace only.  WOW64 and Windows 7 64 bit
    don't have this problem.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/timerfd.cc | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/winsup/cygwin/timerfd.cc b/winsup/cygwin/timerfd.cc
index b0d4db9..8e4c94e 100644
--- a/winsup/cygwin/timerfd.cc
+++ b/winsup/cygwin/timerfd.cc
@@ -32,6 +32,15 @@ timerfd_tracker::create_timechange_window ()
   wclass.lpfnWndProc = DefWindowProcW;
   wclass.hInstance = user_data->hmodule;
   wclass.lpszClassName = cname;
+  /* This sleep is required on Windows 10 64 bit only, and only when running
+     under strace.  One of the child processes inheriting the timerfd
+     descriptor will get a STATUS_FLOAT_INEXACT_RESULT exception inside of
+     msvcrt.dll.  While this is completely crazy in itself, it's apparently
+     some timing problem.  It occurs in 4 out of 5 runs under strace only.
+     The sleep is required before calling RegisterClassW.  Moving it before
+     CreateWindowExW does not work.  What the heck? */
+  if (being_debugged ())
+    Sleep (1L);
   atom = RegisterClassW (&wclass);
   if (!atom)
     debug_printf ("RegisterClass %E");