* autoload.cc (MsgWaitForMultipleObjectsEx): Define.

	(MsgWaitForMultipleObjects): Remove.
	* select.cc (select_stuff::wait): Use MsgWaitForMultipleObjectsEx with
	QS_ALLPOSTMESSAGE and, if possible, MWMO_INPUTAVAILABLE flags.  Explain
	why.  Fix a potential crash due to a NULL pointer in WAIT_FAILED case.
	(peek_windows): Use filter pattern on NT4.  Explain why.
	* wincap.h (wincaps::has_mwmo_inputavailable): New element.
	* wincap.cc: Implement above element throughout.

5 files changed, 46 insertions, 4 deletions

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index bcbe77b..fba8035 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,14 @@
+2010-08-30  Corinna Vinschen  <corinna@vinschen.de>
+
+	* autoload.cc (MsgWaitForMultipleObjectsEx): Define.
+	(MsgWaitForMultipleObjects): Remove.
+	* select.cc (select_stuff::wait): Use MsgWaitForMultipleObjectsEx with
+	QS_ALLPOSTMESSAGE and, if possible, MWMO_INPUTAVAILABLE flags.  Explain
+	why.  Fix a potential crash due to a NULL pointer in WAIT_FAILED case.
+	(peek_windows): Use filter pattern on NT4.  Explain why.
+	* wincap.h (wincaps::has_mwmo_inputavailable): New element.
+	* wincap.cc: Implement above element throughout.
+
 2010-08-29  Christopher Faylor  <me+cygwin@cgf.cx>
 
 	* winlean.h: New file.
diff --git a/winsup/cygwin/autoload.cc b/winsup/cygwin/autoload.cc
index 30bbec7..07272af 100644
--- a/winsup/cygwin/autoload.cc
+++ b/winsup/cygwin/autoload.cc
@@ -357,7 +357,7 @@ LoadDLLfunc (GetWindowThreadProcessId, 8, user32)
 LoadDLLfunc (GetUserObjectInformationW, 20, user32)
 LoadDLLfunc (MessageBeep, 4, user32)
 LoadDLLfunc (MessageBoxA, 16, user32)
-LoadDLLfunc (MsgWaitForMultipleObjects, 20, user32)
+LoadDLLfunc (MsgWaitForMultipleObjectsEx, 20, user32)
 LoadDLLfunc (OpenClipboard, 4, user32)
 LoadDLLfunc (PeekMessageA, 20, user32)
 LoadDLLfunc (PostMessageA, 16, user32)
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 41636d1..611367b 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -287,7 +287,17 @@ select_stuff::wait (fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
       if (!windows_used)
 	wait_ret = WaitForMultipleObjects (m, w4, FALSE, ms);
       else
-	wait_ret = MsgWaitForMultipleObjects (m, w4, FALSE, ms, QS_ALLINPUT);
+	/* Using MWMO_INPUTAVAILABLE is the officially supported solution for
+	   the problem that the call to PeekMessage disarms the queue state 
+	   so that a subsequent MWFMO hangs, even if there are still messages
+	   in the queue.  Unfortunately this flag didn't exist  prior to Win2K,
+	   so for NT4 we fall back to a different usage of PeekMessage in
+	   peek_windows.  See there for more details. */
+	wait_ret =
+	  MsgWaitForMultipleObjectsEx (m, w4, ms,
+				       QS_ALLINPUT | QS_ALLPOSTMESSAGE,
+				       wincap.has_mwmo_inputavailable ()
+				       ? MWMO_INPUTAVAILABLE : 0);
 
       switch (wait_ret)
       {
@@ -296,7 +306,8 @@ select_stuff::wait (fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
 	  set_sig_errno (EINTR);
 	  return -1;
 	case WAIT_FAILED:
-	  select_printf ("WaitForMultipleObjects failed");
+	  system_printf ("WaitForMultipleObjects failed");
+	  s = &start;
 	  s->set_select_errno ();
 	  return -1;
 	case WAIT_TIMEOUT:
@@ -1531,7 +1542,14 @@ peek_windows (select_record *me, bool)
   if (me->read_selected && me->read_ready)
     return 1;
 
-  if (PeekMessage (&m, (HWND) h, 0, 0, PM_NOREMOVE))
+  /* On NT4 we use a filter pattern which allows to use QS_ALLPOSTMESSAGE
+     to keep the queue state as unread.  Note that this only works if the
+     application itself does not call PeekMessage or GetQueueState the wrong
+     way.  But there's no way around it.  On Win2K and later we rather use
+     MsgWaitForMultipleObjectsEx(MWMO_INPUTAVAILABLE). */
+  if (PeekMessage (&m, (HWND) h, 0,
+		   wincap.has_mwmo_inputavailable () ? 0 : UINT_MAX - 1,
+		   PM_NOREMOVE))
     {
       me->read_ready = true;
       select_printf ("window %d(%p) ready", me->fd, me->fh->get_handle ());
diff --git a/winsup/cygwin/wincap.cc b/winsup/cygwin/wincap.cc
index 889998c..39b1c75 100644
--- a/winsup/cygwin/wincap.cc
+++ b/winsup/cygwin/wincap.cc
@@ -59,6 +59,7 @@ wincaps wincap_unknown __attribute__((section (".cygwin_dll_common"), shared)) =
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:false,
 };
 
 wincaps wincap_nt4 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -99,6 +100,7 @@ wincaps wincap_nt4 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:false,
 };
 
 wincaps wincap_nt4sp4 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -139,6 +141,7 @@ wincaps wincap_nt4sp4 __attribute__((section (".cygwin_dll_common"), shared)) =
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:false,
 };
 
 wincaps wincap_2000 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -179,6 +182,7 @@ wincaps wincap_2000 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_2000sp4 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -219,6 +223,7 @@ wincaps wincap_2000sp4 __attribute__((section (".cygwin_dll_common"), shared)) =
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_xp __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -259,6 +264,7 @@ wincaps wincap_xp __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_xpsp1 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -299,6 +305,7 @@ wincaps wincap_xpsp1 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_xpsp2 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -339,6 +346,7 @@ wincaps wincap_xpsp2 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_2003 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -379,6 +387,7 @@ wincaps wincap_2003 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:false,
   has_localenames:false,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_vista __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -419,6 +428,7 @@ wincaps wincap_vista __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:false,
   has_always_all_codepages:true,
   has_localenames:true,
+  has_mwmo_inputavailable:true,
 };
 
 wincaps wincap_7 __attribute__((section (".cygwin_dll_common"), shared)) = {
@@ -459,6 +469,7 @@ wincaps wincap_7 __attribute__((section (".cygwin_dll_common"), shared)) = {
   has_broken_alloc_console:true,
   has_always_all_codepages:true,
   has_localenames:true,
+  has_mwmo_inputavailable:true,
 };
 
 wincapc wincap __attribute__((section (".cygwin_dll_common"), shared));
diff --git a/winsup/cygwin/wincap.h b/winsup/cygwin/wincap.h
index 6a698d2..8f027d0 100644
--- a/winsup/cygwin/wincap.h
+++ b/winsup/cygwin/wincap.h
@@ -51,6 +51,7 @@ struct wincaps
   unsigned has_broken_alloc_console			: 1;
   unsigned has_always_all_codepages			: 1;
   unsigned has_localenames				: 1;
+  unsigned has_mwmo_inputavailable			: 1;
 };
 
 class wincapc
@@ -107,6 +108,7 @@ public:
   bool	IMPLEMENT (has_broken_alloc_console)
   bool	IMPLEMENT (has_always_all_codepages)
   bool	IMPLEMENT (has_localenames)
+  bool	IMPLEMENT (has_mwmo_inputavailable)
 
 #undef IMPLEMENT
 };