[newlib-cygwin] setup_pseudoconsole(): handle missing/incorrect helper gracefully

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=717db9fd1ce369d5279480613bcf61daf658309a

commit 717db9fd1ce369d5279480613bcf61daf658309a
Author: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Date:   Sat May 2 15:03:07 2020 +0200

    setup_pseudoconsole(): handle missing/incorrect helper gracefully
    
    When `cygwin-console-helper.exe` is either missing, or corresponds to a
    different Cygwin runtime, we currently wait forever while setting up
    access to the pseudo console, even long after the process is gone that
    was supposed to signal that it set up access to the pseudo console.
    
    Let's handle that more gracefully: if the process exited without
    signaling, we cannot use the pseudo console. In that case, let's just
    fall back to not using it.
    
    Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Diff:
---
 winsup/cygwin/fhandler_tty.cc | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index b2e725d5d..8547ec7c4 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -3496,7 +3496,23 @@ fhandler_pty_master::setup_pseudoconsole ()
 			 TRUE, EXTENDED_STARTUPINFO_PRESENT,
 			 NULL, NULL, &si_helper.StartupInfo, &pi_helper))
       goto cleanup_event_and_pipes;
-    WaitForSingleObject (hello, INFINITE);
+    for (;;)
+      {
+        DWORD wait_result = WaitForSingleObject (hello, 500);
+	if (wait_result == WAIT_OBJECT_0)
+	  break;
+	if (wait_result != WAIT_TIMEOUT)
+	  goto cleanup_helper_process;
+	DWORD exit_code;
+	if (!GetExitCodeProcess(pi_helper.hProcess, &exit_code))
+	  goto cleanup_helper_process;
+	if (exit_code == STILL_ACTIVE)
+	  continue;
+	if (exit_code != 0 ||
+	    WaitForSingleObject (hello, 500) != WAIT_OBJECT_0)
+	  goto cleanup_helper_process;
+	break;
+      }
     CloseHandle (hello);
     CloseHandle (pi_helper.hThread);
     /* Retrieve pseudo console handles */