[PATCH] setup_pseudoconsole(): handle missing/incorrect helper gracefully

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[PATCH] setup_pseudoconsole(): handle missing/incorrect helper gracefully

Johannes Schindelin
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 <[hidden email]>
---

        It took me three days to bisect why my test build of the MSYS2
        runtime hung MinTTY. Three complete days.

        The reason? I missed that `cygwin-console-helper.exe` needs to be
        copied into the test environment, too, not just the DLL.

        In hindsight, it would have been smarter to just attach to the
        hanging process, but then, I thought if MinTTY is hanging, then
        surely GDB will hang, too.

 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 */
--
2.26.1.windows.1


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Re: [PATCH] setup_pseudoconsole(): handle missing/incorrect helper gracefully

Corinna Vinschen-2
On May  2 15:03, Johannes Schindelin wrote:
> 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.

Pushed.


Thanks,
Corinna

--
Corinna Vinschen
Cygwin Maintainer