gnu screen crashes on ssh disconnect

[Wayne Davison]

In recent Cygwin versions I've had gnu screen crash if the parent ssh
connection closes before an explicit disconnect is performed. If an
orderly screen disconnect happens first, future closed connections
(after reconnecting to the screen session) no longer crash screen.

To reproduce:

I ssh into my Windows 10 host, move my .screenrc file out of the way
(to keep the config the default) and run "screen" to start up a basic
screen session. I then use the ssh close-connection key sequence
(Enter, tilde, period) to close the connection. When I log back in,
the ps command shows that screen is already dead and "screen -ls"
shows a dead screen to clean up using "screen -wipe". If I start a
fresh screen and use screen's Ctrl+A d key sequence to detach, I can
use "screen -r" to reconnect and from this point on a lost connection
no longer makes screen crash, even on future reconnects.

I haven't seen this crash on Ubuntu, but since it isn't on the same
version, I tried compiling 4.8.0 to see if that might make it crash --
it did not. I then compiled the source on Cygwin (without any
configure options) and that version has the bug, so I guess that this
is either a Cygwin issue or something weird in my Windows setup.

Is anyone else seeing this crash?

I'm attaching a cygcheck.out file that has a couple secrets elided.
I'll note that I just started to run with disable_pcon set, but it's
been crashing with and without that.

..wayne..
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