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Subject: Re: Cygwin/X on Windows 10 won't launch apps from .XWinrc menus
To: Roland Roberts <roland AT astrofoto DOT org>,
        The Cygwin Mailing List <cygwin AT cygwin DOT com>
References: <beb86b97-7c86-3685-dd09-e2f98e5070d9 AT astrofoto DOT org>
From: Jon Turney <jon DOT turney AT dronecode DOT org DOT uk>
Message-ID: <b13207ee-740f-f90a-21bb-0ca29efbc471@dronecode.org.uk>
Date: Sat, 21 Aug 2021 15:49:46 +0100
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On 10/08/2021 13:58, Roland Roberts wrote:
> I have a new, company-supplied Windows 10 laptop, using Cygwin to do 
> development. I’m having a problem getting XWin to launch apps. XWin 
> appears to be mostly working normally, meaning if I launch a Cygwin 
> mintty instance, I can manually set DISPLAY=:0.0 and start up X 
> application from the shell prompt. But trying to launch from my .XWinrc, 
> the application never displays and I can’t find a useful error log to 
> track down the issue. I’m pretty sure it’s some permission someplace my 
> account doesn’t have (and I can probably get IT to change that if I can 
> just identify what it is).

I'm not sure what the evidence for this hypothesis is?

>      [  1490.390] executing '/bin/mintty', pid 772
>      [  1902.312] executing '/bin/mintty', pid 1200
> 
> You can see the last two things that were launched. And here’s the 
> process list
> 
>      29267 rrobert1> ps -ef
>           UID     PID    PPID  TTY        STIME COMMAND
>      rrobert1     610       1 ?        08:31:58 /usr/bin/mintty
>      rrobert1     471       1 ?        08:31:46 /usr/bin/gpg-agent
>      rrobert1     772     605 ?        08:32:24 /usr/bin/XWin
>      rrobert1    1205     611 pty0     08:39:31 /usr/bin/ps
>      rrobert1     403       1 cons0    08:31:42 /usr/bin/sh
>      rrobert1     442       1 ?        08:31:44 /usr/bin/ssh-agent
>      rrobert1     611     610 pty0     08:31:58 /usr/bin/bash
>      rrobert1     604     403 cons0    08:31:49 /usr/bin/xinit
>      rrobert1    1200     605 ?        08:39:16 /usr/bin/XWin
>      rrobert1     605     604 cons0    08:31:49 /usr/bin/XWin
>      rrobert1     609     604 ?        08:31:50 /usr/bin/sh
> 
> where you can see those processes are launch, but they show as 
> additional instances of XWin and mintty was never started. My .XWinrc 
> contain this
> 
>      menu root {
>              "Cygwin Terminal" exec  "/bin/mintty"
>                  "Emacs"           exec     "/bin/emacs"
>              // […]
>      }

The process being created, but not changing command is usually 
symptomatic of problems with cygwin's fork emulation (i.e. the child 
process gets stuck during the complex synchronization it does with the 
parent, before exec gets called)

> Any suggestions on where to poke to diagnose this? My home Windows 10 
> machine has no problem at all. Oh, and cygcheck report version 3.1.4. 
> Yes, that’s a little old, but we are stuck there until we can work out 
> an issue with our build environment and the change for 3.1.5+ in how 
> symlinks are handled.

There are some suggestions about dealing with fork problems in the FAQ, 
but sometimes nothing works and we don't know why.

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