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To: moss@cs.umass.edu
Subject: Re: ExitProcess does not work in =?UTF-8?Q?Cygwin=3F?=
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Date: Thu, 13 Jan 2022 09:07:50 -0800
From: "Kaz Kylheku (Cygwin)" <743-406-3965@kylheku.com>
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On 2022-01-13 05:40, Eliot Moss wrote:
> On 1/13/2022 1:39 AM, Jay K wrote:
>> ExitProcess does not work in Cygwin?
> 
> ExitProcess does not appear to be a POSIX function.

This is a real issue worth looking into. Though ExitProcess isn't a 
POSIX
function, Cygwin can capture the termination status of non-Cygwin 
programs.

The concept of termination status cannot be entirely walled off in a
private Cygwin garden; it belongs to the underlying platform.

In Cygwin, I can do this:

   C:\Cygwin\cygwin64\home\kaz>exit 1
   1:BLACKBOX:~$
   1:BLACKBOX:~$ echo $?
   1
   0:BLACKBOX:~$ cmd
   Microsoft Windows [Version 10.0.19042.1052]
   (c) Microsoft Corporation. All rights reserved.

   C:\Cygwin\cygwin64\home\kaz>exit 0
   0:BLACKBOX:~$

The number in my Bash prompt is the last exit code. As you can see,
the non-Cygwin CMD.EXE program produces a termination code which
is recognized in the Cygwin world.

Most likely it does that via ExitProcess.

It is odd if calling ExitProcess in a Cygwin process causes
a Cygwin parent not to similarly process the status, as seems
to be shown by Jay's test cases.

Cygwin supports non-POSIX programming; you can write GUI applications
using Win32 calls for instance.

(Now I agree that for exiting your process, even if it's a GUI
application using numerous win32 calls, you should probably do it the
Cygwin way, and use exit, or return from main. But still ...)


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