bug#56025: 29.0.50; em-extpipe-test-2 times out on EMBA and Cygwin

[Ken Brown <kbrown@cornell.edu>]

On 6/16/2022 6:01 PM, Ken Brown wrote:
> On 6/16/2022 3:30 PM, Sean Whitton wrote:
>> Hello Ken,
>>
>> On Thu 16 Jun 2022 at 02:30pm -04, Ken Brown wrote:
>>
>>> In commit 231a1ba3, Lars disabled the extpipe tests on EMBA "because they
>>> apparently time out".  The EMBA log he cited in the commit message shows that
>>> only em-extpipe-test-2 times out.  And this same test (but no others) also times
>>> out on Cygwin:
>>
>> That test invokes `sh -c "rev >temp"` as its only subprocess, so that's
>> probably what is timing out.  Is there something different about
>> Cygwin's sh?  Something about EOFs?
> 
> I'm not aware of anything different.  Here's what happens when I run the test 
> interactively:
> 
> $ time echo \"bar\" | sh -c "rev >temp"
> 
> real    0m0.100s
> user    0m0.030s
> sys     0m0.030s
> 
> $ cat temp
> "rab"
> 
> And keep in mind that the test also times out on EMBA.

I just tried a different experiment: In an interactive emacs-29 session, I 
started eshell and typed

   echo \"bar\" | rev *>temp

Nothing visible happens until I type 'C-c C-c'.  Then a prompt appears again, 
and 'ls -l' shows that temp exists and is empty.

Prior to typing 'C-c C-c', 'M-x list-processes' (or 'C-c C-s') shows a bash 
process running but it doesn't show 'rev'.  But running 'ps' outside of emacs 
shows both 'rev' and its parent 'bash' process.

It does seem that there's an actual bug here, not just a test that should be 
skipped because it times out.  It could be a Cygwin bug, of course, but that 
doesn't explain the EMBA failure.

Ken