Pipes/fifos/sockets&&|mmap()|'ed output files in POSIX shell x=$(cmd) and x=${ cmd ; } statements... / was: Re: [regression-3.6] Pipe between Cygwin and non Cygwin (CRT/URT) randomly loses characters

[Jeremy Drake]

On Thu, 20 Feb 2025, Roland Mainz via Cygwin wrote:

> > > Same happens with dash and ksh93.
>
> And THAT statement is BAD, because it means basic shell functionality
> is broken, affecting dash/bash/ksh93 - reading that IMO means Cygwin
> has a problem in the pipe/fifo code... ;-(
>
> Best way forward is to grab the shell testsuite (e.g. both bash and
> ast-ksh/ksh93 ship with test suites), and run the pipe/command
> substitution tests.

This report has to do with the case where the other end of the pipe is a
native Windows program (rather than another Cygwin program), and that
case is (at least used to be) different in the Cygwin pipe code.  It's
doubtful a UNIX shell test suite would exercise that codepath.

BTW, I would not be at all surprised if the following were related
somehow:
https://github.com/msys2/msys2-runtime/issues/230
https://github.com/git-for-windows/msys2-runtime/pull/75