Cygwin programs display output incorrectly when run under conemu

[Paul Moore]

This issue has also been reported to the ConEmu tracker as
https://github.com/Maximus5/ConEmu/issues/2059.

If I run a cygwin command (for example ls, or for a simpler example,
"printf hello\nthere", although the latter needs care to get the
correct level of \n escaping :-)) newlines are displayed by the text
moving down a line, but *not* returning to the left hand margin.

An example, running in Powershell as my shell:

>E:\Utils\Cygwin64\bin\printf.exe hello\nthere
hello
     there

This behaviour is present with the latest version of cygwin1.dll, as
well as with the 20200212 snapshot. It is not present if I replace the
Cygwin dll with version 3.0.7-1.

The problem does not appear with a standard cmd.exe terminal (standard
Windows console host) or the new Windows Terminal application. I
understand that ConEmu handles the console management differently
"behind the scenes" to present a GUI front end, but I don't know
enough about the internals to know how it does that.

I can work around the issue by pinning to cygwin 3.0.7-1, but it's
obviously not ideal. I have been unable to find any details as to what
changed between cygwin 3.0.7-1 and the next version to help me track
down the issue any more specifically.

There are some notes at https://conemu.github.io/en/CygwinMsys.html
that I've read, but to be honest I don't entirely understand. I did,
however, confirm that this issue doesn't occur in a standard `cmd`
window (and I added that information to the ConEmu issue report).

Any information that would help to pin down the cause of this problem
would be very much appreciated.

Paul

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