Strange behaviour with winsymlinks:native

Wed Oct 14 14:56:47 GMT 2020

I've been doing some working around the problems with Cygwin 3.1.5+ WSL
junction points in Docker and found three unexpected pieces of behaviour
with CYGWIN=winsymlinks:native
In all cases, these work as expected with the default symlink behaviour
(i.e. CYGWIN unset or without a winsymlinks option).
1. Relative paths get unnecessarily resolved
 mkdir -p foo/bar
 cd foo/bar
 touch baz
 CYGWIN='winsymlinks:native' ln -s ../bar/baz link
 readlink link
Result is baz, not ../bar/baz
2a. Links in the magic mount directories (/usr/bin and /usr/lib) get extra
bits added (source is a default mount):
 cd /usr/lib
 CYGWIN='winsymlinks:native' ln -s ../share/terminfo terminfo2
 readlink terminfo2
Result is ../usr/share/terminfo, which makes it valid from /lib (the "real"
directory) but not in the virtual one
2b. Same but where target is a default mount
 cd /usr/libexec/p11-kit
 CYGWIN='winsymlinks:native' ln -s ../../bin/update-ca-trust
trust-extract-compat2
 readlink trust-extract-compat2
Result is ../../../bin/update-ca-trust, again it seems to be computing an
extra level back to the "real" lib directory
Are these behaviours expected? I can create those symbolic links manually
with mklink with no problem, so I'm wondering if it's an outright bug or an
unexpected consequence of something else.
Thanks!
David