In https://postgr.es/m/1514541656508-0.post@n3.nabble.com
it's reported that "SELECT pg_ls_dir('c:')" works to allow
display of the root directory on drive C. If true, this
would be a violation of the principle that the core file
access functions only let you get at PG-related directories.
However, I looked at the code, and it sure looks like
path_is_relative_and_below_cwd() contains code to reject use
of Windows drive letters. Am I missing something? Anyone
want to check if they can reproduce this on a Windows build?
regards, tom lane