using root directory C:\ fails on Windows 10

[divinity76]

i have a fairly standard

<?php
declare (strict_types = 1);
use Sabre\DAV;

// The autoloader
require 'vendor/autoload.php';

// Now we're creating a whole bunch of objects
$rootDirectory = new DAV\FS\Directory('C:');

// The server object is responsible for making sense out of the WebDAV protocol
$server = new DAV\Server($rootDirectory);
require_once __DIR__ . "/authentication.php";
// If your server is not on your webroot, make sure the following line has the
// correct information
$server->setBaseUri('/webdav/');

// The lock manager is reponsible for making sure users don't overwrite
// each others changes.
$lockBackend = new DAV\Locks\Backend\File('data/locks');
$lockPlugin = new DAV\Locks\Plugin($lockBackend);
$server->addPlugin($lockPlugin);

// This ensures that we get a pretty index in the browser, but it is
// optional.
$server->addPlugin(new DAV\Browser\Plugin());

// All we need to do now, is to fire up the server
$server->exec();

and have tried several variations of

$rootDirectory = new DAV\FS\Directory('C:');
$rootDirectory = new DAV\FS\Directory('C:\\');
$rootDirectory = new DAV\FS\Directory('C:/');

and pretty much all of them fail with some variation of

<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
  <s:sabredav-version>3.2.2</s:sabredav-version>
  <s:exception>Sabre\DAV\Exception\NotFound</s:exception>
  <s:message>File with name C:/DumpStack.log.tmp could not be located</s:message>
</d:error>

[DeepDiver1975]

solution given in #1460