Symfony version(s) affected: 5.1.6

Description

Path resolution does not work with the newly integrated cache handler cache/Xxx_KernelProdDebugContainer.preload.php

require dirname(__DIR__, 3).'\\vendor/autoload.php';

The two backslashes are resolved to this square character: .\�endor/autoload.php (see picture) since \v is an escape secquence for vertical jumps, as far as I remember.

The screenshot below show the debug output.

How to reproduce

• $ composer dump-env prod
• Open web page
• 💣

Possible Solution
Also, dirname(__DIR__,3) doesnt resolve correctly (might be a configuration issue from my side/app).
The only temp solution is to change to this weird non-scalable path settings:

require __DIR__.'/../../../vendor/autoload.php'; <-- changed
require __DIR__.'/ContainerU2aLZw8/Vince_KernelProdDebugContainer.php';

Additional context