3.1.6 About long filenames

Free Pascal can handle long filenames on all platforms, except DOS. On Windows, it will use support for long filenames if it is available (which is not always the case on older versions of Windows).

If no support for long filenames is present, it will truncate unit names to 8 characters.

It is not recommended to put units in directories that contain spaces in their names, since the external GNU linker doesn’t understand such filenames.