LFN support has been considered, but it's not officially supported. Sorry.
https://www.google.com/search?q=dosbox+lfn+site%3Avogons.org

No game needs this 😉

Dosbox already has LFN support. Instead of typing in "Program Files" though, you would just type in "progra~1". 🤣

Use a HD image and you can use LFN all you want.

Dominus wrote:

No game needs this 😉

The Town With No Name
DOS Mugen games

Shut up 😉

Town With No Name and Psycho Killer both work fine in SVN using IMGMOUNT. The issue is not long filename support, it's *clipping* the long names on the cdroms to 8.3, as real DOS/MSCDEX does, instead of converting them to short names (e.g. LONGNA~1). So far the clipping is only implemented for IMGMOUNT -- doing so for MOUNT would be difficult due to the way directory caching works.

MUGEN was first released in 1999. It was not the only game developed for "DOS" in the late 90's that used long filenames, but as I'm sure you've heard before: the NTVDM ain't real DOS.

ripsaw8080 wrote:

the NTVDM ain't real DOS.

It's really due to carelessness through Windows9x LFN convenience. There's many DOS Mugen games from 99-2000 that do LFN and spew errors about it when DOSBox runs them.

NTVDM doesn't work with Mugen much at all! Allegro always had problems with that.

leileilol wrote:

It's really due to carelessness through Windows9x LFN convenience.

DOS7 ain't real DOS! OK, it sort of is, but DOSBox targets DOS 5/6 in any case. 😜