Johan Walles <johan.walles@gmail.com> writes:

> Try this:
> 1. Set indent-tabs-mode to nil.
> 2. Load a C file indented with tabs.
> 3. c-guess
> 4. Do describe-variable on indent-tabs-mode
>
> Current result:
> "Its value is nil"
>
> Expected result:
> "Its value is t" (since c-guess should have noticed that tabs are used
> for indentation)

This still seems to be the case in Emacs 28.

I've included my test file here.  Perhaps Alan has some insights here?
(Added to the CCs.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no