Re: ptrdiff_t misuse [was :Re: (empty)]

[Eli Zaretskii]

Btw, what's the theory behind using ptrdiff_t in preference to
EMACS_INT to store values that came from Lisp?  E.g., in this snippet:

  static Lisp_Object
  set_window_hscroll (struct window *w, EMACS_INT hscroll)
  {
    ...
    ptrdiff_t hscroll_max = min (MOST_POSITIVE_FIXNUM, PTRDIFF_MAX);
    ptrdiff_t new_hscroll = clip_to_bounds (0, hscroll, hscroll_max);

Won't this do The Wrong Thing when Emacs is configured with wide ints?
It looks like EMACS_INT is always preferable in these contexts, as it
always has the right width.

Likewise for variables that store buffer or string positions.

What am I missing?