Re: unwind-protect and inhibit-quit

[Eli Zaretskii <eliz@gnu.org>]

> From: Felix Dietrich <felix.dietrich@sperrhaken.name>
> Date: Fri, 16 Jul 2021 23:30:31 +0200
> 
> But at which point is the ‘quit-flag’ actually handled?

When the C-level code of the Lisp machine thinks it's a good time to
do that.  In general, whenever the Lisp evaluation is entered,
whenever a Lisp function is called, and inside any loops that might
run for a long time or might not exit.  There's no magic with handling
quit on the C level, it mast be invoked explicitly.

> The macro ‘with-local-quit’ states that the “quit-flag” “will not be
> handled until the next function call”[1].  Could, therefore, a
> careful and cooperative “ftp-setup-buffer” ensure that the process
> is either cleaned-up or returned?

There's no way to ensure atomicity on the Lisp level, because a Lisp
program has no real control of when quit handling happens.  Only
primitives can do that (and actually do that where we think it's
necessary).

> I am thinking of something like the following:

What problem(s) this is intended to fix/handle?