From: Eli Zaretskii <eliz@gnu.org>
To: Yuan Fu <casouri@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Calling Lisp in C functions
Date: Thu, 23 Sep 2021 09:59:33 +0300 [thread overview]
Message-ID: <83r1dfvktm.fsf@gnu.org> (raw)
In-Reply-To: <87357FA2-4AF8-4E7E-BD26-1852D9C8CE6F@gmail.com> (message from Yuan Fu on Wed, 22 Sep 2021 20:59:00 -0700)
> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 22 Sep 2021 20:59:00 -0700
> Cc: Emacs developers <emacs-devel@gnu.org>
>
> I tried to write
>
> ptrdiff_t count = SPECPDL_INDEX ();
> record_unwind_protect_ptr (ts_delete_cursor, cursor);
> ...
> return unbind_to (count, xxx);
>
> But it give a type error, because ts_delete_cursor doesn’t take a void*. I guess I need to define a wrapper function to avoid that error?
Yes, see for example directory_files_internal_unwind and its usage in
dired.c.
> Can I use record_unwind_protect_ptr more than once?
Yes.
> What does that count mean?
It tells unbind_to how much of the unwind-protect stack to unwind.
See the definition of unbind_to in eval.c.
> What is specpdl?
It's an array used for manually managed stack for tracking unwinds and
other stuff by the Emacs Lisp machine. See the comments for 'union
specbinding', starting at line 3135 of lisp.h.
next prev parent reply other threads:[~2021-09-23 6:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-21 19:38 Calling Lisp in C functions Yuan Fu
2021-09-22 5:45 ` Eli Zaretskii
2021-09-23 3:59 ` Yuan Fu
2021-09-23 6:59 ` Eli Zaretskii [this message]
2021-09-23 7:47 ` Andreas Schwab
2021-09-24 17:55 ` Yuan Fu
2021-09-24 17:55 ` Yuan Fu
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