From: defun.foo--- via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 56643@debbugs.gnu.org
Subject: bug#56643: 29.0.50; Help-mode bookmarks not loading with native compilation
Date: Tue, 19 Jul 2022 22:22:57 +0000 [thread overview]
Message-ID: <lzjXW3vhXW--IOZJXTmU5Xl0TSm-nz50UZUhGmiff-7ImxbKPu6OjfMV73fSTGAqKai-qvHKZkc9KOIUz8hhgleZfdcZtIuUA7Y87lSXsP8=@proton.me> (raw)
In-Reply-To: <83k089m4j0.fsf@gnu.org>
I dug into that a little when I was trying to find a work-around. It looks like help-mode maintains a stack of previously-visited help items which is what enables users to jump back and forth between different items they've viewed. From "C-h v help-xref-stack":
"A stack of ways by which to return to help buffers after following xrefs.
Used by ‘help-follow-symbol’ and ‘help-xref-go-back’.
An element looks like (POSITION FUNCTION ARGS...).
To use the element, do (apply FUNCTION ARGS) then goto the point."
So basically the FUNCTION element is a recipe for recreating a specific help item, and "help-bookmark-make-record" just drops that FUNCTION element intact into "help-fn" when creating a bookmark:
`(,@(bookmark-make-record-default 'NO-FILE 'NO-CONTEXT)
(help-fn . ,(car help-xref-stack-item))
(help-args . ,(mapcar (lambda (a)
(if (bufferp a) (buffer-name a) a))
(cdr help-xref-stack-item)))
(position . ,(point))
(handler . help-bookmark-jump))
The catch is that every function that generates a help buffer also defines its own way of setting up an xref stack item. Some pass in a symbol while some pass in a lambda, so after a while the stack might end up looking like this:
((1 #<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_20>
(("\x18\x03" .
[24 3]))
#<buffer *Help*>)
(232 describe-variable help-xref-stack #<buffer *Help*>)
(1 #<subr F616e6f6e796d6f75732d6c616d626461_anonymous_lambda_7> describe-package #<buffer *Help*>))
Then when bookmark.el saves all the bookmarks ("bookmark-write-file"), it just calls "pp" on each one:
(dolist (i bookmark-alist) (pp i (current-buffer)))
which apparently is able to create a readable representation of byte-compiled lambdas, but not native-compiled ones.
And that's where my knowledge ends. :) I have very little C programming experience and have no idea if it's even possible to serialize a compiled thing into something the reader can understand, or whether there's some processing help-mode could do on each function before it even becomes part of a bookmark.
------- Original Message -------
On Tuesday, July 19th, 2022 at 12:49 PM, Eli Zaretskii <eliz@gnu.org> wrote:
>
> Thanks.
>
> I started looking into this, but gave up when I got to help-mode.el
> (which is where the bookmark support for Help lives, and which is
> where we signal an error trying to read an unreadable object.)
>
> We basically have no usable documentation for what bookmark support in
> help-mode does. Someone who knows what that code does will have to
> see how to process a help-fn that is a natively-compiled function.
next prev parent reply other threads:[~2022-07-19 22:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-19 13:45 bug#56643: 29.0.50; Help-mode bookmarks not loading with native compilation defun.foo--- via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-19 16:49 ` Eli Zaretskii
2022-07-19 22:22 ` defun.foo--- via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2022-07-20 9:51 ` Andrea Corallo
2022-07-20 11:21 ` Andrea Corallo
2022-07-20 11:45 ` Eli Zaretskii
2022-07-20 18:31 ` Andrea Corallo
2022-07-20 19:16 ` Eli Zaretskii
2022-07-20 22:47 ` Michael Heerdegen
2022-07-21 5:13 ` Eli Zaretskii
2022-07-21 10:01 ` defun.foo--- via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-07-21 12:33 ` Eli Zaretskii
2022-07-22 13:40 ` Eli Zaretskii
2022-07-22 13:41 ` Andrea Corallo
2022-07-22 14:40 ` Eli Zaretskii
2022-07-23 9:57 ` Eli Zaretskii
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