bug#24573: 25.1; Setting bookmark in buffer *Help* makes bookmarks non-loadable

[Win Treese <treese@acm.org>]

I ran into the same problem.

To reproduce:

1. C-h f find-file

2. In the *Help* buffer:

    C-x r m  ; create a bookmark to the help for find-file

3. Exit Emacs (which should save the bookmark)

4. In a fresh Emacs,
   C-x r b    ; to visit any bookmark

This results in an error:

   bookmark-alist-from-buffer: Invalid read syntax: "#"

Note that the bookmark works fine until Emacs attempts to restore
the bookmarks saved to a file. In normal use, it only shows up after
Emacs is restarted.

Finding the problem:

The problem appears to be in the definition for describe-function i
help-fns.el. help-setup-xref is called with a lambda instead of a
function symbol (as it was before this code was changed).
When the bookmark is saved, the syntax for the lambda is not
parsable by read to restore it.

I don't understand the code well enough to propose an appropriate change.

I am using Aquamacs, but the code noted is the same in the master git
branch now. Version information;

Aquamacs 3.4 development
Emacs version 25.2.1

Regards,

Win Treese
treese@acm.org