Re: Question about composite.c

[Gerry Agbobada]

> Is the overlay a necessary part of the problem?
Yes, because it's the overlay that tries to print a composed "=>" combination.


> Also, is it necessaryto define a separate char-table, instead of using
> composition-function-table?
> The example looks quite complex, and I wonder whether you could
> prepare a simplified variant that only included the parts that are
> necessary?  That would make debugging this issue much easier.
I agree that it might still be a little complex. I'll try to work on
this again to provide
the minimum amount of basic elisp functions code, but it's a little hard for me
to pindown the exact issue so I'm just making baby steps for the moment.

> From this, I don't think I understand why the problem is triggered by
> a '+' character.  If I do the following in "emacs -Q":
The problem is not triggered by the '+' character but by eros-mode
which will try to
output an overlay on the cursor with the content "=> 5".

> In what version of Emacs do you see these infloops, btw?
I was at e1f0e0892 (tip of emacs-27 on Wed Mar 25 21:54:21 2020 +0200 )
I will build from master right now to continue the investigation.

Thanks for your time answering me

Gerry AGBOBADA

Le sam. 25 avr. 2020 à 14:44, Eli Zaretskii <address@hidden> a écrit :
>
> > From: Gerry Agbobada <address@hidden>
> > Date: Wed, 15 Apr 2020 00:43:59 +0200
> > Cc: address@hidden
> >
> > It took me a good while, but I found a case where :
> > - I can reproduce with =emacs -q=  (Reproducing infinite looping in
> > composition_get_gstring with an empty non-nil string)
> > - prettify-symbols-mode is not enabled
> >
> > The example includes the code of eros.el package, which creates an
> > overlay when calling eval-last-sexp. The overlay is supposed to start
> > with `=>`, and when I have this in my composition-function-table it
> > triggers the loop.
> > As explained in the file linked below, with the cursor on `(+ 3 2)|`
> > I'd expect `C-x C-e` to create an overlay with `=> 5`. Instead, it
> > loops indefinitely and the only way out is to kill -9 emacs (kill
> > -USR2 doesn't help)
>
> Is the overlay a necessary part of the problem?  Also, is it necessary
> to define a separate char-table, instead of using
> composition-function-table?
>
> The example looks quite complex, and I wonder whether you could
> prepare a simplified variant that only included the parts that are
> necessary?  That would make debugging this issue much easier.
>
> > (let ((alist
> >        '(
> >          (?= . "=>") ; Matches =>
> >          )))
> >   (dolist (char-regexp alist)
> >     (set-char-table-range other-composition-ligature-table (car char-regexp)
> >                           `([,(cdr char-regexp) 0 font-shape-gstring]))))
> >
> > (set-char-table-parent other-composition-ligature-table 
> > composition-function-table)
> >
> > (setq-local composition-function-table other-composition-ligature-table)
>
> From this, I don't think I understand why the problem is triggered by
> a '+' character.  If I do the following in "emacs -Q":
>
>   (set-char-table-range composition-function-table
>                         #x3d
>                         (list (vector "=>" 0 'compose-gstring-for-graphic)))
>
> and then type (+ 2 3)C-x C-e, I don't get any loop, and no characters
> related to the => ligatures anywhere.  What am I missing?
>
> In what version of Emacs do you see these infloops, btw?