bug#60691: 29.0.60; Slow tree-sitter font-lock in ruby-ts-mode

[Eli Zaretskii <eliz@gnu.org>]

> From: Yuan Fu <casouri@gmail.com>
> Date: Fri, 13 Jan 2023 01:15:09 -0800
> Cc: Dmitry Gutov <dgutov@yandex.ru>,
>  60691@debbugs.gnu.org,
>  Juri Linkov <juri@linkov.net>,
>  Stefan Monnier <monnier@iro.umontreal.ca>
> 
> > On Jan 12, 2023, at 11:57 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> Cc: 60691@debbugs.gnu.org, juri@linkov.net
> >> Date: Fri, 13 Jan 2023 01:40:56 +0200
> >> From: Dmitry Gutov <dgutov@yandex.ru>
> >> 
> >> Managed to reproduce this after running the test in a couple of 
> >> different files.
> >> 
> >> But 'M-x memory-usage' says no such command, and 'M-x memory-report' 
> >> ends up with this error:
> >> 
> >> Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
> >>   memory-report--gc-elem(nil strings)
> >>   memory-report--garbage-collect()
> >>   memory-report()
> > 
> > This means GC is disabled in this session at the time you invoke
> > memory-report.  Which shouldn't happen, of course.  It sounds like
> > your pure Lisp storage overflowed, and that disabled GC.
> > 
> > And I think I see the problem: we use build_pure_c_string in treesit.c
> > in places that we shouldn't.
> > 
> > Yuan, build_pure_c_string should only be used in places such as
> > syms_of_treesit, which are called just once, during dumping.  Look at
> > all the other calls to this function in the sources, and you will see
> > it.  In all other cases, you should do one of the following:
> > 
> >  . for strings whose text is fixed, define a variable, give it the
> >    value in syms_of_treesit using build_pure_c_string, then use that
> >    variable elsewhere in the source
> 
> Can I define a bunch of static C variables and initialize them in syms_of_treesit, or they have to be all Lisp variables? Eg,
> 
> static Lisp_Object TREESIT_STAR;
> 
> ...
> 
> void
> syms_of_treesit (void)
> {
> ...
> TREESIT_STAR = build_pure_c_string ("*");
> ...
> }

Yes, of course.  Look, for example, how coding.c does that:

  /* A string that serves as name of the reusable work buffer, and as base
     name of temporary work buffers used for code-conversion operations.  */
  static Lisp_Object Vcode_conversion_workbuf_name;
  [...]
  void
  syms_of_coding (void)
  {
  [...]
    staticpro (&Vcode_conversion_workbuf_name);
    Vcode_conversion_workbuf_name = build_pure_c_string (" *code-conversion-work*");

But please keep the convention of naming such variables Vsome_thing,
both regarding the "V" and the fact that the name is otherwise
lower-case.

Thanks.