bug#71681: 29.3.50; tree-sitter crash

[Yuan Fu]

> On Jun 23, 2024, at 10:38 AM, Juri Linkov <juri@linkov.net> wrote:
> 
>>> Evaluating this expression causes a crash:
>>> 
>>> (progn
>>> (find-file (expand-file-name "src/treesit.c" installation-directory))
>>> (c-ts-mode)
>>> (font-lock-ensure 63209 63387))
>>> 
>>> in latest master, but not in latest emacs-29 (only in 5-months old 
>>> emacs-29).
>>> 
>>> If this is not reproducible, I could provide more details.
>>> 
>>> libtree-sitter is at the latest version.
>> 
>> Hmm, I can’t reproduce with latest master and libtree-sitter. Maybe you can 
>> send me the exact commits that you used?
>> 
>> Here’s mine:
>> 
>> Emacs: 72f2b01e318
>> Tree-sitter: 6ec478c1
> 
> Probably reproducibility depends on the content of the src/treesit.c file.
> Then the most reliable way to reproduce it is this:
> 
> 0. emacs -Q
> 1. eval: (add-to-list 'major-mode-remap-alist '(c-mode . c-ts-mode))
> 2. C-x v L
> 3. in the *vc-change-log* buffer move point to the commit 20af58d3a13
> 4. type D
> 5. crash caused by diff-font-lock-syntax fontification that uses treesit
> 
> The numbers in (font-lock-ensure 63209 63387) above were extracted
> from diff hunk boundaries that might be different when the file was edited.

I reproduce it once with the first set of commits you provided, but for some 
reason couldn’t reproduce it again. I’m sure it’s something wrong that I did. 
I’ll report back when I make progress. TBH it seems like something wrong with 
tree-sitter itself, but I’ll make sure to figure out what’s the problem exactly.

Yuan