bug#75226: [31.0.50] C++ ts-mode missing "alignof" as keyword

[Yuan Fu <casouri@gmail.com>]

> On Jan 1, 2025, at 10:41 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> Cc: 75226@debbugs.gnu.org
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Wed, 1 Jan 2025 19:28:35 -0800
>> 
>> 
>> 
>>> On Dec 31, 2024, at 8:01 AM, Jacob Faibussowitsch <jacob.fai@gmail.com> wrote:
>>> 
>>> C++ ts-mode is missing “alignof” as a builtin keyword like sizeof.
>>> 
>>> Best Regards,
>>> 
>>> Jacob Faibussowitsch
>>> (Jacob Fai - booss - oh - vitch)
>>> 
>> 
>> Thanks for reporting this. It seems tree-sitter-c/cpp supports '__alignof__', '__alignof', '_alignof', 'alignof', ‘_Alignof’, I can add all of them as keywords. The feature is added in tree-sitter-c in Aug 9, 2023 [1], and appears in v0.20.5.
>> 
>> Eli, what’s the status of Emacs 30 right now? Can I push to emacs-30 and have this change queued for Emacs 30.2? Or should I wait a bit?
> 
> If this just adds a bunch of strings to c-ts-mode--keywords, it's okay
> to add them on emacs-30.

Not quite, right now emacs-30’s c-ts-mode works with grammar as far back as v0.19.0 [1]. If we just add the keywords, c-ts-mode wouldn’t work with grammar v0.20.4 and earlier. So I’m going to add the new keywords with a check, which disables the new keywords if grammar doesn’t recognize them. Also there’re many missing keywords, none of which I have seen before :-), I need time to go over them and see how are they supposed by be fontified (keyword face or something else).

So let’s wait for 30.2.

[1] It might work with even earlier versions but I didn’t test, v0.19.0 (4 years ago) is the earliest version that still has compatible LANGUAGE_VERSION (13) with the latest tree-sitter lib.

Yuan