gh-89886: Use Autoconf quadrigraphs where appropriate

[erlend-aasland]

• Issue: Improve and simplify configure.ac checks #89886

[erlend-aasland]

@corona10 are you ok with this? In my editor (Vim), this fix is very helpful, not specifically because of the highlighting, but also because it enables Vim to correctly recognise closing parentheses and brackets. This makes hacking Autoconf way easier, since I can quickly verify opening/closing brackets and parentheses using the % char.

[corona10]

Yeah yeah, I understood what you intended. I have the same issue with my vim editor.
What do you think about writing documentation for configure.ac?
Now some semantics is not intuitive to the unfamiliar user. But if the documentation exists, it would be helpful to write new things or maintain the configure.ac

[erlend-aasland]

What do you think about writing documentation for configure.ac?

I don't think we need to maintain our own Autoconf docs; the GNU Autoconf docs are well written and full of good examples.

[vstinner]

The code correctly works as expected. %:@include is surprising and looks specific to autotools, whereas C uses #include. The benefit is to fix syntax highlight? I'm not convinced that it's worth it.

@corona10 are you ok with this? In my editor (Vim), this fix is very helpful, not specifically because of the highlighting, but also because it enables Vim to correctly recognise closing parentheses and brackets. This makes hacking Autoconf way easier, since I can quickly verify opening/closing brackets and parentheses using the % char.

Well, that was just my opinion. Now it's up to you. You're way more active on changing configure than me :-)

[erlend-aasland]

Now it's up to you. You're way more active on changing configure than me :-)

Thanks for you input. I'll abide with Dong-hee's final word on this :)

I won't repeat my arguments as to why I think this is worth it (see #105226 (comment)), but (surprise, surprise) I still would like to land this :) An alternative could be to make sure strings including # are not followed by a closing bracket (quote) on the same line, however such a PR will introduce a larger diff to configure.ac, and it will also introduce changes to the generated configure file; I don't think that alternative is a better choice. This PR was designed to not alter the generated configure file, in order to keep the amount of churn to a minimum. IMO, it is an improvement to status quo.

[corona10]

Okay, let's go.
From my conservative view it is +0.5.. but doing something is always better than doing nothing.
Someone may complain but soon adapt to a new convention.

[erlend-aasland]

Someone may complain but soon adapt to a new convention.

As I said in #105226 (comment), there is already precedent for using quadrigraphs in configure.ac (we already do for stuff like brackets) ;)

Thanks, both!

[miss-islington]

Thanks @erlend-aasland for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

[miss-islington]

Sorry @erlend-aasland, I had trouble checking out the 3.12 backport branch.
Please retry by removing and re-adding the "needs backport to 3.12" label.
Alternatively, you can backport using cherry_picker on the command line.
cherry_picker 27c68a6d8f20090310450862c2c299bb7ba3c160 3.12

[bedevere-bot]

GH-105423 is a backport of this pull request to the 3.12 branch.