They have to be numbered sequentially throughout the document:
https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor350
They're also not allowed to have titles, but maybe a stable tag would be acceptable

Making stable hyperlinks into the unstable draft is a non-goal IMHO. Paragraph numbers are unstable too, it's just a smaller problem because the numbers are relative to a specific subclause. Maybe the html generator software could create its own IDs for footnotes based on the subclause tag and paragraph number. The html anchor didn't have to be based on the footnote number used in the PDF.

They have to be numbered sequentially throughout the document:
https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor350
They're also not allowed to have titles, but maybe a stable tag would be acceptable

Ah, I should have guessed that the ISO straightjacket might be an obstacle here, too. ;) Thanks for the link.

Making stable hyperlinks into the unstable draft is a non-goal IMHO. Paragraph numbers are unstable too, it's just a smaller problem because the numbers are relative to a specific subclause.

That makes it not just a marginally smaller problem, but a vastly smaller problem. Vastly reducing problems seems like a worthwhile goal.

Maybe the html generator software could create its own IDs for footnotes based on the subclause tag and paragraph number. The html anchor didn't have to be based on the footnote number used in the PDF.

Well, right now if you see a link like https://eel.is/c++draft/basic#footnote-19, but you prefer the PDF, you can tell just from the URL where you need to go in the PDF without having to visit eel.is/c++draft. The links are not tied to the website.

This is really useful, because it also means that one can freely use eel.is/c++draft links in messages (e.g. on a mailing list) without worrying that the link will become meaningless if the website eventually goes down.

Introducing new IDs for the anchors would break that important property, which is why I'm very reluctant to do it.

Introducing new IDs for the anchors would break that important property, which is why I'm very reluctant to do it.

You could do something like https://eel.is/c++draft/basic#officialfootnote-19-stablefootnote-12, although if you want that to work stably, you would need to use some JS to update document.location if the officialfootnote-N component is stale.

What if the HTML generator software would number footnotes sequentially from the start of each paragraph, so that the link would look like https://eel.is/c++draft/basic#def.odr-3-footnote-1 ?

There is rarely more than one footnote per paragraph, so that both helps with external links as well as stability.

In general, we tend to avoid footnotes in favor of notes for new text, but there's of course so much legacy.

What if the HTML generator software would number footnotes sequentially from the start of each paragraph, so that the link would look like https://eel.is/c++draft/basic#def.odr-3-footnote-1 ?

Problem is, if the link looks like that but we don't also number footnotes that way in the PDF, then someone who sees that link in a mailing list post and who is using the PDF (either because they just prefer the PDF or because eel.is is down) will go looking for footnote 1 in that section, but footnote 1 won't be there because the footnote numbering in the PDF will be something else.

You could do something like https://eel.is/c++draft/basic#officialfootnote-19-stablefootnote-12

Verbose as that is, at this point I'm desperate enough to consider it a serious option! Thanks for the suggestion, I'll think about it. :)

What if the HTML generator software would number footnotes sequentially from the start of each paragraph, so that the link would look like https://eel.is/c++draft/basic#def.odr-3-footnote-1 ?

Problem is, if the link looks like that but we don't also number footnotes that way in the PDF, then someone who sees that link in a mailing list post and who is using the PDF (either because they just prefer the PDF or because eel.is is down) will go looking for footnote 1 in that section, but footnote 1 won't be there because the footnote numbering in the PDF will be something else.

There will likely be at most one footnote in that paragraph. If you want to optimize for the 99% case, you can make the link look like https://eel.is/c++draft/basic#def.odr-3-footnote instead and avoid any reference to the footnote number.

Oh, you mean you'd simply deem it acceptable that the user is told the wrong footnote number. I guess that's one way of solving the problem. :D

To make that a little bit more palatable, I could perhaps use explicitly written out ordinals, e.g. http://eel.is/c++draft/ding.dong#second-footnote. Having the "second footnote" on a page be footnote 124 seems more tolerable than having "footnote 2" on a page be footnote 124.

The numbers are way off to be confused, I believe.

They have to be numbered sequentially throughout the document:
https://www.iso.org/sites/directives/current/part2/index.xhtml#_idTextAnchor350
They're also not allowed to have titles, but maybe a stable tag would be acceptable

Well I wouldn't want to propose inventing stable tags for footnotes, because that sounds like a lot of work for something insignificant.

So maybe there's nothing reasonable that can be done, in which case this ticket can of course be closed.

Thanks for brainstorming with me! I'll figure something out for cxxdraft-htmlgen. :)