References to C23 (ISO/IEC 9899:2024) clause still use C17 clause numbers

[morinmorin]

Many references to C23 clauses haven't been updated and still use C17 clause numbers.

For example, in [charconv.from.chars] p7,

See also: ISO/IEC 9899:2024, 7.22.1.3, 7.22.1.4

needs to be updated to

See also: ISO/IEC 9899:2024, 7.24.2.6, 7.24.2.8

These clause numbers are taken from N3299 (often referred to as the C23 working draft). I believe they match the official ISO/IEC 9899:2024 clause numbers, but I'd appreciate it if someone could verify that N3299's clause numbers match those of ISO/IEC 9899:2024 exactly (down to the lowest-level subclause).

[jensmaurer]

Do you have a full list of offenders?

[frederick-vs-ja]

I've already verified these and opened a PR to fix the bugs.

[morinmorin]

@frederick-vs-ja
I also confirmed that #8113 (and #8111) are correct. Amazing job — that must have been really tough!

[morinmorin]

During migrations to a newer C version, mixing clause numbers from different C versions force contributors to first determine which version each number refers to. Making the version explicit at the point of use reduces friction and enables semi-automatic checks for future migrations.

A. Require an explicit "C version tag" at each \xrefc use (recorded only in source, not typeset):
Add one argument to \xrefc so it can be invoked as \xrefc{1.2.3}{C23}. The added argument exists solely to record a C version tag and is not used for typesetting.

% current
\newcommand{\xrefc}[1]{\xref{\IsoC{}, #1}}

% proposed — the second parameter is a C version tag
\newcommand{\xrefc}[2]{\xref{\IsoC{}, #1}}

If WG14 provides stable names, the extra argument can be removed.

B. Cover references that don't use \xref:
Provide an \xrefc macro variant without the "see also:" prefix, so a macro can be used even for cases like in \IsoC{}, 1.2.3. Alternatively, add an optional argument to \xrefc (defaulting to "see also:") to cover both forms.