fix(libc): support FreeBSD wide printf conversions

[MarcZX10]

What

Fixes #5293. The wide printf family now accepts FreeBSD's q length modifier and %D, %O, and %U conversions, prints unknown conversion characters with their width, and stops cleanly at a trailing %. The secure snwprintf_s path continues rejecting these extensions. The tests cover surrogate-pair and lone-surrogate conversion characters as well.

The two upstream implementation commits retain Hussein Kadhim as their author. A separate test-placement commit is authored by MarcZX100.

Tested

• Debian 12, Linux x86_64, GCC 12.2: guest_wide_formatting and guest_formatting passed (2/2).
• Conventions check and git diff --check passed.
• The issue report includes Windows builds and FreeBSD differential testing; no Windows or FreeBSD local run.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw; silent stubs are listed under technical debt
• No notes, investigation .md files or images added to the repository
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• Unblocks: none
• GPUs tested: n/a
• AI-assisted: yes

[oneandonlydean]

Which title prints %q, %D/%O/%U, an unknown conversion or a trailing % through the wide printf family? The source here is FreeBSD 11.4, but the console's libc.prx formats through Dinkumware's _Printf, which can handle unknown conversions and q differently (same question as the review on #3987). Until a title reaches it, or _Printf in a title's libc.prx confirms these cases, main's throw is the safer behaviour.

[MarcZX10]

I do not have title traces or Dinkumware _Printf evidence for these wide-format cases. The current evidence is FreeBSD 11.4 behavior and Linux-side tests, so I cannot claim console compatibility for %q, %D/%O/%U, unknown conversions, or a trailing %. I agree this leaves the added behavior unverified against the console; absent title or _Printf evidence, main’s throw is safer. I will avoid presenting these cases as title-required until we have that evidence.

[adriadam10]

Thanks for the fix. Blocking points:

• The console's libc.prx formats through Dinkumware's _Printf, not FreeBSD's vfwprintf. As discussed above, neither a title nor _Printf evidence shows that %q, %D/%O/%U, unknown conversions (with width) or a trailing % behave as FreeBSD 11.4 does there; main's throw is the safe behaviour until then. Evidence that would unblock it: the relevant branches of _Printf disassembled from a title's libc.prx (same approach as in #3987), or a title that reaches these cases.
• Once evidence exists, the branch conflicts with main in core/libs/tests/GuestWideFormatting.cpp; it needs a rebase.

[github-actions]

Some comparisons could not be completed because a pull request conflicts with the base branch. Review these shared files manually before concluding that there is no overlap.

Pull request	Shared files not compared
PR 3965	docs/dev/debt/libc.md
PR 5021	docs/dev/debt/libc.md
PR 6044	core/libs/tests/GuestWideFormatting.cpp
PR 6226	docs/dev/debt/libc.md
PR 6334	docs/dev/debt/libc.md
PR 6345	docs/dev/debt/libc.md
PR 6469	docs/dev/debt/libc.md
PR 6541	docs/dev/debt/libc.md
PR 6565	docs/dev/debt/libc.md
PR 6610	docs/dev/debt/libc.md
PR 6686	docs/dev/debt/libc.md
PR 6707	docs/dev/debt/libc.md
PR 6713	docs/dev/debt/libc.md
PR 6819	docs/dev/debt/libc.md
PR 6842	docs/dev/debt/libc.md
PR 6975	docs/dev/debt/libc.md
PR 6985	docs/dev/debt/libc.md
PR 7039	docs/dev/debt/libc.md
PR 7081	docs/dev/debt/libc.md
PR 7332	docs/dev/debt/libc.md
PR 7386	docs/dev/debt/libc.md
PR 7411	docs/dev/debt/libc.md
PR 7417	docs/dev/debt/libc.md
PR 7447	docs/dev/debt/libc.md
PR 7473	docs/dev/debt/libc.md
PR 7506	docs/dev/debt/libc.md
PR 7525	docs/dev/debt/libc.md
PR 7529	docs/dev/debt/libc.md
PR 7544	docs/dev/debt/libc.md
PR 7545	docs/dev/debt/libc.md
PR 7546	docs/dev/debt/libc.md
PR 7634	docs/dev/debt/libc.md
PR 7648	docs/dev/debt/libc.md

[MarcZX10]

Thanks for the detailed blocking review. I have no new title trace or Dinkumware _Printf evidence, so the current FreeBSD/Linux results still do not justify claiming console behavior. I’ll leave the PR unrebased until that evidence exists; the relevant _Printf branches or a title reaching these conversions remain the needed next step.