[StoneDC]

What

Adds independent guarded runtime coverage for C-locale UTF-16 transformation capacities. Capacity-zero, exact/short/larger destinations, returned full unit lengths and complete output when capacity suffices. It does not assert unspecified destination contents when capacity is insufficient.

Implementation basis: Calls the actual production function(s) through the canonical public Api.hpp; expected results derive from constructed inputs, snapshots, membership tables or standard C++ algorithms. Public contract: https://github.com/freebsd/freebsd-src/blob/833d39bd2e38421a14ea489a956261a0fa993fbc/lib/libc/string/wmemchr.3.

Known limits: Tests valid live spans and buffers only; no invalid-pointer or undefined-overlap behavior is added. No PS5/title execution or firmware object layout is inferred. Uses the existing char16_t declaration, not host wchar_t; code units are opaque and this is not Unicode validation or a width measurement. Only the existing/default C-locale contract is exercised, not other locale collation. Insufficient-capacity transformation bytes are not asserted.

Source/schema: core/libs/prx/libc/src/Strings.cpp core/libs/prx/libc/include/Api.hpp

Exact topic head ec2a173edd49e7f8ae7f91429ba04a70bcf2d9af is one independent commit on main da026c70655a132031d45e2008c24f993870d801. The current-main repository overlap checker against da026c70655a132031d45e2008c24f993870d801 reported no confirmed overlap. It could not finish comparisons for these older PRs already conflicting with main: #5021, #6085, #7081, #7447, #7715, #8150, #8965, #11628, #11661, #11689, #11698, #12688, #12700, #12965. Their shared-file diffs were reviewed separately. 12 scoped file changes projected onto main and then combined with this topic without a new conflict; 2 peer file changes already conflict with main and are not claimed automatically mergeable. They do not provide this command or test matrix. Registration uses a separate target/name and there is no landing-order dependency. Changes to shared registration before landing need a refreshed merge/test check. Depends on: none. The twenty current topic heads are also merged into tested integration 3990a2bd7e0abeaaeeef963a30a3d6508d9b5be3.

Tested

Topic head: ec2a173edd49e7f8ae7f91429ba04a70bcf2d9af. Combined integration: 3990a2bd7e0abeaaeeef963a30a3d6508d9b5be3, based on main da026c70655a132031d45e2008c24f993870d801. Ubuntu/WSL GCC 15.2, CMake 4.2.3, Python 3.14.4; Windows MinGW GCC 15.2, CMake 4.3.1, Python 3.14.3.

The registered test calls the actual libc through canonical headers, using OS-protected pages and real input/output buffers. A separate exact-head control compiled the whole relevant production source unit with this fixture: unchanged production code passed, and the fixture rejected an intentional production-function defect. This is a source-unit control, separately from the product build below.

Registered CTest guest_wide_transform_boundary passed on Linux and Windows as part of the filtered twenty-topic run: ctest --test-dir <build> -R <20-topic-pattern> -j 8 -V --output-on-failure, 20/20 passed on each platform, zero skips. cmake --build <linux-full-build> --parallel 8: complete default Linux product build passed. Windows used the full configuration and built the sixteen affected libc test targets plus relinker with --parallel 8; a complete default Windows build is not claimed. Conventions, whitespace, script registration and the public-header declaration/umbrella audit passed. No PS5, title or GPU validation run is claimed. macOS, WASM execution and hosted full-build CI are not reported as passed.

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 (NotImplemented_nid_no_patch); silent stubs are listed under Silent stubs in their library's technical debt file
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• Fixes: none
• Unblocks: none
• GPUs tested: n/a
• AI-assisted: yes

[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 5021	core/libs/prx/libc/CMakeLists.txt
PR 6085	core/libs/prx/libc/CMakeLists.txt
PR 7081	core/libs/prx/libc/CMakeLists.txt
PR 7447	core/libs/prx/libc/CMakeLists.txt
PR 7715	core/libs/prx/libc/CMakeLists.txt
PR 8150	core/libs/prx/libc/CMakeLists.txt
PR 8965	core/libs/prx/libc/CMakeLists.txt
PR 10324	core/libs/prx/libc/CMakeLists.txt
PR 11628	core/libs/prx/libc/CMakeLists.txt
PR 11661	core/libs/prx/libc/CMakeLists.txt
PR 11689	core/libs/prx/libc/CMakeLists.txt
PR 11698	core/libs/prx/libc/CMakeLists.txt
PR 12688	core/libs/prx/libc/CMakeLists.txt
PR 12700	core/libs/prx/libc/CMakeLists.txt
PR 12965	core/libs/prx/libc/CMakeLists.txt

[adriadam10]

Closing: this PR does not match its description, and it duplicates #13387.

• The title and body describe C-locale UTF-16 transformation capacities (citing wmemchr.3), but the diff only adds core/libs/tests/GuestStrnstrBoundary.cpp and the guest_strnstr_boundary registration in core/libs/prx/libc/CMakeLists.txt. It contains no UTF-16 or transformation test; it tests strnstr_nid_postfix.
• The added lines are identical to those of test(libc): bound substring searches at protected pages #13387, opened by the same author seconds earlier, with the same file and ctest name. Both cannot land, and test(libc): bound substring searches at protected pages #13387 already carries the correct title.

The UTF-16 transformation test described here is not in the PR. You are welcome to reopen, or open a new PR, with the test that matches the description.