[Danigamer05]

What

Add the ten missing stdc_leading_zeros_{uc,us,ui,ul,ull} and stdc_trailing_zeros_{uc,us,ui,ul,ull} libc exports. They return the zero-bit run before the highest set bit or after the lowest set bit, using C++20 std::countl_zero and std::countr_zero. Zero returns the argument's width: 8, 16, 32, 64 or 64. The guest ul argument is explicitly 64-bit on Windows. Each export has one public declaration and its own regression case.

Contract evidence is PPSA03671 v01.001.005's bundled libc.prx (SHA256 483961e086b8a1fffa8138b3c0badf798987fb5f35ec908d828946408be2d8a6), read from disassembly and run directly on a Windows host. All ten functions are call-free leaves. The signatures and semantics also follow C23 draft N3220, sections 7.18.3 and 7.18.5 and the LLVM libc stdbit declarations.

Export	NID	Input bits	Original RVA
stdc_leading_zeros_uc	GEWnLZqp9Hk	8	0x303f0
stdc_leading_zeros_us	7FB0t5y2r6A	16	0x30400
stdc_leading_zeros_ui	pkc1bZWixqw	32	0x30410
stdc_leading_zeros_ul	bJLACmBx3bI	64	0x30420
stdc_leading_zeros_ull	UO464WICdrU	64	0x30430
stdc_trailing_zeros_uc	chy93WuEyPw	8	0x30490
stdc_trailing_zeros_us	xRF+BzlARZo	16	0x304a0
stdc_trailing_zeros_ui	XS0cqoqWgNY	32	0x304b0
stdc_trailing_zeros_ul	jMnJyLF8kPk	64	0x304c0
stdc_trailing_zeros_ull	jqsveb-7TE4	64	0x304d0

No original binary, byte dump, third-party source, investigation notes or logs are committed. The remaining console-verification gap is recorded in libc's debt file.

Tested

Runtime-tested head: dc3999b2747bf068c0e229b0281cfc903dafaa0e, based on main 61924d4637aaaeab35bc7ba3e4d3156f9ebd025d. Published head: 504111f10c8bc83a8a9ae36a85bdd03c124528b5, based on main 19f71094a71751d5026bc2452452bb539979b463 (28 October 2026).

After the runtime tests, main received other libraries' implementation changes, regression tests, documentation and the import-audit tool update. All libc production sources, headers, CMake and the focused regression sources are byte-identical between the runtime-tested and published heads. The runtime and native-comparison results below belong to the stated tested head. Conventions, whitespace, strict main synchronization and the overlap comparison were checked on the published head.

• Windows 11 / WinLibs MinGW-w64 GCC 15.2.0 and Ubuntu 24.04 WSL / GCC 13.3.0, Release, existing full-project configurations: rebuilt production libc, guest_zero_runs_tests and guest_integer_builtins_tests. ctest --test-dir build -R "^(guest_zero_runs_(leading|trailing)_(uc|us|ui|ul|ull)|guest_integer_builtins|public_headers)$" -V --output-on-failure passes 12/12 on each platform on the runtime-tested head above. Windows also rebuilt the NID-patched production libc used below.
• The ten cases check zero/all-ones, every single-bit and two-bit position, complements and guest errno preservation. The reference examines bit positions without using the production counting primitives. Every 8- and 16-bit input is covered in both directions; each wider export also gets 100,000 deterministic random inputs and their complements. Each case has a separate 20-second timeout.
• Negative control on Windows before the main refresh: all ten cases fail with all new bodies replaced by NotImplemented_nid_no_patch(__func__), and pass after restoring production with the identical test executable (SHA256 0f7038460d5712c81723c5abcce8331028894ec89448dae93875c12f591b8509). Production bodies and test assertions are byte-identical after the refresh; the complete focused selection and native comparison were rerun on the runtime-tested head above.
• Direct original-versus-production comparison on Windows: 269,763 input vectors, 2,697,630 original calls and 2,697,630 production calls, zero mismatches, also checked against an independent bit-position reference. Production is reached through all ten patched NIDs; the names were independently hashed and resolved in the original dynamic export table. Only the ten original call-free leaves were executed from mapped load segments; no original initialization, relocation, other export or title execution was performed. This is host evidence, not a console measurement.
• Earlier same-day baseline evidence on main cccdaa2734a71d27e6c907325c60fdf2d3baf0af: guest_integer_builtins and public_headers passed 2/2 on Windows and Ubuntu during the count-zeros investigation. That baseline evidence is reused, with no new baseline run claimed. Libc production, headers, CMake and the existing integer regression are byte-identical between that base and the current main; the focused checks and native comparison were rerun on the stated runtime-tested revision.
• Conventions, PR whitespace and strict main synchronization pass: one commit ahead, zero behind the stated main. No new dependency or comments in code.
• Required official full overlap scans were followed by an incremental update on the published main base, covering all 1357 open PR heads. Classifications of unchanged PR heads that shared no relevant file/export were reused; 5 new/updated heads were probed and 164 shared branches were normalized again using the official comparison functions. No confirmed line, export or new-file overlap and no duplicate exports on main. 39 already-conflicting branches could not be fully compared: feat(aot): consolidate native ARM64 compiler, runtime and consumers #5021, feat(libc): export _FDsign/_Dsign like MSVC CRT (PPSA34015) #6085, fix(libc): use the default heap for an executable without process parameters #6713, fix(libs): share Sony CRT handler and lconv state between libc and libSceAmpr #7081, feat(libc): scan 16-bit wide conversions on Linux #7386, feat(libc): support archive-backed stdio reads #7447, feat(libc): implement std::_Throw_C_error #7648, fix(libc): provide ASOBI_ROOT environment variable for title path resolution #7715, fix(libc): support character reads from random device streams #8150, feat(libc): implement fesetenv #8937, fix(libc): follow a Windows symbolic link before .. in a guest path #9371, feat(libc): add the std::__sce_v2 thread start, timed wait, clock and processor count calls #9447, feat(libc): add std::__sce_v2::_Random_device, _Fiopen and setw #9526, fix(libc): count clock() as the process time, like the console #9677, test(libc): cover the unwind context accessors #9775, fix(libc): compute tanhf with FreeBSD msun's algorithm, as titles' libc.prx does #9867, fix(libc): restore syslog program-name fallback #9929, fix(libc): compute expf with FreeBSD msun's algorithm, as titles' libc.prx does #10113, fix(libc): compute expm1f with FreeBSD msun's algorithm, as titles' libc.prx does #10222, fix(libc): compute erff and erfcf with fdlibm's algorithm, as titles' libc.prx does #10226, fix(libc): compute atan and atan2 with FreeBSD msun's algorithm, as titles' libc.prx does #10229, fix(libc): compute log with FreeBSD msun's algorithm, as titles' libc.prx does #10245, fix(libc): compute log10 with fdlibm's algorithm, as titles' libc.prx does #10247, fix(libc): compute sin, cos and tan with FreeBSD msun's algorithm, as titles' libc.prx does #10250, fix(libc): compute asin and acos with FreeBSD msun's algorithm, as titles' libc.prx does #10253, fix(libc): compute pow with fdlibm's algorithm, as titles' libc.prx does #10265, feat(libc): track stream orientation and implement fwide #10324, fix(libc): compute remainder and remquo with fprem1, as titles' libc.prx does #10349, fix(libc): open a directory with freopen in a read mode on Windows #10433, fix(libc): reopen a stream onto /dev/random or /dev/urandom with freopen #10620, fix(libc): bound narrow formatting fields #11332, feat(libc): implement fcloseall with tracked stream lifetimes #11831, feat(libc): implement freezero #11848, fix(libc): return an aligned empty block from reallocalign to 0 bytes #11850, fix(libc): reject a malloc_stats_fast block that is not size 0x28 version 1 #11870, feat(libkernel): cancel blocked POSIX reads safely #11872, feat(libkernel): cancel blocked POSIX writes safely #11969, fix(libc): compute _FSinh as titles do #12053, fix(libc): compute cosh with fdlibm's algorithm, as titles' libc.prx does #12122. Their shared-file changes were inspected from their own merge bases; none adds these ten names/NIDs or their test. Those stale branches are not claimed merge-clean.
• This contribution, count-ones feat(libc): add C23 count-ones exports #11663 and count-zeros feat(libc): add C23 count-zeros exports #12187 normalize onto the same main and merge cleanly in all six orders, producing the same content tree with each of the twenty exports declared and defined once. They are independent. This is a content check; the combined tree was not runtime-tested.

The full CTest suite, all standalone-header compilation batches, macOS, console, title and GPU execution were not tested. No performance or title-unblock claim.

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]

Progress report (09d952f → 504111f)

📈 System libraries: 46.6% (+0.04%, +10 implemented functions)

✅ 10 implemented

Library	Name
libc	stdc_leading_zeros_uc_nid_postfix
libc	stdc_leading_zeros_ui_nid_postfix
libc	stdc_leading_zeros_ul_nid_postfix
libc	stdc_leading_zeros_ull_nid_postfix
libc	stdc_leading_zeros_us_nid_postfix
libc	stdc_trailing_zeros_uc_nid_postfix
libc	stdc_trailing_zeros_ui_nid_postfix
libc	stdc_trailing_zeros_ul_nid_postfix
libc	stdc_trailing_zeros_ull_nid_postfix
libc	stdc_trailing_zeros_us_nid_postfix

Changed libraries (implemented exports)

Library	Before	After	Change
libc	1404/1417 (99.08%)	1414/1427 (99.09%)	+0.01 pp

[MarcZX10]

Independent exact-head review of 504111f10c8bc83a8a9ae36a85bdd03c124528b5: the ten exports use the correct width-specific C++20 operations, zero-input widths and ul 64-bit PS5 ABI; all ten NIDs independently match tools/nid_names.py. The public-header audit passes (368 libraries, 12,994 exports), conventions and diff checks pass, the merge preview against current main is clean, and both changed C++ files pass GCC 12 C++20 syntax-only compilation. The official overlap scan found no confirmed duplicate or code-line overlap; its 39 historical-branch warnings are confined to shared/conflicted files. I checked the warned PR diffs for these ten names; #5021 exceeds GitHub’s 300-file diff limit, but its paginated changed-file list and relevant CMake/debt hunks do not touch the new declarations or implementations. Author-reported exhaustive fixed-width/random tests and original-binary comparisons are detailed in the PR. Hosted policy checks, Linux/Windows/macOS relinker and register-context jobs, and macOS write-watch jobs pass; the full Windows build is still pending, while Linux full build is skipped by path selection. I found no code blocker in the review completed so far; I’m leaving this as a comment until the Windows build finishes.

[MarcZX10]

The full Windows build has now completed successfully on the same reviewed head 504111f10c8bc83a8a9ae36a85bdd03c124528b5; the earlier Linux/macOS relinker, register-context, write-watch, and policy checks also passed. My exact-head review found no code blocker, and the independent NID, public-header, convention, syntax, merge-preview, and overlap checks are recorded in my earlier review comment. Linux full build was skipped by path selection. I approve this revision.

[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 docs/dev/debt/libc.md
PR 6085	core/libs/prx/libc/CMakeLists.txt
PR 6713	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 7081	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 7386	docs/dev/debt/libc.md
PR 7447	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 7715	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 8150	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 8937	core/libs/prx/libc/CMakeLists.txt core/libs/prx/libc/include/Api.hpp docs/dev/debt/libc.md
PR 9371	docs/dev/debt/libc.md
PR 9447	docs/dev/debt/libc.md
PR 9526	docs/dev/debt/libc.md
PR 9688	docs/dev/debt/libc.md
PR 9775	core/libs/prx/libc/CMakeLists.txt
PR 9929	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 10253	docs/dev/debt/libc.md
PR 10324	core/libs/prx/libc/CMakeLists.txt core/libs/prx/libc/include/Api.hpp docs/dev/debt/libc.md
PR 10433	docs/dev/debt/libc.md
PR 10620	docs/dev/debt/libc.md
PR 11270	docs/dev/debt/libc.md
PR 11332	docs/dev/debt/libc.md
PR 11625	core/libs/prx/libc/CMakeLists.txt docs/dev/debt/libc.md
PR 11849	docs/dev/debt/libc.md
PR 11872	core/libs/prx/libc/CMakeLists.txt core/libs/prx/libc/include/Api.hpp docs/dev/debt/libc.md
PR 11892	docs/dev/debt/libc.md
PR 11969	core/libs/prx/libc/CMakeLists.txt core/libs/prx/libc/include/Api.hpp docs/dev/debt/libc.md
PR 12397	docs/dev/debt/libc.md
PR 12598	docs/dev/debt/libc.md
PR 12605	docs/dev/debt/libc.md