[MarcZX10]

What

Carry Hussein Kadhim's getdirentries basep fix onto current main, preserving his commit author. Windows now reports the directory entry index at the start of a successful read and leaves basep unchanged on failure. The Linux path likewise writes basep only after a successful read. Add a Linux regression assertion that a too-small-buffer error leaves the caller's basep untouched.

Closes #5237.

Tested

• Linux: built guest_directory_entry_tests; guest_directory_entries passed (1/1).
• Linux: guest_directory and guest_fdopendir passed (2/2).
• The new Linux failure-path assertion fails against unchanged main and passes with this change.
• Linux: python3 tools/check_conventions.py --base upstream/main passed.
• The dedicated successful-offset regression target is Windows-only. Hussein's issue report records Windows builds and passing guest_directory_buffer, guest_directory and guest_fdopendir checks. I could not rerun the Windows target here: MinGW configuration stops because libgcc_s_seh-1.dll is unavailable.

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: fix(libkernel): fail getdents on a descriptor that is not open with EBADF #4999 (merge order for the shared libkernel.md debt entry; the runtime fix is independent)
• Unblocks: none
• GPUs tested: n/a
• AI-assisted: yes

[MarcZX10]

Commit history is now split by authorship: Hussein Kadhim’s original getdirentries fix remains its own commit, and my added Linux failure-path regression is a separate MarcZX100-authored test commit. Linux validation recorded in the PR remains unchanged; the latest conventions check is running.

[simonbronk]

On Windows this no longer builds once merged onto current main (cf5f5b53b), although Git merges it without conflicts (Windows 11 Pro 26200, WinLibs GCC 15.2.0 r7; AI-assisted: Claude Code):

core/libs/tests/GuestDirectoryBuffer.cpp:109:13: error: 'getdirentries_nid_postfix' was not declared in this scope

d31e28308 (fix(libkernel): throw for unsupported directory entry names) removed the then-unused getdents_nid_postfix, getdirentries_nid_postfix and __error_nid_postfix declarations from GuestDirectoryBuffer.cpp, and CheckBase here still calls getdirentries_nid_postfix. The test is registered only on Windows, so a Linux build does not compile it. A rebase that restores int APS5_VABI getdirentries_nid_postfix(int, char*, int, std::int64_t*); in the extern "C" block fixes it.

With that line restored, and #4999 also applied: guest_directory_buffer passes 20/20 and the full ctest passes. With this PR and #4999, guest_directory_entries (Linux-only today) also passes on Windows.

[oneandonlydean]

Closing: no title is known to reach this. With the queue at 700+ open PRs, please hold off on new PRs that don't name a title needing the change until it's down. If a title stops on this on current main, reopen with the title ID and the log line.