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SchOS/.claude/memory/schunix-linux-open-flags.md
Nexoniarz a1c965da1e include: one folder per subsystem, and includes that name it 
Sixty-five headers sat side by side in include/, so `#include "irq.h"`
said nothing about where irq.h was or what it belonged to, and errno.h,
stat.h and fcntl.h at the top shadowed the system's for any host tool
built with -I./include. They are in folders now -- arch/ core/ fs/
dev/ gfx/ net/ uapi/ (and ldls/ for the Linux driver layer) -- and
every include names the folder, as Linux's do: "core/proc.h".

Done mechanically and checked the hard way: the kernel built from this
tree disassembles identically to the one built from the tree before
it. The full image boots, and userland is the same set of programs.
Paths in docs and comments follow; docs/guides/layout.md has a table
of what is where, and tools/fix-includes.py rewrites old-style
includes from the folders in the tree, for code written before this.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
2026-10-23 15:05:12 +02:00

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name description metadata
schunix-linux-open-flags include/uapi/fcntl.h must hold Linux's open-flag values — the userland is all Linux-ABI, and a mismatch silently corrupts files
node_type type originSessionId modified
memory project a665e14b-86bd-4b41-a228-51377f3e9225 2026-08-03T13:59:19.392Z

include/uapi/fcntl.h holds Linux x86-64 open-flag values, and must keep holding them. Every program in the userland is built against a libc that sends Linux values; the kernel reads them with these constants. Do not "tidy" them into a neat sequence — they are an external interface.

They disagreed until 2026-08-03, and the symptoms looked like filesystem corruption rather than a header mistake:

  • Linux O_APPEND (0x400) landed on Schunix's O_TRUNC, so cmd >> file truncated the file it was supposed to extend.
  • Linux O_TRUNC (0x200) landed on O_CREATE, so cmd > file did not truncate and left whatever was past the new end in place.

Found by making tools/bootcheck.ps1 do ordinary shell work — write a file, append to it, wc -c the result — instead of only booting to a prompt. The byte count was the only thing that said which failure had happened. See schunix-verify-by-driving-shell.

Two related traps fixed at the same time, both worth re-checking after any syscall work:

  • sys_openat silently dropped O_TRUNC and O_APPEND while sys_open honoured both, so the same redirection behaved differently depending on which entry point libc called. Any flag handled in one must be handled in both.
  • rmdir was NO_LINUX in kernel/sys/table.inc, so every Linux-ABI program got ENOSYS. A syscall with no Linux number is unreachable from userland — see schunix-syscall-single-table.