nexoniarz/SchOS
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SchOS/.claude/memory/schunix-console-tty.md
Nexoniarz 3182da3965 Carry project memory in the repo, with tools/memory-sync.sh 
Claude Code keeps per-project memory at <home>/.claude/projects/<key>/,
where <key> is the project's absolute path with every separator and the
drive colon turned into a dash. That makes it both rename-fragile and
machine-specific, and this project has hit each of those once:

  - D:\DEV\Schunix -> D:\DEV\SchOS changed the key, and 43 memories were
    invisible until moved across by hand.
  - Development happens from Windows and from Linux, and each looks in a
    different place for the same checkout.

Committing .claude/memory/ fixes both -- git carries it across renames
and between hosts -- and `import` puts it wherever the local machine
expects. .claude/settings.local.json stays ignored: those are per-machine
permissions.

The colon maps to a dash rather than being dropped. Deleting it gives
D-DEV-SchOS, which matches nothing and silently finds zero memories; that
was the first attempt. On Git Bash the key comes from `cygpath -w`,
because Claude Code is a Windows program and sees D:\DEV\SchOS, not
/d/DEV/SchOS.
2026-08-09 14:27:22 +02:00

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name description metadata
schunix-console-tty The console has an ANSI parser, real termios and UTF-8; the font is CP437 not Latin-1, and five bugs that looked like broken commands
node_type type originSessionId modified
memory project a665e14b-86bd-4b41-a228-51377f3e9225 2026-08-04T21:10:44.835Z

kernel/core/console.c was rewritten on 2026-08-04: ANSI escape parser, real termios, signals, and UTF-8.

The serial line and the framebuffer are treated differently on purpose. Escapes are passed through to serial verbatim -- a real terminal emulator is on the other end and understands them better than we ever will -- and interpreted only for the framebuffer. So a serial transcript can never tell you whether the escape parser works; it holds the raw bytes either way. Use pwsh -File tools/ttyshot.ps1, which drives colour/cursor/erase/UTF-8 and screendumps the result.

The font is CP437, not Latin-1. include/font.h's per-glyph comments label index N with Unicode codepoint N, which is fiction above 127: index 0xE9 is annotated "e-acute" and draws a capital theta. Trusting it turned "café" into "caf" + theta. console.c maps Unicode through latin1_to_cp437[] plus a small table of box-drawing characters. Verify glyphs by rendering the bitmap, never by reading the comment.

font_data was also declared [128][16] while containing 256 glyphs, so the compiler silently discarded the entire upper half -- the wall of "excess elements in array initializer" warnings was that.

Five bugs that all presented as broken commands, none of which were:

  • ls /bin | wc -l said 48 instead of 240 -- sys_ioctl answered every unrecognised request with 0, so TIOCGWINSZ on a pipe "succeeded" and every program thought pipes were terminals. It returns -ENOTTY now. isatty() is built on this call, so the blast radius was everything.
  • yes | head -2 failed with "Invalid argument" -- readv/writev capped iovcnt at 16 (POSIX's minimum) and toybox's yes builds 256. Now UIO_MAXIOV = 1024, Linux's value.
  • cat big | head -c 4 killed the shell at rip 0x1 -- SIG_IGN is handler value 1, and deliver_signals() only skipped 0 (SIG_DFL), so it jumped to address 1. Nothing sent SIGPIPE until pipes learned to, at which point every shell that ignores SIGPIPE died.
  • Pipes returned a bare -1 with no signal on a closed read end; now SIGPIPE plus -EPIPE.
  • Ctrl-C did proc->killed = 1, and proc in an interrupt handler is whatever was running on that CPU -- almost never the foreground job. It sends a real SIGINT to tty_fg_pgrp now.

Control characters must never reach the glyph path. vga_putc had no tab case, so '\t' fell through to vga_draw_char(9) -- CP437 glyph 9 is a hollow circle, so pressing Tab printed a circle. The font has a picture for every control code and none of them is what the character means. Tab now advances to the next eight-column stop (erasing as it goes, so it overwrites rather than skipping); everything else below 0x20 is dropped.

termios is real: TCGETS returns what was last set, TCSETS is honoured, and the console implements ICANON, ECHO, ECHOE, ECHONL, ISIG, ICRNL, INLCR, IGNCR, ISTRIP and VMIN. Raw mode returns bytes as they arrive rather than waiting for a newline -- that is what zsh and any line editor need. EOF is a flag, not a ^D byte stuffed into the buffer.

Check with pwsh -File tools/bootcheck.ps1 -Tty (six assertions, including a real Ctrl-C against a running sleep). See schunix-verify-by-driving-shell and schunix-tty-fg-pgrp-coupling.