shoney.arickathil
ab8ef64cd9
- five stories under docs/stories/runtime-v2/: 1 streaming subprocess (42's follow-up; five forks incl. the mailbox-cap collision), 2 PTY, 3 signals-as-events (signalfd lean), 4 termios adoption, 5 SCM_RIGHTS fd passing; 00-story states the arc — the plane learned sockets in 8/11/35, files in 6, this adds processes/terminals/signals - build order 1 -> 2 -> 3; 4 and 5 startable alone; all readiness: refine, brainstormed on demand - board: Five tracks; "▸ runtime-v2" pending section; wmux section now points at it; graph section 6 nodes carry runtime-v2 numbers + links - wmux stories re-reference the track; prefix `rt2` claimed - linkcheck: 0 broken Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> (cherry picked from commit e0451cb4889bb3d03429c0276d03c090269a5ced)
47 lines
1.9 KiB
Markdown
47 lines
1.9 KiB
Markdown
---
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track: runtime-v2
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iteration: "2"
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status: pending
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readiness: refine
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---
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# runtime-v2 2 — PTY: a child that believes it owns a terminal
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> Part of [Story — runtime-v2: the runtime beyond sockets](00-story.md).
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> After [1](01-streaming-subprocess.md): a streaming child whose stdio
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> is a pseudo-terminal instead of pipes. A shell run over pipes disables
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> its prompt, its line editing and its job control; a multiplexer is
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> pointless without them.
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>
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> **The problem.** Nothing can allocate a PTY pair, place the child on
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> the slave side as its controlling terminal, or resize it. The
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> reference reading is `.dev/reference/tmux` `spawn.c` +
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> `compat/fdforkpty.c` (~450 lines of C covering five platforms; Linux
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> alone is far smaller).
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## Info — the forks (open)
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1. **Surface.** A `pty: true` option on iteration 1's spawn verb (the
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lean — one spawn shape, two transports) versus a separate
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`proc.spawn_pty`.
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2. **Resize.** A verb on the handle (`resize(cols, rows)` → TIOCSWINSZ)
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— needed the moment [3](03-signals-as-events.md) delivers SIGWINCH.
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The fork is only whether it ships here or with 3.
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3. **The master fd's transport** is settled by iteration 1's fork 2 —
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whatever won there carries the PTY master identically.
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4. **Encoding edge.** A PTY master delivers the child's output with tty
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post-processing (ONLCR and friends): raw the master by default versus
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expose termios knobs. Lean: raw, no knobs, until a consumer asks.
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## Acceptance sketch
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- A real shell spawned on a PTY prints a PROMPT (it never does over
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pipes) — asserted on the bytes.
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- Resize: the child (a script reading TIOCGWINSZ) observes the new size.
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- `isatty` inside the child answers yes on all three fds.
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- Kill/reap/stop legs identical to 1's, PTY edition; fd count flat.
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## Consumers
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wmux 1 (every pane), the alacritty study's stage A (the headless
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expect-clone is exactly "spawn on a PTY, script it, assert").
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