53 lines
2.3 KiB
Plaintext
53 lines
2.3 KiB
Plaintext
;;;; A program that stops on a bad index, for driving the break loop over one.
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;;;;
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;;;; bounds-condition.flan is the other half of the same change and covers the
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;;;; path where a `handler-bind` answers. This one covers the path the change
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;;;; is actually *for*: **nothing handles it**, so the signal walks the
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;;;; handlers, finds none, and reaches `flan_break_hook` — which is where an
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;;;; editor picks up a stopped program with the stack, the locals and the
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;;;; globals readable and the restarts on offer.
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;;;;
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;;;; That is the claim `docs/PORTING.md` said was missing, and it is worth testing
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;;;; end to end rather than reasoning about: before this, a bad index called
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;;;; exit(134), and with `flan dev` running as one process that took the
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;;;; compiler and the session with it.
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;;;;
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;;;; The shape is a frame loop's: one `restart-case` offering `continue` around
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;;;; the work, which is sand.flan's shape and the game's. No restart is
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;;;; established at the failing index — nothing a handler could do would make
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;;;; index 9 valid for a length-4 array — so `continue` is the *program's* own
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;;;; restart, found by the ordinary walk, and taking it is the proof that a
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;;;; bounds failure now lands somewhere a session can be recovered from.
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(import agent "vendor:agent")
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(defvar grid [4 i32])
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(defvar skipped i64)
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;;; One frame deep under the restart-case, so the transfer has something to
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;;; cross and the backtrace has something to show.
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(defn touch [i i32] ()
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(set (at grid i) 1))
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(defn frame [i i32] ()
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(restart-case
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(do (touch i) (println "frame done"))
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(continue [] (set skipped (+ skipped 1)))))
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(defvar ticks i64)
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(defn main [] i32
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(agent/start "/tmp/flan-dev-break-bounds-fallback.sock")
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;; Out of bounds on the first frame, with nothing handling it: the daemon
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;; meets a program that has already stopped, which is the state an editor
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;; has to cope with and the hardest one to arrange later.
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(frame 9)
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;; 1 once `continue` was taken. Printing it is how the transcript says which
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;; way the program left the break, rather than that it left.
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(print skipped) (println "")
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;; And it keeps polling on the far side, because the claim worth testing is
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;; that everything still works after a break over a bad index.
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(dotimes [i 4000]
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(agent/wait 5)
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(set ticks (+ ticks 1)))
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0)
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