49 lines
1.9 KiB
Plaintext
49 lines
1.9 KiB
Plaintext
;;;; (bytes s) copies, (bytes-view s) aliases — the ruling from the
|
|
;;;; INSERTIONSORT dogfooding session. The pin is the exact inverse of the
|
|
;;;; old aliasing: a write through the copy leaves the original string
|
|
;;;; printing unchanged, where the old (bytes s) either showed the write
|
|
;;;; through or trapped, depending on where the string's storage was.
|
|
|
|
(defonce frame Allocator)
|
|
|
|
(defn main [] i32
|
|
;; 1. The copy is writable and independent. Under the old reinterpret this
|
|
;; second line printed ZNSERTIONSORT too (or the whole program died in
|
|
;; .rodata) — the original staying itself is the whole of the change.
|
|
(let [s "INSERTIONSORT"
|
|
b (bytes s)]
|
|
(set (at b 0) \Z)
|
|
(println (str b)) ; ZNSERTIONSORT
|
|
(println s) ; INSERTIONSORT
|
|
;; The copy's block came from the context allocator, and free hands it
|
|
;; back there — which is what keeps this program leak-free.
|
|
(free b))
|
|
|
|
;; 2. A literal's copy is writable — the exact form that used to segfault
|
|
;; at -O0 and silently do nothing at -O2.
|
|
(let [b (bytes "hi")]
|
|
(set (at b 0) \H)
|
|
(println (str b)) ; Hi
|
|
(free b))
|
|
|
|
;; 3. The view still costs nothing and reads the string's own storage.
|
|
(let [v (bytes-view "abc")]
|
|
(println (length v)) ; 3
|
|
(println (at v 2))) ; 99
|
|
|
|
;; 4. (bytes s a) names the allocator, like (vec-new T a) and (clone v a):
|
|
;; the copy's block comes from the arena and free-all reclaims it.
|
|
(set frame (arena-new 4096))
|
|
(let [b (bytes "arena" frame)]
|
|
(set (at b 4) \A)
|
|
(println (str b))) ; arenA
|
|
(free-all frame)
|
|
(arena-destroy frame)
|
|
|
|
;; 5. (clone xs) with no allocator is the context's too, and free releases
|
|
;; it the same way.
|
|
(let [c (clone (slice [1 2 3]))]
|
|
(println (at c 2)) ; 3
|
|
(free c))
|
|
0)
|