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