Joseph Ferano
d11dfd8a44
bounds.flan covers this already and the x86 survey cannot see it: the program picks its case out of (at args 1) and survey.sh runs everything with no arguments, so re-gating x86's lo <= hi would have failed nothing. This probe reaches the reversed slice on its own, through (len args) so that neither optimiser can fold the branch and the checker has no literal to object to. It matches under the default sweep and under SURVEY_FLAGS=--no-bounds-checks, which is the claim. Also records what the same reading turned up and did not fix: x86 still reports a negative slice-from-ptr promise through flan_slice_error, so the two backends print different sentences for it, and no corpus program reaches that case without arguments.
27 lines
1.3 KiB
Plaintext
27 lines
1.3 KiB
Plaintext
;;;; A slice built backwards, for the survey rather than for a person.
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;;;;
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;;;; test/programs/bounds.flan already covers this, and cannot cover it here:
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;;;; it picks its case out of (at args 1) and survey.sh runs every program
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;;;; with no arguments at all. So the one backend comparison that would catch
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;;;; check_slice's lo <= hi being re-gated on --no-bounds-checks is a program
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;;;; that reaches the reversed slice on its own.
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;;;;
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;;;; What it pins is that both backends die here in *every* build. lo <= hi is
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;;;; not a bounds check — it is the claim that the length word of the %slice
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;;;; this expression builds is a count, and hi - lo is -1 — so
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;;;; --no-bounds-checks has nothing here to drop, and running this sweep with
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;;;; SURVEY_FLAGS=--no-bounds-checks must report the same MATCH as without it.
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;;;; A backend that quietly builds the slice exits 0 while the other exits 134
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;;;; and the survey says DIFFER.
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;;;;
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;;;; The two ends come from (len args), which is 1 for a program run with no
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;;;; arguments and is not a number either optimiser can see, so the branch
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;;;; cannot be folded away and the checker has no literal to object to.
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(defn main [args [string]] i32
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(let [s (bytes "hello")
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hi (i32 (len args))
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lo (+ hi 1)]
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(print (slice s lo hi))
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(println ""))
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0)
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