Fix :noub inference for pointerset/pointerref, getfield with bounds checking disabled #57295
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Keno
reviewed
Feb 7, 2025
| @@ -1033,7 +1033,7 @@ end | |||
| # we may assume that we don't throw | |||
| @assert !boundscheck | |||
| ismod && return false | |||
| name ⊑ Int || name ⊑ Symbol || return false | |||
| name ⊑ Int || return false | |||
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I was under the impression that boundscheck=false was a no-op when name is a symbol, since we always throw a FieldError if it doesn't exist. Pre-change:
julia> Base.infer_effects(x -> getfield(x, :foo, false), (Pair{String, Bool},))
(+c,+e,+n,+t,+s,+m,+u,+o,+r)
julia> (x -> getfield(x, :foo, false))(Pair("abc", false))
ERROR: type Pair has no field foo
Stacktrace:
[1] (::var"#15#16")(x::Pair{String, Bool})
@ Main ./REPL[6]:1
[2] top-level scope
@ REPL[6]:1
There was a problem hiding this comment.
Post change:
julia> Base.infer_effects(x -> getfield(x, :foo, false), (Pair{String, Bool},))
(+c,+e,!n,+t,+s,+m,!u,+o,+r)
julia> Base.infer_effects(x -> getfield(x, :foo, true), (Pair{String, Bool},))
(+c,+e,!n,+t,+s,+m,+u,+o,+r)
julia> Base.infer_effects(x -> getfield(x, 1, false), (Pair{String, Bool},))
(+c,+e,+n,+t,+s,+m,+u,+o,+r)
julia> Base.infer_effects(x -> getfield(x, 3, false), (Pair{String, Bool},))
(+c,+e,+n,+t,+s,+m,!u,+o,+r)
Keno
reviewed
Feb 7, 2025
| # If we cannot independently prove inboundsness, taint `:noub`. | ||
| # The inbounds-ness assertion requires dynamic reachability, | ||
| # while `:noub` needs to be true for all input values. | ||
| # However, as a special exception, we do allow literal `:boundscheck`. |
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This doesn't look like it's true anymore (and wasn't before?)
Also document the bounds check disabling flag on getfield, add docs for pointerref/pointerset/memorynew. getfield with symbol will throw even if boundschecking is turned off.
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:noubforpointerref(andpointerset), fixingunsafe_loaddoes not taint:noubeffect #56056pointerset,pointerref.unsafe_loaddoes not taint:noubeffect #56056 (comment), namely thatgetfieldwith bounds checking off didn't taint:noub.:nothrowwhen bounds checking is off but the field name is a symbol, since we'll throw aFieldError.Intinstead ofSymbol.getfieldto document the boundscheck argument.builtins.md