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Check that move arguments are disjoint in the mir verifier #103363

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bjorn3 opened this issue Oct 21, 2022 · 6 comments
Open

Check that move arguments are disjoint in the mir verifier #103363

bjorn3 opened this issue Oct 21, 2022 · 6 comments
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-Zvalidate-mir Unstable option: MIR validation A-MIR Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html F-unsized_fn_params `#![feature(unsized_fn_params)]` T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@bjorn3
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bjorn3 commented Oct 21, 2022

See https://rust-lang.zulipchat.com/#narrow/stream/136281-t-lang.2Fwg-unsafe-code-guidelines/topic/stack.20slot.20reuse.20Q/near/305409193 and #103362.

Basically the check would disallow foo(move _1, move _1) (where _1 is of any type) and foo(move *_1, move *_1) (where _1 is a box).
@bjorn3 bjorn3 added A-MIR Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html F-unsized_fn_params `#![feature(unsized_fn_params)]` -Zvalidate-mir Unstable option: MIR validation labels Oct 21, 2022
@RalfJung
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It should also reject foo(move _1, move *_1), probably.

@tmiasko
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tmiasko commented Oct 21, 2022

One additional case that probably should be rejected: f(move _1, _1).

@scottmcm
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Is f(_1, move _1) allowed?

@bjorn3
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bjorn3 commented Oct 21, 2022

It could be, but it did be more consistent to disallow it and require an explicit copy rather than an implicit one.

@tmiasko
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tmiasko commented Dec 7, 2022

There is an interesting report of a destination propagation introducing an overlap between moved argument and call destination in dead code #105344 (comment).

@bjorn3
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bjorn3 commented Dec 7, 2022

I think destination propagation should be fixed in that case.

@Noratrieb Noratrieb added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 5, 2023
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Labels
-Zvalidate-mir Unstable option: MIR validation A-MIR Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html F-unsized_fn_params `#![feature(unsized_fn_params)]` T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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@RalfJung @bjorn3 @scottmcm @Noratrieb @tmiasko