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Under Miri, disable debug asserts for things Miri always checks #101079
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r? @m-ou-se (rust-highfive has picked a reviewer for you, use r? to override) |
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☔ The latest upstream changes (presumably #100759) made this pull request unmergeable. Please resolve the merge conflicts. |
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☔ The latest upstream changes (presumably #103562) made this pull request unmergeable. Please resolve the merge conflicts. |
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☔ The latest upstream changes (presumably #103623) made this pull request unmergeable. Please resolve the merge conflicts. |
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I'm not sure the magnitude of the effect here is worth the complexity of implementation. Maybe if we had a different implementation strategy it might make sense, but the scary heavyweight debug assertions for container invariants aren't/can't be covered by this strategy. |
Context: rust-lang/miri#2497, Miri currently disables debug assertions in the standard library out of concern for how much slower code runs under Miri. A significant contributor there are these checks, which are entirely redundant and occur before Miri's, resulting in a much worse user experience if they are actually hit. So there is no reason to have them enabled under Miri.
However, this leaves some checks still enabled. Most notably, the bounds check(s) on
slice::get_unchecked
is staying put. This precondition originates in the requirements of Stacked Borrows, which can be disabled, and also has nothing to say about ZSTs, where the library API forbids out-of-bounds indexing, even for ZSTs.