Make non-power-of-two alignments a validity error in Layout#95361
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bors merged 1 commit intorust-lang:masterfrom Apr 9, 2022
Merged
Make non-power-of-two alignments a validity error in Layout#95361bors merged 1 commit intorust-lang:masterfrom
Layout#95361bors merged 1 commit intorust-lang:masterfrom
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(rust-highfive has picked a reviewer for you, use r? to override) |
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@bors rollup=iffy (I manually crafted a 32-bit stderr, which I could easily have done wrong) |
bjorn3
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This error message is not exactly clear about what property the value needs to have.
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I think that's ok. It's a best-effort UB check -- the place to look is at the # Safety comment, not the error message.
One gets essentially the same error from things like this too:
pub const BAD_ORDERING: std::cmp::Ordering = unsafe { std::mem::transmute(3_u8) };So it'll get better here if the error in general gets better for enums, which seems fine for this PR.
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This feels like overall a good change to me, modulo the one nit -- r=me with that fixed or we can discuss if you disagree. I would prefer for the commits to all be squashed into one as well. |
Inspired by the zulip conversation about how `Layout` should better enforce `size < isize::MAX as usize`, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld. This was MIRI can catch it, and means there's a more-specific type for `Layout` to store than just `NonZeroUsize`.
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Removed the macro and squashed. @bors r=Mark-Simulacrum |
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📌 Commit fe0c08a has been approved by |
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…crum Make non-power-of-two alignments a validity error in `Layout` Inspired by the zulip conversation about how `Layout` should better enforce `size <= isize::MAX as usize`, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld. This was MIRI can catch it, and means there's a more-specific type for `Layout` to store than just `NonZeroUsize`. It's left as `pub(crate)` here; a future PR could consider giving it a tracking issue for non-internal usage.
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Rollup of 7 pull requests Successful merges: - rust-lang#94794 (Clarify indexing into Strings) - rust-lang#95361 (Make non-power-of-two alignments a validity error in `Layout`) - rust-lang#95369 (Fix `x test src/librustdoc` with `download-rustc` enabled ) - rust-lang#95805 (Left overs of rust-lang#95761) - rust-lang#95808 (expand: Remove `ParseSess::missing_fragment_specifiers`) - rust-lang#95817 (hide another #[allow] directive from a docs example) - rust-lang#95831 (Use bitwise XOR in to_ascii_uppercase) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Inspired by the zulip conversation about how
Layoutshould better enforcesize <= isize::MAX as usize, this uses an N-variant enum on N-bit platforms to require at the validity level that the existing invariant of "must be a power of two" is upheld.This was MIRI can catch it, and means there's a more-specific type for
Layoutto store than justNonZeroUsize.It's left as
pub(crate)here; a future PR could consider giving it a tracking issue for non-internal usage.