Guarantee char layout
#1401
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Guarantee char layout
#1401
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Ping 🙂 |
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Nominated to get lang's attention. |
| ## Bit validity | ||
| ## Layout and bit validity | ||
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| `char` is guaranteed to have the same size and alignment as `u32` on all platforms. |
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Suggested change
| `char` is guaranteed to have the same size and alignment as `u32` on all platforms. | |
| `char` is guaranteed to have the same size and alignment as `u32` on all platforms. | |
| `Option<char>` is guaranteed to have the same size and alignment as `char` on all platforms. |
(Unless we want to put this somewhere else.)
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This suggestion should probably be handled separately, not in this PR.
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Filed #1426 to track this.
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Consensus from lang is to merge. std docs should also be updated. |
scottmcm
reviewed
Oct 18, 2023
| ## Bit validity | ||
| ## Layout and bit validity | ||
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| `char` is guaranteed to have the same size and alignment as `u32` on all platforms. |
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TBH I was surprised this was to the reference directly, not to core like the other guarantees have been done. We currently have no guarantees written for specific alignment of anything, as far as I could find.
I was going to suggest something like
/// ```
/// use std::alloc::Layout;
/// assert_eq!(Layout::new::<char>(), Layout::new::<u32>());
/// assert_eq!(Layout::new::<Option<char>>(), Layout::new::<u32>());
/// ```but then this wasn't a docs change...
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No opposition to this going in core as well of course, but we already have text in the Reference about the sizes of primitive types: https://doc.rust-lang.org/reference/type-layout.html#primitive-data-layout
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Put up a PR to add the same text to core: rust-lang/rust#116894
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@rustbot labels -I-lang-nominated |
scottmcm
approved these changes
Oct 25, 2023
matthiaskrgr
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Nov 7, 2023
Update books ## rust-lang/reference 4 commits in 16fd3c06d9e558dae2d52000818274ae70c9e90a..cd8193e972f61b92117095fc73b67af767b4d6bc 2023-11-04 17:19:39 UTC to 2023-10-30 16:04:52 UTC - Guarantee that raw pointer conversions preserve slice element count (rust-lang/reference#1417) - some asm block flags also mean there can be no fences (rust-lang/reference#1413) - Guarantee `char` layout (rust-lang/reference#1401) - Doc: Add the RISC-V stabilized target features (rust-lang/reference#1415) ## rust-lang/rust-by-example 3 commits in 6709beeb7d0fbc5ffc91ac4893a24434123b9bfa..311b84962016b28c75525c86e7b3f49fd9101a39 2023-10-31 18:32:09 UTC to 2023-10-31 18:30:39 UTC - Fixed explanation mistake in comment (rust-lang/rust-by-example#1761) - Fix typos (rust-lang/rust-by-example#1759) - docs(9.2): fix typo (rust-lang/rust-by-example#1754) ## rust-lang/rustc-dev-guide 6 commits in b0ee9ec8fa59a6c7620165e061f4747202377a62..77dbe5782b2488af3bb489ad702eaff438f465bf 2023-11-06 16:14:34 UTC to 2023-10-29 17:16:02 UTC - add a new type system invariant (rust-lang/rustc-dev-guide#1822) - Update some outdated descriptions of coverage instrumentation (rust-lang/rustc-dev-guide#1809) - Add some documentation for unsizing (rust-lang/rustc-dev-guide#1817) - Bibliography: fixing author of "You Can't Spell Trust Without Rust" (rust-lang/rustc-dev-guide#1815) - remove change-id from sample build configuration (rust-lang/rustc-dev-guide#1813) - Update name of "active" features to "unstable" (rust-lang/rustc-dev-guide#1814)
rust-timer
added a commit
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Nov 7, 2023
Rollup merge of rust-lang#117639 - rustbot:docs-update, r=ehuss Update books ## rust-lang/reference 4 commits in 16fd3c06d9e558dae2d52000818274ae70c9e90a..cd8193e972f61b92117095fc73b67af767b4d6bc 2023-11-04 17:19:39 UTC to 2023-10-30 16:04:52 UTC - Guarantee that raw pointer conversions preserve slice element count (rust-lang/reference#1417) - some asm block flags also mean there can be no fences (rust-lang/reference#1413) - Guarantee `char` layout (rust-lang/reference#1401) - Doc: Add the RISC-V stabilized target features (rust-lang/reference#1415) ## rust-lang/rust-by-example 3 commits in 6709beeb7d0fbc5ffc91ac4893a24434123b9bfa..311b84962016b28c75525c86e7b3f49fd9101a39 2023-10-31 18:32:09 UTC to 2023-10-31 18:30:39 UTC - Fixed explanation mistake in comment (rust-lang/rust-by-example#1761) - Fix typos (rust-lang/rust-by-example#1759) - docs(9.2): fix typo (rust-lang/rust-by-example#1754) ## rust-lang/rustc-dev-guide 6 commits in b0ee9ec8fa59a6c7620165e061f4747202377a62..77dbe5782b2488af3bb489ad702eaff438f465bf 2023-11-06 16:14:34 UTC to 2023-10-29 17:16:02 UTC - add a new type system invariant (rust-lang/rustc-dev-guide#1822) - Update some outdated descriptions of coverage instrumentation (rust-lang/rustc-dev-guide#1809) - Add some documentation for unsizing (rust-lang/rustc-dev-guide#1817) - Bibliography: fixing author of "You Can't Spell Trust Without Rust" (rust-lang/rustc-dev-guide#1815) - remove change-id from sample build configuration (rust-lang/rustc-dev-guide#1813) - Update name of "active" features to "unstable" (rust-lang/rustc-dev-guide#1814)
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