Add align_offset intrinsic #43903
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Add align_offset intrinsic #43903
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r? @aturon (rust_highfive has picked a reviewer for you, use r? to override) |
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scottmcm
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Aug 17, 2017
src/libcore/intrinsics.rs
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| /// overflow or go beyond the allocation that `ptr` points into. | ||
| /// It is up to the caller to ensure that the returned offset is correct | ||
| /// in all terms other than alignment. | ||
| pub fn align_offset(ptr: *const (), align: usize) -> usize { |
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nit: Should this be unsafe, for consistency with the real intrinsic?
| /// There are no guarantees whatsover that offsetting the pointer will not | ||
| /// overflow or go beyond the allocation that `ptr` points into. | ||
| /// It is up to the caller to ensure that the returned offset is correct | ||
| /// in all terms other than alignment. |
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Consider adding an # Examples doctest to demo a few simple cases.
kennytm
reviewed
Aug 18, 2017
src/libcore/intrinsics.rs
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| /// # use std::mem::align_of; | ||
| /// let x = [5u8, 6u8, 7u8, 8u8, 9u8]; | ||
| /// let ptr = &x[n] as *const u8; | ||
| /// let offset = align_offset(ptr as *const (), align_of::<u16>()); |
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doc test failed.
[00:56:48] failures:
[00:56:48]
[00:56:48] ---- intrinsics.rs - intrinsics::align_offset (line 1361) stdout ----
[00:56:48] error: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library (see issue #0)
[00:56:48] --> intrinsics.rs:9:14
[00:56:48] |
[00:56:48] 9 | let offset = align_offset(ptr as *const (), align_of::<u16>());
[00:56:48] | ^^^^^^^^^^^^
[00:56:48] |
[00:56:48] = help: add #![feature(core_intrinsics)] to the crate attributes to enable
[00:56:48]
[00:56:48] error: use of unstable library feature 'core_intrinsics': intrinsics are unlikely to ever be stabilized, instead they should be used through stabilized interfaces in the rest of the standard library (see issue #0)
[00:56:48] --> intrinsics.rs:5:5
[00:56:48] |
[00:56:48] 5 | use std::intrinsics::align_offset;
[00:56:48] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[00:56:48] |
[00:56:48] = help: add #![feature(core_intrinsics)] to the crate attributes to enable
[00:56:48]
[00:56:48] error[E0308]: mismatched types
[00:56:48] --> intrinsics.rs:11:30
[00:56:48] |
[00:56:48] 11 | let u16_ptr = ptr.offset(offset) as *const u16;
[00:56:48] | ^^^^^^ expected isize, found usize
[00:56:48]
[00:56:48] thread 'rustc' panicked at 'couldn't compile the test', /checkout/src/librustdoc/test.rs:280:12
[00:56:48] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:56:48]
[00:56:48]
[00:56:48] failures:
[00:56:48] intrinsics.rs - intrinsics::align_offset (line 1361)
[00:56:48]
[00:56:48] test result: FAILED. 1231 passed; 1 failed; 1 ignored; 0 measured; 0 filtered out
[00:56:48]
[00:56:48] error: test failed, to rerun pass '--doc'
see rust-lang/rfcs#2043 for details
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ping @aturon |
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@bors: r+ |
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📌 Commit be96ad2 has been approved by |
bors
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Aug 30, 2017
Add align_offset intrinsic see rust-lang/rfcs#2043 for details and the plan towards stabilization (reexport in `core::mem` via various convenience functions) as per @scottmcm 's [comment](rust-lang/rfcs#2043 (comment)), this is just the intrinsic (which is obviously unstable).
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☀️ Test successful - status-appveyor, status-travis |
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GuillaumeGomez
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Dec 18, 2017
…trochenkov Fix the wrong subtraction in align_offset intrinsic. Given how the stage0 implementation in rust-lang#43903 is written, as well as that in the RFC, I suppose the current implementation has a typo. cc rust-lang#44488, cc @oli-obk.
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see rust-lang/rfcs#2043 for details and the plan towards stabilization (reexport in
core::memvia various convenience functions)as per @scottmcm 's comment, this is just the intrinsic (which is obviously unstable).