Hint that choose_pivot returns index in bounds
Instead of using `unsafe` in multiple places, one `hint::assert_unchecked` allows use of safe code instead.
Part of #rust-lang/rust#144326
flt2dec: replace for loop by iter_mut
Perf is explored in https://github.com/rust-lang/rust/issues/144118, which initially showed small losses, but then also showed significant gains. Both are real, but given the smallness of the losses, this seems a good change.
address clippy formatting nits
- int_log10.rs: change top level doc comments to outer
- collect.rs: remove empty line after doc comment
- clippy fix: markdown indentation for indented items after line break: a markdown list item continued over multiples lines, but those following lines which are part of the same item are not indented
- clippy fix: bound in one place: when there is a bound in angle brackets and another bound on the same variable in a where clause
Remove deprecated `MaybeUninit` slice methods
These were left in to make migration a bit easier, although they should be removed now since they were never stable.
fix Zip unsoundness (again)
Some history: The Zip TrustedRandomAccess specialization has tried to emulate the side-effects of the naive implementation for a long time, including backwards iteration. #82292 tried to fix unsoundness (#82291) in that side-effect-preservation code, but this introduced some panic-safety unsoundness (#86443), but the fix#86452 didn't fix it for nested Zip iterators (#137255).
Rather than piling yet another fix ontop of this heap of fixes this PR reduces the number of cases in which side-effects will be preserved; the necessary API guarantee change was approved in #83791 but we haven't made use of that so far.
fixes#137255
According to
https://discourse.llvm.org/t/rfc-volatile-access-to-non-dereferenceable-memory-may-be-well-defined/86303/4,
LLVM allows volatile operations on null and handles it correctly. This
should be allowed in Rust as well, because I/O memory may be hard-coded
to address 0 in some cases, like the AVR chip ATtiny1626.
A test case that ensured a failure when passing null to volatile was
removed, since it's now valid.
Due to the addition of `maybe_is_aligned` to `ub_checks`,
`maybe_is_aligned_and_not_null` was refactored to use it.
docs: revise restrictions on volatile operations
A distinction between usage on Rust memory vs. non-Rust memory was
introduced. Documentation was reworded to explain what that means, and
make explicit that:
- No trapping can occur from volatile operations;
- On Rust memory, all safety rules must be respected;
- On Rust memory, the primary difference from regular access is that
volatile always involves a memory dereference;
- On Rust memory, the only data affected by an operation is the one
pointed to in the argument(s) of the function;
- On Rust memory, provenance follows the same rules as non-volatile
access;
- On non-Rust memory, any address known to not contain Rust memory is
valid (including 0 and usize::MAX);
- On non-Rust memory, no Rust memory may be affected (it is implicit
that any other non-Rust memory may be affected, though, even if not
referenced by the pointer). This should be relevant when, for example,
reading register A causes a flag to change in register B, or writing
to A causes B to change in some way. Everything affected mustn't be
inside an allocation.
- On non-Rust memory, provenance is irrelevant and a pointer with none
can be used in a valid way.
fix: don't lint null as UB for volatile
Also remove a now-unneeded `allow` line.
fix: additional wording nits
Make slice comparisons const
This needed a fix for `derive_const`, too, as it wasn't usable in libcore anymore as trait impls need const stability attributes. I think we can't use the same system as normal trait impls while `const_trait_impl` is still unstable.
r? ```@fee1-dead```
cc rust-lang/rust#143800
constify `Option` methods
r? ```````@fee1-dead```````
tracking issue: rust-lang/rust#143956
these unblock making `PartialOrd` and `Ord` const without resorting to inlining some of these at call sites.
Trim `BorrowedCursor` API
This PR removes some method from the unstable `BorrowedCursor` type. A rational for each change can be found in the message of each commit.
I don't think that an ACP is required for this, please tell me if it is not the case.
Cc rust-lang/rust#78485rust-lang/rust#117693
Constify `Index` traits
tracking issue: rust-lang/rust#143775
the `SliceIndex` trait cannot be implemented by users as it is sealed. While it would be useful for the `get` method on slices, it seems weird to have a feature gate for that that isn't also gating index syntax at the same time, so I put them under the same feature gate.
r? ```````@fee1-dead```````
wrapping shift: remove first bitmask and table
```rust
#[inline(always)]
pub const fn wrapping_shl(self, rhs: u32) -> Self {
// SAFETY: the masking by the bitsize of the type ensures that we do not shift
// out of bounds
unsafe {
self.unchecked_shl(rhs & (Self::BITS - 1))
}
}
```
already does the bitmask, so it seems unnecessary here.
More context: internals.rust-lang.org/t/wrapping-shift-operator-code-doing-bitmasking-twice/23167
update `cfg_select!` documentation
tracking issue: https://github.com/rust-lang/rust/issues/115585
After rust-lang/rust#143461, and with an eye on a soon(ish) stabilization, I think the docs need some work.
The existing text read more like a motivation for the feature existing to me, so I've tried to now be a bit more descriptive. Still, suggestions are very welcome.
I also added a test for an empty `select! {}` because it's just the sort of thing that might break.
r? ``@traviscross``
core: Add `BorrowedCursor::with_unfilled_buf`
Implementation of https://github.com/rust-lang/libs-team/issues/367.
This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`.
Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly.
Cc rust-lang/rust#78485rust-lang/rust#117693
