core: avoid `extern type`s in formatting infrastructure
```@RalfJung``` [said](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Use.20of.20.60extern.20type.60.20in.20formatting.20machinery/near/446552837):
>How attached are y'all to using `extern type` in the formatting machinery?
Seems like this was introduced a [long time ago](34ef8f5441). However, it's also [not really compatible with Stacked Borrows](https://github.com/rust-lang/unsafe-code-guidelines/issues/256), and only works currently because we effectively treat references-to-extern-type almost like raw pointers in Stacked Borrows -- which of course is unsound, it's not how LLVM works. I was planning to make Miri emit a warning when this happens to avoid cases like [this](https://github.com/rust-lang/rust/issues/126814#issuecomment-2183816373) where people use extern type specifically to silence Miri without realizing what happens. but with the formatting machinery using extern type, this warning would just show up everywhere...
>
> The "proper" way to do this in Stacked Borrows is to use raw pointers (or `NonNull`).
This PR does just that.
r? ```@RalfJung```
While the numbers are parsed to the correct value, the decimal numbers in the
source were rounded to zero instead of to the nearest, making the literals
different from the values shown in the documentation.
Add more constants, functions, and tests for `f16` and `f128`
This adds everything that was in some way blocked on const eval, since https://github.com/rust-lang/rust/pull/126429 landed. There is a lot of `cfg(bootstrap)` since that is a fairly recent change.
`f128` tests are disabled on everything except x86_64 and Linux aarch64, which are two platforms I know have "good" support for these types - meaning basic math symbols are available and LLVM doesn't hit selection crashes. `f16` tests are enabled on almost everything except for known LLVM crashes. Doctests are only enabled on x86_64.
Tracking issue: https://github.com/rust-lang/rust/issues/116909
fix Drop items getting leaked in Filter::next_chunk
The optimization only makes sense for non-drop elements anyway. Use the default implementation for items that are Drop instead.
It also simplifies the implementation.
fixes#126872
tracking issue #98326
The optimization only makes sense for non-drop elements anyway.
Use the default implementation for items that are Drop instead.
It also simplifies the implementation.
core: VaArgSafe is an unsafe trait
`T: VaArgSafe` is relied on for soundness. Safe impls promise nothing. Therefore this must be an unsafe trait. Slightly pedantic, as only core can impl this, but we *could* choose to unseal the trait. That would allow soundly (but unsafely) implementing this for e.g. a `#[repr(C)] struct` that should be passable by varargs.
Relates to https://github.com/rust-lang/rust/issues/44930
Detect unused structs which derived Default
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Fixes#98871
This adds everything that was directly or transitively blocked on const
arithmetic for these types, which was recently merged.
Since const arithmetic is recent, most of these need to be gated by
`bootstrap`.
Anything that relies on intrinsics that are still missing is excluded.
The symbols that these tests rely on are not available on all platforms
and some ABIs are buggy, tests that rely on external functions are
configured to only run on x86 (`f128`) or aarch64 (`f16`).
`T: VaArgSafe` is relied on for soundness. Safe impls promise nothing.
Therefore this must be an unsafe trait. Slightly pedantic, as
only core can impl this, but we could choose to unseal the trait.
That would allow soundly (but unsafely) implementing this for e.g.
a `#[repr(C)] struct` that should be passable by varargs.
SmartPointer derive-macro
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Possibly replacing #123472 for continued upkeep of the proposal rust-lang/rfcs#3621 and implementation of the tracking issue #123430.
cc `@Darksonn` `@wedsonaf`
This is possible now that inline const blocks are stable; the idea was
even mentioned as an alternative when `uninit_array()` was added:
<https://github.com/rust-lang/rust/pull/65580#issuecomment-544200681>
> if it’s stabilized soon enough maybe it’s not worth having a
> standard library method that will be replaceable with
> `let buffer = [MaybeUninit::<T>::uninit(); $N];`
Const array repetition and inline const blocks are now stable (in the
next release), so that circumstance has come to pass, and we no longer
have reason to want `uninit_array()` other than convenience. Therefore,
let’s evaluate the inconvenience by not using `uninit_array()` in
the standard library, before potentially deleting it entirely.
Update docs for AtomicBool/U8/I8 with regard to alignment
Fixes#126084.
Since `AtomicBool`/`AtomicU8`/`AtomicI8` are guaranteed to have size == 1, and Rust guarantees that `size % align == 0`, they also must have alignment equal to 1, so some current docs are contradictory/confusing when describing their alignment requirements.
Specifically:
* Fix `AtomicBool::from_ptr` claiming that `align_of::<AtomicBool>() > align_of::<bool>()` on some platforms. (same for `AtomicU8::from_ptr`/`AtomicI8::from_ptr`)
* Explicitly state that `AtomicU8`/`AtomicI8` have the same alignment as `u8`/`i8` (in addition to size and bit validity)
* (internal) Change the `if_not_8_bit` macro to be `if_8_bit` and to allow an "if-else"-like structure, instead of just "if"-like.
---
I opted to leave the "`ptr` must be aligned" wording in `from_ptr`'s docs and just clarify that it is always satsified, instead of just removing the wording entirely. If that is instead preferred I can do that.
Rollup of 3 pull requests
Successful merges:
- #126140 (Rename `std::fs::try_exists` to `std::fs::exists` and stabilize fs_try_exists)
- #126318 (Add a `x perf` command for integrating bootstrap with `rustc-perf`)
- #126552 (Remove use of const traits (and `feature(effects)`) from stdlib)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove use of const traits (and `feature(effects)`) from stdlib
The current uses are already unsound because they are using non-const impls in const contexts. We can reintroduce them by reverting the commit in this PR, after #120639 lands.
Also, make `effects` an incomplete feature.
cc `@rust-lang/project-const-traits`
r? `@compiler-errors`
Generalize `{Rc,Arc}::make_mut()` to unsized types.
* `{Rc,Arc}::make_mut()` now accept any type implementing the new unstable trait `core::clone::CloneToUninit`.
* `CloneToUninit` is implemented for `T: Clone` and for `[T] where T: Clone`.
* `CloneToUninit` is a generalization of the existing internal trait `alloc::alloc::WriteCloneIntoRaw`.
* New feature gate: `clone_to_uninit`
This allows performing `make_mut()` on `Rc<[T]>` and `Arc<[T]>`, which was not previously possible.
---
Previous PR description, now obsolete:
> Add `{Rc, Arc}::make_mut_slice()`
>
> These functions behave identically to `make_mut()`, but operate on `Arc<[T]>` instead of `Arc<T>`.
>
> This allows performing the operation on slices, which was not previously possible because `make_mut()` requires `T: Clone` (and slices, being `!Sized`, do not and currently cannot implement `Clone`).
>
> Feature gate: `make_mut_slice`
try-job: test-various
This trait allows cloning DSTs, but is unsafe to implement and use
because it writes to possibly-uninitialized memory which must be of the
correct size, and must initialize that memory.
It is only implemented for `T: Clone` and `[T] where T: Clone`, but
additional implementations could be provided for specific `dyn Trait`
or custom-DST types.
Stop using `unlikely` in `strict_*` methods
The `strict_*` methods don't need (un)likely, because the `overflow_panic` calls are all `#[cold]`, [meaning](https://llvm.org/docs/LangRef.html#function-attributes) that LLVM knows any branch to them is unlikely without us needing to say so.
r? libs
