Rollup of 4 pull requests
Successful merges:
- #124520 (Document that `create_dir_all` calls `mkdir`/`CreateDirW` multiple times)
- #124724 (Prefer lower vtable candidates in select in new solver)
- #124771 (Don't consider candidates with no failing where clauses when refining obligation causes in new solver)
- #124808 (Use `super_fold` in `RegionsToStatic` visitor)
r? `@ghost`
`@rustbot` modify labels: rollup
Add constants for f16 and f128
- Commit 1 adds associated constants for `f16`, excluding NaN and infinities as these are implemented using arithmetic for `f32` and `f64`.
- Commit 2 adds associated constants for `f128`, excluding NaN and infinities.
- Commit 3 adds constants in `std::f16::consts`.
- Commit 4 adds constants in `std::f128::consts`.
Document That `f16` And `f128` Hardware Support is Limited (v2)
This PR is identical to #123892, which was approved and merged but then removed from master by a force-push due to a [CI bug](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/ci.20broken.3F).
r? ghost
Original PR description:
---
This adds a small paragraph to the recently added f16 and f128 types explaining that hardware support may be limited, and that performance may suffer as a result of that.
I mainly wrote this because I felt it may be useful to express in some form; as a launchpoint for readers of the documentation if they have issues with performance.
I tried to word the documentation in a way that doesn't create false assumptions (that f16/f128 is too slow to use, for instance), removing the software implementation part could mislead people to thinking that f16/f128 is only available on some platforms, not all, so I believe it is important to keep in.\
"not all *major* platforms" is specifically said so as to not be redundant, because not all platforms implement many things, but the average rustacean is probably going to be using x86_64 or aarch64 derived ISA's, which is who this documentation is targeted towards.
I'm not sure of the best way to word the documentation, or if it should even be added, but I feel like it may be useful to have (potentially in a reworded way, I'm not very confident in the current wording and cannot decide if that is because it is too vague to be useful or too specific to be generally correct).
The code is written in a way to support 32-bit iOS and tvOS ARM devices,
for future compatibility even though we currently only have a target for
32-bit iOS ARM.
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Update library/core/src/primitive_docs.rs
Remove orphaned doc link and clean up grammar a bit
Update library/core/src/primitive_docs.rs
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Update library/core/src/primitive_docs.rs
Rewrite f16 and f128 hw support comments to match PR feedback
I wrote RISC-V allcaps in all cases, and wrote amd64 lowercase in all
cases, im not sure if either is the more correct way for either
platform, thats just how I normally write them, if theres a precedent
elsewhere it should probably be changed to match though.
Update library/core/src/primitive_docs.rs
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Update library/core/src/primitive_docs.rs
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Update library/core/src/primitive_docs.rs
library/std: Fix build for NetBSD targets with 32-bit `c_long`
This fixes building `std` for targets like `mipsel-unknown-netbsd`.
If `c_long` is an `i64`, this conversion works with `Into`. But if it's an `i32`, this failed to convert a `u32` to an `i32`.
This fixes building `std` for targets like `mipsel-unknown-netbsd`.
If `c_long` is an `i64`, this conversion works with `Into`. But if it's
an `i32`, this failed to convert a `u32` to an `i32`.
Use `unchecked_sub` in `split_at`
LLVM currently isn't figuring it out on its own, even in the checked version where it hypothetically could.
Before: <https://rust.godbolt.org/z/PEY38YrKs>
```llvm
bb1: ; preds = %start
%4 = getelementptr inbounds float, ptr %x.0, i64 %n
%5 = sub i64 %x.1, %n
```
After:
```llvm
bb1: ; preds = %start
%4 = getelementptr inbounds float, ptr %x.0, i64 %n
%5 = sub nuw i64 %x.1, %n
```
This is not using the wrapper because there's already a ubcheck covering it, so I don't want this to get a second one once #121571 lands.
---
This is basically the same as #108763, since `split_at` is essentially doing two `get_unchecked`s.
Improve several `Read` implementations
- `read_to_end` and `read_to_string` for `Cursor`
- Error on OOM in `read_to_string` of `&[u8]` and `VecDeque<u8>`
- Avoid making the slices contiguous in `VecDeque::read_to_string`
- ~`read_exact` and (unstable) `read_buf_exact` for `Take`~
- ~`read_buf` for `UnixStream` and `&UnixStream`~ (moved to #123084)
- `read_to_end` for `ChildStdErr`
Docs: suggest `uN::checked_sub` instead of check-then-unchecked
As of #124114 it's exactly the same in codegen, so might as well not use `unsafe`.
Note that this is only for *unsigned*, since the overflow conditions for `iN::checked_sub` are more complicated.
Remove an unnecessary cast
Very minor thing, obviously, but I randomly saw this unnecessary cast showing up in the UbChecks, so might as well get rid of it.
Move thread parking to `sys::sync`
Part of #117276.
I'll leave the platform-specific API abstractions in `sys::pal`, as per the initial proposal. I'm not entirely sure whether we'll want to keep it that way, but that remains to be seen.
r? ``@ChrisDenton`` (if you have time)
Reduce code size of `thread::set_current`
#123265 introduced a rather large binary size regression, because it added an `unwrap()` call on a `Result<(), Thread>`, which in turn pulled its rather heavy `Debug` implementation. This PR fixes this by readding the `rtassert!` that was removed.
As of 124114 it's exactly the same in codegen, so might as well not use `unsafe`.
Note that this is only for *unsigned*, since the overflow conditions for `iN::checked_sub` are more complicated.
zkvm: fix run_tests
`zkvm` is single-threaded, similar to `emscripten` and `wasm`. The `cfg` for `zkvm` seems to have been dropped. This PR adds the `cfg` again.
Stabilize `split_at_checked`
Closes#119128
For the const version of `slice::split_at_mut_checked`, I'm reusing the `const_slice_split_at_mut` feature flag (#101804). I don't if it okay to reuse tracking issues or if it preferred to create new ones...
Change `SIGPIPE` ui from `#[unix_sigpipe = "..."]` to `-Zon-broken-pipe=...`
In the stabilization [attempt](https://github.com/rust-lang/rust/pull/120832) of `#[unix_sigpipe = "sig_dfl"]`, a concern was [raised ](https://github.com/rust-lang/rust/pull/120832#issuecomment-2007394609) related to using a language attribute for the feature: Long term, we want `fn lang_start()` to be definable by any crate, not just libstd. Having a special language attribute in that case becomes awkward.
So as a first step towards the next stabilization attempt, this PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag `-Zon-broken-pipe=...` to remove that concern, since now the language is not "contaminated" by this feature.
Another point was [also raised](https://github.com/rust-lang/rust/pull/120832#issuecomment-1987023484), namely that the ui should not leak **how** it does things, but rather what the **end effect** is. The new flag uses the proposed naming. This is of course something that can be iterated on further before stabilization.
Tracking issue: https://github.com/rust-lang/rust/issues/97889
Describe and use CStr literals in CStr and CString docs
Mention CStr literals in the description of both types, and use them in some of the code samples for CStr. This is intended to make C string literals more discoverable.
Additionally, I don't think the orange "This example is not tested" warnings are very encouraging, so I have made the examples on `CStr` build.
default_alloc_error_hook: explain difference to default __rdl_oom in alloc
Though I'm not sure if that is really the reason that this code is duplicated. On no_std it may already be possible to call user-defined code on allocation failure.
Implement ptr_as_ref_unchecked
Implementation of #122034.
Prefixed the feature name with `ptr_` for clarity.
Linked const-unstability to #91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.
Fix HorizonOS build broken by #124210
HorizonOS (for the Tier-3 target `armv6k-nintendo-3ds`) does not support `dirfd()`, as many other similar targets.
library/std: Remove unused `gimli-symbolize` feature
library/backtrace also declares a feature called `gimli-symbolize` which appear used, but the feature in std with the same name is unused, so remove it.
String.truncate comment microfix (greater or equal)
String.truncate calls Vec.truncate, in turn, and that states "is greater or equal to". Beside common sense.
deref patterns: impl `DerefPure` for more std types
Context: [deref patterns](https://github.com/rust-lang/rust/issues/87121). The requirements of `DerefPure` aren't precise yet, but these types unambiguously satisfy them.
Interestingly, a hypothetical `impl DerefMut for Cow` that does a `Clone` would *not* be eligible for `DerefPure` if we allow mixing deref patterns with normal patterns. If the following is exhaustive then the `DerefMut` would cause UB:
```rust
match &mut Cow::Borrowed(&()) {
Cow::Owned(_) => ..., // Doesn't match
deref!(_x) if false => ..., // Causes the variant to switch to `Owned`
Cow::Borrowed(_) => ..., // Doesn't match
// We reach unreachable
}
```
