glibc destroys[1] the passed pthread_attr_t if pthread_getattr_np()
fails.  Destroying it again leads to a segfault.  Fix it by only
destroying it on success for glibc.

[1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/pthread_getattr_np.c;h=ce437205e41dc05653e435f6188768cccdd91c99;hb=HEAD#l205

…ibcs

The calling convention of pthread_getattr_np() is to initialize the
pthread_attr_t, so _destroy() is only necessary on success (and _init()
isn't necessary beforehand).  On the other hand, FreeBSD wants the
attr_t to be initialized before pthread_attr_get_np(), and therefore it
should always be destroyed afterwards.

Previously, `x.py` would unconditionally run `x.py build` to get the
help message. After rust-lang#76165,
when checking the CI stage was moved into `Config`, that would cause an
assertion failure (but only only in CI!):

```
thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `2`', src/bootstrap/config.rs:619:49
```

This changes bootstrap to only generate a help message when it needs
to (when someone passes `--help`).

Use `SyncOnceCell` to only compile it once.
I believe this still adds some kind of locking mechanism?

The use of arith_offset was added in 803e9ae
before the stable wrapper of the intrinsic was available.

https://doc.rust-lang.org/stable/std/intrinsics/fn.arith_offset.html

The latter is on the path to stabilization.

… length (clippy::manual_strip)

Co-authored-by: est31 <est31@users.noreply.github.com>

Libc isn't used by alloc.
And std and panic_* use libc from crates.io now,
which isn't feature gated.

Co-authored-by: Joshua Nelson <joshua@yottadb.com>

…roy, r=Amanieu

Fix segfault if pthread_getattr_np fails

glibc [destroys][1] the passed pthread_attr_t if pthread_getattr_np()
fails.  Destroying it again leads to a segfault.  Fix it by only
destroying it on success for glibc.

[1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/pthread_getattr_np.c;h=ce437205e41dc05653e435f6188768cccdd91c99;hb=HEAD#l205

…ulacrum

Test and fix Send and Sync traits of BTreeMap artefacts

Fixes rust-lang#76686.

I'm not quite sure what all this implies. E.g. comparing with the definitions for `NodeRef` in node.rs,  maybe an extra bound `T: 'a` is useful for something. The test compiles on stable/beta (apart from `drain_filter`) so I bet `Sync` is equally desirable.

r? @Mark-Simulacrum

Don't generate bootstrap usage unless it's needed

Previously, `x.py` would unconditionally run `x.py build` to get the
help message. After rust-lang#76165,
when checking the CI stage was moved into `Config`, that would cause an
assertion failure (but only only in CI!):

```
thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `2`', src/bootstrap/config.rs:619:49
```

This changes bootstrap to only generate a help message when it needs
to (when someone passes `--help`).

r? @Mark-Simulacrum
This should fix the CI failures in rust-lang#76797 and rust-lang#75991.

simplfy condition in ItemLowerer::with_trait_impl_ref()

Fix wording in mir doc

…me, r=ecstatic-morse

Don't compile regex at every function call.

Use `SyncOnceCell` to only compile it once.
I believe this still adds some kind of locking mechanism?

Related issue: rust-lang#76817

…ures, r=oli-obk,Mark-Simulacrum

Remove redundant nightly features

Removes a bunch of redundant/outdated nightly features. The first commit removes a `core_intrinsics` use for which a stable wrapper has been provided since. The second commit replaces the `const_generics` feature with `min_const_generics` which might get stabilized this year. The third commit is the result of a trial/error run of removing every single feature and then adding it back if compile failed. A bunch of unused features are the result that the third commit removes.

…lett

black_box: silence unused_mut warning when building with cfg(miri)

use `array_windows` instead of `windows` in the compiler

I do think these changes are beautiful, but do have to admit that using type inference for the window length
can easily be confusing. This seems like a general issue with const generics, where inferring constants adds an additional
complexity which users have to learn and keep in mind.

…hievink

fix array_windows docs

r? @Dylan-DPC

…=lcnr

use strip_prefix over starts_with and manual slicing based on pattern length (clippy::manual_strip)

…d-future, r=jyn514

Move to intra doc links in core/src/future

Helps with rust-lang#75080.

@rustbot modify labels: T-doc A-intra-doc-links

r? @jyn514

Use intra docs links in core::{ascii, option, str, pattern, hash::map}

Partial fix for rust-lang#75080

@rustbot modify labels: T-doc A-intra-doc-links

r? @jyn514

…ake, r=jyn514

Use intra-doc links in library/core/src/task/wake.rs

Helps with rust-lang#75080.

@rustbot modify labels: T-doc, A-intra-doc-links

Remove unused feature gates from library/ crates

Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.