This is a straightforward wrapper that uses the existing helpers for C
string handling and errno handling.
Having this available is convenient for UNIX utility programs written in
Rust, and avoids having to call the unsafe `libc::chroot` directly and
handle errors manually, in a program that may otherwise be entirely safe
code.
Drop alias `reduce` for `fold` - we have a `reduce` function
Searching for "reduce" currently puts the `reduce` alias for `fold`
above the actual `reduce` function. The `reduce` function already has a
cross-reference for `fold`, and vice versa.
Link between std::env::{var, var_os} and std::env::{vars, vars_os}
In #84551 I linked between `std::env::{args, args_os}` and this PR does the same but for `std::env::{var, var_os}` and `std::env::{vars, vars_os}`. Now all of `std::env::{var, var_os, vars, vars_os, args, args_os}` should each mention their `_os` or non-`_os` equivalent in the docs so that you can easily navigate between them.
Minor grammar tweaks for readability to btree internals
I was reading through the btree implementation and I noticed some grammar that could be improved in Node.rs so here is what I think would be a minor improvement.
Point out that behavior might be switched on 2015 and 2018 too one day
Reword documentation to make it clear that behaviour can be switched on older editions too, one day in the future. It doesn't *have* to be switched, but I think it's good to have it as an option and re-evaluate it a few months/years down the line when e.g. the crates that showed up in crater were broken by different changes in the language already.
cc #25725, #65819, #66145, #84147 , and https://github.com/rust-lang/rust/issues/84133#issuecomment-818005314
On arm64 we have seen on several databases that ISB (instruction synchronization
barrier) is better to use than yield in a spin loop. The yield instruction is a
nop. The isb instruction puts the processor to sleep for some short time. isb
is a good equivalent to the pause instruction on x86.
Below is an experiment that shows the effects of yield and isb on Arm64 and the
time of a pause instruction on x86 Intel processors. The micro-benchmarks use
https://github.com/google/benchmark.git
$ cat a.cc
static void BM_scalar_increment(benchmark::State& state) {
int i = 0;
for (auto _ : state)
benchmark::DoNotOptimize(i++);
}
BENCHMARK(BM_scalar_increment);
static void BM_yield(benchmark::State& state) {
for (auto _ : state)
asm volatile("yield"::);
}
BENCHMARK(BM_yield);
static void BM_isb(benchmark::State& state) {
for (auto _ : state)
asm volatile("isb"::);
}
BENCHMARK(BM_isb);
BENCHMARK_MAIN();
$ g++ -o run a.cc -O2 -lbenchmark -lpthread
$ ./run
--------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------
AWS Graviton2 (Neoverse-N1) processor:
BM_scalar_increment 0.485 ns 0.485 ns 1000000000
BM_yield 0.400 ns 0.400 ns 1000000000
BM_isb 13.2 ns 13.2 ns 52993304
AWS Graviton (A-72) processor:
BM_scalar_increment 0.897 ns 0.874 ns 801558633
BM_yield 0.877 ns 0.875 ns 800002377
BM_isb 13.0 ns 12.7 ns 55169412
Apple Arm64 M1 processor:
BM_scalar_increment 0.315 ns 0.315 ns 1000000000
BM_yield 0.313 ns 0.313 ns 1000000000
BM_isb 9.06 ns 9.06 ns 77259282
static void BM_pause(benchmark::State& state) {
for (auto _ : state)
asm volatile("pause"::);
}
BENCHMARK(BM_pause);
Intel Skylake processor:
BM_scalar_increment 0.295 ns 0.295 ns 1000000000
BM_pause 41.7 ns 41.7 ns 16780553
Tested on Graviton2 aarch64-linux with `./x.py test`.
Searching for "reduce" currently puts the `reduce` alias for `fold`
above the actual `reduce` function. The `reduce` function already has a
cross-reference for `fold`, and vice versa.
use correct feature flag for impl-block-level trait bounds on const fn
I am not sure what that special hack was needed for, but it doesn't seem needed any more...
This removes the last use of the `const_fn` feature flag -- Cc https://github.com/rust-lang/rust/issues/84510
r? `@oli-obk`
Remove `DropGuard` in `sys::windows::process` and use `StaticMutex` instead
`StaticMutex` is a mutex that when locked provides a guard that unlocks the mutex again when dropped, thus provides the exact same functionality as `DropGuard`. `StaticMutex` is used in more places, and is thus preferred over an ad-hoc construct like `DropGuard`.
````@rustbot```` label: +T-libs-impl
Simplify `Mutex::into_inner`
Thanks to #77147, `Mutex` do not implement `Drop` directly, so the old unsafe implementation of `into_inner` is not relevant anymore.
Adds feature-gated `#[no_coverage]` function attribute, to fix derived Eq `0` coverage issue #83601
Derived Eq no longer shows uncovered
The Eq trait has a special hidden function. MIR `InstrumentCoverage`
would add this function to the coverage map, but it is never called, so
the `Eq` trait would always appear uncovered.
Fixes: #83601
The fix required creating a new function attribute `no_coverage` to mark
functions that should be ignored by `InstrumentCoverage` and the
coverage `mapgen` (during codegen).
Adding a `no_coverage` feature gate with tracking issue #84605.
r? `@tmandry`
cc: `@wesleywiser`
The Eq trait has a special hidden function. MIR `InstrumentCoverage`
would add this function to the coverage map, but it is never called, so
the `Eq` trait would always appear uncovered.
Fixes: #83601
The fix required creating a new function attribute `no_coverage` to mark
functions that should be ignored by `InstrumentCoverage` and the
coverage `mapgen` (during codegen).
While testing, I also noticed two other issues:
* spanview debug file output ICEd on a function with no body. The
workaround for this is included in this PR.
* `assert_*!()` macro coverage can appear covered if followed by another
`assert_*!()` macro. Normally they appear uncovered. I submitted a new
Issue #84561, and added a coverage test to demonstrate this issue.
Reuse modules on `hermit`
Reuse the following modules on `hermit`:
- `unix::path` (contents identical)
- `unsupported::io` (contents identical)
- `unsupported::thread_local_key` (contents functionally identical, only changes are the panic error messages)
`@rustbot` label: +T-libs-impl
Add the `try_trait_v2` library basics
No compiler changes as part of this -- just new unstable traits and impls thereof.
The goal here is to add the things that aren't going to break anything, to keep the feature implementation simpler in the next PR.
(Draft since the FCP won't end until Saturday, but I was feeling optimistic today -- and had forgotten that FCP was 10 days, not 7 days.)
Unify the docs of std::env::{args_os, args} more
I noticed that `args_os` was missing some information and I thought it should mention `args` for when you want more safety just like how `args` mentions `args_os` if you don't want it to panic on invalid Unicode.
Stabilize Duration::MAX
Following the suggested direction from https://github.com/rust-lang/rust/issues/76416#issuecomment-817278338, this PR proposes that `Duration::MAX` should have been part of the `duration_saturating_ops` feature flag all along, having been
0. heavily referenced by that feature flag
1. an odd duck next to most of `duration_constants`, as I expressed in https://github.com/rust-lang/rust/issues/57391#issuecomment-717681193
2. introduced in #76114 which added `duration_saturating_ops`
and accordingly should be folded into `duration_saturating_ops` and therefore stabilized.
r? `@m-ou-se`
Remove slice diagnostic item
...because it is unusally placed on an impl and is redundant with a lang item.
Depends on rust-lang/rust-clippy#7074 (next clippy sync). ~I expect clippy tests to fail in the meantime.~ Nope tests passed...
CC `@flip1995`
Get rid of is_min_const_fn
This removes the last trace of the min_const_fn mechanism by making the unsafety checker agnostic about whether something is a min or "non-min" const fn. It seems this distinction was used to disallow some features inside `const fn`, but that is the responsibility of the const checker, not of the unsafety checker. No test seems to even notice this change in the unsafety checker so I guess we are good...
r? `@oli-obk`
Cc https://github.com/rust-lang/rust/issues/84510
Inline most raw socket, fd and handle conversions
Now that file descriptor types on Unix have niches, it is advantageous for user libraries which provide file descriptor wrappers (e.g. `Socket` from socket2) to store a `File` internally instead of a `RawFd`, so that the niche can be taken advantage of. However, doing so will currently result in worse performance as `IntoRawFd`, `FromRawFd` and `AsRawFd` are not inlined. This change adds `#[inline]` to those methods on std types that wrap file descriptors, handles or sockets.
move core::hint::black_box under its own feature gate
The `black_box` function had its own RFC and is tracked separately from the `test` feature at https://github.com/rust-lang/rust/issues/64102. Let's reflect this in the feature gate.
To avoid breaking all the benchmarks, libtest's `test::black_box` is a wrapping definition, not a reexport -- this means it is still under the `test` feature gate.
Cautiously add IntoIterator for arrays by value
Add the attribute described in #84133, `#[rustc_skip_array_during_method_dispatch]`, which effectively hides a trait from method dispatch when the receiver type is an array.
Then cherry-pick `IntoIterator for [T; N]` from #65819 and gate it with that attribute. Arrays can now be used as `IntoIterator` normally, but `array.into_iter()` has edition-dependent behavior, returning `slice::Iter` for 2015 and 2018 editions, or `array::IntoIter` for 2021 and later.
r? `@nikomatsakis`
cc `@LukasKalbertodt` `@rust-lang/libs`
Rework `init` and `cleanup`
This PR reworks the code in `std` that runs before and after `main` and centralizes this code respectively in the functions `init` and `cleanup` in both `sys_common` and `sys`. This makes is easy to see what code is executed during initialization and cleanup on each platform just by looking at e.g. `sys::windows::init`.
Full list of changes:
- new module `rt` in `sys_common` to contain `init` and `cleanup` and the runtime macros.
- `at_exit` and the mechanism to register exit handlers has been completely removed. In practice this was only used for closing sockets on windows and flushing stdout, which have been moved to `cleanup`.
- <s>On windows `alloc` and `net` initialization is now done in `init`, this saves a runtime check in every allocation and network use.</s>
Duration is used in std to represent a difference between two Instants.
As such, it has to at least contain that span of time in it. However,
Instant can vary by platform. Thus, we should explain the impl of
Duration::MAX is sensitive to these vagaries of the platform.
further split up const_fn feature flag
This continues the work on splitting up `const_fn` into separate feature flags:
* `const_fn_trait_bound` for `const fn` with trait bounds
* `const_fn_unsize` for unsizing coercions in `const fn` (looks like only `dyn` unsizing is still guarded here)
I don't know if there are even any things left that `const_fn` guards... at least libcore and liballoc do not need it any more.
`@oli-obk` are you currently able to do reviews?
Explicitly implement `!Send` and `!Sync` for `sys::{Args, Env}`
Remove the field `_dont_send_or_sync_me: PhantomData<*mut ()>` in favor of an explicit implementation of `!Send` and `!Sync`.
Mention FusedIterator case in Iterator::fuse doc
Using `fuse` on an iterator that incorrectly implements
`FusedIterator` does not fuse the iterator. This commit adds a
note about this in the documentation of this method to increase
awareness about this potential issue (esp. when relying on fuse
in unsafe code).
Closes#83969
implement `TrustedRandomAccess` for `Take` iterator adapter
`TrustedRandomAccess` requires the iterator length to fit within `usize`. `take(n)` only constrains the upper bound of an iterator. So if the inner is `TrustedRandomAccess` (which already implies a finite length) then so can be `Take`.
```````@rustbot``````` label T-libs-impl
Move `sys_common::poison` to `sync::poison`
`sys_common` should not contain publicly exported types, only platform-independent abstractions on top of `sys`, which `sys_common::poison` is not. There is thus no reason for the module to not live under `sync`.
Part of #84187.
Remove duplicated fn(Box<[T]>) -> Vec<T>
`<[T]>::into_vec()` does the same thing as `Vec::from::<Box<[T]>>()`, so they can be implemented in terms of each other. This was the previous implementation of `Vec::from()`, but was changed in #78461. I'm not sure what the rationale was for that change, but it seems preferable to maintain a single implementation.
Improve `Iterator::by_ref` example
I split the example into two: one that fails to compile, and one that
works. I also made them identical except for the addition of `by_ref`
so we don't confuse readers with random differences.
cc `@steveklabnik,` who is the one that added the previous version of this example
Using `fuse` on an iterator that incorrectly implements
`FusedIterator` does not fuse the iterator. This commit adds a
note about this in the documentation of this method to increase
awareness about this potential issue (esp. when relying on fuse
in unsafe code).
Added CharIndices::offset function
The CharIndices iterator has a field internally called front_offset, that I think would be very useful to have access to.
You can already do something like ``char_indices.next().map(|(offset, _)| offset)``, but that is wordy, in addition to not handling the case where the iterator has ended, where you'd want the offset to be equal to the length.
I'm very new to the open source world and the rust repository, so I'm sorry if I missed a step or did something weird.
Improve rebuilding behaviour of BinaryHeap::retain.
This changes `BinaryHeap::retain` such that it doesn't always fully rebuild the heap, but only rebuilds the parts for which that's necessary.
This makes use of the fact that retain gives out `&T`s and not `&mut T`s.
Retaining every element or removing only elements at the end results in no rebuilding at all. Retaining most elements results in only reordering the elements that got moved (those after the first removed element), using the same logic as was already used for `append`.
cc `@KodrAus` `@sfackler` - We briefly discussed this possibility in the meeting last week while we talked about stabilization of this function (#71503).
Rollup of 7 pull requests
Successful merges:
- #84343 (Remove `ScopeTree::closure_tree`)
- #84376 (Uses flex to fix formatting of h1 at any width)
- #84377 (Followup to #83944)
- #84396 (Update LLVM submodule)
- #84402 (Move `sys_common::rwlock::StaticRWLock` etc. to `sys::unix::rwlock`)
- #84404 (Check for intrinsics before coercing to a function pointer)
- #84413 (Remove `sys::args::Args::inner_debug` and use `Debug` instead)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Remove `sys::args::Args::inner_debug` and use `Debug` instead
This removes the method `sys::args::Args::inner_debug` on all platforms and implements `Debug` for `Args` instead.
I believe this creates a more natural API for the different platforms under `sys`: export a type `Args: Debug + Iterator + ...` vs. `Args: Iterator + ...` and with a method `inner_debug`.
Move `sys_common::rwlock::StaticRWLock` etc. to `sys::unix::rwlock`
This moves `sys_common::rwlock::StaticRwLock`, `RWLockReadGuard` and `RWLockWriteGuard` to `sys::unix::rwlock`. They are already `#[cfg(unix)]` and don't need to be in `sys_common`.
Implement indexing slices with pairs of core::ops::Bound<usize>
Closes#49976.
I am not sure about code duplication between `check_range` and `into_maybe_range`. Should be former implemented in terms of the latter? Also this PR doesn't address code duplication between `impl SliceIndex for Range*`.
Format `Struct { .. }` on one line even with `{:#?}`.
The result of `debug_struct("A").finish_non_exhaustive()` before this change:
```
A {
..
}
```
And after this change:
```
A { .. }
```
If there's any fields, the result stays unchanged:
```
A {
field: value,
..
}
fix 'const-stable since' for NonZeroU*::new_unchecked
For the unsigned `NonZero` types, `new_unchecked` was const-stable from the start with https://github.com/rust-lang/rust/pull/50808. Fix the docs to accurately reflect that.
I think this `since` is also incorrect:
```rust
#[stable(feature = "from_nonzero", since = "1.31.0")]
impl From<$Ty> for $Int {
```
The signed nonzero types were only stabilized in 1.34, so that `From` impl certainly didn't exist before. But I had enough of digging through git histories after I figured out when `new_unchecked` became const-stable...^^
Replace `Void` in `sys` with never type
This PR replaces several occurrences in `sys` of the type `enum Void {}` with the Rust never type (`!`).
The name `Void` is unfortunate because in other languages (C etc.) it refers to a unit type, not an uninhabited type.
Note that the previous stabilization of the never type was reverted, however all uses here are implementation details and not publicly visible.
Move `sys::vxworks` code to `sys::unix`
Follow-up to #77666, `sys::vxworks` is almost identical to `sys::unix`, the only differences are the `rand`, `thread_local_dtor`, and `process` implementation. Since `vxworks` is `target_family = unix` anyway, there is no reason for the code not to live inside of `sys::unix` like all the other unix-OSes.
e41f378f82/compiler/rustc_target/src/spec/vxworks_base.rs (L12)
``@rustbot`` label: +T-libs-impl
Replace all `fmt.pad` with `debug_struct`
This replaces any occurrence of:
- `f.pad("X")` with `f.debug_struct("X").finish()`
- `f.pad("X { .. }")` with `f.debug_struct("X").finish_non_exhaustive()`
This is in line with existing formatting code such as
1255053067/library/std/src/sync/mpsc/mod.rs (L1470-L1475)
