Add documentation for `Ipv6MulticastScope`
Adds basic documentation to the unstable `Ipv6MulticastScope`, as well as marking it `#[non_exhaustive]` because future IETF RFCs may introduce additional scopes. The documentation mentions this in a section "Stability Guarantees":
> /// Not all possible values for a multicast scope have been assigned.
/// Future RFCs may introduce new scopes, which will be added as variants to this enum;
/// because of this the enum is marked as `#[non_exhaustive]`.
Move `os_str_bytes` to `sys::unix`
Followup to #84967, with `OsStrExt` and `OsStringExt` moved out of `sys_common`, there is no reason anymore for `os_str_bytes` to live in `sys_common` and not in sys. This pr moves it to the location `sys::unix::os_str` and reuses the code on other platforms via `#[path]` (as is common in `sys`) instead of importing.
Remove `Ipv4Addr::is_ietf_protocol_assignment`
This PR removes the unstable method `Ipv4Addr::is_ietf_protocol_assignment`, as I suggested in https://github.com/rust-lang/rust/issues/85612#issuecomment-847863404. The method was added in #60145, as far as I can tell primarily for the implementation of `Ipv4Addr::is_global` (addresses reserved for IETF protocol assignment are not globally reachable unless otherwise specified).
The method was added in 2019, but I haven't been able to find any open-source code using this method so far. I'm also having a hard time coming up with a usecase for specifically this method; knowing that an address is reserved for future protocols doesn't allow you to do much with it, especially since now some of those addresses are indeed assigned to a protocol and have their own behaviour (and might even be defined to be globally reachable, so if that is what you care about it is always more accurate to call `!is_global()`, instead of `is_ietf_protocol_assignment()`).
Because of these reasons, I propose removing the method (or alternatively make it a private helper for `is_global`) and also not introduce `Ipv6Addr::is_ietf_protocol_assignment` and `IpAddr::is_ietf_protocol_assignment` in the future.
Change environment variable getters to error recoverably
This PR changes the standard library environment variable getter functions to error recoverably (i.e. not panic) when given an invalid value.
On some platforms, it is invalid for environment variable names to contain `'\0'` or `'='`, or for their values to contain `'\0'`. Currently, the standard library panics when manipulating environment variables with names or values that violate these invariants. However, this behavior doesn't make a lot of sense, at least in the case of getters. If the environment variable is missing, the standard library just returns an error value, rather than panicking. It doesn't make sense to treat the case where the variable is invalid any differently from that. See the [internals thread](https://internals.rust-lang.org/t/why-should-std-var-panic/14847) for discussion. Thus, this PR changes the functions to error recoverably in this case as well.
If desired, I could change the functions that manipulate environment variables in other ways as well. I didn't do that here because it wasn't entirely clear what to change them to. Should they error silently or do something else? If someone tells me how to change them, I'm happy to implement the changes.
This fixes#86082, an ICE that arises from the current behavior. It also adds a regression test to make sure the ICE does not occur again in the future.
`@rustbot` label +T-libs
r? `@joshtriplett`
Bump bootstrap compiler to 1.55
Changing the cfgs for stdarch is missing, but my understanding is that we don't need to do it as part of this PR?
r? `@Mark-Simulacrum`
Add Linux-specific pidfd process extensions (take 2)
Continuation of #77168.
I addressed the following concerns from the original PR:
- make `CommandExt` and `ChildExt` sealed traits
- wrap file descriptors in `PidFd` struct representing ownership over the fd
- add `take_pidfd` to take the fd out of `Child`
- close fd when dropped
Tracking Issue: #82971
Move UnwindSafe, RefUnwindSafe, AssertUnwindSafe to core
They were previously only available in std::panic, not core::panic.
- https://doc.rust-lang.org/1.51.0/std/panic/trait.UnwindSafe.html
- https://doc.rust-lang.org/1.51.0/std/panic/trait.RefUnwindSafe.html
- https://doc.rust-lang.org/1.51.0/std/panic/struct.AssertUnwindSafe.html
Where this is relevant: trait objects! Inside a `#![no_std]` library it's otherwise impossible to have a struct holding a trait object, and at the same time can be used from downstream std crates in a way that doesn't interfere with catch_unwind.
```rust
// common library
#![no_std]
pub struct Thing {
pub(crate) x: &'static (dyn SomeTrait + Send + Sync),
}
pub(crate) trait SomeTrait {...}
```
```rust
// downstream application
fn main() {
let thing: library::Thing = ...;
let _ = std::panic::catch_unwind(|| { let _ = thing; }); // does not work :(
}
```
See a4131708e2/src/gradient.rs (L7-L15) for a real life example of needing to work around this problem. In particular that workaround would not even be viable if implementors of the trait were provided externally by a caller, as the `feature = "std"` would become non-additive in that case.
What happens without the UnwindSafe constraints:
```rust
fn main() {
let gradient = colorous::VIRIDIS;
let _ = std::panic::catch_unwind(|| { let _ = gradient; });
}
```
```console
error[E0277]: the type `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
--> src/main.rs:3:13
|
3 | let _ = std::panic::catch_unwind(|| { let _ = gradient; });
| ^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
|
::: .rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:430:40
|
430 | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
| ---------- required by this bound in `catch_unwind`
|
= help: within `Gradient`, the trait `RefUnwindSafe` is not implemented for `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)`
= note: required because it appears within the type `&'static (dyn colorous::gradient::EvalGradient + Send + Sync + 'static)`
= note: required because it appears within the type `Gradient`
= note: required because of the requirements on the impl of `UnwindSafe` for `&Gradient`
= note: required because it appears within the type `[closure@src/main.rs:3:38: 3:62]`
```
Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default
This PR makes the `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint warn by default.
To avoid showing a large number of un-actionable warnings to users, we only enable the lint for macros defined in the same crate. This ensures that users will be able to fix the warning by simply removing a semicolon.
In the future, I'd like to enable this lint unconditionally, and eventually make it into a hard error in a future edition. This PR is a step towards that goal.
[backtraces]: look for the `begin` symbol only after seeing `end`
On `x86_64-pc-windows-msvc`, we often get backtraces which look like
this:
```
10: 0x7ff77e0e9be5 - std::panicking::rust_panic_with_hook
11: 0x7ff77e0e11b4 - std::sys_common::backtrace::__rust_begin_short_backtrace::h5769736bdb11136c
12: 0x7ff77e0e116f - std::sys_common::backtrace::__rust_end_short_backtrace::h61c7ecb1b55338ae
13: 0x7ff77e0f89dd - std::panicking::begin_panic::h8e60ef9f82a41805
14: 0x7ff77e0e108c - d
15: 0x7ff77e0e1069 - c
16: 0x7ff77e0e1059 - b
17: 0x7ff77e0e1049 - a
18: 0x7ff77e0e1039 - core::ptr::drop_in_place<std::rt::lang_start<()>::{{closure}}>::h1bfcd14d5e15ba81
19: 0x7ff77e0e1186 - std::sys_common::backtrace::__rust_begin_short_backtrace::h5769736bdb11136c
20: 0x7ff77e0e100c - std::rt::lang_start::{{closure}}::ha054184bbf9921e3
```
Notice that `__rust_begin_short_backtrace` appears on frame 11 before
`__rust_end_short_backtrace` on frame 12. This is because in typical
release binaries without debug symbols, dbghelp.dll, which we use to walk
and symbolize the stack, does not know where CGU internal functions
start or end and so the closure invoked by `__rust_end_short_backtrace`
is incorrectly described as `__rust_begin_short_backtrace` because it
happens to be near that symbol.
While that can obviously change, this has been happening quite
consistently since #75048. Since this is a very small change to the std
and the change makes sense by itself, I think this is worth doing.
This doesn't completely resolve the situation for release binaries on
Windows, since without debug symbols, the stack printed can still show
incorrect symbol names (this is why the test uses `#[no_mangle]`) but it
does slightly improve the situation in that you see the same backtrace
you would see with `RUST_BACKTRACE=full` or in a debugger (without the
uninteresting bits at the top and bottom).
Fixes part of #87481
Fix may not to appropriate might not or must not
I went through and changed occurrences of `may not` to be more explicit with `might not` and `must not`.
On `x86_64-pc-windows-msvc`, we often get backtraces which look like
this:
```
10: 0x7ff77e0e9be5 - std::panicking::rust_panic_with_hook
11: 0x7ff77e0e11b4 - std::sys_common::backtrace::__rust_begin_short_backtrace::h5769736bdb11136c
12: 0x7ff77e0e116f - std::sys_common::backtrace::__rust_end_short_backtrace::h61c7ecb1b55338ae
13: 0x7ff77e0f89dd - std::panicking::begin_panic::h8e60ef9f82a41805
14: 0x7ff77e0e108c - d
15: 0x7ff77e0e1069 - c
16: 0x7ff77e0e1059 - b
17: 0x7ff77e0e1049 - a
18: 0x7ff77e0e1039 - core::ptr::drop_in_place<std::rt::lang_start<()>::{{closure}}>::h1bfcd14d5e15ba81
19: 0x7ff77e0e1186 - std::sys_common::backtrace::__rust_begin_short_backtrace::h5769736bdb11136c
20: 0x7ff77e0e100c - std::rt::lang_start::{{closure}}::ha054184bbf9921e3
```
Notice that `__rust_begin_short_backtrace` appears on frame 11 before
`__rust_end_short_backtrace` on frame 12. This is because in typical
release binaries without debug symbols, dbghelp.dll, which we use to walk
and symbolize the stack, does not know where CGU internal functions
start or end and so the closure invoked by `__rust_end_short_backtrace`
is incorrectly described as `__rust_begin_short_backtrace` because it
happens to be near that symbol.
While that can obviously change, this has been happening quite
consistently since #75048. Since this is a very small change to the std
and the change makes sense by itself, I think this is worth doing.
This doesn't completely resolve the situation for release binaries on
Windows, since without debug symbols, the stack printed can still show
incorrect symbol names (this is why the test uses `#[no_mangle]`) but it
does slightly improve the situation in that you see the same backtrace
you would see with `RUST_BACKTRACE=full` or in a debugger (without the
uninteresting bits at the top and bottom).
I looked in stdlib and as @BurntSushi thought, `raw` is generally
used for raw pointers, or other hazardous kinds of thing. stdlib does
not have `into_parts` apart from the one I added to `IntoInnerError`.
I did an ad-hoc search of the rustdocs for my current game project
Otter, which includes quite a large number of dependencies.
`into_parts` seems heavily used for things quite like this.
So change this name.
Suggested-by: Andrew Gallant <jamslam@gmail.com>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
I didn't notice the submodule, which means I failed to re-export this
to make it actually-public.
Reported-by: Andrew Gallant <jamslam@gmail.com>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Make const panic!("..") work in Rust 2021.
During const eval, this replaces calls to core::panicking::panic_fmt and std::panicking::being_panic_fmt with a call to a new const fn: core::panicking::const_panic_fmt. That function uses fmt::Arguments::as_str() to get the str and calls panic_str with that instead.
panic!() invocations with formatting arguments are still not accepted, as the creation of such a fmt::Arguments cannot be done in constant functions right now.
r? `@RalfJung`
Stabilize core::task::ready!
_Tracking issue: https://github.com/rust-lang/rust/issues/70922_
This PR stabilizes the `task::ready!` macro. Similar to https://github.com/rust-lang/rust/pull/80886, this PR was waiting on https://github.com/rust-lang/rust/issues/74355 to be fixed.
The `task::ready!` API has existed in the futures ecosystem for several years, and was added on nightly last year in https://github.com/rust-lang/rust/pull/70817. The motivation for this macro is the same as it was back then: virtually every single manual future implementation makes use of this; so much so that it's one of the few things included in the [futures-core](https://docs.rs/futures-core/0.3.12/futures_core) library.
r? ``@tmandry``
cc/ ``@rust-lang/wg-async-foundations`` ``@rust-lang/libs``
## Example
```rust
use core::task::{Context, Poll};
use core::future::Future;
use core::pin::Pin;
async fn get_num() -> usize {
42
}
pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
let mut f = get_num();
let f = unsafe { Pin::new_unchecked(&mut f) };
let num = ready!(f.poll(cx));
// ... use num
Poll::Ready(())
}
```
During const eval, this replaces calls to core::panicking::panic_fmt and
std::panicking::being_panic_fmt with a call to a new const fn:
core::panicking::const_panic_fmt. That function uses
fmt::Arguments::as_str() to get the str and calls panic_str with that
instead.
panic!() invocations with formatting arguments are still not accepted,
as the creation of such a fmt::Arguments cannot be done in constant
functions right now.
Use hashbrown's `extend_reserve()` in `HashMap`
When we added `extend_reserve()` to our implementation of `Extend` for `HashMap`, hashbrown didn't have a version we could use. Now that hashbrown has added it, we should use its version instead of implementing it ourself.
Update VxWork's UNIX support
1. VxWorks does not provide glibc
2. VxWorks does provide `sigemptyset` and `sigaddset`
Note: these changes are concurrent to [this PR](https://github.com/rust-lang/libc/pull/2295) in libc.
Stabilize `impl From<[(K, V); N]> for HashMap` (and friends)
In addition to allowing HashMap to participate in Into/From conversion, this adds the long-requested ability to use constructor-like syntax for initializing a HashMap:
```rust
let map = HashMap::from([
(1, 2),
(3, 4),
(5, 6)
]);
```
This addition is highly motivated by existing precedence, e.g. it is already possible to similarly construct a Vec from a fixed-size array:
```rust
let vec = Vec::from([1, 2, 3]);
```
...and it is already possible to collect a Vec of tuples into a HashMap (and vice-versa):
```rust
let vec = Vec::from([(1, 2)]);
let map: HashMap<_, _> = vec.into_iter().collect();
let vec: Vec<(_, _)> = map.into_iter().collect();
```
...and of course it is likewise possible to collect a fixed-size array of tuples into a HashMap ([but not vice-versa just yet](https://github.com/rust-lang/rust/issues/81615)):
```rust
let arr = [(1, 2)];
let map: HashMap<_, _> = std::array::IntoIter::new(arr).collect();
```
Therefore this addition seems like a no-brainer.
As for any impl, this would be insta-stable.
Stabilize `into_parts()` and `into_error()`
This stabilizes `IntoInnerError`'s `into_parts()` and `into_error()` methods, currently gated behind the `io_into_inner_error_parts` feature. The FCP has [already completed.](https://github.com/rust-lang/rust/issues/79704#issuecomment-880652967)
Closes#79704.
Document iteration order of `retain` functions
For `HashSet` and `HashMap`, this simply copies the comment from
`BinaryHeap::retain`.
For `BTreeSet` and `BTreeMap`, this adds an additional guarantee that
wasn't previously documented. I think that because these data structures
are inherently ordered and other functions guarantee ordered iteration,
it makes sense to provide this guarantee for `retain` as well.
Add comments explaining the unix command-line argument support.
Following up on #87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.
r? ```@RalfJung```
Background:
Over the last year, pidfd support was added to the Linux kernel. This
allows interacting with other processes. In particular, this allows
waiting on a child process with a timeout in a race-free way, bypassing
all of the awful signal-handler tricks that are usually required.
Pidfds can be obtained for a child process (as well as any other
process) via the `pidfd_open` syscall. Unfortunately, this requires
several conditions to hold in order to be race-free (i.e. the pid is not
reused).
Per `man pidfd_open`:
```
· the disposition of SIGCHLD has not been explicitly set to SIG_IGN
(see sigaction(2));
· the SA_NOCLDWAIT flag was not specified while establishing a han‐
dler for SIGCHLD or while setting the disposition of that signal to
SIG_DFL (see sigaction(2)); and
· the zombie process was not reaped elsewhere in the program (e.g.,
either by an asynchronously executed signal handler or by wait(2)
or similar in another thread).
If any of these conditions does not hold, then the child process
(along with a PID file descriptor that refers to it) should instead
be created using clone(2) with the CLONE_PIDFD flag.
```
Sadly, these conditions are impossible to guarantee once any libraries
are used. For example, C code runnng in a different thread could call
`wait()`, which is impossible to detect from Rust code trying to open a
pidfd.
While pid reuse issues should (hopefully) be rare in practice, we can do
better. By passing the `CLONE_PIDFD` flag to `clone()` or `clone3()`, we
can obtain a pidfd for the child process in a guaranteed race-free
manner.
This PR:
This PR adds Linux-specific process extension methods to allow obtaining
pidfds for processes spawned via the standard `Command` API. Other than
being made available to user code, the standard library does not make
use of these pidfds in any way. In particular, the implementation of
`Child::wait` is completely unchanged.
Two Linux-specific helper methods are added: `CommandExt::create_pidfd`
and `ChildExt::pidfd`. These methods are intended to serve as a building
block for libraries to build higher-level abstractions - in particular,
waiting on a process with a timeout.
I've included a basic test, which verifies that pidfds are created iff
the `create_pidfd` method is used. This test is somewhat special - it
should always succeed on systems with the `clone3` system call
available, and always fail on systems without `clone3` available. I'm
not sure how to best ensure this programatically.
This PR relies on the newer `clone3` system call to pass the `CLONE_FD`,
rather than the older `clone` system call. `clone3` was added to Linux
in the same release as pidfds, so this shouldn't unnecessarily limit the
kernel versions that this code supports.
Unresolved questions:
* What should the name of the feature gate be for these newly added
methods?
* Should the `pidfd` method distinguish between an error occurring
and `create_pidfd` not being called?
add `Stdin::lines`, `Stdin::split` forwarder methods
Add forwarder methods `Stdin::lines` and `Stdin::split`, which consume
and lock a `Stdin` handle, and forward on to the corresponding `BufRead`
methods. This should make it easier for beginners to use those iterator
constructors without explicitly dealing with locks or lifetimes.
Replaces #86412.
~~Based on #86846 to get the tracking issue number for the `stdio_locked` feature.~~ Rebased after merge, so it's only one commit now.
r? `@joshtriplett`
`@rustbot` label +A-io +C-enhancement +D-newcomer-roadblock +T-libs-api
Following up on #87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.
Simplify command-line argument initialization on unix
Simplify Rust's command-line argument initialization code on unix:
- The cleanup code isn't needed, because it was just zeroing out non-owning variables at runtime cleanup time. After 91c3eee173, Rust's command-line initialization code on unix no longer allocates `CString`s and a `Vec` at startup time.
- The `Mutex` isn't needed; if there's somehow a call to `args()` before argument initialization has happened, the code returns return an empty list, which we can do with a null check.
With these changes, a simple cdylib that doesn't use threads avoids getting `pthread_mutex_lock`/`pthread_mutex_unlock` in its symbol table.
Move asm! and global_asm! to core::arch
Follow-up to https://github.com/rust-lang/stdarch/pull/1183 .
Implements the libs-api team decision from rust-lang/rust#84019 (comment) .
In order to not break nightly users, this PR also adds the newly-moved items to the prelude. However, a decision will need to be made before stabilization as to whether these items should remain in the prelude. I will file an issue for this separately.
Fixes#84019 .
r? `@Amanieu`
Add diagnostic items for Clippy
This adds a bunch of diagnostic items to `std`/`core`/`alloc` functions, structs and traits used in Clippy. The actual refactorings in Clippy to use these items will be done in a different PR in Clippy after the next sync.
This PR doesn't include all paths Clippy uses, I've only gone through the first 85 lines of Clippy's [`paths.rs`](ecf85f4bdc/clippy_utils/src/paths.rs) (after rust-lang/rust-clippy#7466) to get some feedback early on. I've also decided against adding diagnostic items to methods, as it would be nicer and more scalable to access them in a nicer fashion, like adding a `is_diagnostic_assoc_item(did, sym::Iterator, sym::map)` function or something similar (Suggested by `@camsteffen` [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/Diagnostic.20Item.20Naming.20Convention.3F/near/225024603))
There seems to be some different naming conventions when it comes to diagnostic items, some use UpperCamelCase (`BinaryHeap`) and some snake_case (`hashmap_type`). This PR uses UpperCamelCase for structs and traits and snake_case with the module name as a prefix for functions. Any feedback on is this welcome.
cc: rust-lang/rust-clippy#5393
r? `@Manishearth`
In the command-line argument initialization code, remove the Mutex
around the `ARGV` and `ARGC` variables, and simply check whether
ARGV is non-null before dereferencing it. This way, if either of
ARGV or ARGC is not initialized, we'll get an empty argument list.
This allows simple cdylibs to avoid having
`pthread_mutex_lock`/`pthread_mutex_unlock` appear in their symbol
tables if they don't otherwise use threads.
Add forwarder methods `Stdin::lines` and `Stdin::split`, which consume
and lock a `Stdin` handle, and forward on to the corresponding `BufRead`
methods. This should make it easier for beginners to use those iterator
constructors without explicitly dealing with locks or lifetimes.
stdio_locked: add tracking issue
Add the tracking issue number #86845 to the stability attributes for the implementation in #86799.
r? `@joshtriplett`
`@rustbot` label +A-io +C-cleanup +T-libs-api
Remove unstable `io::Cursor::remaining`
Adding `io::Cursor::remaining` in #86037 caused a conflict with the implementation of `bytes::Buf` for `io::Cursor`, leading to an error in nightly, see https://github.com/rust-lang/rust/issues/86369#issuecomment-867723485.
This fixes the error by temporarily removing the `remaining` function.
r? `@yaahc`
[docs] Clarify behaviour of f64 and f32::sqrt when argument is negative zero
From IEEE 754 section 6.3:
> Except that squareRoot(−0) shall be −0, every numeric squareRoot result shall have a positive sign.
Fix linker error
Currently, `fs::hard_link` determines whether platforms have `linkat` based on the OS, and uses `link` if they don't. However, this heuristic does not work well if a platform provides `linkat` on newer versions but not on older ones. On old MacOS, this currently causes a linking error.
This commit fixes `fs::hard_link` by telling it to use `weak!` on macOS. This means that, on that operating system, we now check for `linkat` at runtime and use `link` if it is not available.
Fixes#80804.
`@rustbot` label T-libs-impl
On old macos systems, `fs::hard_link()` will follow symlinks.
This changes the test `symlink_hard_link` to exit early on
these systems, so that tests can pass.
`weak!` is needed in a test in another module. With macros
1.0, importing `weak!` would require reordering module
declarations in `std/src/lib.rs`, which is a bit too
evil.
Use diagnostic items instead of lang items for rfc2229 migrations
This PR removes the `Send`, `UnwindSafe` and `RefUnwindSafe` lang items introduced in https://github.com/rust-lang/rust/pull/84730, and uses diagnostic items instead to check for `Send`, `UnwindSafe` and `RefUnwindSafe` traits for RFC2229 migrations.
r? ```@nikomatsakis```
rewrote documentation for thread::yield_now()
The old documentation suggested the use of yield_now for repeated
polling instead of discouraging it; it also made the false claim that
channels are implemented using yield_now. (They are not, except for
a corner case).
Add Integer::log variants
_This is another attempt at landing https://github.com/rust-lang/rust/pull/70835, which was approved by the libs team but failed on Android tests through Bors. The text copied here is from the original issue. The only change made so far is the addition of non-`checked_` variants of the log methods._
_Tracking issue: #70887_
---
This implements `{log,log2,log10}` methods for all integer types. The implementation was provided by `@substack` for use in the stdlib.
_Note: I'm not big on math, so this PR is a best effort written with limited knowledge. It's likely I'll be getting things wrong, but happy to learn and correct. Please bare with me._
## Motivation
Calculating the logarithm of a number is a generally useful operation. Currently the stdlib only provides implementations for floats, which means that if we want to calculate the logarithm for an integer we have to cast it to a float and then back to an int.
> would be nice if there was an integer log2 instead of having to either use the f32 version or leading_zeros() which i have to verify the results of every time to be sure
_— [`@substack,` 2020-03-08](https://twitter.com/substack/status/1236445105197727744)_
At higher numbers converting from an integer to a float we also risk overflows. This means that Rust currently only provides log operations for a limited set of integers.
The process of doing log operations by converting between floats and integers is also prone to rounding errors. In the following example we're trying to calculate `base10` for an integer. We might try and calculate the `base2` for the values, and attempt [a base swap](https://www.rapidtables.com/math/algebra/Logarithm.html#log-rules) to arrive at `base10`. However because we're performing intermediate rounding we arrive at the wrong result:
```rust
// log10(900) = ~2.95 = 2
dbg!(900f32.log10() as u64);
// log base change rule: logb(x) = logc(x) / logc(b)
// log2(900) / log2(10) = 9/3 = 3
dbg!((900f32.log2() as u64) / (10f32.log2() as u64));
```
_[playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6bd6c68b3539e400f9ca4fdc6fc2eed0)_
This is somewhat nuanced as a lot of the time it'll work well, but in real world code this could lead to some hard to track bugs. By providing correct log implementations directly on integers we can help prevent errors around this.
## Implementation notes
I checked whether LLVM intrinsics existed before implementing this, and none exist yet. ~~Also I couldn't really find a better way to write the `ilog` function. One option would be to make it a private method on the number, but I didn't see any precedent for that. I also didn't know where to best place the tests, so I added them to the bottom of the file. Even though they might seem like quite a lot they take no time to execute.~~
## References
- [Log rules](https://www.rapidtables.com/math/algebra/Logarithm.html#log-rules)
- [Rounding error playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6bd6c68b3539e400f9ca4fdc6fc2eed0)
- [substack's tweet asking about integer log2 in the stdlib](https://twitter.com/substack/status/1236445105197727744)
- [Integer Logarithm, A. Jaffer 2008](https://people.csail.mit.edu/jaffer/III/ilog.pdf)
The old documentation suggested the use of yield_now for repeated
polling instead of discouraging it; it also made the false claim that
channels are implementing using yield_now. (They are not, except for
a corner case).
Before this, `std`'s env var getter functions would panic on
receiving certain invalid inputs. This commit makes them
return a `None` or `Err` instead.
Remove some doc aliases
As per the new doc alias policy in https://github.com/rust-lang/std-dev-guide/pull/25, this removes some controversial doc aliases:
- `malloc`, `alloc`, `realloc`, etc.
- `length` (alias for `len`)
- `delete` (alias for `remove` in collections and also file/directory deletion)
r? `@joshtriplett`
Stabilize `Seek::rewind()`
This stabilizes `Seek::rewind`. It seemed to fit into one of the existing tests, so I extended that test rather than adding a new one.
Closes#85149.
aborts: Clarify documentation and comments
In the docs for intrinsics::abort():
* Strengthen the recommendation by to use process::abort instead.
* Document the fact that it sometimes (ab)uses an LLVM debug trap and what the likely consequences are.
* State that the precise behaviour is unstable.
In the docs for process::abort():
* Promise that we have the same behaviour as C `abort()`.
* Document the likely consequences, including, specifically, the consequences on Unix.
In the internal comment for unix::abort_internal:
* Refer to the public docs for the public API functions.
* Correct and expand the description of libc::abort. Specifically:
* Do not claim that abort() unregisters signal handlers. It doesn't; it honours the SIGABRT handler.
* Discuss, extensively, the issue with abort() flushing stdio buffers.
* Describe the glibc behaviour in some detail.
Co-authored-by: Mark Wooding <mdw@distorted.org.uk>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Fixes#40230
Add std::os::unix::fs::DirEntryExt2::file_name_ref(&self) -> &OsStr
Greetings!
This is my first PR here, so please forgive me if I've missed an important step or otherwise done something wrong. I'm very open to suggestions/fixes/corrections.
This PR adds a function that allows `std::fs::DirEntry` to vend a borrow of its filename on Unix platforms, which is especially useful for sorting. (Windows has (as I understand it) encoding differences that require an allocation.) This new function sits alongside the cross-platform [`file_name(&self) -> OsString`](https://doc.rust-lang.org/std/fs/struct.DirEntry.html#method.file_name) function.
I pitched this idea in an [internals thread](https://internals.rust-lang.org/t/allow-std-direntry-to-vend-borrows-of-its-filename/14328/4), and no one objected vehemently, so here we are.
I understand features in general, I believe, but I'm not at all confident that my whole-cloth invention of a new feature string (as required by the compiler) was correct (or that the name is appropriate). Further, there doesn't appear to be a test for the sibling `ino` function, so I didn't add one for this similarly trivial function either. If it's desirable that I should do so, I'd be happy to [figure out how to] do that.
The following is a trivial sample of a use-case for this function, in which directory entries are sorted without any additional allocations:
```rust
use std::os::unix::fs::DirEntryExt;
use std::{fs, io};
fn main() -> io::Result<()> {
let mut entries = fs::read_dir(".")?.collect::<Result<Vec<_>, io::Error>>()?;
entries.sort_unstable_by(|a, b| a.file_name_ref().cmp(b.file_name_ref()));
for p in entries {
println!("{:?}", p);
}
Ok(())
}
```
In the docs for intrinsics::abort():
* Strengthen the recommendation by to use process::abort instead.
* Document the fact that it (ab)uses an LLVM debug trap and what the
likely consequences are.
* State that the precise behaviour is unstable.
In the docs for process::abort():
* Promise that we have the same behaviour as C `abort()`.
* Document the likely consequences, including, specifically, the
consequences on Unix.
In the internal comment for unix::abort_internal:
* Refer to the public docs for the public API functions.
* Correct and expand the description of libc::abort. Specifically:
* Do not claim that abort() unregisters signal handlers. It doesn't;
it honours the SIGABRT handler.
* Discuss, extensively, the issue with abort() flushing stdio buffers.
* Describe the glibc behaviour in some detail.
Co-authored-by: Mark Wooding <mdw@distorted.org.uk>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Remove the deprecated `core::raw` and `std::raw` module.
A few months has passed since #84207. I think now it's time for the final removal.
Closes#27751.
r? `@m-ou-se`
When using `process::Command` on Windows, environment variable names must be case-preserving but case-insensitive
When using `Command` to set the environment variables, the key should be compared as uppercase Unicode but when set it should preserve the original case.
Fixes#85242
add owned locked stdio handles
Add stderr_locked, stdin_locked, and stdout_locked free functions
to obtain owned locked stdio handles in a single step. Also add
into_lock methods to consume a stdio handle and return an owned
lock. These methods will make it easier to use locked stdio
handles without having to deal with lifetime problems or keeping
bindings to the unlocked handles around.
Fixes#85383; enables #86412.
r? `@joshtriplett`
`@rustbot` label +A-io +C-enhancement +D-newcomer-roadblock +T-libs-api
More ErrorKinds for common errnos
From the commit message of the main commit here (as revised):
```
There are a number of IO error situations which it would be very
useful for Rust code to be able to recognise without having to resort
to OS-specific code. Taking some Unix examples, `ENOTEMPTY` and
`EXDEV` have obvious recovery strategies. Recently I was surprised to
discover that `ENOSPC` came out as `ErrorKind::Other`.
Since I am familiar with Unix I reviwed the list of errno values in
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
Here, I add those that most clearly seem to be needed.
`@CraftSpider` provided information about Windows, and references, which
I have tried to take into account.
This has to be insta-stable because we can't sensibly have a different
set of ErrorKinds depending on a std feature flag.
I have *not* added these to the mapping tables for any operating
systems other than Unix and Windows. I hope that it is OK to add them
now for Unix and Windows now, and maybe add them to other OS's mapping
tables as and when someone on that OS is able to consider the
situation.
I adopted the general principle that it was usually a bad idea to map
two distinct error values to the same Rust error code. I notice that
this principle is already violated in the case of `EACCES` and
`EPERM`, which both map to `PermissionDenied`. I think this was
probably a mistake but it would be quite hard to change now, so I
don't propose to do anything about that.
However, for Windows, there are sometimes different error codes for
identical situations. Eg there are WSA* versions of some error
codes as well as ERROR_* ones. Also Windows seems to have a great
many more erorr codes. I don't know precisely what best practice
would be for Windows.
```
<strike>
```
Errno values I wasn't sure about so *haven't* included:
EMFILE ENFILE ENOBUFS ENOLCK:
These are all fairly Unix-specific resource exhaustion situations.
In practice it seemed not very likely to me that anyone would want
to handle these differently to `Other`.
ENOMEM ERANGE EDOM EOVERFLOW
Normally these don't get exposed to the Rust callers I hope. They
don't tend to come out of filesystem APIs.
EILSEQ
Hopefully Rust libraries open files in binary mode and do the
converstion in Rust. So Rust code ought not to be exposed to
EILSEQ.
EIO
The range of things that could cause this is troublesome. I found
it difficult to describe. I do think it would be useful to add this
at some point, because EIO on a filesystem operation is much more
serious than most other errors.
ENETDOWN
I wasn't sure if this was useful or, indeed, if any modern systems
use it.
ENOEXEC
It is not clear to me how a Rust program could respond to this. It
seems rather niche.
EPROTO ENETRESET ENODATA ENOMSG ENOPROTOOPT ENOSR ENOSTR ETIME
ENOTRECOVERABLE EOWNERDEAD EBADMSG EPROTONOSUPPORT EPROTOTYPE EIDRM
These are network or STREAMS related errors which I have never in
my own Unix programming found the need to do anything with. I think
someone who understands these better should be the one to try to
find good Rust names and descriptions for them.
ENOTTY ENXIO ENODEV EOPNOTSUPP ESRCH EALREADY ECANCELED ECHILD
EINPROGRESS
These are very hard to get unless you're already doing something
very Unix-specific, in which case the raw_os_error interface is
probably more suitable than relying on the Rust ErrorKind mapping.
EFAULT EBADF
These would seem to be the result of application UB.
```
</strike>
<i>(omitted errnos are discussed below, especially in https://github.com/rust-lang/rust/pull/79965#issuecomment-810468334)
Fix double import in wasm thread
The `unsupported` type is imported two times, as `super::unsupported` and as `crate::sys::unsupported`, throwing an error. Remove `super::unsupported` in favor of the other.
As reported in #86802.
Fix#86802
Remove & from Command::args calls in documentation
Now that arrays implement `IntoIterator`, using `&` is no longer necessary. This makes examples easier to understand.
Merge `sys_common::bytestring` back into `os_str_bytes`
`bytestring` contains code for correctly debug formatting a byte slice (`[u8]`). This functionality is and has historically only been used to provide the debug formatting of byte-based os-strings (on unix etc.).
Having this functionality in the separate `bytestring` module was useful in the past to reduce duplication, as [when it was added](https://github.com/rust-lang/rust/pull/46798) `os_str_bytes` was still split into `sys::{unix, redox, wasi, etc.}::os_str`. However, now that is no longer the case, there is not much reason for the `bytestring` functionality to be separate from `os_str_bytes`; I don't think it is very likely that another part of std will need to handle formatting byte strings that are not os-strings in the future (everything should be `utf8`). This is why this PR merges the functionality of `bytestring` directly into the debug implementation in `os_str_bytes`.
The `unsupported` type is imported two times, as `super::unsupported` and as `crate::sys::unsupported`, throwing an error. Remove `super::unsupported` in favor of the other.
Redefine `ErrorKind::Other` and stop using it in std.
This implements the idea I shared yesterday in the libs meeting when we were discussing how to handle adding new `ErrorKind`s to the standard library: This redefines `Other` to be for *user defined errors only*, and changes all uses of `Other` in the standard library to a `#[doc(hidden)]` and permanently `#[unstable]` `ErrorKind` that users can not match on. This ensures that adding `ErrorKind`s at a later point in time is not a breaking change, since the user couldn't match on these errors anyway. This way, we use the `#[non_exhaustive]` property of the enum in a more effective way.
Open questions:
- How do we check this change doesn't cause too much breakage? Will a crate run help and be enough?
- How do we ensure we don't accidentally start using `Other` again in the standard library? We don't have a `pub(not crate)` or `#[deprecated(in this crate only)]`.
cc https://github.com/rust-lang/rust/pull/79965
cc `@rust-lang/libs` `@ijackson`
r? `@dtolnay`
Add stderr_locked, stdin_locked, and stdout_locked free functions
to obtain owned locked stdio handles in a single step. Also add
into_lock methods to consume a stdio handle and return an owned
lock. These methods will make it easier to use locked stdio
handles without having to deal with lifetime problems or keeping
bindings to the unlocked handles around.
For `HashSet` and `HashMap`, this simply copies the comment from
`BinaryHeap::retain`.
For `BTreeSet` and `BTreeMap`, this adds an additional guarantee that
wasn't previously documented. I think that because these data structures
are inherently ordered and other functions guarantee ordered iteration,
it makes sense to provide this guarantee for `retain` as well.
The omission of Sink: Default is causing me a slight inconvenience in
a test harness. There seems little reason for this and Empty not to
be Clone and Copy too.
I have made all three of these insta-stable, because:
AIUI Copycan only be derived, and I was not able to find any
examples of how to unstably derive it. I think it is probably not
possible.
I hunted through the git history for precedent and found
79b8ad84c8
Implement `Copy` for `IoSlice`
https://github.com/rust-lang/rust/pull/69403
which was also insta-stable.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Use HTTPS links where possible
While looking at #86583, I wondered how many other (insecure) HTTP links were in `rustc`. This changes most other `http` links to `https`. While most of the links are in comments or documentation, there are a few other HTTP links that are used by CI that are changed to HTTPS.
Notes:
- I didn't change any to or in licences
- Some links don't support HTTPS :(
- Some `http` links were dead, in those cases I upgraded them to their new places (all of which used HTTPS)
