Improve math log documentation examples
using 2.0.log(2.0) in examples does not make it clear which is the base and number. This example makes it clear for programmers who take a glance at the example by following the calculation. It is more intuitive, and eliminates the need for executing the example in the playground.
Enhance the documentation of BufReader for potential data loss
This is (IMO) and enhancement of the `std::io::BufReader` documentation, that aims to highlight how relatively easy is to end up with data loss when improperly using an instance of this class.
This is following the issue I had figuring out why my application was loosing data, because I focused my attention on the word *multiple instances* of `BufReader` in its `struct` documentation, even if I ever only had one instance.
Link to the issue: https://github.com/tokio-rs/tokio/issues/1662
Improve std:🧵:Result documentation
Thanks to @dtolnay for pointing out the different premise of the contents of the `Err` variant in `std:🧵:Result` WRT normal error handling.
gate rustc_on_unimplemented under rustc_attrs
Move `rustc_on_implemented` from the `on_implemented` gate to `rustc_attrs` as it is internal.
Closes#29628
r? @varkor
Use KERN_ARND syscall for random numbers on NetBSD, same as FreeBSD.
This system call is present on all supported NetBSD versions and provides an endless stream of non-blocking random data from the kernel's ChaCha20-based CSPRNG. It doesn't require a file like `/dev/urandom` to be opened.
The system call is documented here (under kern.arandom):
https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7+NetBSD-7.0
And defined here:
https://nxr.netbsd.org/xref/src/sys/sys/sysctl.h#273
The semantics are the same as FreeBSD so reading 256 bytes per call is fine.
Similar change for getrandom crate: rust-random/getrandom#115
This system call is present on all supported NetBSD versions and
provides an endless stream of non-blocking random data from the
kernel's ChaCha20-based CSPRNG. It doesn't require a file descriptor
to be opened.
The system call is documented here (under kern.arandom):
https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7+NetBSD-7.0
And defined here:
https://nxr.netbsd.org/xref/src/sys/sys/sysctl.h#273
The semantics are the same as FreeBSD so reading 256 bytes per call
is fine.
Similar change for getrandom crate: rust-random/getrandom#115
Add lint and tests for unnecessary parens around types
This is my first contribution to the Rust project, so I apologize if I'm not doing things the right way.
The PR fixes#64169. It adds a lint and tests for unnecessary parentheses around types. I've run `tidy` and `rustfmt` — I'm not totally sure it worked right, though — and I've tried to follow the instructions linked in the readme.
I tried to think through all the variants of `ast::TyKind` to find exceptions to this lint, and I could only find the one mentioned in the original issue, which concerns types with `dyn`. I'm not a Rust expert, thought, so I may well be missing something.
There's also a problem with getting this to build. The new lint catches several things in the, e.g., `core`. Because `x.py` seems to build with an equivalent of `-Werror`, what would have been warnings cause the build to break. I got it to build and the tests to pass with `--warnings warn` on my `x.py build` and `x.py test` commands.
This allows us to remove `static_panic_msg` from the SSA<->LLVM
boundary, along with its fat pointer representation for &str.
Also changes the signature of PanicInfo::internal_contructor to
avoid copying.
Closes#65856.
Redesign the interface to the unikernel HermitCore
We are developing the unikernel HermitCore, where the kernel is written in Rust and is already part of the Rust Standard Library. The interface between the standard library and the kernel based on a small C library. With this pull request, we remove completely the dependency to C and use lld as linker. Currently, the kernel will be linked to the application as static library, which is published at https://github.com/hermitcore/libhermit-rs.
We don’t longer support the C interface to the kernel. Consequently, we remove this part from the Rust Standard Library.
SGX: Clear additional flag on enclave entry
An attacker could set both the AC flag in CR0 as in rflags. This causes the enclave to perform an AEX upon a misaligned memory access, and an attacker learns some information about the internal enclave state.
The AC flag in rflags is copied from userspace upon an enclave entry. Upon AEX it is copied and later restored. This patch forces the rflag.AC bit to be reset right after an enter.
Prevent unnecessary allocation in PathBuf::set_extension.
It was allocating a new `OsString` that was immediately dropped after using it with `set_file_name`. Now it directly changes the extension in the original buffer, without touching the rest of the file name or allocating a temporary string.
Fix check of `statx` and handle EPERM
Should fix#65662https://github.com/rust-lang/rust/issues/65662#issuecomment-544593939
> I think a reasonable solution might be to do something like try to stat AT_CWD initially and if that fails with EPERM or ENOSYS we disable the syscall entirely, otherwise it's cached as always good to use.
r? @alexcrichton
Add the `matches!( $expr, $pat ) -> bool` macro
# Motivation
This macro is:
* General-purpose (not domain-specific)
* Simple (the implementation is short)
* Very popular [on crates.io](https://crates.io/crates/matches) (currently 37th in all-time downloads)
* The two previous points combined make it number one in [left-pad index](https://twitter.com/bascule/status/1184523027888988160) score
As such, I feel it is a good candidate for inclusion in the standard library.
In fact I already felt that way five years ago: https://github.com/rust-lang/rust/pull/14685 (Although the proof of popularity was not as strong at the time.)
# API
<details>
<del>
Back then, the main concern was that this macro may not be quite universally-enough useful to belong in the prelude.
Therefore, this PR adds the macro such that using it requires one of:
```rust
use core::macros::matches;
use std::macros::matches;
```
</del>
</details>
Like arms of a `match` expression, the macro supports multiple patterns separated by `|` and optionally followed by `if` and a guard expression:
```rust
let foo = 'f';
assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
let bar = Some(4);
assert!(matches!(bar, Some(x) if x > 2));
```
<details>
<del>
# Implementation constraints
A combination of reasons make it tricky for a standard library macro not to be in the prelude.
Currently, all public `macro_rules` macros in the standard library macros end up “in the prelude” of every crate not through `use std::prelude::v1::*;` like for other kinds of items, but through `#[macro_use]` on `extern crate std;`. (Both are injected by `src/libsyntax_ext/standard_library_imports.rs`.)
`#[macro_use]` seems to import every macro that is available at the top-level of a crate, even if through a `pub use` re-export.
Therefore, for `matches!` not to be in the prelude, we need it to be inside of a module rather than at the root of `core` or `std`.
However, the only way to make a `macro_rules` macro public outside of the crate where it is defined appears to be `#[macro_export]`. This exports the macro at the root of the crate regardless of which module defines it. See [macro scoping](https://doc.rust-lang.org/reference/macros-by-example.html#scoping-exporting-and-importing) in the reference.
Therefore, the macro needs to be defined in a crate that is not `core` or `std`.
# Implementation
This PR adds a new `matches_macro` crate as a private implementation detail of the standard library. This crate is `#![no_core]` so that libcore can depend on it. It contains a `macro_rules` definition with `#[macro_export]`.
libcore and libstd each have a new public `macros` module that contains a `pub use` re-export of the macro. Both the module and the macro are unstable, for now.
The existing private `macros` modules are renamed `prelude_macros`, though their respective source remains in `macros.rs` files.
</del>
</details>
It was allocating a new OsString that was immediately dropped after
using it with set_file_name. Now it directly changes the extension in
the original buffer, without touching the rest of the file name or
allocating a temporary string.
