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.
# 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.)
Back then, the main concern was that this macro may not be quite
universally-enough useful to belong in the prelude.
# API
Therefore, this PR adds the macro such that using it requires one of:
```
use core::macros::matches;
use std::macros::matches;
```
Like arms of a `match` expression,
the macro supports multiple patterns separated by `|`
and optionally followed by `if` and a guard expression:
```
let foo = 'f';
assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
let bar = Some(4);
assert!(matches!(bar, Some(x) if x > 2));
```
# 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.
Change untagged_unions to not allow union fields with drop
This is a rebase of #56440, massaged to solve merge conflicts and make the test suite pass.
Change untagged_unions to not allow union fields with drop
Union fields may now never have a type with attached destructor. This for example allows unions to use arbitrary field types only by wrapping them in `ManuallyDrop` (or similar).
The stable rule remains, that union fields must be `Copy`. We use the new rule for the `untagged_union` feature.
Tracking issue: https://github.com/rust-lang/rust/issues/55149
Remove leading :: from paths in doc examples
Noted some pre-2018 path syntax in the doc examples, for example:
https://doc.rust-lang.org/std/process/fn.exit.html
```rust
fn main() {
::std::process::exit(match run_app() {
Ok(_) => 0,
...
```
Couldn't find an existing issue on this (then again, "::" makes for an annoying thing to search for) so if there is already something fixing this and/or there's a reason to not fix it, just close this PR.
(Also fixed indentation in the `process::exit()` docs)
Avoid realloc in `CString::new`
If `&[u8]` or `&str` is given, `CString::new` allocates a new `Vec` with the exact capacity, and then `CString::from_vec_unchecked` calls `.reserve_exact(1)` for nul byte. This PR avoids the reallocation by allocationg `len + 1` bytes beforehand. In microbenchmark this PR speeds up `CString::new(&[u8])` by 30%.
