Add targets for HermitCore (https://hermitcore.org) to the Rust compiler and port libstd to it.
As a start, the port uses the simplest possible configuration (no jemalloc, abort on panic) and makes use of existing Unix-specific code wherever possible.
It adds targets for x86_64 (current main HermitCore platform) and aarch64 (HermitCore platform under development).
Together with the patches to "liblibc" (https://github.com/rust-lang/libc/pull/1048) and llvm (https://github.com/rust-lang/llvm/pull/122), this enables HermitCore applications to be written in Rust.
Document From trait implementations for OsStr, OsString, CString, and CStr
As part of issue #51430 (cc @skade).
The allocation and copy claims should be double-checked.
r? @steveklabnik
As a start, the port uses the simplest possible configuration (no jemalloc, abort on panic)
and makes use of existing Unix-specific code wherever possible.
It adds targets for x86_64 (current main HermitCore platform) and aarch64 (HermitCore platform
under development).
Together with the patches to "liblibc" and "llvm", this enables HermitCore applications to be
written in Rust.
Don't format!() string literals
Prefer `to_string()` to `format!()` take 2, this time targetting string literals. In some cases (`&format!("...")` -> `"..."`) also removes allocations. Occurences of `format!("")` are changed to `String::new()`.
Replace push loops with extend() where possible
Or set the vector capacity where I couldn't do it.
According to my [simple benchmark](https://gist.github.com/ljedrz/568e97621b749849684c1da71c27dceb) `extend`ing a vector can be over **10 times** faster than `push`ing to it in a loop:
10 elements (6.1 times faster):
```
test bench_extension ... bench: 75 ns/iter (+/- 23)
test bench_push_loop ... bench: 458 ns/iter (+/- 142)
```
100 elements (11.12 times faster):
```
test bench_extension ... bench: 87 ns/iter (+/- 26)
test bench_push_loop ... bench: 968 ns/iter (+/- 3,528)
```
1000 elements (11.04 times faster):
```
test bench_extension ... bench: 311 ns/iter (+/- 9)
test bench_push_loop ... bench: 3,436 ns/iter (+/- 233)
```
Seems like a good idea to use `extend` as much as possible.
Impl Send & Sync for JoinHandle
This is just a cosmetic change - it slightly relaxes and clarifies the public API without effectively promising any new guarantees.
Currently we have [these auto trait implementations](https://doc.rust-lang.org/nightly/std/thread/struct.JoinHandle.html#synthetic-implementations):
```rust
impl<T: Send> Send for JoinHandle<T> {}
impl<T: Sync> Sync for JoinHandle<T> {}
```
Bound `T: Send` doesn't make much sense because `JoinHandle<T>` can be created only when `T: Send`. Note that [`JoinHandle::<T>::join`](https://doc.rust-lang.org/nightly/std/thread/struct.JoinHandle.html#method.join) doesn't require `T: Send` so why should the `Send` impl?
And the `Sync` impl doesn't need `T: Sync` because `JoinHandle<T>` cannot even share `T` - it can only send it to the thread that calls `join`.
Rollup of bare_trait_objects PRs
All deny attributes were moved into bootstrap so they can be disabled with a line of config.
Warnings for external tools are allowed and it's up to the tool's maintainer to keep it warnings free.
r? @Mark-Simulacrum
cc @ljedrz @kennytm
Prefer `Option::map`/etc over `match` wherever it improves clarity
This isn't intended to change behavior anywhere. A lot of times statements like `match x { None => None, Some(y) => [...] }` can be rewritten using `Option::map` or `Option::and_then` in a way that preserves or improves clarity, so that's what I've done here.
I think it's particularly valuable to keep things in `libcore` and `libstd` pretty/idiomatic since it's not uncommon to follow the `[src]` links when browsing the rust-lang.org docs for std/core. If there's any concern about pushing style-based changes though, I'll happily back out the non-std/core commits here.
Cursor: update docs to clarify Cursor only works with in-memory buffers
Reduce misconceptions about Cursor being more general than it really is.
Fixes: #52470
Improve suggestion for missing fmt str in println
Avoid using `concat!(fmt, "\n")` to improve the diagnostics being
emitted when the first `println!()` argument isn't a formatting string
literal.
Fix#52347.
