Add internal io::Error::new_const to avoid allocations.
This makes it possible to have a io::Error containing a message with zero allocations, and uses that everywhere to avoid the *three* allocations involved in `io::Error::new(kind, "message")`.
The function signature isn't perfect, because it needs a reference to the `&str`. So for now, this is just a `pub(crate)` function. Later, we'll be able to use `fn new_const<MSG: &'static str>(kind: ErrorKind)` to make that a bit better. (Then we'll also be able to use some ZST trickery if that would result in more efficient code.)
See https://github.com/rust-lang/rust/issues/83352
Move `std::sys::unix::platform` to `std::sys::unix::ext`
This moves the operating system dependent alias `platform` (`std::os::{linux, android, ...}`) from `std::sys::unix` to `std::sys::unix::ext` (a.k.a. `std::os::unix`), removing the need for compatibility code in `unix_ext` when documenting on another platform.
This is also a step in making it possible to properly move `std::sys::unix::ext` to `std::os::unix`, as ideally `std::sys` should not depend on the rest of `std`.
Deprecate std::os::haiku::raw, which accidentally wasn't deprecated
In early 2016, all `std::os::*::raw` modules [were deprecated](aa23c98450) in accordance with [RFC 1415](https://github.com/rust-lang/rfcs/blob/master/text/1415-trim-std-os.md). However, at this same time support for Haiku was being added to libstd, landing shortly after the aforementioned commit, and due to some crossed wires a `std::os::haiku::raw` module was added and was not marked as deprecated.
I have been in correspondence with the author of the Haiku patch, ````@nielx,```` who has confirmed that this was simply an oversight and that the definitions from the libc crate should be preferred instead.
Clarify docs for Read::read's return value
Right now the docs for `Read::read`'s return value are phrased in a way that makes it easy for the reader to assume that the return value is never larger than the passed buffer. This PR clarifies that this is a requirement for implementations of the trait, but that callers have to expect a buggy yet safe implementation failing to do so, especially if unchecked accesses to the buffer are done afterwards.
I fell into this trap recently, and when I noticed, I looked at the docs again and had the feeling that I might not have been the first one to miss this.
The same issue of trusting the return value of `read` was also present in std itself for about 2.5 years and only fixed recently, see #80895.
I hope that clarifying the docs might help others to avoid this issue.
Reuse `std::sys::unsupported::pipe` on `hermit`
Pipes are not supported on `hermit` and `hermit/pipe.rs` is identical to `unsupported/pipe.rs`. This PR reduces duplication between the two by doing the following on `hermit`:
```rust
#[path = "../unsupported/pipe.rs"]
pub mod pipe;
```
Add more links between hash and btree collections
- Link from `core::hash` to `HashMap` and `HashSet`
- Link from HashMap and HashSet to the module-level documentation on
when to use the collection
- Link from several collections to Wikipedia articles on the general
concept
See also https://github.com/rust-lang/rust/pull/81989#issuecomment-783920840.
Deprecate `intrinsics::drop_in_place` and `collections::Bound`, which accidentally weren't deprecated
Fixes#82080.
I've taken the liberty of updating the `since` values to 1.52, since an unobservable deprecation isn't much of a deprecation (even the detailed release notes never bothered to mention these deprecations).
As mentioned in the issue I'm *pretty* sure that using a type alias for `Bound` is semantically equivalent to the re-export; [the reference implies](https://doc.rust-lang.org/reference/items/type-aliases.html) that type aliases only observably differ from types when used on unit structs or tuple structs, whereas `Bound` is an enum.
Deprecate RustcEncodable and RustcDecodable.
We can't remove the `RustcEncodable` and `RustcDecodable` derive macros from the prelude, but we can deprecate them.
Added `try_exists()` method to `std::path::Path`
This method is similar to the existing `exists()` method, except it
doesn't silently ignore the errors, leading to less error-prone code.
This change intentionally does NOT touch the documentation of `exists()`
nor recommend people to use this method while it's unstable.
Such changes are reserved for stabilization to prevent confusing people.
Apart from that it avoids conflicts with #80979.
`@joshtriplett` requested this PR in [internals discussion](https://internals.rust-lang.org/t/the-api-of-path-exists-encourages-broken-code/13817/25?u=kixunil)
use RWlock when accessing os::env (take 2)
This reverts commit acdca316c3 (#82877) i.e. redoes #81850 since the invalid unlock attempts in the child process have been fixed in #82949
r? `@joshtriplett`
Demonstrate best practice for feeding stdin of a child processes
Documentation change.
It's possible to create a deadlock with stdin/stdout I/O on a single thread:
* the child process may fill its stdout buffer, and have to wait for the parent process to read it,
* but the parent process may be waiting until its stdin write finishes before reading the stdout.
Therefore, the parent process should use separate threads for writing and reading.
These examples are not deadlocking in practice, because they use short strings, but I think it's better to demonstrate code that works even for long writes. The problem is non-obvious and tricky to debug (it seems that even libstd has a similar issue: #45572).
This also demonstrates how to use stdio with threads: it's not obvious that `.take()` can be used to avoid fighting with the borrow checker.
I've checked that the modified examples run fine.
std: Fix a bug on the wasm32-wasi target opening files
This commit fixes an issue pointed out in #82758 where LTO changed the
behavior of a program. It turns out that LTO was not at fault here, it
simply uncovered an existing bug. The bindings to
`__wasilibc_find_relpath` assumed that the relative portion of the path
returned was always contained within thee input `buf` we passed in. This
isn't actually the case, however, and sometimes the relative portion of
the path may reference a sub-portion of the input string itself.
The fix here is to use the relative path pointer coming out of
`__wasilibc_find_relpath` as the source of truth. The `buf` used for
local storage is discarded in this function and the relative path is
copied out unconditionally. We might be able to get away with some
`Cow`-like business or such to avoid the extra allocation, but for now
this is probably the easiest patch to fix the original issue.
Implement Extend and FromIterator for OsString
Add the following trait impls:
- `impl Extend<OsString> for OsString`
- `impl<'a> Extend<&'a OsStr> for OsString`
- `impl FromIterator<OsString> for OsString`
- `impl<'a> FromIterator<&'a OsStr> for OsString`
Because `OsString` is a platform string with no particular semantics, concatenating them together seems acceptable.
I came across a use case for these trait impls in https://github.com/artichoke/artichoke/pull/1089:
Artichoke is a Ruby interpreter. Its CLI accepts multiple `-e` switches for executing inline Ruby code, like:
```console
$ cargo -q run --bin artichoke -- -e '2.times {' -e 'puts "foo: #{__LINE__}"' -e '}'
foo: 2
foo: 2
```
I use `clap` for command line argument parsing, which collects these `-e` commands into a `Vec<OsString>`. To pass these commands to the interpreter for `Eval`, I need to join them together. Combining these impls with `Iterator::intersperse` https://github.com/rust-lang/rust/issues/79524 would enable me to build a single bit of Ruby code.
Currently, I'm doing something like:
```rust
let mut commands = commands.into_iter();
let mut buf = if let Some(command) = commands.next() {
command
} else {
return Ok(Ok(()));
};
for command in commands {
buf.push("\n");
buf.push(command);
}
```
If there's interest, I'd also like to add impls for `Cow<'a, OsStr>`, which would avoid allocating the `"\n"` `OsString` in the concatenate + intersperse use case.
Fix io::copy specialization using copy_file_range when writer was opened with O_APPEND
fixes#82410
While `sendfile()` returns `EINVAL` when the output was opened with O_APPEND, `copy_file_range()` does not and returns `EBADF` instead, which – unlike other `EBADF` causes – is not fatal for this operation since a regular `write()` will likely succeed.
We now treat `EBADF` as a non-fatal error for `copy_file_range` and fall back to a read-write copy as we already did for several other errors.
Do not attempt to unlock envlock in child process after a fork.
This implements the first two points from https://github.com/rust-lang/rust/issues/64718#issuecomment-793030479
This is a breaking change for cases where the environment is accessed in a Command::pre_exec closure. Except for single-threaded programs these uses were not correct anyway since they aren't async-signal safe.
Note that we had a ui test that explicitly tried `env::set_var` in `pre_exec`. As expected it failed with these changes when I tested locally.
Edition-specific preludes
This changes `{std,core}::prelude` to export edition-specific preludes under `rust_2015`, `rust_2018` and `rust_2021`. (As suggested in https://github.com/rust-lang/rust/issues/51418#issuecomment-395630382.) For now they all just re-export `v1::*`, but this allows us to add things to the 2021edition prelude soon.
This also changes the compiler to make the automatically injected prelude import dependent on the selected edition.
cc `@rust-lang/libs` `@djc`
Fixes to ExitStatus and its docs
* On Unix, properly display every possible wait status (and don't panic on weird values)
* In the documentation, be clear and consistent about "exit status" vs "wait status".
Stabilize `unsafe_op_in_unsafe_fn` lint
This makes it possible to override the level of the `unsafe_op_in_unsafe_fn`, as proposed in https://github.com/rust-lang/rust/issues/71668#issuecomment-729770896.
Tracking issue: #71668
r? ```@nikomatsakis``` cc ```@SimonSapin``` ```@RalfJung```
# Stabilization report
This is a stabilization report for `#![feature(unsafe_block_in_unsafe_fn)]`.
## Summary
Currently, the body of unsafe functions is an unsafe block, i.e. you can perform unsafe operations inside.
The `unsafe_op_in_unsafe_fn` lint, stabilized here, can be used to change this behavior, so performing unsafe operations in unsafe functions requires an unsafe block.
For now, the lint is allow-by-default, which means that this PR does not change anything without overriding the lint level.
For more information, see [RFC 2585](https://github.com/rust-lang/rfcs/blob/master/text/2585-unsafe-block-in-unsafe-fn.md)
### Example
```rust
// An `unsafe fn` for demonstration purposes.
// Calling this is an unsafe operation.
unsafe fn unsf() {}
// #[allow(unsafe_op_in_unsafe_fn)] by default,
// the behavior of `unsafe fn` is unchanged
unsafe fn allowed() {
// Here, no `unsafe` block is needed to
// perform unsafe operations...
unsf();
// ...and any `unsafe` block is considered
// unused and is warned on by the compiler.
unsafe {
unsf();
}
}
#[warn(unsafe_op_in_unsafe_fn)]
unsafe fn warned() {
// Removing this `unsafe` block will
// cause the compiler to emit a warning.
// (Also, no "unused unsafe" warning will be emitted here.)
unsafe {
unsf();
}
}
#[deny(unsafe_op_in_unsafe_fn)]
unsafe fn denied() {
// Removing this `unsafe` block will
// cause a compilation error.
// (Also, no "unused unsafe" warning will be emitted here.)
unsafe {
unsf();
}
}
```
This is a breaking change for cases where the environment is
accessed in a Command::pre_exec closure. Except for
single-threaded programs these uses were not correct
anyway since they aren't async-signal safe.
It's possible to create a deadlock with stdin/stdout I/O on a single thread:
* the child process may fill its stdout buffer, and have to wait for the parent process to read it,
* but the parent process may be waiting until its stdin write finishes before reading the stdout.
Therefore, the parent process should use separate threads for writing and reading.
Bump libc dependency of std to 0.2.88.
This PR bumps the `libc` dependency of `std` to 0.2.88. This will fix `TcpListener::accept` for Android on x86 platforms (31a2777d8f).
This will really finally fix https://github.com/rust-lang/rust/issues/82400 for the main branch :)
r? ``@JohnTitor``
Revert switch of env locking to rwlock, to fix deadlock in process spawning
This reverts commit 354f19cf24, reversing changes made to 0cfba2fd09.
PR https://github.com/rust-lang/rust/pull/81850 switched the environment lock from a mutex to an rwlock. However, process spawning (when not able to use `posix_spawn`) locks the environment before forking, and unlocks it after forking (in both the parent and the child). With a mutex, this works (although probably not correct even with a mutex). With an rwlock, on at least some targets, unlocking in the child does not work correctly, resulting in a deadlock.
This has manifested as CI hangs on i686 Linux; that target doesn't use `posix_spawn` in the CI environment due to the age of the installed C library (currently glibc 2.23). (Switching to `posix_spawn` would just mask this issue, though, which would still arise in any case that can't use `posix_spawn`.)
Some additional cleanup of environment handling around process spawning may help, but for now, revert the PR and go back to a standard mutex.
Fixes#82221
