Automatically convert paths to verbatim for filesystem operations that support it
This allows using longer paths without the user needing to `canonicalize` or manually prefix paths. If the path is already verbatim then this has no effect.
Fixes: #32689
Rollup of 5 pull requests
Successful merges:
- #90239 (Consistent big O notation in map.rs)
- #90267 (fix: inner attribute followed by outer attribute causing ICE)
- #90288 (Add hint for people missing `TryFrom`, `TryInto`, `FromIterator` import pre-2021)
- #90304 (Add regression test for #75961)
- #90344 (Add tracking issue number to const_cstr_unchecked)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Clean up special function const checks
Mark them as const and `#[rustc_do_not_const_check]` instead of hard-coding them in const-eval checks.
r? `@oli-obk`
`@rustbot` label A-const-eval T-compiler
Remove fNN::lerp
Lerp is [surprisingly complex with multiple tradeoffs depending on what guarantees you want to provide](https://github.com/rust-lang/rust/issues/86269#issuecomment-869108301) (and what you're willing to drop for raw speed), so we don't have consensus on what implementation to use, let alone what signature - `t.lerp(a, b)` nicely puts `a, b` together, but makes dispatch to lerp custom types with the same signature basically impossible, and major ecosystem crates (e.g. nalgebra, glium) use `a.lerp(b, t)`, which is easily confusable. It was suggested to maybe provide a `Lerp<T>` trait and `t.lerp([a, b])`, which _could_ be implemented by downstream math libraries for their types, but also significantly raises the bar from a simple fNN method to a full trait, and does nothing to solve the implementation question. (It also raises the question of whether we'd support higher-order bezier interpolation.)
The only consensus we have is the lack of consensus, and the [general temperature](https://github.com/rust-lang/rust/issues/86269#issuecomment-951347135) is that we should just remove this method (giving the method space back to 3rd party libs) and revisit this if (and likely only if) IEEE adds lerp to their specification.
If people want a lerp, they're _probably_ already using (or writing) a math support library, which provides a lerp function for its custom math types and can provide the same lerp implementation for the primitive types via an extension trait.
See also [previous Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/lerp.20API.20design)
cc ``@clarfonthey`` (original PR author), ``@m-ou-se`` (original r+), ``@scottmcm`` (last voice in tracking issue, prompted me to post this)
Closes#86269 (removed)
Stabilise unix_process_wait_more, extra ExitStatusExt methods
This stabilises the feature `unix_process_wait_more`. Tracking issue #80695, FCP needed.
This was implemented in #79982 and merged in January.
My change to use `Type::def_id()` (formerly `Type::def_id_full()`) in
more places caused some docs to show up that used to be missed by
rustdoc. Those docs contained unescaped square brackets, which triggered
linkcheck errors. This commit escapes the square brackets and adds this
particular instance to the linkcheck exception list.
Inline CStr::from_ptr
Inlining this function is valuable, as it allows LLVM to apply `strlen`-specific optimizations without having to enable LTO.
For instance, the following function:
```rust
pub fn f(p: *const c_char) -> Option<u8> {
unsafe { CStr::from_ptr(p) }.to_bytes().get(0).copied()
}
```
Looks like this if `CStr::from_ptr` is allowed to be inlined.
```asm
before:
push rax
call qword ptr [rip + std::ffi::c_str::CStr::from_ptr@GOTPCREL]
mov rcx, rax
cmp rdx, 1
sete dl
test rax, rax
sete al
or al, dl
jne .LBB1_2
mov dl, byte ptr [rcx]
.LBB1_2:
xor al, 1
pop rcx
ret
after:
mov dl, byte ptr [rdi]
test dl, dl
setne al
ret
```
Note that optimization turned this from O(N) to O(1) in terms of performance, as LLVM knows that it doesn't really need to call `strlen` to determine whether a string is empty or not.
Stabilize feature `saturating_div` for rust 1.58.0
The tracking issue is #89381
This seems like a reasonable simple change(?). The feature `saturating_div` was added as part of the ongoing effort to implement a `Saturating` integer type (see #87921). The implementation has been discussed [here](https://github.com/rust-lang/rust/pull/87921#issuecomment-899357720) and [here](https://github.com/rust-lang/rust/pull/87921#discussion_r691888556). It extends the list of saturating operations on integer types (like `saturating_add`, `saturating_sub`, `saturating_mul`, ...) by the function `fn saturating_div(self, rhs: Self) -> Self`.
The stabilization of the feature `saturating_int_impl` (for the `Saturating` type) needs to have this stabilized first.
Closes#89381
Previously, it wasn't clear whether "This could include" was referring
to logic errors, or undefined behaviour. Tweak wording to clarify this
sentence does not relate to UB.
Stabilize CString::from_vec_with_nul[_unchecked]
Closes the tracking issue #73179. I am keeping this in _draft_ mode until the FCP has ended.
This is my first time stabilizing a feature, so I would appreciate any guidance on things I should do differently.
Closes#73179
Remove unnecessary condition in Barrier::wait()
This is my first pull request for Rust, so feel free to call me out if anything is amiss.
After some examination, I realized that the second condition of the "spurious-wakeup-handler" loop in ``std::sync::Barrier::wait()`` should always evaluate to ``true``, making it redundant in the ``&&`` expression.
Here is the affected function before the fix:
```rust
#[stable(feature = "rust1", since = "1.0.0")]
pub fn wait(&self) -> BarrierWaitResult {
let mut lock = self.lock.lock().unwrap();
let local_gen = lock.generation_id;
lock.count += 1;
if lock.count < self.num_threads {
// We need a while loop to guard against spurious wakeups.
// https://en.wikipedia.org/wiki/Spurious_wakeup
while local_gen == lock.generation_id && lock.count < self.num_threads { // fixme
lock = self.cvar.wait(lock).unwrap();
}
BarrierWaitResult(false)
} else {
lock.count = 0;
lock.generation_id = lock.generation_id.wrapping_add(1);
self.cvar.notify_all();
BarrierWaitResult(true)
}
}
```
At first glance, it seems that the check that ``lock.count < self.num_threads`` would be necessary in order for a thread A to detect when another thread B has caused the barrier to reach its thread count, making thread B the "leader".
However, the control flow implicitly results in an invariant that makes observing ``!(lock.count < self.num_threads)``, i.e. ``lock.count >= self.num_threads`` impossible from thread A.
When thread B, which will be the leader, calls ``.wait()`` on this shared instance of the ``Barrier``, it locks the mutex in the first line and saves the ``MutexGuard`` in the ``lock`` variable. It then increments the value of ``lock.count``. However, it then proceeds to check if ``lock.count < self.num_threads``. Since it is the leader, it is the case that (after the increment of ``lock.count``), the lock count is *equal* to the number of threads. Thus, the second branch is immediately taken and ``lock.count`` is zeroed. Additionally, the generation ID is incremented (with wrap). Then, the condition variable is signalled. But, the other threads are waiting at the line ``lock = self.cvar.wait(lock).unwrap();``, so they cannot resume until thread B's call to ``Barrier::wait()`` returns, which drops the ``MutexGuard`` acquired in the first ``let`` statement and unlocks the mutex.
The order of events is thus:
1. A thread A calls `.wait()`
2. `.wait()` acquires the mutex, increments `lock.count`, and takes the first branch
3. Thread A enters the ``while`` loop since the generation ID has not changed and the count is less than the number of threads for the ``Barrier``
3. Spurious wakeups occur, but both conditions hold, so the thread A waits on the condition variable
4. This process repeats for N - 2 additional times for non-leader threads A'
5. *Meanwhile*, Thread B calls ``Barrier::wait()`` on the same barrier that threads A, A', A'', etc. are waiting on. The thread count reaches the number of threads for the ``Barrier``, so all threads should now proceed, with B being the leader. B acquires the mutex and increments the value ``lock.count`` only to find that it is not less than ``self.num_threads``. Thus, it immediately clamps ``self.num_threads`` back down to 0 and increments the generation. Then, it signals the condvar to tell the A (prime) threads that they may continue.
6. The A, A', A''... threads wake up and attempt to re-acquire the ``lock`` as per the internal operation of a condition variable. When each A has exclusive access to the mutex, it finds that ``lock.generation_id`` no longer matches ``local_generation`` **and the ``&&`` expression short-circuits -- and even if it were to evaluate it, ``self.count`` is definitely less than ``self.num_threads`` because it has been reset to ``0`` by thread B *before* B dropped its ``MutexGuard``**.
Therefore, it my understanding that it would be impossible for the non-leader threads to ever see the second boolean expression evaluate to anything other than ``true``. This PR simply removes that condition.
Any input would be appreciated. Sorry if this is terribly verbose. I'm new to the Rust community and concurrency can be hard to explain in words. Thanks!
Reject octal zeros in IPv4 addresses
This fixes#86964 by rejecting octal zeros in IP addresses, such that `192.168.00.00000000` is rejected with a parse error, since having leading zeros in front of another zero indicates it is a zero written in octal notation, which is not allowed in the strict mode specified by RFC 6943 3.1.1. Octal rejection was implemented in #83652, but due to the way it was implemented octal zeros were still allowed.
removing TLS support in x86_64-unknown-none-hermitkernel
HermitCore's kernel itself doesn't support TLS. Consequently, the entries in x86_64-unknown-none-hermitkernel should be removed. This commit should help to finalize #89062.
linux/aarch64 Now() should be actually_monotonic()
While issues have been seen on arm64 platforms the Arm architecture requires
that the counter monotonically increases and that it must provide a uniform
view of system time (e.g. it must not be possible for a core to receive a
message from another core with a time stamp and observe time going backwards
(ARM DDI 0487G.b D11.1.2). While there have been a few 64bit SoCs that have
bugs (#49281, #56940) which cause time to not monotonically increase, these have
been fixed in the Linux kernel and we shouldn't penalize all Arm SoCs for those
who refuse to update their kernels:
SUN50I_ERRATUM_UNKNOWN1 - Allwinner A64 / Pine A64 - fixed in 5.1
FSL_ERRATUM_A008585 - Freescale LS2080A/LS1043A - fixed in 4.10
HISILICON_ERRATUM_161010101 - Hisilicon 1610 - fixed in 4.11
ARM64_ERRATUM_858921 - Cortex A73 - fixed in 4.12
255a3f3e18 std: Force `Instant::now()` to be monotonic added a Mutex to work around
this problem and a small test program using glommio shows the majority of time spent
acquiring and releasing this Mutex. 3914a7b0da tries to improve this, but actually
makes it worse on big systems as for 128b atomics a ldxp/stxp pair (and successful loop)
for v8.4 systems that don't support FEAT_LSE2 is required which is expensive as a lock
and because of how the load/store-exclusives scale on large Arm systems is both unfair
to threads and tends to go backwards in performance.
A small sample program using glommio improves by 70x on a 32 core Graviton2
system with this change.
[fuchsia] Update process info struct
The fuchsia platform is in the process of softly transitioning over to
using a new value for ZX_INFO_PROCESS with a new corresponding struct.
This change migrates libstd.
See [fxrev.dev/510478](https://fxrev.dev/510478) and [fxbug.dev/30751](https://fxbug.dev/30751) for more detail.
Add abstract namespace support for Unix domain sockets
Hello! The other day I wanted to mess around with UDS in Rust and found that abstract namespaces ([unix(7)](https://man7.org/linux/man-pages/man7/unix.7.html)) on Linux still needed development. I took the approach of adding `_addr` specific public functions to reduce conflicts.
Feature name: `unix_socket_abstract`
Tracking issue: #85410
Further context: #42048
## Non-platform specific additions
`UnixListener::bind_addr(&SocketAddr) -> Result<UnixListener>`
`UnixStream::connect_addr(&SocketAddr) -> Result<()>`
`UnixDatagram::bind_addr(&SocketAddr) -> Result<UnixDatagram>`
`UnixDatagram::connect_addr(&SocketAddr) -> Result<()>`
`UnixDatagram::send_to_addr(&self, &[u8], &SocketAddr) -> Result<usize>`
## Platform-specific (Linux) additions
`SocketAddr::from_abstract_namespace(&[u8]) -> SocketAddr`
`SockerAddr::as_abstract_namespace() -> Option<&[u8]>`
## Example
```rust
#![feature(unix_socket_abstract)]
use std::os::unix::net::{UnixListener, SocketAddr};
fn main() -> std::io::Result<()> {
let addr = SocketAddr::from_abstract_namespace(b"namespace")?; // Linux only
let listener = match UnixListener::bind_addr(&addr) {
Ok(sock) => sock,
Err(err) => {
println!("Couldn't bind: {:?}", err);
return Err(err);
}
};
Ok(())
}
```
## Further Details
The main inspiration for the implementation came from the [nix-rust](https://github.com/nix-rust/nix/blob/master/src/sys/socket/addr.rs#L558) crate but there are also other [historical](c4db0685b1) [attempts](https://github.com/tormol/uds/blob/master/src/addr.rs#L324) with similar approaches.
A comment I did have was with this change, we now allow a `SocketAddr` to be constructed explicitly rather than just used almost as a handle for the return of `peer_addr` and `local_addr`. We could consider adding other explicit constructors (e.g. `SocketAddr::from_pathname`, `SockerAddr::from_unnamed`).
Cheers!
Use BCryptGenRandom instead of RtlGenRandom on Windows.
This removes usage of RtlGenRandom on Windows, in favour of BCryptGenRandom.
BCryptGenRandom isn't available on XP, but we dropped XP support a while ago.
The fuchsia platform is in the process of softly transitioning over to
using a new value for ZX_INFO_PROCESS with a new corresponding struct.
This change migrates libstd.
See fxrev.dev/510478 and fxbug.dev/30751 for more detail.
Fix ctrl-c causing reads of stdin to return empty on Windows.
Pressing ctrl+c (or ctrl+break) on Windows caused a blocking read of stdin to unblock and return empty, unlike other platforms which continue to block.
On ctrl-c, `ReadConsoleW` will return success, but also set `LastError` to `ERROR_OPERATION_ABORTED`.
This change detects this case, and re-tries the call to `ReadConsoleW`.
Fixes#89177. See issue for further details.
Tested on Windows 7 and Windows 10 with both MSVC and GNU toolchains
Improve `std:🧵:available_parallelism` docs
_Tracking issue: https://github.com/rust-lang/rust/issues/74479_
This PR reworks the documentation of `std:🧵:available_parallelism`, as requested [here](https://github.com/rust-lang/rust/pull/89324#issuecomment-934343254).
## Changes
The following changes are made:
- We've removed prior mentions of "hardware threads" and instead centers the docs around "parallelism" as a resource available to a program.
- We now provide examples of when `available_parallelism` may return numbers that differ from the number of CPU cores in the host machine.
- We now mention that the amount of available parallelism may change over time.
- We make note of which platform components we don't take into account which more advanced users may want to take note of.
- The example has been updated, which should be a bit easier to use.
- We've added a docs alias to `num-cpus` which provides similar functionality to `available_parallelism`, and is one of the most popular crates on crates.io.
---
Thanks!
r? `@BurntSushi`
The unifying theme for this commit is weak, admittedly. I put together a
list of "expensive" functions when I originally proposed this whole
effort, but nobody's cared about that criterion. Still, it's a decent
way to bite off a not-too-big chunk of work.
Given the grab bag nature of this commit, the messages I used vary quite
a bit.
Add #[must_use] to is_condition tests
I threw in `std::path::Path::has_root` for funsies.
A continuation of #89718.
Parent issue: #89692
r? ```@joshtriplett```
Add #[must_use] to non-mutating verb methods
These are methods that could be misconstrued to mutate their input, similar to #89694. I gave each one a different custom message.
I wrote that `upgrade` and `downgrade` don't modify the input pointers. Logically they don't, but technically they do...
Parent issue: #89692
r? ```@joshtriplett```
Add #[must_use] to from_value conversions
I added two methods to the list myself. Clippy did not flag them because they take `mut` args, but neither modifies their argument.
```rust
core::str const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str;
std::ffi::CString unsafe fn from_raw(ptr: *mut c_char) -> CString;
```
I put a custom note on `from_raw`:
```rust
#[must_use = "call `drop(from_raw(ptr))` if you intend to drop the `CString`"]
pub unsafe fn from_raw(ptr: *mut c_char) -> CString {
```
Parent issue: #89692
r? ``@joshtriplett``
Add new tier-3 target: armv7-unknown-linux-uclibceabihf
This change adds a new tier-3 target: armv7-unknown-linux-uclibceabihf
This target is primarily used in embedded linux devices where system resources are slim and glibc is deemed too heavyweight. Cross compilation C toolchains are available [here](https://toolchains.bootlin.com/) or via [buildroot](https://buildroot.org).
The change is based largely on a previous PR #79380 with a few minor modifications. The author of that PR was unable to push the PR forward, and graciously allowed me to take it over.
Per the [target tier 3 policy](https://github.com/rust-lang/rfcs/blob/master/text/2803-target-tier-policy.md), I volunteer to be the "target maintainer".
This is my first PR to Rust itself, so I apologize if I've missed things!
Add #[must_use] to string/char transformation methods
These methods could be misconstrued as modifying their arguments instead of returning new values.
Where possible I made the note recommend a method that does mutate in place.
Parent issue: #89692
Fix minor std::thread documentation typo
callers of spawn_unchecked() need to make sure that the thread
not outlive references in the passed closure, not the other way around.
Optimize File::read_to_end and read_to_string
Reading a file into an empty vector or string buffer can incur unnecessary `read` syscalls and memory re-allocations as the buffer "warms up" and grows to its final size. This is perhaps a necessary evil with generic readers, but files can be read in smarter by checking the file size and reserving that much capacity.
`std::fs::read` and `std::fs::read_to_string` already perform this optimization: they open the file, reads its metadata, and call `with_capacity` with the file size. This ensures that the buffer does not need to be resized and an initial string of small `read` syscalls.
However, if a user opens the `File` themselves and calls `file.read_to_end` or `file.read_to_string` they do not get this optimization.
```rust
let mut buf = Vec::new();
file.read_to_end(&mut buf)?;
```
I searched through this project's codebase and even here are a *lot* of examples of this. They're found all over in unit tests, which isn't a big deal, but there are also several real instances in the compiler and in Cargo. I've documented the ones I found in a comment here:
https://github.com/rust-lang/rust/issues/89516#issuecomment-934423999
Most telling, the documentation for both the `Read` trait and the `Read::read_to_end` method both show this exact pattern as examples of how to use readers. What this says to me is that this shouldn't be solved by simply fixing the instances of it in this codebase. If it's here it's certain to be prevalent in the wider Rust ecosystem.
To that end, this commit adds specializations of `read_to_end` and `read_to_string` directly on `File`. This way it's no longer a minor footgun to start with an empty buffer when reading a file in.
A nice side effect of this change is that code that accesses a `File` as `impl Read` or `dyn Read` will benefit. For example, this code from `compiler/rustc_serialize/src/json.rs`:
```rust
pub fn from_reader(rdr: &mut dyn Read) -> Result<Json, BuilderError> {
let mut contents = Vec::new();
match rdr.read_to_end(&mut contents) {
```
Related changes:
- I also added specializations to `BufReader` to delegate to `self.inner`'s methods. That way it can call `File`'s optimized implementations if the inner reader is a file.
- The private `std::io::append_to_string` function is now marked `unsafe`.
- `File::read_to_string` being more efficient means that the performance note for `io::read_to_string` can be softened. I've added `@camelid's` suggested wording from https://github.com/rust-lang/rust/issues/80218#issuecomment-936806502.
r? `@joshtriplett`
These methods could be misconstrued as modifying their arguments instead
of returning new values.
Where possible I made the note recommend a method that does mutate in
place.
Reading a file into an empty vector or string buffer can incur
unnecessary `read` syscalls and memory re-allocations as the buffer
"warms up" and grows to its final size. This is perhaps a necessary evil
with generic readers, but files can be read in smarter by checking the
file size and reserving that much capacity.
`std::fs::read` and `read_to_string` already perform this optimization:
they open the file, reads its metadata, and call `with_capacity` with
the file size. This ensures that the buffer does not need to be resized
and an initial string of small `read` syscalls.
However, if a user opens the `File` themselves and calls
`file.read_to_end` or `file.read_to_string` they do not get this
optimization.
```rust
let mut buf = Vec::new();
file.read_to_end(&mut buf)?;
```
I searched through this project's codebase and even here are a *lot* of
examples of this. They're found all over in unit tests, which isn't a
big deal, but there are also several real instances in the compiler and
in Cargo. I've documented the ones I found in a comment here:
https://github.com/rust-lang/rust/issues/89516#issuecomment-934423999
Most telling, the `Read` trait and the `read_to_end` method both show
this exact pattern as examples of how to use readers. What this says to
me is that this shouldn't be solved by simply fixing the instances of it
in this codebase. If it's here it's certain to be prevalent in the wider
Rust ecosystem.
To that end, this commit adds specializations of `read_to_end` and
`read_to_string` directly on `File`. This way it's no longer a minor
footgun to start with an empty buffer when reading a file in.
A nice side effect of this change is that code that accesses a `File` as
a bare `Read` constraint or via a `dyn Read` trait object will benefit.
For example, this code from `compiler/rustc_serialize/src/json.rs`:
```rust
pub fn from_reader(rdr: &mut dyn Read) -> Result<Json, BuilderError> {
let mut contents = Vec::new();
match rdr.read_to_end(&mut contents) {
```
Related changes:
- I also added specializations to `BufReader` to delegate to
`self.inner`'s methods. That way it can call `File`'s optimized
implementations if the inner reader is a file.
- The private `std::io::append_to_string` function is now marked
`unsafe`.
- `File::read_to_string` being more efficient means that the performance
note for `io::read_to_string` can be softened. I've added @camelid's
suggested wording from:
https://github.com/rust-lang/rust/issues/80218#issuecomment-936806502
Make cfg imply doc(cfg)
This is a reopening of #79341, rebased and modified a bit (we made a lot of refactoring in rustdoc's types so they needed to be reflected in this PR as well):
* `hidden_cfg` is now in the `Cache` instead of `DocContext` because `cfg` information isn't stored anymore on `clean::Attributes` type but instead computed on-demand, so we need this information in later parts of rustdoc.
* I removed the `bool_to_options` feature (which makes the code a bit simpler to read for `SingleExt` trait implementation.
* I updated the version for the feature.
There is only one thing I couldn't figure out: [this comment](https://github.com/rust-lang/rust/pull/79341#discussion_r561855624)
> I think I'll likely scrap the whole `SingleExt` extension trait as the diagnostics for 0 and >1 items should be different.
How/why should they differ?
EDIT: this part has been solved, the current code was fine, just needed a little simplification.
cc `@Nemo157`
r? `@jyn514`
Original PR description:
This is only active when the `doc_cfg` feature is active.
The implicit cfg can be overridden via `#[doc(cfg(...))]`, so e.g. to hide a `#[cfg]` you can use something like:
```rust
#[cfg(unix)]
#[doc(cfg(all()))]
pub struct Unix;
```
By adding `#![doc(cfg_hide(foobar))]` to the crate attributes the cfg `#[cfg(foobar)]` (and _only_ that _exact_ cfg) will not be implicitly treated as a `doc(cfg)` to render a message in the documentation.
Rename `std:🧵:available_conccurrency` to `std:🧵:available_parallelism`
_Tracking issue: https://github.com/rust-lang/rust/issues/74479_
This PR renames `std:🧵:available_conccurrency` to `std:🧵:available_parallelism`.
## Rationale
The API was initially named `std:🧵:hardware_concurrency`, mirroring the [C++ API of the same name](https://en.cppreference.com/w/cpp/thread/thread/hardware_concurrency). We eventually decided to omit any reference to the word "hardware" after [this comment](https://github.com/rust-lang/rust/pull/74480#issuecomment-662045841). And so we ended up with `available_concurrency` instead.
---
For a talk I was preparing this week I was reading through ["Understanding and expressing scalable concurrency" (A. Turon, 2013)](http://aturon.github.io/academic/turon-thesis.pdf), and the following passage stood out to me (emphasis mine):
> __Concurrency is a system-structuring mechanism.__ An interactive system that deals with disparate asynchronous events is naturally structured by division into concurrent threads with disparate responsibilities. Doing so creates a better fit between problem and solution, and can also decrease the average latency of the system by preventing long-running computations from obstructing quicker ones.
> __Parallelism is a resource.__ A given machine provides a certain capacity for parallelism, i.e., a bound on the number of computations it can perform simultaneously. The goal is to maximize throughput by intelligently using this resource. For interactive systems, parallelism can decrease latency as well.
_Chapter 2.1: Concurrency is not Parallelism. Page 30._
---
_"Concurrency is a system-structuring mechanism. Parallelism is a resource."_ — It feels like this accurately captures the way we should be thinking about these APIs. What this API returns is not "the amount of concurrency available to the program" which is a property of the program, and thus even with just a single thread is effectively unbounded. But instead it returns "the amount of _parallelism_ available to the program", which is a resource hard-constrained by the machine's capacity (and can be further restricted by e.g. operating systems).
That's why I'd like to propose we rename this API from `available_concurrency` to `available_parallelism`. This still meets the criteria we previously established of not attempting to define what exactly we mean by "hardware", "threads", and other such words. Instead we only talk about "concurrency" as an abstract resource available to our program.
r? `@joshtriplett`
Use the 64b inner:monotonize() implementation not the 128b one for aarch64
aarch64 prior to v8.4 (FEAT_LSE2) doesn't have an instruction that guarantees
untorn 128b reads except for completing a 128b load/store exclusive pair
(ldxp/stxp) or compare-and-swap (casp) successfully. The requirement to
complete a 128b read+write atomic is actually more expensive and more unfair
than the previous implementation of monotonize() which used a Mutex on aarch64,
especially at large core counts. For aarch64 switch to the 64b atomic
implementation which is about 13x faster for a benchmark that involves many
calls to Instant::now().
path.push() should work as expected on windows verbatim paths
On Windows, std::fs::canonicalize() returns an so-called UNC path. UNC paths differ with regular paths because:
- This type of path can much longer than a non-UNC path (32k vs 260 characters).
- The prefix for a UNC path is ``Component::Prefix(Prefix::DiskVerbatim(..)))``
- No `/` is allowed
- No `.` is allowed
- No `..` is allowed
Rust has poor handling of such paths. If you join a UNC path with a path with any of the above, then this will not work.
I've implemented a new method `fn join_fold()` which joins paths and also removes any `.` and `..` from it, and replaces `/` with `\` on Windows. Using this function it is possible to use UNC paths without issue. In addition, this function is useful on Linux too; paths can be appended without having to call `canonicalize()` to remove the `.` and `..`.
This PR needs test cases, which can I add. I hope this will a start of a discussion.
Manual Debug for Unix ExitCode ExitStatus ExitStatusError
These structs have misleading names. An ExitStatus[Error] is actually a Unix wait status; an ExitCode is actually an exit status. These misleading names appear in the `Debug` output.
The `Display` impls on Unix have been improved, but the `Debug` impls are still misleading, as reported in #74832.
Fix this by pretending that these internal structs are called `unix_exit_status` and `unix_wait_status` as applicable. (We can't actually rename the structs because of the way that the cross-platform machinery works: the names are cross-platform.)
After this change, this program
```
#![feature(exit_status_error)]
fn main(){
let x = std::process::Command::new("false").status().unwrap();
dbg!(x.exit_ok());
eprintln!("x={:?}",x);
}
```
produces this output
```
[src/main.rs:4] x.exit_ok() = Err(
ExitStatusError(
unix_wait_status(
256,
),
),
)
x=ExitStatus(unix_wait_status(256))
```
Closes#74832
Remove unnecessary unsafe block in `process_unix`
Because it's nested under this unsafe fn!
This block isn't detected as unnecessary because of a bug in the compiler: #88260.
Add `Ipv6Addr::is_benchmarking`
This PR adds the unstable method `Ipv6Addr::is_benchmarking`. This method is added for parity with `Ipv4Addr::is_benchmarking`, and I intend to use it in a future rework of `Ipv6Addr::is_global` (edit: #86634) to more accurately follow the [IANA Special Address Registry](https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml) (like is done in `Ipv4Addr::is_global`).
With `Ipv6Addr::is_benchmarking` and `Ipv4Addr::is_benchmarking` now both existing, `IpAddr::is_benchmarking` is also added.
Fix read_to_end to not grow an exact size buffer
If you know how much data to expect and use `Vec::with_capacity` to pre-allocate a buffer of that capacity, `Read::read_to_end` will still double its capacity. It needs some space to perform a read, even though that read ends up returning `0`.
It's a bummer to carefully pre-allocate 1GB to read a 1GB file into memory and end up using 2GB.
This fixes that behavior by special casing a full buffer and reading into a small "probe" buffer instead. If that read returns `0` then it's confirmed that the buffer was the perfect size. If it doesn't, the probe buffer is appended to the normal buffer and the read loop continues.
Fixing this allows several workarounds in the standard library to be removed:
- `Take` no longer needs to override `Read::read_to_end`.
- The `reservation_size` callback that allowed `Take` to inhibit the previous over-allocation behavior isn't needed.
- `fs::read` doesn't need to reserve an extra byte in `initial_buffer_size`.
Curiously, there was a unit test that specifically checked that `Read::read_to_end` *does* over-allocate. I removed that test, too.
This allows using longer paths for filesystem operations without the user needing to `canonicalize` or manually prefix paths.
If the path is already verbatim than this has no effect.
On MinGW toolchains the various features (such as function sections)
necessary to eliminate dead function references are disabled due to
various bugs. This means that the windows sockets library will most
likely remain linked to any mingw toolchain built program that also
utilizes libstd.
That said, I made an attempt to also enable `function-sections` and
`--gc-sections` during my experiments, but the symbol references
remained, sadly.
Restructure std::rt
These changes should reduce binary size slightly while at the same slightly improving performance of startup, thread spawning and `std:🧵:current()`. I haven't verified if the compiler is able to optimize some of these cases already, but at least for some others the compiler is unable to do these optimizations as they slightly change behavior in cases where program startup would crash anyway by omitting a backtrace and panic location.
I can remove 6f6bb16 if preferred.
The reference automatically coerces to a pointer. Writing an explicit
cast here is slightly misleading because that's most commonly used when
a pointer needs to be converted from one pointer type to another, e.g.
`*const c_void` to `*const sigaction` or vice versa.
Add SOLID targets
This PR introduces new tier 3 targets for [SOLID](https://www.kmckk.co.jp/eng/SOLID/) embedded development platform by Kyoto Microcomputer Co., Ltd.
| Target name | `target_arch` | `target_vendor` | `target_os` |
|--------------------------------|---------------|-----------------|--------------|
| `aarch64-kmc-solid_asp3` | `aarch64` | `kmc` | `solid_asp3` |
| `armv7a-kmc-solid_asp3-eabi` | `arm` | `kmc` | `solid_asp3` |
| `armv7a-kmc-solid_asp3-eabihf` | `arm` | `kmc` | `solid_asp3` |
## Related PRs
- [ ] `libc`: https://github.com/rust-lang/libc/pull/2227
- [ ] `cc`: https://github.com/alexcrichton/cc-rs/pull/609
## Non-blocking Issues
- [ ] The target kernel can support `Thread::unpark` directly, but this property is not utilized because the underlying kernel feature is used to implement `Condvar` and it's unclear whether `std` should guarantee that parking tokens are not clobbered by other synchronization primitives.
- [ ] The rustc book: The page title "\*-kmc-solid-\*" shows up as "-kmc-solid-" in TOC
## Tier 3 Target Policy
As tier 3 targets, the new targets are required to adhere to [the tier 3 target policy](https://doc.rust-lang.org/nightly/rustc/target-tier-policy.html#tier-3-target-policy) requirements. This section quotes each requirement in entirety and describes how they are met.
> - A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
See [`src/doc/rustc/src/platform-support/kmc-solid.md`](https://github.com/kawadakk/rust/blob/release-add-solid-support/src/doc/rustc/src/platform-support/kmc-solid.md).
> - Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
> - Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
The new target names follow this format: `$ARCH-$VENDOR-$OS-$ABI`, which is already adopted by most existing targets. `$ARCH` and `$ABI` follow the convention: `aarch64-*` for AArch64, `armv7a-*-eabi` for Armv7-A with EABI. `$OS` is used to distinguish multiple variations of the platform in a somewhat similar way to the Apple targets, though we are only adding one variation in this PR. `$VENDOR` denotes the platform vendor name similarly to the Apple, Solaris, SGX, and VxWorks targets.
`$OS` corresponds to the value of `target_os` and takes the format `solid-$KERNEL`. The inclusion of a hyphen prevents unique decomposition of target names, though the mapping between target names and target attributes isn't trivial in the first place, e.g., because of the Android targets.
More targets may be added later, as we support other base kernels (there are at least three at the point of writing) and are interested in supporting other processor architectures in the future.
> - Tier 3 targets may have unusual requirements to build or use, but must not create legal issues or impose onerous legal terms for the Rust project or for Rust developers or users.
> - The target must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust license (`MIT OR Apache-2.0`).
> - The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the `tidy` tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to be subject to any new license requirements.
> - If the target supports building host tools (such as `rustc` or `cargo`), those host tools must not depend on proprietary (non-FOSS) libraries, other than ordinary runtime libraries supplied by the platform and commonly used by other binaries built for the target. For instance, `rustc` built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.
> - Targets should not require proprietary (non-FOSS) components to link a functional binary or library.
> - "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are *not* limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
We intend to make the contribution fully available under the standard Rust license with no additional legal restrictions whatsoever. This PR does not introduce any new dependency less permissive than the Rust license policy, and we are willing to ensure this doesn't happen for future contributions regarding the new targets.
The new targets don't support building host tools.
Although the new targets use a platform-provided C compiler toolchain, it can be substituted by [GNU Arm Embedded Toolchain](https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm) for testing purposes.
> - Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (`core` for most targets, `alloc` for targets that can support dynamic memory allocation, `std` for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.
Most features are implemented. The following features are not implemented due to the lack of native support:
- `fs::File::{file_attr, truncate, duplicate, set_permissions}`
- `fs::{symlink, link, canonicalize}`
- Process creation
- Command-line arguments
~~Networking is not implemented yet, and we intend to add it as soon as it's ready.~~
Edit (2021-07-07): Networking is now implemented.
Backtrace generation is not really a good fit for embedded targets, so it's intentionally left unimplemented. Unwinding is functional, however.
> - The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running tests (even if they do not pass), the documentation must explain how to run tests for the target, using emulation if possible or dedicated hardware if necessary.
See [`src/doc/rustc/src/platform-support/kmc-solid.md`](https://github.com/kawadakk/rust/blob/release-add-solid-support/src/doc/rustc/src/platform-support/kmc-solid.md). Running tests is not supported.
> - Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
> - This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.
> - Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via ``@`)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
> - Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.
> - Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
> - In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.
We acknowledge these requirements and intend to ensure they are met.
There are no closely related targets at the moment.
SOLID[1] is an embedded development platform provided by Kyoto
Microcomputer Co., Ltd. This commit introduces a basic Tier 3 support
for SOLID.
# New Targets
The following targets are added:
- `aarch64-kmc-solid_asp3`
- `armv7a-kmc-solid_asp3-eabi`
- `armv7a-kmc-solid_asp3-eabihf`
SOLID's target software system can be divided into two parts: an
RTOS kernel, which is responsible for threading and synchronization,
and Core Services, which provides filesystems, networking, and other
things. The RTOS kernel is a μITRON4.0[2][3]-derived kernel based on
the open-source TOPPERS RTOS kernels[4]. For uniprocessor systems
(more precisely, systems where only one processor core is allocated for
SOLID), this will be the TOPPERS/ASP3 kernel. As μITRON is
traditionally only specified at the source-code level, the ABI is
unique to each implementation, which is why `asp3` is included in the
target names.
More targets could be added later, as we support other base kernels
(there are at least three at the point of writing) and are interested
in supporting other processor architectures in the future.
# C Compiler
Although SOLID provides its own supported C/C++ build toolchain, GNU Arm
Embedded Toolchain seems to work for the purpose of building Rust.
# Unresolved Questions
A μITRON4 kernel can support `Thread::unpark` natively, but it's not
used by this commit's implementation because the underlying kernel
feature is also used to implement `Condvar`, and it's unclear whether
`std` should guarantee that parking tokens are not clobbered by other
synchronization primitives.
# Unsupported or Unimplemented Features
Most features are implemented. The following features are not
implemented due to the lack of native support:
- `fs::File::{file_attr, truncate, duplicate, set_permissions}`
- `fs::{symlink, link, canonicalize}`
- Process creation
- Command-line arguments
Backtrace generation is not really a good fit for embedded targets, so
it's intentionally left unimplemented. Unwinding is functional, however.
## Dynamic Linking
Dynamic linking is not supported. The target platform supports dynamic
linking, but enabling this in Rust causes several problems.
- The linker invocation used to build the shared object of `std` is
too long for the platform-provided linker to handle.
- A linker script with specific requirements is required for the
compiled shared object to be actually loadable.
As such, we decided to disable dynamic linking for now. Regardless, the
users can try to create shared objects by manually invoking the linker.
## Executable
Building an executable is not supported as the notion of "executable
files" isn't well-defined for these targets.
[1] https://solid.kmckk.com/SOLID/
[2] http://ertl.jp/ITRON/SPEC/mitron4-e.html
[3] https://en.wikipedia.org/wiki/ITRON_project
[4] https://toppers.jp/
