Add doc aliases for memory allocations
This patch adds doc aliases for various C allocation functions, making it possible to search for the C-equivalent of a function and finding the (safe) Rust counterpart:
- `Vec::with_capacity` / `Box::new` / `vec!` -> alloc + malloc, allocates memory
- `Box::new_zeroed` -> calloc, allocates zeroed-out memory
- `Vec::{reserve,reserve_exact,try_reserve_exact,shrink_to_fit,shrink_to}` -> realloc, reallocates a previously allocated slice of memory
It's worth noting that `Vec::new` does not allocate, so we don't link to it. Instead people are probably looking for `Vec::with_capacity` or `vec!`. I hope this will allow people comfortable with the system allocation APIs to make it easier to find what they may be looking for.
Thanks!
Following traits are now diagnostic items:
- `From` (unchanged)
- `Into`
- `TryFrom`
- `TryInto`
This also adds symbols for those items:
- `into_trait`
- `try_from_trait`
- `try_into_trait`
Enforce statically that `MIN_NON_ZERO_CAP` is calculated at compile time
Previously, it would usually get computed by LLVM, but this enforces it. This removes the need for the comment saying "LLVM is smart enough".
I don't expect this to make a performance difference, but I do think it makes the performance properties easier to reason about.
Document why not use concat! in dbg! macro
Original title: Reduce code generated by `dbg!` macro
The expanded code before/after: <https://rust.godbolt.org/z/hE3j95>.
---
We cannot use `concat!` since `file!` could contains `{` or the expression is a block (`{ .. }`).
Using it will generated malformed format strings.
So let's document this reason why we don't use `concat!` macro at all.
Expand docs on Iterator::intersperse
Unstable feature in #79524. This expands on the docs to bring them more in line with how other methods of `Iterator` are demonstrated.
The minimum supported Windows version is now Windows 7. Windows XP
and Windows Vista are no longer supported; both are already broken, and
require extra steps to use.
This commit removes the delayed-binding support for Windows API
functions that are present on all supported Windows targets. This has
several benefits: Removes needless complexity. Removes a load and
dynamic call on hot paths in mutex acquire / release. This may have
performance benefits.
* "Drop official support for Windows XP"
https://github.com/rust-lang/compiler-team/issues/378
* "Firefox has ended support for Windows XP and Vista"
https://support.mozilla.org/en-US/kb/end-support-windows-xp-and-vista
Fix broken links with `--document-private-items` in the standard library
As it was suggested in #81037 `SpecFromIter` is not
in the scope and therefore we get a warning when we try to
do document private intems in `rust/library/alloc/`.
This addresses #81037 by adding the trait in the scope as ```@jyn514```
suggested and also adding an `allow(unused_imports)` flag so that
the compiler does not complain, Since the trait is not used
per se in the code, it's just needed to have properly documented
docs.
Improve grammar in documentation of format strings
The docs previously were
* using some weird `<` and `>` around some nonterminals
* _correct me if these **did** have any meaning_
* using of a (not explicitly defined) `text` nonterminal that didn’t explicitly disallow productions containing `'{'` or `'}'`
* incorrect in not allowing for `x?` and `X?` productions of `type`
* unnecessarily ambiguous, both
* allowing `type` to be `''`, and
* using an optional `[type]`
* using inconsistent underscore/hyphenation style between `format_string` and `format_spec` vs `maybe-format`
_Rendered:_
_(current docs: https://doc.rust-lang.org/nightly/std/fmt/#syntax)_
```@rustbot``` modify labels: T-doc
Visualize vector while differentiating between stack and heap.
Inspired by cheats.rs, as this is probably the first place beginner go,
they could understand stack and heap, length and capacity with this. Not
sure if adding this means we should add to other places too.
Superseeds #76066
std: Update wasi-libc commit of the wasm32-wasi target
This brings in an implementation of `current_dir` and `set_current_dir`
(emulation in `wasi-libc`) as well as an updated version of finding
relative paths. This also additionally updates clang to the latest
release to build wasi-libc with.
BufWriter: Provide into_raw_parts
If something goes wrong, one might want to unpeel the layers of nested
Writers to perform recovery actions on the underlying writer, or reuse
its resources.
`into_inner` can be used for this when the inner writer is still
working. But when the inner writer is broken, and returning errors,
`into_inner` simply gives you the error from flush, and the same
`Bufwriter` back again.
Here I provide the necessary function, which I have chosen to call
`into_raw_parts`.
I had to do something with `panicked`. Returning it to the caller as
a boolean seemed rather bare. Throwing the buffered data away in this
situation also seems unfriendly: maybe the programmer knows something
about the underlying writer and can recover somehow.
So I went for a custom Error. This may be overkill, but it does have
the nice property that a caller who actually wants to look at the
buffered data, rather than simply extracting the inner writer, will be
told by the type system if they forget to handle the panicked case.
If a caller doesn't need the buffer, it can just be discarded. That
WriterPanicked is a newtype around Vec<u8> means that hopefully the
layouts of the Ok and Err variants can be very similar, with just a
boolean discriminant. So this custom error type should compile down
to nearly no code.
*If this general idea is felt appropriate, I will open a tracking issue, etc.*
BTreeMap: prefer bulk_steal functions over specialized ones
The `steal_` functions (apart from their return value) are basically specializations of the more general `bulk_steal_` functions. This PR removes the specializations. The library/alloc benchmarks say this is never slower and up to 6% faster.
r? ``@Mark-Simulacrum``
As it was suggested in #81037 `SpecFromIter` is not
in the scope and therefore (even it should fail),
we get a warning when we try do document private
intems in `rust/library/alloc/`.
This fixes#81037 by adding the trait in the scope
and also adding an `allow(unused_imports)` flag so that
the compiler does not complain, Since the trait is not used
per se in the code, it's just needed to have properly documented
docs.
Stability oddity with const intrinsics
cc `@RalfJung`
In https://github.com/rust-lang/rust/pull/80699#discussion_r551495670 `@usbalbin` realized we accepted some intrinsics as `const` without a `#[rustc_const_(un)stable]` attribute. I did some digging, and that example works because intrinsics inherit their stability from their parents... including `#[rustc_const_(un)stable]` attributes. While we may want to fix that (not sure, wasn't there just a MCPed PR that caused this on purpose?), we definitely want tests for it, thus this PR adding tests and some fun tracing statements.
BTreeMap: convert search functions to methods
And further tweak the signature of `search_linear`, in preparation of a better #81094.
r? `@Mark-Simulacrum`
Don't use posix_spawn_file_actions_addchdir_np on macOS.
There is a bug on macOS where using `posix_spawn_file_actions_addchdir_np` with a relative executable path will cause `posix_spawnp` to return ENOENT, even though it successfully spawned the process in the given directory.
`posix_spawn_file_actions_addchdir_np` was introduced in macOS 10.15 first released in Oct 2019. I have tested macOS 10.15.7 and 11.0.1.
Example offending program:
```rust
use std::fs;
use std::os::unix::fs::PermissionsExt;
use std::process::*;
fn main() {
fs::create_dir_all("bar").unwrap();
fs::create_dir_all("foo").unwrap();
fs::write("foo/foo.sh", "#!/bin/sh\necho hello ${PWD}\n").unwrap();
let perms = fs::Permissions::from_mode(0o755);
fs::set_permissions("foo/foo.sh", perms).unwrap();
let c = Command::new("../foo/foo.sh").current_dir("bar").spawn();
eprintln!("{:?}", c);
}
```
This prints:
```
Err(Os { code: 2, kind: NotFound, message: "No such file or directory" })
hello /Users/eric/Temp/bar
```
I wanted to open this PR to get some feedback on possible solutions. Alternatives:
* Do nothing.
* Document the bug.
* Try to detect if the executable is a relative path on macOS, and avoid using `posix_spawn_file_actions_addchdir_np` only in that case.
I looked at the [XNU source code](https://opensource.apple.com/source/xnu/xnu-6153.141.1/bsd/kern/kern_exec.c.auto.html), but I didn't see anything obvious that would explain the behavior. The actual chdir succeeds, it is something else further down that fails, but I couldn't see where.
EDIT: I forgot to mention, relative exe paths with `current_dir` in general are discouraged (see #37868). I don't know if #37868 is fixable, since normalizing it would change the semantics for some platforms. Another option is to convert the executable to an absolute path with something like joining the cwd with the new cwd and the executable, but I'm uncertain about that.
Don't make tools responsible for checking unknown and renamed lints
Previously, clippy (and any other tool emitting lints) had to have their
own separate UNKNOWN_LINTS pass, because the compiler assumed any tool
lint could be valid. Now, as long as any lint starting with the tool
prefix exists, the compiler will warn when an unknown lint is present.
This may interact with the unstable `tool_lint` feature, which I don't entirely understand, but it will take the burden off those external tools to add their own lint pass, which seems like a step in the right direction to me.
- Don't mark `ineffective_unstable_trait_impl` as an internal lint
- Use clippy's more advanced lint suggestions
- Deprecate the `UNKNOWN_CLIPPY_LINTS` pass (and make it a no-op)
- Say 'unknown lint `clippy::x`' instead of 'unknown lint x'
This is tested by existing clippy tests. When https://github.com/rust-lang/rust/pull/80527 merges, it will also be tested in rustdoc tests. AFAIK there is no way to test this with rustc directly.
Add NonZeroUn::is_power_of_two
This saves instructions on both new and old machines <https://rust.godbolt.org/z/4fjTMz>
- On the default x64 target (with no fancy instructions available) it saves a few instructions by not needing to also check for zero.
- On newer targets (with BMI1) it uses `BLSR` for super-short assembly.
This can be used for things like checks against alignments stored in `NonZeroUsize`.
Force vec![] to expression position only
r? `@oli-obk`
I went with the lazy way of only changing what broke. I moved the test to ui/macros because the diagnostics no longer give suggestions.
Closes#61933
Add benchmark and fast path for BufReader::read_exact
At work, we have a wrapper type that implements this optimization. It would be nice if the standard library were faster.
Before:
```
test io::buffered::tests::bench_buffered_reader_small_reads ... bench: 7,670 ns/iter (+/- 45)
```
After:
```
test io::buffered::tests::bench_buffered_reader_small_reads ... bench: 4,457 ns/iter (+/- 41)
```
BTreeMap: expose new_internal function and sanitize from_new_internal
`new_internal` is the functional core of the imperative `push_internal_level`, and `from_new_internal` can easily do a proper job instead of returning a half-baked node.
r? `@Mark-Simulacrum`
Add `as_rchunks` (and friends) to slices
`@est31` mentioned (https://github.com/rust-lang/rust/issues/76354#issuecomment-717027175) that, for completeness, there needed to be an `as_chunks`-like method that chunks from the end (with the remainder at the beginning) like `rchunks` does.
So here's a PR for `as_rchunks: &[T] -> (&[T], &[[T; N]])` and `as_rchunks_mut: &mut [T] -> (&mut [T], &mut [[T; N]])`.
But as I was doing this and copy-pasting `from_raw_parts` calls, I thought that I should extract that into an unsafe method. It started out a private helper, but it seemed like `as_chunks_unchecked` could be reasonable as a "real" method, so I added docs and made it public. Let me know if you think it doesn't pull its weight.
Rollup of 17 pull requests
Successful merges:
- #78455 (Introduce {Ref, RefMut}::try_map for optional projections in RefCell)
- #80144 (Remove giant badge in README)
- #80614 (Explain why borrows can't be held across yield point in async blocks)
- #80670 (TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips)
- #80681 (Clarify what the effects of a 'logic error' are)
- #80764 (Re-stabilize Weak::as_ptr and friends for unsized T)
- #80901 (Make `x.py --color always` apply to logging too)
- #80902 (Add a regression test for #76281)
- #80941 (Do not suggest invalid code in pattern with loop)
- #80968 (Stabilize the poll_map feature)
- #80971 (Put all feature gate tests under `feature-gates/`)
- #81021 (Remove doctree::Import)
- #81040 (doctest: Reset errors before dropping the parse session)
- #81060 (Add a regression test for #50041)
- #81065 (codegen_cranelift: Fix redundant semicolon warn)
- #81069 (Add sample code for Rc::new_cyclic)
- #81081 (Add test for #34792)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Re-stabilize Weak::as_ptr and friends for unsized T
As per [T-lang consensus](https://hackmd.io/7r3_is6uTz-163fsOV8Vfg), this uses a branch to handle the dangling case. The discussed optimization of only doing the branch in the T: ?Sized case is left for a followup patch, as doing so is not trivial (as it requires specialization) and not _obviously_ better (as it requires using `wrapping_offset` rather than `offset` more).
<details><summary>Basically said optimization</summary>
Specialize on `T: Sized`:
```rust
fn as_ptr(&self) -> *const T {
if [ T is Sized ] || !is_dangling(ptr) {
(ptr as *mut T).set_ptr_value( (ptr as *mut u8).wrapping_offset(data_offset) )
} else {
ptr::null()
}
}
fn from_raw(*const T) -> Self {
if [ T is Sized ] || !ptr.is_null() {
let ptr = (ptr as *mut RcBox).set_ptr_value( (ptr as *mut u8).wrapping_offset(-data_offset) );
Weak { ptr }
} else {
Weak::new()
}
}
```
(but with more `set_ptr_value` to avoid `Sized` restrictions and maintain metadata.)
Written in this fashion, this is not a correctness-critical specialization (i.e. so long as `[ T is Sized ]` is false for unsized `T`, it can be `rand()` for sized `T` without breaking correctness), but it's still touchy, so I'd rather do it in another PR with separate review.
---
</details>
This effectively reverts #80422 and re-establishes #74160. T-libs [previously signed off](https://github.com/rust-lang/rust/pull/74160#issuecomment-660539373) on this stable API change in #74160.
Clarify what the effects of a 'logic error' are
This clarifies what a 'logic error' is (which is a term used to describe what happens if you put things in a hash table or btree and then use something like a refcell to break the internal ordering). This tries to be as vague as possible, as we don't really want to promise what happens, except "bad things, but not UB". This was discussed in #80657
TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips
I found this while working on improvements for TRA.
After partially consuming a Zip adapter and then wrapping it into another Zip where the adapters use their `TrustedRandomAccess` specializations leads to the outer adapter returning elements which should have already been consumed.
If the optimizer gets tripped up by the addition this might affect performance for chained `zip()` iterators even when the inner one is not partially advanced but it would require more extensive fixes to `TrustedRandomAccess` to communicate those offsets earlier.
Included test fails on nightly, [playground link](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=24fa1edf8a104ff31f5a24830593b01f)
Introduce {Ref, RefMut}::try_map for optional projections in RefCell
This fills a usability gap of `RefCell` I've personally encountered to perform optional projections, mostly into collections such as `RefCell<Vec<T>>` or `RefCell<HashMap<U, T>>`:
> This kind of API was briefly featured under Open questions in #10514 back in 2013 (!)
```rust
let values = RefCell::new(vec![1, 2, 3, 4]);
let b = Ref::opt_map(values.borrow(), |vec| vec.get(2));
```
It primarily avoids this alternative approach to accomplish the same kind of projection which is both rather noisy and panicky:
```rust
let values = RefCell::new(vec![1, 2, 3, 4]);
let b = if values.get(2).is_some() {
Some(Ref::map(values.borrow(), |vec| vec.get(2).unwrap()))
} else {
None
};
```
### Open questions
The naming `opt_map` is preliminary. I'm not aware of prior art in std to lean on here, but this name should probably be improved if this functionality is desirable.
Since `opt_map` consumes the guard, and alternative syntax might be more appropriate which instead *tries* to perform the projection, allowing the original borrow to be recovered in case it fails:
```rust
pub fn try_map<U: ?Sized, F>(orig: Ref<'b, T>, f: F) -> Result<Ref<'b, U>, Self>
where
F: FnOnce(&T) -> Option<&U>;
```
This would be more in line with the `try_map` method [provided by parking lot](https://docs.rs/lock_api/0/lock_api/struct.RwLockWriteGuard.html#method.try_map).
implement ptr::write without dedicated intrinsic
This makes `ptr::write` more consistent with `ptr::write_unaligned`, `ptr::read`, `ptr::read_unaligned`, all of which are implemented in terms of `copy_nonoverlapping`.
This means we can also remove `move_val_init` implementations in codegen and Miri, and its special handling in the borrow checker.
Also see [this Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/ptr.3A.3Aread.20vs.20ptr.3A.3Awrite).
It's not an internal lint:
- It's not in the rustc::internal lint group
- It's on unconditionally, because it actually lints `staged_api`, not
the compiler
This fixes a bug where `#[deny(rustc::internal)]` would warn that
`rustc::internal` was an unknown lint.
