Add `Arc::into_inner` for safely discarding `Arc`s without calling the destructor on the inner type.
ACP: rust-lang/libs-team#162
Reviving #79665.
I want to get this merged this time; this does not contain changes (apart from very minor changes in comments/docs).
See #79665 for further description of the PR. The only “unresolved” points that led to that PR being closed, AFAICT, were
* The desire to also implement a `Rc::into_inner` function
* however, this can very well also happen as a subsequent PR
* Possible need for further discussion on the naming “`into_inner`” (?)
* `into_inner` seems fine to me; also, this PR introduces unstable API, and names can be changed later, too
* ~~I don't know if a tracking issue for the feature flag is supposed to be opened before or after this PR gets merged (if *before*, then I can add the issue number to the `#[unstable…]` attribute)~~ There is a [tracking issue](https://github.com/rust-lang/rust/issues/106894) now.
I say “unresolved” in quotation marks because from my point of view, if reviewers agree, the PR can be merged immediately and as-is :-)
Unify stable and unstable sort implementations in same core module
This moves the stable sort implementation to the core::slice::sort module. By virtue of being in core it can't access `Vec`. The two `Vec` used by merge sort, `buf` and `runs`, are modelled as custom types that implement the very limited required `Vec` interface with the help of provided allocation and free functions. This is done to allow future re-use of functions and logic between stable and unstable sort. Such as `insert_head`.
This is in preparation of #100856 and #104116. It only moves code, it *doesn't* change any of the sort related logic. This unlocks the ability to share `insert_head`, `insert_tail`, `swap_if_less` `merge` and more.
Tagging ````@Mark-Simulacrum```` I hope this allows progress on #100856, by moving `merge_sort` here I hope future changes will be easier to review.
Implement `alloc::vec::IsZero` for `Option<$NUM>` types
Fixes#106911
Mirrors the `NonZero$NUM` implementations with an additional `assert_zero_valid`.
`None::<i32>` doesn't stricly satisfy `IsZero` but for the purpose of allocating we can produce more efficient codegen.
Don't do pointer arithmetic on pointers to deallocated memory
vec::Splice can invalidate the slice::Iter inside vec::Drain. So we replace them with dangling pointers which, unlike ones to deallocated memory, are allowed.
Fixes miri test failures.
Fixes https://github.com/rust-lang/miri/issues/2759
vec::Splice can invalidate the slice::Iter inside vec::Drain.
So we replace them with dangling pointers which, unlike ones to
deallocated memory, are allowed.
Leak amplification for peek_mut() to ensure BinaryHeap's invariant is always met
In the libs-api team's discussion around #104210, some of the team had hesitations around exposing malformed BinaryHeaps of an element type whose Ord and Drop impls are trusted, and which does not contain interior mutability.
For example in the context of this kind of code:
```rust
use std::collections::BinaryHeap;
use std::ops::Range;
use std::slice;
fn main() {
let slice = &mut ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
let cut_points = BinaryHeap::from(vec![4, 2, 7]);
println!("{:?}", chop(slice, cut_points));
}
// This is a souped up slice::split_at_mut to split in arbitrary many places.
//
// usize's Ord impl is trusted, so 1 single bounds check guarantees all those
// output slices are non-overlapping and in-bounds
fn chop<T>(slice: &mut [T], mut cut_points: BinaryHeap<usize>) -> Vec<&mut [T]> {
let mut vec = Vec::with_capacity(cut_points.len() + 1);
let max = match cut_points.pop() {
Some(max) => max,
None => {
vec.push(slice);
return vec;
}
};
assert!(max <= slice.len());
let len = slice.len();
let ptr: *mut T = slice.as_mut_ptr();
let get_unchecked_mut = unsafe {
|range: Range<usize>| &mut *slice::from_raw_parts_mut(ptr.add(range.start), range.len())
};
vec.push(get_unchecked_mut(max..len));
let mut end = max;
while let Some(start) = cut_points.pop() {
vec.push(get_unchecked_mut(start..end));
end = start;
}
vec.push(get_unchecked_mut(0..end));
vec
}
```
```console
[['7', '8', '9'], ['4', '5', '6'], ['2', '3'], ['0', '1']]
```
In the current BinaryHeap API, `peek_mut()` is the only thing that makes the above function unsound.
```rust
let slice = &mut ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
let mut cut_points = BinaryHeap::from(vec![4, 2, 7]);
{
let mut max = cut_points.peek_mut().unwrap();
*max = 0;
std::mem::forget(max);
}
println!("{:?}", chop(slice, cut_points));
```
```console
[['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'], [], ['2', '3'], ['0', '1']]
```
Or worse:
```rust
let slice = &mut ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'];
let mut cut_points = BinaryHeap::from(vec![100, 100]);
{
let mut max = cut_points.peek_mut().unwrap();
*max = 0;
std::mem::forget(max);
}
println!("{:?}", chop(slice, cut_points));
```
```console
[['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'], [], ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '\u{1}', '\0', '?', '翾', '?', '翾', '\0', '\0', '?', '翾', '?', '翾', '?', '啿', '?', '啿', '?', '啿', '?', '啿', '?', '啿', '?', '翾', '\0', '\0', '', '啿', '\u{5}', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\0', '\u{8}', '\0', '`@',` '\0', '\u{1}', '\0', '?', '翾', '?', '翾', '?', '翾', '
thread 'main' panicked at 'index out of bounds: the len is 33 but the index is 33', library/core/src/unicode/unicode_data.rs:319:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
---
This PR makes `peek_mut()` use leak amplification (https://doc.rust-lang.org/1.66.0/nomicon/leaking.html#drain) to preserve the heap's invariant even in the situation that `PeekMut` gets leaked.
I'll also follow up in the tracking issue of unstable `drain_sorted()` (#59278) and `retain()` (#71503).
mv binary_heap.rs binary_heap/mod.rs
I confess this request is somewhat selfish, as it's made in order to ease synchronisation with my [copse](https://crates.io/crates/copse) crate (see eggyal/copse#6 for explanation). I wholly understand that such grounds may be insufficient to justify merging this request—but no harm in asking, right?
Document that `Vec::from_raw_parts[_in]` must be given a pointer from the correct allocator.
Currently, the documentation of `Vec::from_raw_parts` and `Vec::from_raw_parts_in` says nothing about what allocator the pointer must come from. This PR adds that missing information explicitly.
Loosen the bound on the Debug implementation of Weak.
Both `rc::Weak<T>` and `sync::Weak<T>` currently require `T: Debug` in their own `Debug` implementations, but they don't currently use it; they only ever print a fixed string.
A general implementation of Debug for Weak that actually attempts to upgrade and rely on the contents is unlikely in the future because it may have unbounded recursion in the presence of reference cycles, which Weak is commonly used in. (This was the justification for why the current implementation [was implemented the way it is](f0976e2cf3)).
When I brought it up [on the forum](https://internals.rust-lang.org/t/could-the-bound-on-weak-debug-be-relaxed/15504), it was suggested that, even if an implementation is specialized in the future that relies on the data stored within the Weak, it would likely rely on specialization anyway, and could therefore easily specialize on the Debug bound as well.
Update `rand` in the stdlib tests, and remove the `getrandom` feature from it.
The main goal is actually removing `getrandom`, so that eventually we can allow running the stdlib test suite on tier3 targets which don't have `getrandom` support. Currently those targets can only run the subset of stdlib tests that exist in uitests, and (generally speaking), we prefer not to test libstd functionality in uitests, which came up recently in https://github.com/rust-lang/rust/pull/104095 and https://github.com/rust-lang/rust/pull/104185. Additionally, the fact that we can't update `rand`/`getrandom` means we're stuck with the old set of tier3 targets, so can't test new ones.
~~Anyway, I haven't checked that this actually does allow use on tier3 targets (I think it does not, as some work is needed in stdlib submodules) but it moves us slightly closer to this, and seems to allow at least finally updating our `rand` dep, which definitely improves the status quo.~~ Checked and works now.
For the most part, our tests and benchmarks are fine using hard-coded seeds. A couple tests seem to fail with this (stuff manipulating the environment expecting no collisions, for example), or become pointless (all inputs to a function become equivalent). In these cases I've done a (gross) dance (ab)using `RandomState` and `Location::caller()` for some extra "entropy".
Trying to share that code seems *way* more painful than it's worth given that the duplication is a 7-line function, even if the lines are quite gross. (Keeping in mind that sharing it would require adding `rand` as a non-dev dep to std, and exposing a type from it publicly, all of which sounds truly awful, even if done behind a perma-unstable feature).
See also some previous attempts:
- https://github.com/rust-lang/rust/pull/86963 (in particular https://github.com/rust-lang/rust/pull/86963#issuecomment-885438936 which explains why this is non-trivial)
- https://github.com/rust-lang/rust/pull/89131
- https://github.com/rust-lang/rust/pull/96626#issuecomment-1114562857 (I tried in that PR at the same time, but settled for just removing the usage of `thread_rng()` from the benchmarks, since that was the main goal).
- https://github.com/rust-lang/rust/pull/104185
- Probably more. It's very tempting of a thing to "just update".
r? `@Mark-Simulacrum`
default OOM handler: use non-unwinding panic, to match std handler
The OOM handler in std will by default abort. This adjusts the default in liballoc to do the same, using the `can_unwind` flag on the panic info to indicate a non-unwinding panic.
In practice this probably makes little difference since the liballoc default will only come into play in no-std situations where people write a custom panic handler, which most likely will not implement unwinding. But still, this seems more consistent.
Cc `@rust-lang/wg-allocators,` https://github.com/rust-lang/rust/issues/66741
Revert "Implement allow-by-default `multiple_supertrait_upcastable` lint"
This is a clean revert of #105484.
I confirmed that reverting that PR fixes the regression reported in #106247. ~~I can't say I understand what this code is doing, but maybe it can be re-landed with a different implementation.~~ **Edit:** https://github.com/rust-lang/rust/issues/106247#issuecomment-1367174384 has an explanation of why #105484 ends up surfacing spurious `where_clause_object_safety` errors. The implementation of `where_clause_object_safety` assumes we only check whether a trait is object safe when somebody actually uses that trait with `dyn`. However the implementation of `multiple_supertrait_upcastable` added in the problematic PR involves checking *every* trait for whether it is object-safe.
FYI `@nbdd0121` `@compiler-errors`
Implement allow-by-default `multiple_supertrait_upcastable` lint
The lint detects when an object-safe trait has multiple supertraits.
Enabled in libcore and liballoc as they are low-level enough that many embedded programs will use them.
r? `@nikomatsakis`
Test leaking of BinaryHeap Drain iterators
Add test cases about forgetting the `BinaryHeap::Drain` iterator, and slightly fortifies some other test cases.
Consists of separate commits that I don't think are relevant on their own (but I'll happily turn these into more PRs if desired).
The lint "clippy::uninlined_format_args" recommends inline
variables in format strings. Fix two places in the docs that do
not do this. I noticed this because I copy/pasted one example in
to my project, then noticed this lint error. This fixes:
error: variables can be used directly in the `format!` string
--> src/main.rs:30:22
|
30 | let string = format!("{:.*}", decimals, magnitude);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: variables can be used directly in the `format!` string
--> src/main.rs:39:2
|
39 | write!(&mut io::stdout(), "{}", args).unwrap();
