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Since just `ops::Try` will need to change meaning.
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Stablize {HashMap,BTreeMap}::into_{keys,values}
I would propose to stabilize `{HashMap,BTreeMap}::into_{keys,values}`( aka. `map_into_keys_values`).
Closes #75294.
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For certain sorts of systems, programming, it's deemed essential that
all allocation failures be explicitly handled where they occur. For
example, see Linus Torvald's opinion in [1]. Merely not calling global
panic handlers, or always `try_reserving` first (for vectors), is not
deemed good enough, because the mere presence of the global OOM handlers
is burdens static analysis.
One option for these projects to use rust would just be to skip `alloc`,
rolling their own allocation abstractions. But this would, in my
opinion be a real shame. `alloc` has a few `try_*` methods already, and
we could easily have more. Features like custom allocator support also
demonstrate and existing to support diverse use-cases with the same
abstractions.
A natural way to add such a feature flag would a Cargo feature, but
there are currently uncertainties around how std library crate's Cargo
features may or not be stable, so to avoid any risk of stabilizing by
mistake we are going with a more low-level "raw cfg" token, which
cannot be interacted with via Cargo alone.
Note also that since there is no notion of "default cfg tokens" outside
of Cargo features, we have to invert the condition from
`global_oom_handling` to to `not(no_global_oom_handling)`. This breaks
the monotonicity that would be important for a Cargo feature (i.e.
turning on more features should never break compatibility), but it
doesn't matter for raw cfg tokens which are not intended to be
"constraint solved" by Cargo or anything else.
To support this use-case we create a new feature, "global-oom-handling",
on by default, and put the global OOM handler infra and everything else
it that depends on it behind it. By default, nothing is changed, but
users concerned about global handling can make sure it is disabled, and
be confident that all OOM handling is local and explicit.
For this first iteration, non-flat collections are outright disabled.
`Vec` and `String` don't yet have `try_*` allocation methods, but are
kept anyways since they can be oom-safely created "from parts", and we
hope to add those `try_` methods in the future.
[1]: https://lore.kernel.org/lkml/CAHk-=wh_sNLoz84AUUzuqXEsYH35u=8HV3vK-jbRbJ_B-JjGrg@mail.gmail.com/
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Replace 'NULL' with 'null'
This replaces occurrences of "NULL" with "null" in docs, comments, and compiler error/lint messages. This is for the sake of consistency, as the lowercase "null" is already the dominant form in Rust. The all-caps NULL looks like the C macro (or SQL keyword), which seems out of place in a Rust context, given that NULL does not exist in the Rust language or standard library (instead having [`ptr::null()`](https://doc.rust-lang.org/stable/std/ptr/fn.null.html)).
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i8 and u8::to_string() specialisation (far less asm).
Take 2. Around 1/6th of the assembly to without specialisation.
https://godbolt.org/z/bzz8Mq
(partially fixes #73533 )
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Remove slice diagnostic item
...because it is unusally placed on an impl and is redundant with a lang item.
Depends on rust-lang/rust-clippy#7074 (next clippy sync). ~I expect clippy tests to fail in the meantime.~ Nope tests passed...
CC `@flip1995`
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further split up const_fn feature flag
This continues the work on splitting up `const_fn` into separate feature flags:
* `const_fn_trait_bound` for `const fn` with trait bounds
* `const_fn_unsize` for unsizing coercions in `const fn` (looks like only `dyn` unsizing is still guarded here)
I don't know if there are even any things left that `const_fn` guards... at least libcore and liballoc do not need it any more.
`@oli-obk` are you currently able to do reviews?
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Document From implementations for Waker and RawWaker
CC #51430
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Remove duplicated fn(Box<[T]>) -> Vec<T>
`<[T]>::into_vec()` does the same thing as `Vec::from::<Box<[T]>>()`, so they can be implemented in terms of each other. This was the previous implementation of `Vec::from()`, but was changed in #78461. I'm not sure what the rationale was for that change, but it seems preferable to maintain a single implementation.
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It now doesn't fully rebuild the heap, but only the parts that are
necessary.
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Replace all `fmt.pad` with `debug_struct`
This replaces any occurrence of:
- `f.pad("X")` with `f.debug_struct("X").finish()`
- `f.pad("X { .. }")` with `f.debug_struct("X").finish_non_exhaustive()`
This is in line with existing formatting code such as
https://github.com/rust-lang/rust/blob/125505306744a0a5bb01d62337260a95d9ff8d57/library/std/src/sync/mpsc/mod.rs#L1470-L1475
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Address comments for vecdeque_binary_search #78021
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Correct outdated documentation for rc::Weak
This was overlooked in ~~#50357~~ #51901
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Co-authored-by: Mara Bos <m-ou.se@m-ou.se>
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#78021
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Improve code example for length comparison
Small fix/improvement: it's much safer to check that you're under the length of an array rather than chacking that you're equal to it. It's even more true in case you update the length of the array while iterating.
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This should do roughly the same as the TrustedLen specialization
but result in less IR by using __iterator_get_unchecked
instead of iterator.for_each.
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Add strong_count mutation methods to Rc
The corresponding methods were stabilized on `Arc` in #79285 (tracking: #71983). This patch implements and stabilizes identical methods on the `Rc` types as well.
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Bump bootstrap to 1.52 beta
This includes the standard bump, but also a workaround for new cargo behavior around clearing out the doc directory when the rustdoc version changes.
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BTree: move blocks around in node.rs
Without changing any names or implementation, reorder some members:
- Move down the ones defined long ago on the demised `struct Root`, to below the definition of their current host `struct NodeRef`.
- Move up some defined on `struct NodeRef` that are interspersed with those defined on `struct Handle`.
- Move up the `correct_…` methods squeezed between the two flavours of `push`.
- Move the unchecked static downcasts (`cast_to_…`) after the upcasts (`forget_`) and the (weirdly named) dynamic downcasts (`force`).
r? ````@Mark-Simulacrum````
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r=Mark-Simulacrum
BTree: no longer search arrays twice to check Ord
A possible addition to / partial replacement of #83147: no longer linearly search the upper bound of a range in the initial portion of the keys we already know are below the lower bound.
- Should be faster: fewer key comparisons at the cost of some instructions dealing with offsets
- Makes code a little more complicated.
- No longer detects ill-defined `Ord` implementations, but that wasn't a publicised feature, and was quite incomplete, and was only done in the `range` and `range_mut` methods.
r? `@Mark-Simulacrum`
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Fix double-drop in `Vec::from_iter(vec.into_iter())` specialization when items drop during panic
This fixes the double-drop but it leaves a behavioral difference compared to the default implementation intact: In the default implementation the source and the destination vec are separate objects, so they get dropped separately. Here they share an allocation and the latter only exists as a pointer into the former. So if dropping the former panics then this fix will leak more items than the default implementation would. Is this acceptable or should the specialization also mimic the default implementation's drops-during-panic behavior?
Fixes #83618
`@rustbot` label T-libs-impl
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Reduce the impact of Vec::reserve calls that do not cause any allocation
I think a lot of callers expect `Vec::reserve` to be nearly free when no resizing is required, but unfortunately that isn't the case. LLVM makes remarkably poor inlining choices (along the path from `Vec::reserve` to `RawVec::grow_amortized`), so depending on the surrounding context you either get a huge blob of `RawVec`'s resizing logic inlined into some seemingly-unrelated function, or not enough inlining happens and/or the actual check in `needs_to_grow` ends up behind a function call. My goal is to make the codegen for `Vec::reserve` match the mental that callers seem to have: It's reliably just a `sub cmp ja` if there is already sufficient capacity.
This patch has the following impact on the serde_json benchmarks: https://github.com/serde-rs/json-benchmark/tree/ca3efde8a5b75ff59271539b67452911860248c7 run with `cargo +stage1 run --release -- -n 1024`
Before:
```
DOM STRUCT
======= serde_json ======= parse|stringify ===== parse|stringify ====
data/canada.json 340 MB/s 490 MB/s 630 MB/s 370 MB/s
data/citm_catalog.json 460 MB/s 540 MB/s 1010 MB/s 550 MB/s
data/twitter.json 330 MB/s 840 MB/s 640 MB/s 630 MB/s
======= json-rust ======== parse|stringify ===== parse|stringify ====
data/canada.json 580 MB/s 990 MB/s
data/citm_catalog.json 720 MB/s 660 MB/s
data/twitter.json 570 MB/s 960 MB/s
```
After:
```
DOM STRUCT
======= serde_json ======= parse|stringify ===== parse|stringify ====
data/canada.json 330 MB/s 510 MB/s 610 MB/s 380 MB/s
data/citm_catalog.json 450 MB/s 640 MB/s 970 MB/s 830 MB/s
data/twitter.json 330 MB/s 880 MB/s 670 MB/s 960 MB/s
======= json-rust ======== parse|stringify ===== parse|stringify ====
data/canada.json 560 MB/s 1130 MB/s
data/citm_catalog.json 710 MB/s 880 MB/s
data/twitter.json 530 MB/s 1230 MB/s
```
That's approximately a one-third increase in throughput on two of the benchmarks, and no effect on one (The benchmark suite has sufficient jitter that I could pick a run where there are no regressions, so I'm not convinced they're meaningful here).
This also produces perf increases on the order of 3-5% in a few other microbenchmarks that I'm tracking. It might be useful to see if this has a cascading effect on inlining choices in some large codebases.
Compiling this simple program demonstrates the change in codegen that causes the perf impact:
```rust
fn main() {
reserve(&mut Vec::new());
}
#[inline(never)]
fn reserve(v: &mut Vec<u8>) {
v.reserve(1234);
}
```
Before:
```rust
00000000000069b0 <scratch::reserve>:
69b0: 53 push %rbx
69b1: 48 83 ec 30 sub $0x30,%rsp
69b5: 48 8b 47 08 mov 0x8(%rdi),%rax
69b9: 48 8b 4f 10 mov 0x10(%rdi),%rcx
69bd: 48 89 c2 mov %rax,%rdx
69c0: 48 29 ca sub %rcx,%rdx
69c3: 48 81 fa d1 04 00 00 cmp $0x4d1,%rdx
69ca: 77 73 ja 6a3f <scratch::reserve+0x8f>
69cc: 48 81 c1 d2 04 00 00 add $0x4d2,%rcx
69d3: 72 75 jb 6a4a <scratch::reserve+0x9a>
69d5: 48 89 fb mov %rdi,%rbx
69d8: 48 8d 14 00 lea (%rax,%rax,1),%rdx
69dc: 48 39 ca cmp %rcx,%rdx
69df: 48 0f 47 ca cmova %rdx,%rcx
69e3: 48 83 f9 08 cmp $0x8,%rcx
69e7: be 08 00 00 00 mov $0x8,%esi
69ec: 48 0f 47 f1 cmova %rcx,%rsi
69f0: 48 85 c0 test %rax,%rax
69f3: 74 17 je 6a0c <scratch::reserve+0x5c>
69f5: 48 8b 0b mov (%rbx),%rcx
69f8: 48 89 0c 24 mov %rcx,(%rsp)
69fc: 48 89 44 24 08 mov %rax,0x8(%rsp)
6a01: 48 c7 44 24 10 01 00 movq $0x1,0x10(%rsp)
6a08: 00 00
6a0a: eb 08 jmp 6a14 <scratch::reserve+0x64>
6a0c: 48 c7 04 24 00 00 00 movq $0x0,(%rsp)
6a13: 00
6a14: 48 8d 7c 24 18 lea 0x18(%rsp),%rdi
6a19: 48 89 e1 mov %rsp,%rcx
6a1c: ba 01 00 00 00 mov $0x1,%edx
6a21: e8 9a fe ff ff call 68c0 <alloc::raw_vec::finish_grow>
6a26: 48 8b 7c 24 20 mov 0x20(%rsp),%rdi
6a2b: 48 8b 74 24 28 mov 0x28(%rsp),%rsi
6a30: 48 83 7c 24 18 01 cmpq $0x1,0x18(%rsp)
6a36: 74 0d je 6a45 <scratch::reserve+0x95>
6a38: 48 89 3b mov %rdi,(%rbx)
6a3b: 48 89 73 08 mov %rsi,0x8(%rbx)
6a3f: 48 83 c4 30 add $0x30,%rsp
6a43: 5b pop %rbx
6a44: c3 ret
6a45: 48 85 f6 test %rsi,%rsi
6a48: 75 08 jne 6a52 <scratch::reserve+0xa2>
6a4a: ff 15 38 c4 03 00 call *0x3c438(%rip) # 42e88 <_GLOBAL_OFFSET_TABLE_+0x490>
6a50: 0f 0b ud2
6a52: ff 15 f0 c4 03 00 call *0x3c4f0(%rip) # 42f48 <_GLOBAL_OFFSET_TABLE_+0x550>
6a58: 0f 0b ud2
6a5a: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
```
After:
```asm
0000000000006910 <scratch::reserve>:
6910: 48 8b 47 08 mov 0x8(%rdi),%rax
6914: 48 8b 77 10 mov 0x10(%rdi),%rsi
6918: 48 29 f0 sub %rsi,%rax
691b: 48 3d d1 04 00 00 cmp $0x4d1,%rax
6921: 77 05 ja 6928 <scratch::reserve+0x18>
6923: e9 e8 fe ff ff jmp 6810 <alloc::raw_vec::RawVec<T,A>::reserve::do_reserve_and_handle>
6928: c3 ret
6929: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
```
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alloc: Added `as_slice` method to `BinaryHeap` collection
I initially asked about whether it is useful addition on https://internals.rust-lang.org/t/should-i-add-as-slice-method-to-binaryheap/13816, and it seems there were no objections, so went ahead with this PR.
> There is [`BinaryHeap::into_vec`](https://doc.rust-lang.org/std/collections/struct.BinaryHeap.html#method.into_vec), but it consumes the value. I wonder if there is API design limitation that should be taken into account. Implementation-wise, the inner buffer is just a Vec, so it is trivial to expose as_slice from it.
Please, guide me through if I need to add tests or something else.
UPD: Tracking issue #83659
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