fix Zip unsoundness (again)
Some history: The Zip TrustedRandomAccess specialization has tried to emulate the side-effects of the naive implementation for a long time, including backwards iteration. #82292 tried to fix unsoundness (#82291) in that side-effect-preservation code, but this introduced some panic-safety unsoundness (#86443), but the fix#86452 didn't fix it for nested Zip iterators (#137255).
Rather than piling yet another fix ontop of this heap of fixes this PR reduces the number of cases in which side-effects will be preserved; the necessary API guarantee change was approved in #83791 but we haven't made use of that so far.
fixes#137255
Make slice comparisons const
This needed a fix for `derive_const`, too, as it wasn't usable in libcore anymore as trait impls need const stability attributes. I think we can't use the same system as normal trait impls while `const_trait_impl` is still unstable.
r? ```@fee1-dead```
cc rust-lang/rust#143800
docs(alloc::fmt): Make type optional, instead of matching empty string
Think this is clearer.
Noticed as I was implementing [`tree-sitter-rust-format-args`](https://github.com/nik-rev/tree-sitter-rust-format-args), and attempting to match the empty string results in an error.
constify `Option` methods
r? ```````@fee1-dead```````
tracking issue: rust-lang/rust#143956
these unblock making `PartialOrd` and `Ord` const without resorting to inlining some of these at call sites.
update to literal-escaper-0.0.5
Quoting from the changelog, this version brings:
- Use `NonZero<char/u8>` in `unescape_c_str` and `check_raw_c_str` to statically exclude nuls
- Add `#[inline]` to small functions for improved performance
Linting public reexport of private dependencies
Part of public/private dependencies rust-lang/rust#44663
Partially addresses rust-lang/rust#71043
I'm adding a warning for reexports of private dependencies into `rustc_resolve`. I get that this should not be a warning, but should instead be a lint to be controlled by the feature gate, but I did not figure out how exactly to do that at that point. I tried doing the same thing as is done in `rustc_privacy`, but the linting system is not ready yet as far as I understand the error I got, so I made a warning for now instead. Some guidance on how to emit lints with `dcx` would be appreciated.
This also sets the `std_detect` crate as a public dependency of `std` because some macros are reexported from there. I did not check closer, but the other option may be to allow the specific reexports instead.
Trim `BorrowedCursor` API
This PR removes some method from the unstable `BorrowedCursor` type. A rational for each change can be found in the message of each commit.
I don't think that an ACP is required for this, please tell me if it is not the case.
Cc rust-lang/rust#78485rust-lang/rust#117693
UWP: link ntdll functions using raw-dylib
Lazy loading isn't necessary so there's no need for the added complexity and overhead. However, it may be that people using UWP rust libraries don't have the necessary import libraries linked by Visual Studio so this uses raw-dylib, which allows linking to DLL functions without having an import library. This is a somewhat temporary situation as raw-dylib is intended to eventually be the default for all imports. When that happens, this special case can be removed.
Closesrust-lang/rust#143530
Constify `Index` traits
tracking issue: rust-lang/rust#143775
the `SliceIndex` trait cannot be implemented by users as it is sealed. While it would be useful for the `get` method on slices, it seems weird to have a feature gate for that that isn't also gating index syntax at the same time, so I put them under the same feature gate.
r? ```````@fee1-dead```````
Move several float tests to floats/mod.rs
This PR moves several tests to `floats/mod.rs`, as discussed in https://github.com/rust-lang/rust/issues/141726. The tests moved are:
- `test_num_f*`
- `test_infinity`
- `test_neg_infinity`
- `test_zero`
- `test_neg_zero`
- `test_one`
- `test_is_nan`
- `test_is_infinite`
- `test_is_finite`
- `test_is_normal`
- `test_classify`
Each test is its own commit, so it may be easiest to review each commit individually.
r? tgross35
wrapping shift: remove first bitmask and table
```rust
#[inline(always)]
pub const fn wrapping_shl(self, rhs: u32) -> Self {
// SAFETY: the masking by the bitsize of the type ensures that we do not shift
// out of bounds
unsafe {
self.unchecked_shl(rhs & (Self::BITS - 1))
}
}
```
already does the bitmask, so it seems unnecessary here.
More context: internals.rust-lang.org/t/wrapping-shift-operator-code-doing-bitmasking-twice/23167
`std::vec`: Add UB check for `set_len`, `from_raw_parts_in`, and etc.
Closesrust-lang/rust#143813
I noticed that `from_parts_in` do the similar things like `from_raw_parts_in`, so I add the UB check in the last commit. If it is not appropriate, I will remove it.
And I fix a typo in the first commit.
r? `@scottmcm`
update `cfg_select!` documentation
tracking issue: https://github.com/rust-lang/rust/issues/115585
After rust-lang/rust#143461, and with an eye on a soon(ish) stabilization, I think the docs need some work.
The existing text read more like a motivation for the feature existing to me, so I've tried to now be a bit more descriptive. Still, suggestions are very welcome.
I also added a test for an empty `select! {}` because it's just the sort of thing that might break.
r? ``@traviscross``
Add experimental `backtrace-trace-only` std feature
This experimentally allows building std with backtrace but without symbolisation. It does not affect stable and requires build-std to use. This doesn't change the backtrace crate itself so relies on the optimizer to remove the unused parts.
Example usage:
```toml
# .cargo/config.toml
[unstable]
build-std = ["core", "alloc", "panic_unwind", "std"]
build-std-features = ["backtrace", "backtrace-trace-only", "panic-unwind"]
```
```toml
# Cargo.toml
[profile.release]
opt-level = 3
lto = "thin"
codegen-units = 1
```
Ideally we should split the backtrace feature into `backtrace-trace` and `backtrace-symbolize` (with the latter dependent on the former) because Cargo features tend to work better when they're positive rather than negative. But I'm keen for this experiment not to break existing users.
cc ``@joshtriplett``
core: Add `BorrowedCursor::with_unfilled_buf`
Implementation of https://github.com/rust-lang/libs-team/issues/367.
This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`.
Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly.
Cc rust-lang/rust#78485rust-lang/rust#117693
Updates to random number generation APIs
Updates based on discussions about random number generation.
- Add comment on `RandomSource::fill_bytes` about multiple calls, to allow
efficient implementations for random sources that generate a word at a time.
- Drop the `Random` trait in favor of `Distribution<T>`, which will let people
make calls like random(1..=6), and which allows for future expansion to
non-uniform distributions, as well as floating-point. (For now, this is only
implemented for `RangeFull`, to get the interface in place. Subsequent PRs
will implement it for other range types.)
Use zero for initialized Once state
By re-labeling which integer represents which internal state for `Once` we can ensure that the initialized state is the all-zero state. This is beneficial because some CPU architectures (such as Arm) have specialized instructions to specifically branch on non-zero, and checking for the initialized state is by far the most important operation.
As an example, take this:
```rust
use std::sync::atomic::{AtomicU32, Ordering};
const INIT: u32 = 3;
#[inline(never)]
#[cold]
pub fn slow(state: &AtomicU32) {
state.store(INIT, Ordering::Release);
}
pub fn ensure_init(state: &AtomicU32) {
if state.load(Ordering::Acquire) != INIT {
slow(state)
}
}
```
If `INIT` is 3 (as is currently the state for `Once`), we see the following assembly on `aarch64-apple-darwin`:
```asm
example::ensure_init::h332061368366e313:
ldapr w8, [x0]
cmp w8, #3
b.ne LBB1_2
ret
LBB1_2:
b example::slow::ha042bd6a4f33724e
```
By changing the `INIT` state to zero we get the following:
```asm
example::ensure_init::h332061368366e313:
ldapr w8, [x0]
cbnz w8, LBB1_2
ret
LBB1_2:
b example::slow::ha042bd6a4f33724e
```
So this PR saves 1 instruction every time a `LazyLock` gets accessed on platforms such as these.
make `cfg_select` a builtin macro
tracking issue: https://github.com/rust-lang/rust/issues/115585
This parses mostly the same as the `macro cfg_select` version, except:
1. wrapping in double brackets is no longer supported (or needed): `cfg_select {{ /* ... */ }}` is now rejected.
2. in an expression context, the rhs is no longer wrapped in a block, so that this now works:
```rust
fn main() {
println!(cfg_select! {
unix => { "foo" }
_ => { "bar" }
});
}
```
3. a single wildcard rule is now supported: `cfg_select { _ => 1 }` now works
I've also added an error if none of the rules evaluate to true, and warnings for any arms that follow the `_` wildcard rule.
cc `@traviscross` if I'm missing any feature that should/should not be included
r? `@petrochenkov` for the macro logic details
constify `From` and `Into`
tracking issue rust-lang/rust#143773
r? ``````@fee1-dead``````
I did not mark any impls elsewhere as `const`, those can happen on their own timeframe and don't need to be part of this MVP. But if there are some core ones you think should be in there I'll happily add them, just couldn't think of any
