Make `try_exists` return `Ok(true)` for Windows Unix Sockets
This is a follow up to #109106 but for[ `fs::try_exists`](https://doc.rust-lang.org/std/fs/fn.try_exists.html), which doesn't need to get the metadata of a file (which can fail even if a file exists).
`fs::try_exists` currently fails on Windows if encountering a Unix Domain Socket (UDS). This PR fixes it by checking for an error code that's returned when there's a failure to use a reparse point.
## Reparse points
A reparse point is a way to invoke a filesystem filter on a file instead of the file being opened normally. This is used to implement symbolic links (by redirecting to a different path) but also to implement other types of special files such as Unix domain sockets. If the reparse point is not a link type then opening it with `CreateFileW` may fail with `ERROR_CANT_ACCESS_FILE` because the filesystem filter does not implement that operation. This differs from resolving links which may fail with errors such as `ERROR_FILE_NOT_FOUND` or `ERROR_CANT_RESOLVE_FILENAME`.
So `ERROR_CANT_ACCESS_FILE` means that the file exists but that we can't open it normally. Still, the file does exist on the filesystem so `try_exists` should report that as `Ok(true)`.
r? libs
optimize zipping over array iterators
Fixes#115339 (somewhat)
the new assembly:
```asm
zip_arrays:
.cfi_startproc
vmovups (%rdx), %ymm0
leaq 32(%rsi), %rcx
vxorps %xmm1, %xmm1, %xmm1
vmovups %xmm1, -24(%rsp)
movq $0, -8(%rsp)
movq %rsi, -88(%rsp)
movq %rdi, %rax
movq %rcx, -80(%rsp)
vmovups %ymm0, -72(%rsp)
movq $0, -40(%rsp)
movq $32, -32(%rsp)
movq -24(%rsp), %rcx
vmovups (%rsi,%rcx), %ymm0
vorps -72(%rsp,%rcx), %ymm0, %ymm0
vmovups %ymm0, (%rsi,%rcx)
vmovups (%rsi), %ymm0
vmovups %ymm0, (%rdi)
vzeroupper
retq
```
This is still longer than the slice version given in the issue but at least it eliminates the terrible `vpextrb`/`orb` chain. I guess this is due to excessive memcpys again (haven't looked at the llvmir)?
The `TrustedLen` specialization is a drive-by change since I had to do something for the default impl anyway to be able to specialize the `TrustedRandomAccessNoCoerce` impl.
Fix broken build on ESP-IDF caused by #115108
`@ijackson` #115108 broke the build for ESP-IDF. I'm still checking whether this PR fixes everything - once I'm ready will remove the "Draft" status.
`@dtolnay` FYI
* Remove duplicate alignment note that mentioned `AtomicBool` with other
types
* Update safety requirements about when non-atomic operations are
allowed
Fix exit status / wait status on non-Unix cfg(unix) platforms
Fixes#114593
Needs FCP due to behavioural changes (NB only on non-Unix `#[cfg(unix)]` platforms).
Also, I think this is likely to break in CI. I have not been yet able to compile the new bits of `process_unsupported.rs`, although I have compiled the new module. I'd like some help from people familiar with eg emscripten and fuchsia (which are going to be affected, I think).
`fs::try_exists` currently fails on Windows if encountering a Unix Domain Socket (UDS). Fix this by checking for an error code that's returned when there's a failure to use a reparse point.
A reparse point is a way to invoke a filesystem filter on a file instead of the file being opened normally. This is used to implement symbolic links (by redirecting to a different path) but also to implement other types of special files such as Unix domain sockets. If the reparse point is not a link type then opening it with `CreateFileW` may fail with `ERROR_CANT_ACCESS_FILE` because the filesystem filter does not implement that operation. This differs from resolving links which may fail with errors such as `ERROR_FILE_NOT_FOUND` or `ERROR_CANT_RESOLVE_FILENAME`.
So `ERROR_CANT_ACCESS_FILE` means that the file exists but that we can't open it normally. Still, the file does exist so `try_exists` should report that as `Ok(true)`.
Remove unnecessary tmp variable in default_read_exact
This `tmp` variable has existed since the original implementation (added in ff81920f03), but it's not necessary (maybe non-lexical lifetimes helped?).
It's common to read std source code to understand how things actually work, and this tripped me up on my first read.
Implement `slice::split_once` and `slice::rsplit_once`
Feature gate is `slice_split_once` and tracking issue is #112811. These are equivalents to the existing `str::split_once` and `str::rsplit_once` methods.
Add explicit-endian String::from_utf16 variants
This adds the following APIs under `feature(str_from_utf16_endian)`:
```rust
impl String {
pub fn from_utf16le(v: &[u8]) -> Result<String, FromUtf16Error>;
pub fn from_utf16le_lossy(v: &[u8]) -> String;
pub fn from_utf16be(v: &[u8]) -> Result<String, FromUtf16Error>;
pub fn from_utf16be_lossy(v: &[u8]) -> String;
}
```
These are versions of `String::from_utf16` that explicitly take [UTF-16LE and UTF-16BE](https://unicode.org/faq/utf_bom.html#gen7). Notably, we can do better than just the obvious `decode_utf16(v.array_chunks::<2>().copied().map(u16::from_le_bytes)).collect()` in that:
- We handle the case where the byte slice is not an even number of bytes, and
- In the case that the UTF-16 is native endian and the slice is aligned, we can forward to `String::from_utf16`.
If the Unicode Consortium actively defines how to handle character replacement when decoding a UTF-16 bytestream with a trailing odd byte, I was unable to find reference. However, the behavior implemented here is fairly self-evidently correct: replace the single errant byte with the replacement character.
Fix generic bound of `str::SplitInclusive`'s `DoubleEndedIterator` impl
`str::SplitInclusive`'s `DoubleEndedIterator` implementation currently uses a `ReverseSearcher` bound for the corresponding searcher. A `DoubleEndedSearcher` bound should have been used instead.
`DoubleEndedIterator` requires that repeated `next_back` calls produce the same items as repeated `next` calls, in opposite order. `ReverseSearcher` lets you search starting from the back of a string, but it makes no guarantees about how its matches correspond to the matches found by a forward search. `DoubleEndedSearcher` is a subtrait of `ReverseSearcher` and does require that the same matches are found in both directions.
This bug fix is a breaking change. Calling `next_back` on `"a+++b".split_inclusive("++")` is currently accepted with repeated calls producing `"b"` and `"a+++"`, while forward iteration yields `"a++"` and `"+b"`. Also see https://github.com/rust-lang/rust/issues/100756#issuecomment-1221307166 for more details.
I believe that this is the only iterator that uses this bound incorrectly — other related iterators such as `str::Split` do have a `DoubleEndedSearcher` bound for their `DoubleEndedIterator` implementation. And `slice::SplitInclusive` doesn't face this problem at all because it doesn't use patterns, only a predicate.
cc `@SkiFire13`
Rollup of 4 pull requests
Successful merges:
- #116277 (dont call mir.post_mono_checks in codegen)
- #116400 (Detect missing `=>` after match guard during parsing)
- #116458 (Properly export function defined in test which uses global_asm!())
- #116500 (Add tvOS to target_os for register_dtor)
r? `@ghost`
`@rustbot` modify labels: rollup
Reuse existing `Some`s in `Option::(x)or`
LLVM still has trouble re-using discriminants sometimes when rebuilding a two-variant enum, so when we have the correct variant already built, just use it.
That's shorter in the Rust code, as well as simpler in MIR and the optimized LLVM, so might as well: <https://rust.godbolt.org/z/KhdE8eToW>
Thanks to `@veber-alex` for pointing out this opportunity in https://github.com/rust-lang/rust/issues/101210#issuecomment-1732470941
Rollup of 6 pull requests
Successful merges:
- #115454 (Clarify example in docs of str::char_slice)
- #115522 (Clarify ManuallyDrop bit validity)
- #115588 (Fix a comment in std::iter::successors)
- #116198 (Add more diagnostic items for clippy)
- #116329 (update some comments around swap())
- #116475 (rustdoc-search: fix bug with multi-item impl trait)
r? `@ghost`
`@rustbot` modify labels: rollup
Fix a comment in std::iter::successors
The `unfold` function have since #58062 been renamed to `from_fn`.
(I'm not sure if this whole comment is still useful—it's not like there are many iterators that *can't* be based on `from_fn`. Anyway, in its current form this comment is not correct, and it sent me into a half-hour research of what happened to `unfold` function, so I want to do *something* with it 🙃 deleting these three lines is a perfectly fine alternative, in my opinion.)
