Reexport types from `c_size_t` in `std`
These are unstably available in `core` and should be in `std` too, but are not currently reexported. Resolve this here.
Tracking issue: https://github.com/rust-lang/rust/issues/88345
make `OsString::new` and `PathBuf::new` unstably const
Since #129041, `String::into_bytes` is `const`, which allows making `OsString::new` and `PathBuf::new` unstably const now.
Not sure what the exact process for this is; does it need an ACP?
Clarify WTF-8 safety docs
This PR is a follow-up to PR #140159, which clarifies ~~two things~~:
- the WTF-8 safety comment [was confusing](https://github.com/rust-lang/rust/pull/140159#discussion_r2082766965), either surrogate condition is actually sufficient for safety, both are not required
- ~~the private `os_str::Slice` type name is easily confused with `std::slice`~~
~~Happy to bikeshed the `OsSlice` name, other alternatives are `OsStrSlice` and `StrSlice`. Now it's got a distinct name from `std::slice`, it's easy to search and replace.~~
cc ``@thaliaarchi`` ``@workingjubilee``
limit impls of `VaArgSafe` to just types that are actually safe
tracking issue: https://github.com/rust-lang/rust/issues/44930
Retrieving 8- or 16-bit integer arguments from a `VaList` is not safe, because such types are subject to upcasting. See https://github.com/rust-lang/rust/issues/61275#issuecomment-2193942535 for more detail.
This PR also makes the instances of `VaArgSafe` visible in the documentation, and uses a private sealed trait to make sure users cannot create additional impls of `VaArgSafe`, which would almost certainly cause UB.
r? `@workingjubilee`
8 and 16-bit integers are subject to upcasting in C, and hence are not reliably safe. users should perform their own casting and deal with the consequences
use `Self` alias in self types rather than manually substituting it
Of the rougly 145 uses of `self: Ty` in the standard library, 5 of them don't use `Self` but instead choose to manually "substitute" the `impl`'s self type into the type.
This leads to weird behavior sometimes (https://github.com/rust-lang/rust/issues/140611#issuecomment-2883761300) -- **to be clear**, none of these usages actually trigger any bugs, but it's possible that they may break in the future (or at least lead to lints), so let's just "fix" them proactively.
Avoid redundant WTF-8 checks in `PathBuf`
Eliminate checks for WTF-8 boundaries in `PathBuf::set_extension` and `add_extension`, where joining WTF-8 surrogate halves is impossible. Don't convert the `str` to `OsStr`, because `OsString::push` specializes to skip the joining when given strings.
To assist in this, mark the internal methods `OsString::truncate` and `extend_from_slice` as `unsafe` to communicate their safety invariants better than with module privacy.
Similar to #137777.
cc `@joboet` `@ChrisDenton`
Stabilise `std::ffi::c_str`
This finished FCP in #112134 but never actually got a stabilisation PR. Since the FCP in #120048 recently passed to add the `os_str` module, it would be nice to also merge this too, to ensure that both get added in the next version.
Note: The added stability attributes which *somehow* were able to be omitted before (rustc bug?) were added based on the fact that they were added in 302551388b, which ended up in 1.85.0.
Closes: https://github.com/rust-lang/rust/issues/112134
r? libs-api
The WTF-8 version of `OsString` tracks whether it is known to be valid
UTF-8 with its `is_known_utf8` field. Specialize `From<AsRef<OsStr>>` so
this can be set for UTF-8 string types.
When concatenating two WTF-8 strings, surrogate pairs at the boundaries
need to be joined. However, since UTF-8 strings cannot contain surrogate
halves, this check can be skipped when one string is UTF-8. Specialize
`OsString::push` to use a more efficient concatenation in this case.
Unfortunately, a specialization for `T: AsRef<str>` conflicts with
`T: AsRef<OsStr>`, so stamp out string types with a macro.
Rustdoc has no way to show that an item is stable,
but only at a different path. `std::ffi::c_str::NulError` is
not stable, but `std::ffi::NulError` is.
To avoid marking these types as unstable when someone just
wants to follow a link from `CString`, inline them into their
stable paths.
Since the stabilization in #127679 has reached stage0, 1.82-beta, we can
start using `&raw` freely, and even the soft-deprecated `ptr::addr_of!`
and `ptr::addr_of_mut!` can stop allowing the unstable feature.
I intentionally did not change any documentation or tests, but the rest
of those macro uses are all now using `&raw const` or `&raw mut` in the
standard library.
Document overrides of `clone_from()` in core/std
As mentioned in https://github.com/rust-lang/rust/pull/96979#discussion_r1379502413
Specifically, when an override doesn't just forward to an inner type, document the behavior and that it's preferred over simply assigning a clone of source. Also, change instances where the second parameter is "other" to "source".
I reused some of the wording over and over for similar impls, but I'm not sure that the wording is actually *good*. Would appreciate feedback about that.
Also, now some of these seem to provide pretty specific guarantees about behavior (e.g. will reuse the exact same allocation iff the len is the same), but I was basing it off of the docs for [`Box::clone_from`](https://doc.rust-lang.org/1.75.0/std/boxed/struct.Box.html#method.clone_from-1) - I'm not sure if providing those strong guarantees is actually good or not.
Specifically, when an override doesn't just forward to an inner type,
document the behavior and that it's preferred over simply assigning
a clone of source. Also, change instances where the second parameter is
"other" to "source".
