Add methods to go from a nul-terminated Vec<u8> to a CString
Fixes#73100.
Doc tests have been written and the documentation on the error type
updated too.
I used `#[stable(feature = "cstring_from_vec_with_nul", since = "1.46.0")]` but I don't know if the version is correct.
impl From<Cow> for Box, Rc, and Arc
These forward `Borrowed`/`Owned` values to existing `From` impls.
- `Box<T>` is a fundamental type, so it would be a breaking change to add a blanket impl. Therefore, `From<Cow>` is only implemented for `[T]`, `str`, `CStr`, `OsStr`, and `Path`.
- For `Rc<T>` and `Arc<T>`, `From<Cow>` is implemented for everything that implements `From` the borrowed and owned types separately.
These forward `Borrowed`/`Owned` values to existing `Box::from` impls.
- `From<Cow<'_, [T]>> for Box<[T]>`
- `From<Cow<'_, str>> for Box<str>`
- `From<Cow<'_, CStr>> for Box<CStr>`
- `From<Cow<'_, OsStr>> for Box<OsStr>`
- `From<Cow<'_, Path>> for Box<Path>`
Added From<Vec<NonZeroU8>> for CString
Added a `From<Vec<NonZeroU8>>` `impl` for `CString`
# Rationale
- `CString::from_vec_unchecked` is a subtle function, that makes `unsafe` code harder to audit when the generated `Vec`'s creation is non-trivial. This `impl` allows to write safer `unsafe` code thanks to the very explicit semantics of the `Vec<NonZeroU8>` type.
- One such situation is when trying to `.read()` a `CString`, see issue #59229.
- this lead to a PR: #59314, that was closed for being too specific / narrow (it only targetted being able to `.read()` a `CString`, when this pattern could have been generalized).
- the issue suggested another route, based on `From<Vec<NonZeroU8>>`, which is indeed a less general and more concise code pattern.
- quoting @shnatsel:
- > For me the main thing about making this safe is simplifying auditing - people have spent like an hour looking at just this one unsafe block in libflate because it's not clear what exactly is unchecked, so you have to look it up when auditing anyway. This has distracted us from much more serious memory safety issues the library had.
Having this trivial impl in stdlib would turn this into safe code with compiler more or less guaranteeing that it's fine, and save anyone auditing the code a whole lot of time.
Updated tracking issue number
Added safeguards for transmute_vec potentially being factored out elsewhere
Clarified comment about avoiding mem::forget
Removed unneeded unstable guard
Added back a stability annotation for CI
Minor documentation improvements
Thanks to @Centril's code review
Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>
Improved layout checks, type annotations and removed unaccurate comment
Removed unnecessary check on array layout
Adapt the stability annotation to the new 1.41 milestone
Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>
Simplify the implementation.
Use `Vec::into_raw_parts` instead of a manual implementation of
`Vec::transmute`.
If `Vec::into_raw_parts` uses `NonNull` instead, then the code here
will need to be adjusted to take it into account (issue #65816)
Reduce the whitespace of safety comments
These notes are about a distinction that is not going to be observable
in the API. Whether or not the UTF-8 check knows the string length ahead
of time, these methods require linear time.
`description` has been documented as soft-deprecated since 1.27.0 (17
months ago). There is no longer any reason to call it or implement it.
This commit:
- adds #[rustc_deprecated(since = "1.41.0")] to Error::description;
- moves description (and cause, which is also deprecated) below the
source and backtrace methods in the Error trait;
- reduces documentation of description and cause to take up much less
vertical real estate in rustdocs, while preserving the example that
shows how to render errors without needing to call description;
- removes the description function of all *currently unstable* Error
impls in the standard library;
- marks #[allow(deprecated)] the description function of all *stable*
Error impls in the standard library;
- replaces miscellaneous uses of description in example code and the
compiler.
This commit applies rustfmt with rust-lang/rust's default settings to
files in src/libstd *that are not involved in any currently open PR* to
minimize merge conflicts. THe list of files involved in open PRs was
determined by querying GitHub's GraphQL API with this script:
https://gist.github.com/dtolnay/aa9c34993dc051a4f344d1b10e4487e8
With the list of files from the script in outstanding_files, the
relevant commands were:
$ find src/libstd -name '*.rs' \
| xargs rustfmt --edition=2018 --unstable-features --skip-children
$ rg libstd outstanding_files | xargs git checkout --
Repeating this process several months apart should get us coverage of
most of the rest of libstd.
To confirm no funny business:
$ git checkout $THIS_COMMIT^
$ git show --pretty= --name-only $THIS_COMMIT \
| xargs rustfmt --edition=2018 --unstable-features --skip-children
$ git diff $THIS_COMMIT # there should be no difference
IntoStringError only implemented Error::cause, which is
deprecated. This implemements Error::source instead.
Error::cause will still work as before, thanks to the default
implementation.
Add #[repr(transparent)] for several types
In some functions, types mentioned in this PR are transmuted into their inner value.
Example for `PathBuf`: https://github.com/rust-lang/rust/blob/master/src/libstd/path.rs#L1132.
This PR adds `#[repr(transparent)]` to those types, so their correct behavior doesn't depend on compiler details. (As far as I understand, currently that line, converting `PathBuf` to `Vec<u8>`, is UB).
Fix miri error in into_inner() of CString
Fix#62553
I choice to not transmute because I think it's more unsafe and in case the structure change this code should always work.
r? @RalfJung
