Duration div mul extras
Successor of #52556.
This PR adds the following `impl`s:
- `impl Mul<Duration> for u32` (to allow `10*SECOND` in addition to `SECOND*10`)
- `impl Mul<f64> for Duration` (to allow `2.5*SECOND` vs `2*SECOND + 500*MILLISECOND`)
- `impl Mul<Duration> for f64`
- `impl MulAssign<f64> for Duration`
- `impl Div<f64> for Duration`
- `impl DivAssign<f64> for Duration`
- `impl Div<Duration> for Duration` (`Output = f64`, can be useful e.g. for `duration/MINUTE`)
`f64` is chosen over `f32` to minimize rounding errors. (52 bits fraction precision vs `Duration`'s ~94 bit)
This is a safe wrapper around ptr::copy, for regions within a single
slice. Previously, safe in-place copying was only available as a side
effect of Vec::drain.
Update to a new pinning API.
~~Blocked on #53843 because of method resolution problems with new pin type.~~
@r? @cramertj
cc @RalfJung @pythonesque anyone interested in #49150
stabilize slice_align_to
This is very hard to implement correctly, and leads to [serious bugs](https://github.com/llogiq/bytecount/pull/42) when done incorrectly. Moreover, this is needed to be able to run code that opportunistically exploits alignment on miri. So code using `align_to`/`align_to_mut` gets the benefit of a well-tested implementation *and* of being able to run in miri to test for (some kinds of) UB.
This PR also clarifies the guarantee wrt. the middle part being as long as possible. Should the docs say under which circumstances the middle part could be shorter? Currently, that can only happen when running in miri.
Add a implementation of `From` for converting `&'a Option<T>` into `Option<&'a T>`
I'm not sure if any annotations regarding the stabilization are needed or in general what's the correct process of adding such an impl.
cc @sgrif (We have talked about this)
Remove `#[repr(transparent)]` from atomics
Added in #52149 the discussion in #53514 is showing how we may not want to
actually add this attribute to the atomic types. While we continue to
debate #53514 this commit reverts the addition of the `transparent` attribute.
This should be a more conservative route which leaves us the ability to tweak
this in the future but in the meantime allows us to continue discussion as well.
Updated core/macros.rs to note it works in a no_std environment.
Fixes#45797
This PR updates the documentation of `write!` to note it works in a `no_std` environment, and adds an
example to showcase this. In a `no_std` environment, the author of the code is responsible for the
implementation of the `Write` trait. This example will work out of the box with `no_std`, but the
implementation of `Write` is expected to be provided by the user.
r? @steveklabnik
Added in #52149 the discussion in #53514 is showing how we may not want to
actually add this attribute to the atomic types. While we continue to
debate #53514 this commit reverts the addition of the `transparent` attribute.
This should be a more conservative route which leaves us the ability to tweak
this in the future but in the meantime allows us to continue discussion as well.
set cfg(rustdoc) when rustdoc is running on a crate
When using `#[doc(cfg)]` to document platform-specific items, it's a little cumbersome to get all the platforms' items to appear all at once. For example, the standard library adds `--cfg dox` to rustdoc's command line whenever it builds docs, and the documentation for `#![feature(doc_cfg)]` suggests using a Cargo feature to approximate the same thing. This is a little awkward, because you always need to remember to set `--features dox` whenever you build documentation.
This PR proposes making rustdoc set `#[cfg(rustdoc)]` whenever it runs on a crate, to provide an officially-sanctioned version of this that is set automatically. This way, there's a standardized way to declare that a certain version of an item is specifically when building docs.
To try to prevent the spread of this feature from happening too quickly, this PR also restricts the use of this flag to whenever `#![feature(doc_cfg)]` is active. I'm sure there are other uses for this, but right now i'm tying it to this feature. (If it makes more sense to give this its own feature, i can easily do that.)
bench: libcore: fix build failure of any.rs benchmark (use "dyn Any")
fixes
````
error: trait objects without an explicit `dyn` are deprecated
--> libcore/../libcore/benches/any.rs:18:36
|
18 | let mut y = &mut x as &mut Any;
| ^^^ help: use `dyn`: `dyn Any`
|
= note: requested on the command line with `-D bare-trait-objects`
````
Implement the `min_const_fn` feature gate
cc @RalfJung @eddyb
r? @Centril
implements the feature gate for #53555
I added a hack so the `const_fn` feature gate also enables the `min_const_fn` feature gate. This ensures that nightly users of `const_fn` don't have to touch their code at all.
The `min_const_fn` checks are run first, and if they succeeded, the `const_fn` checks are run additionally to ensure we didn't miss anything.
This splits "valid" into "valid for reads" and "valid for writes", and
also adds the concept of operation size to validity. Now functions which
operate on sequences state that e.g. pointer args must be "valid for reads of
size x".
The enumerated list of conditions is replaced by an explanation that
rust doesn't have a formal memory model. It does say that pointers
created directly from references are guaranteed to be valid, and links
to both the "Unsafe Code" section of the book and the "Undefined
Behavior" section of the reference.
- Add links to the GNU libc docs for `memmove`, `memcpy`, and
`memset`, as well as internally linking to other functions in `std::ptr`
- List invariants which, when violated, cause UB for all functions
- Add example to `ptr::drop_in_place` and compares it to `ptr::read`.
- Add examples which more closely mirror real world uses for the
functions in `std::ptr`. Also, move the reimplementation of `mem::swap`
to the examples of `ptr::read` and use a more interesting example for
`copy_nonoverlapping`.
- Change module level description
- Define what constitutes a "valid" pointer.
- Centralize discussion of ownership of bitwise copies in `ptr::read` and
provide an example.
move the Pin API into its own module for centralized documentation
This implements the change proposed by @withoutboats in #49150, as suggested by @RalfJung in the review of #53104,
along with the documentation that was originally in it, that was deemed more appropriate in module-level documentation.
r? @RalfJung
Suggest direct raw-pointer dereference
People often come looking for some kind of `as_ref_unchecked` method on
raw pointers that would give them `&T` and not `Option<&T>` when they
are sure the pointer is not NULL.
There's no such method, but taking a reference of the dereferenced
pointer accomplishes the same thing. Therefore, suggest using that, at
the `as_ref` site ‒ it's a place people are likely going to look into.
People often come looking for some kind of `as_ref_unchecked` method on
raw pointers that would give them `&T` and not `Option<&T>` when they
are sure the pointer is not NULL.
There's no such method, but taking a reference of the dereferenced
pointer accomplishes the same thing. Therefore, suggest using that, at
the `as_ref` site ‒ it's a place people are likely going to look into.
expand the documentation on the `Unpin` trait
provides an overview of the Pin API which the trait is for,
and show how it can be used in making self referencial structs
part of #49150
debug_assert to ensure that from_raw_parts is only used properly aligned
This does not help nearly as much as I would hope because everybody uses the distributed libstd which is compiled without debug assertions. For this reason, I am not sure if this is even worth it. OTOH, this would have caught the misalignment fixed by https://github.com/rust-lang/rust/issues/42789 *if* there had been any tests actually using ZSTs with alignment >1 (we have a CI runner which has debug assertions in libstd enabled), and it seems to currently [fail in the rg testsuite](https://ci.appveyor.com/project/rust-lang/rust/build/1.0.8403/job/v7dfdcgn8ay5j6sb). So maybe it is worth it, after all.
I have seen the attribute `#[rustc_inherit_overflow_checks]` in some places, does that make it so that the *caller's* debug status is relevant? Is there a similar attribute for `debug_assert!`? That could even subsume `rustc_inherit_overflow_checks`: Something like `rustc_inherit_debug_flag` could affect *all* places that change the generated code depending on whether we are in debug or release mode. In fact, given that we have to keep around the MIR for generic functions anyway, is there ever a reason *not* to handle the debug flag that way? I guess currently we apply debug flags like `cfg` so this is dropped early during the MIR pipeline?
EDIT: I learned from @eddyb that because of how `debug_assert!` works, this is not realistic. Well, we could still have it for the rustc CI runs and then maybe, eventually, when libstd gets compiled client-side and there is both a debug and a release build... then this will also benefit users.^^
Use #[non_exhaustive] on internal enums
This replaces `__Nonexhaustive` variants (and variants thereof) with `#[non_exhaustive]`. These were mostly unstable previously, with the exception of the `cloudabi` enums and `Level` in proc_macro: these were `#[doc(hidden)]`, so clearly intended not to be used directly. It should be safe to replace all of these.
Don't accept non-string literals for the format string in writeln
This is to improve diagnostics.
`println` and `eprintln` were already fixed by #52394.
Fixes#30143
unsized ManuallyDrop
I think this matches what @eddyb had in https://github.com/rust-lang/rust/pull/52711 originally.
~~However, I have never added a `CoerceUnsized` before so I am not sure if I did this right. I copied the `unstable` attribute on the `impl` from elsewhere, but AFAIK it is useless because `impl`'s are insta-stable... so shouldn't this rather say "stable since 1.30"?~~
This is insta-stable and hence requires FCP, at least.
Fixes https://github.com/rust-lang/rust/issues/47034
Add links to std::char::REPLACEMENT_CHARACTER from docs.
There are a few places where we mention the replacement character in the
docs, and it could be helpful for users to utilize the constant which is
available in the standard library, so let’s link to it!
There are a few places where we mention the replacement character in the
docs, and it could be helpful for users to utilize the constant which is
available in the standard library, so let’s link to it!
Place unions, pointer casts and pointer derefs behind extra feature gates
To ensure we don't stabilize these things together with const fn stabilization (or any other stabilization)
This PR moves union field accesses inside `const fn` behind a feature gate. It was possible without a feature gate before, but since `const fn` was behind a feature gate we can do this change.
While "dereferencing raw pointers" and "casting raw pointers to usize" were hard errors before this PR, one could work around them by abusing unions:
```rust
// deref
union Foo<T> {
x: &'static T,
y: *const T,
}
const FOO: u32 = unsafe { *Foo { y: 42 as *const T }.x };
// as usize cast
union Bar<T> {
x: usize,
y: *const T,
}
const BAR: usize = unsafe { Bar { y: &1u8 }.x };
```
r? @eddyb
cc @nikomatsakis
Rename Executor trait to Spawn
Renames the `Executor` trait to `Spawn` and the method on `Context` to `spawner`.
Note: Best only merge this after we've the alpha 3 announcement post ready.
r? @cramertj
Provide `{to,from}_{ne,le,be}_bytes` functions on integers
If one doesn't view integers as containers of bytes, converting them to
bytes necessarily needs the specfication of encoding.
I think Rust is a language that wants to be explicit. The `to_bytes`
function is basically the opposite of that – it converts an integer into
the native byte representation, but there's no mention (in the function
name) of it being very much platform dependent. Therefore, I think it
would be better to replace that method by three methods, the explicit
`to_ne_bytes` ("native endian") which does the same thing and
`to_{le,be}_bytes` which return the little- resp. big-endian encoding.
If one doesn't view integers as containers of bytes, converting them to
bytes necessarily needs the specfication of encoding.
I think Rust is a language that wants to be explicit. The `to_bytes`
function is basically the opposite of that – it converts an integer into
the native byte representation, but there's no mention (in the function
name) of it being very much platform dependent. Therefore, I think it
would be better to replace that method by three methods, the explicit
`to_ne_bytes` ("native endian") which does the same thing and
`to_{le,be}_bytes` which return the little- resp. big-endian encoding.
slices: fix ZST slice iterators making up pointers; debug_assert alignment in from_raw_parts
This fixes the problem that we are fabricating pointers out of thin air. I also managed to share more code between the mutable and shared iterators, while reducing the amount of macros.
I am not sure how useful it really is to add a `debug_assert!` in libcore. Everybody gets a release version of that anyway, right? Is there at least a CI job that runs the test suite with a debug version?
Fixes#42789
Rollup of 15 pull requests
Successful merges:
- #52793 (Add test for NLL: unexpected "free region `` does not outlive" error )
- #52799 (Use BitVector for global sets of AttrId)
- #52809 (Add test for unexpected region for local data ReStatic)
- #52834 ([NLL] Allow conflicting borrows of promoted length zero arrays)
- #52835 (Fix Alias intra doc ICE)
- #52854 (fix memrchr in miri)
- #52899 (tests/ui: Add missing mips{64} ignores)
- #52908 (Use SetLenOnDrop in Vec::truncate())
- #52915 (Don't count MIR locals as borrowed after StorageDead when finding locals live across a yield terminator)
- #52926 (rustc: Trim down the `rust_2018_idioms` lint group)
- #52930 (rustc_resolve: record single-segment extern crate import resolutions.)
- #52939 (Make io::Read::read_to_end consider io::Take::limit)
- #52942 (Another SmallVec.extend optimization)
- #52947 (1.27 actually added the `armv5te-unknown-linux-musleabi` target)
- #52954 (async can begin expressions)
Failed merges:
r? @ghost
fix memrchr in miri
The previous PR https://github.com/rust-lang/rust/pull/52744 was not enough because it assumed that the split between the `mid` and `end` parts returned by `align_to` was aligned. But really the only guarantee we have is that the `mid` part is aligned, so make use of that.
Fix From<LocalWaker>
This is a follow-up to https://github.com/rust-lang/rust/pull/52640
Fixes `From<LocalWaker>` which is affected by the same accidental drop bug (unless I'm totally mistaken)
r? @cramertj
