make MaybeUninit::as_(mut_)ptr const
I think it was just an oversight that they are not const yet.
I also changed their implementation as the old one created references to uninitialized memory.^^
Prevent `__rust_begin_short_backtrace` frames from being tail-call optimised away
I've stumbled across some situations where there (unexpectedly) was no `__rust_begin_short_backtrace` frame on the stack during unwinding.
On closer examination, it appeared that the calls to that function had been tail-call optimised away.
This PR follows [@bjorn3's suggestion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Disabling.20tail.20call.20optimisation.3F/near/205699133), by adding calls to `black_box` that hint to rustc not to perform TCO.
Fixes#47429
- Initialization can use `transmute_copy` to do the bitwise copy.
- `as_slice` can use `get_unchecked` and `MaybeUninit::slice_get_ref`,
and `as_mut_slice` can do similar.
- `next` and `next_back` can use the corresponding `Range` methods.
- `Clone` doesn't need any unsafety, and we can dynamically update the
new range to get partial drops if `T::clone` panics.
Rollup of 4 pull requests
Successful merges:
- #74774 (adds [*mut|*const] ptr::set_ptr_value)
- #75079 (Disallow linking to items with a mismatched disambiguator)
- #75203 (Make `IntoIterator` lifetime bounds of `&BTreeMap` match with `&HashMap` )
- #75227 (Fix ICE when using asm! on an unsupported architecture)
Failed merges:
r? @ghost
Make `IntoIterator` lifetime bounds of `&BTreeMap` match with `&HashMap`
This is a pretty small change on the lifetime bounds of `IntoIterator` implementations of both `&BTreeMap` and `&mut BTreeMap`. This is loosening the lifetime bounds, so more code should be accepted with this PR. This is lifetime bounds will still be implicit since we have `type Item = (&'a K, &'a V);` in the implementation. This change will make the HashMap and BTreeMap share the same signature, so we can share the same function/trait with both HashMap and BTreeMap in the code.
Fixes#74034.
r? @dtolnay hey, I was touching this file on my previous PR and wanted to fix this on the way. Would you mind taking a look at this, or redirecting it if you are busy?
adds [*mut|*const] ptr::set_ptr_value
I propose the addition of these two functions to `*mut T` and `*const T`, respectively. The motivation for this is primarily byte-wise pointer arithmetic on (potentially) fat pointers, i.e. for types with a `T: ?Sized` bound. A concrete use-case has been discussed in [this](https://internals.rust-lang.org/t/byte-wise-fat-pointer-arithmetic/12739) thread.
TL;DR: Currently, byte-wise pointer arithmetic with potentially fat pointers in not possible in either stable or nightly Rust without making assumptions about the layout of fat pointers, which is currently still an implementation detail and not formally stabilized. This PR adds one function to `*mut T` and `*const T` each, allowing to circumvent this restriction without exposing any internal implementation details.
One possible alternative would be to add specific byte-wise pointer arithmetic functions to the two pointer types in addition to the already existing count-wise functions. However, I feel this fairly niche use case does not warrant adding a whole set of new functions like `add_bytes`, `offset_bytes`, `wrapping_offset_bytes`, etc. (times two, one for each pointer type) to `libcore`.
All #[cfg(unix)] platforms follow the POSIX standard and define _SC_IOV_MAX so
that we rely purely on POSIX semantics to determine the limits on I/O vector
count.
Keep the I/O vector count limit in a `SyncOnceCell` to avoid the overhead of
repeatedly calling `sysconf` as these limits are guaranteed to not change during
the lifetime of a process by POSIX.
Both Linux and MacOS enforce limits on the vector count when performing vectored
I/O via the readv and writev system calls and return EINVAL when these limits
are exceeded. This changes the standard library to handle those limits as short
reads and writes to avoid forcing its users to query these limits using
platform specific mechanisms.
Completes support for coverage in external crates
Follow-up to #74959 :
The prior PR corrected for errors encountered when trying to generate
the coverage map on source code inlined from external crates (including
macros and generics) by avoiding adding external DefIds to the coverage
map.
This made it possible to generate a coverage report including external
crates, but the external crate coverage was incomplete (did not include
coverage for the DefIds that were eliminated.
The root issue was that the coverage map was converting Span locations
to source file and locations, using the SourceMap for the current crate,
and this would not work for spans from external crates (compliled with a
different SourceMap).
The solution was to convert the Spans to filename and location during
MIR generation instead, so precompiled external crates would already
have the correct source code locations embedded in their MIR, when
imported into another crate.
@wesleywiser FYI
r? @tmandry
Co-authored-by: Weiyi Wang <wwylele@gmail.com>
Co-authored-by: Adam Reichold <adam.reichold@t-online.de>
Co-authored-by: Josh Stone <cuviper@gmail.com>
Co-authored-by: Scott McMurray <scottmcm@users.noreply.github.com>
Co-authored-by: tmiasko <tomasz.miasko@gmail.com>
The prior PR corrected for errors encountered when trying to generate
the coverage map on source code inlined from external crates (including
macros and generics) by avoiding adding external DefIds to the coverage
map.
This made it possible to generate a coverage report including external
crates, but the external crate coverage was incomplete (did not include
coverage for the DefIds that were eliminated.
The root issue was that the coverage map was converting Span locations
to source file and locations, using the SourceMap for the current crate,
and this would not work for spans from external crates (compliled with a
different SourceMap).
The solution was to convert the Spans to filename and location during
MIR generation instead, so precompiled external crates would already
have the correct source code locations embedded in their MIR, when
imported into another crate.
add `unsigned_abs` to signed integers
Mentioned on rust-lang/rfcs#2914
This PR simply adds an `unsigned_abs` to signed integers function which returns the correct absolute value as a unsigned integer.
Move bulk of BTreeMap::insert method down to new method on handle
Adjust the boundary between the map and node layers for insertion: do more in the node layer, keep root manipulation and pointer dereferencing separate. No change in undefined behaviour or performance.
r? @Mark-Simulacrum
Stabilize `Result::as_deref` and `as_deref_mut`
FCP completed in https://github.com/rust-lang/rust/issues/50264#issuecomment-645681400.
This PR stabilizes two new APIs for `std::result::Result`:
```rust
fn as_deref(&self) -> Result<&T::Target, &E> where T: Deref;
fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E> where T: DerefMut;
```
This PR also removes two rarely used unstable APIs from `Result`:
```rust
fn as_deref_err(&self) -> Result<&T, &E::Target> where E: Deref;
fn as_deref_mut_err(&mut self) -> Result<&mut T, &mut E::Target> where E: DerefMut;
```
Closes#50264
BTreeMap: define forget_type only when relevant
Similar to `forget_node_type` for handles.
No effect on generated code, apart maybe from the superfluous calls that might not have been optimized away.
r? @Mark-Simulacrum
BTreeMap::drain_filter should not touch the root during iteration
Although Miri doesn't point it out, I believe there is undefined behaviour using `drain_filter` when draining the 11th-last element from a tree that was larger. When this happens, the last remaining child nodes are merged, the root becomes empty and is popped from the tree. That last step establishes a mutable reference to the node elected root and writes a pointer in `node::Root`, while iteration continues to visit the same node.
This is mostly code from #74437, slightly adapted.
In the current documentation about the `Copy` marker trait, there is a section
about "additional implementors", which list additional implementors of the `Copy` trait.
The fact that shared references are also `Copy` is mixed with another point,
which makes it hard to recognize and make it seem not as important.
This clarifies the fact that shared references are also `Copy`, by mentioning it as a
separate item in the list of "additional implementors".
Fix std::fs::File::metadata permission on WASI target
Previously `std::fs::File::metadata` on wasm32-wasi would call `fd_filestat_get`
to get metadata associated with fd, but that fd is opened without
RIGHTS_FD_FILESTAT_GET right, so it will failed on correctly implemented WASI
environment.
This change instead to add the missing rights when opening an fd.
Stabilize Vec::leak as a method
Closes https://github.com/rust-lang/rust/issues/62195
The signature is changed to a method rather than an associated function:
```diff
-pub fn leak<'a>(vec: Vec<T>) -> &'a mut [T]
+pub fn leak<'a>(self) -> &'a mut [T]
```
The reason for `Box::leak` not to be a method (`Deref` to an arbitrary `T` which might have its own, different `leak` method) does not apply.
add `slice::array_chunks` to std
Now that #74113 has landed, these methods are suddenly usable. A rebirth of #72334
Tests are directly copied from `chunks_exact` and some additional tests for type inference.
r? @withoutboats as you are both part of t-libs and working on const generics. closes#60735
Previously `std::fs::File::metadata` on wasm32-wasi would call `fd_filestat_get`
to get metadata associated with fd, but that fd is opened without
RIGHTS_FD_FILESTAT_GET right, so it will failed on correctly implemented WASI
environment.
This change instead to add the missing rights when opening an fd.
Make `Option::unwrap` unstably const
This is lumped into the `const_option` feature gate (#67441), which enables a potpourri of `Option` methods.
cc @rust-lang/wg-const-eval
r? @oli-obk
Don't use "weak count" around Weak::from_raw_ptr
As `Rc/Arc::weak_count` returns 0 when having no strong counts, this
could be confusing and it's better to avoid using that completely.
Closes#73840.
`Result::unwrap` is not eligible becuase it formats the contents of the
`Err` variant. `unwrap_or`, `unwrap_or_else` and friends are not
eligible because they drop things or invoke closures.
Make `mem::size_of_val` and `mem::align_of_val` unstably const
Implements #46571 but does not stabilize it. I wanted this while working on something today.
The only reason not to immediately stabilize are concerns around [custom DSTs](https://github.com/rust-lang/rust/issues/46571#issuecomment-387669352). That proposal has made zero progress in the last two years and const eval is rich enough to support pretty much any user-defined `len` function as long as nightly features are allowed (`raw_ptr_deref`).
Currently, this raises a `const_err` lint when passed an `extern type`.
r? @oli-obk
cc @rust-lang/wg-const-eval
Remove links to rejected errata 4406 for RFC 4291
Fixes#74198.
For now I simply removed the links, the docs seems clear enough to me but I'm no expert in the domain so don't hesitate to correct me if more is needed.
cc @ghanan94.
@rustbot modify labels: T-doc, T-libs
Stabilize const_type_id feature
The tracking issue for `const_type_id` points to the ill-fated #41875. So I'm re-energizing `TypeId` shenanigans by opening this one up to see if there's anything blocking us from stabilizing the constification of type ids.
Will wait for CI before pinging teams/groups.
-----
This PR stabilizes the `const_type_id` feature, which allows `TypeId::of` (and the underlying unstable intrinsic) to be called in constant contexts.
There are some [sanity tests](https://github.com/rust-lang/rust/blob/master/src/test/ui/consts/const-typeid-of-rpass.rs) that demonstrate its usage, but I’ve included some more below.
As a simple example, you could create a constant item that contains some type ids:
```rust
use std::any::TypeId;
const TYPE_IDS: [TypeId; 2] = [
TypeId::of::<u32>(),
TypeId::of::<i32>(),
];
assert_eq!(TypeId::of::<u32>(), TYPE_IDS[0]);
```
Type ids can also now appear in associated constants. You could create a trait that associates each type with its constant type id:
```rust
trait Any where Self: 'static {
const TYPE_ID: TypeId = TypeId::of::<Self>();
}
impl<T: 'static> Any for T { }
assert_eq!(TypeId::of::<usize>(), usize::TYPE_ID);
```
`TypeId::of` is generic, which we saw above in the way the generic `Self` argument was used. This has some implications for const evaluation. It means we can make trait impls evaluate differently depending on information that wasn't directly passed through the trait system. This violates the _parametricity_ property, which requires all instances of a generic function to behave the same way with respect to its generic parameters. That's not unique to `TypeId::of`, other generic const functions based on compiler intrinsics like `mem::align_of` can also violate parametricity. In practice Rust doesn't really have type parametricity anyway since it monomorphizes generics into concrete functions, so violating it using type ids isn’t new.
As an example of how impls can behave differently, you could combine constant type ids with the `const_if_match` feature to dispatch calls based on the type id of the generic `Self`, rather than based on information about `Self` that was threaded through trait bounds. It's like a rough-and-ready form of specialization:
```rust
#![feature(const_if_match)]
trait Specialized where Self: 'static {
// An associated constant that determines the function to call
// at compile-time based on `TypeId::of::<Self>`.
const CALL: fn(&Self) = {
const USIZE: TypeId = TypeId::of::<usize>();
match TypeId::of::<Self>() {
// Use a closure for `usize` that transmutes the generic `Self` to
// a concrete `usize` and dispatches to `Self::usize`.
USIZE => |x| Self::usize(unsafe { &*(x as *const Self as *const usize) }),
// For other types, dispatch to the generic `Self::default`.
_ => Self::default,
}
};
fn call(&self) {
// Call the function we determined at compile-time
(Self::CALL)(self)
}
fn default(x: &Self);
fn usize(x: &usize);
}
// Implement our `Specialized` trait for any `Debug` type.
impl<T: fmt::Debug + 'static> Specialized for T {
fn default(x: &Self) {
println!("default: {:?}", x);
}
fn usize(x: &usize) {
println!("usize: {:?}", x);
}
}
// Will print "usize: 42"
Specialized::call(&42usize);
// Will print "default: ()"
Specialized::call(&());
```
Type ids have some edges that this stabilization exposes to more contexts. It's possible for type ids to collide (but this is a bug). Since they can change between compiler versions, it's never valid to cast a type id to its underlying value.
Fix RefUnwindSafe & UnwinsSafe impls for lazy::SyncLazy
I *think* we should implement those unconditionally with respect to `F`.
The user code can't observe the closure in any way, and we poison lazy if the closure itself panics.
But I've never fully wrapped my head around `UnwindSafe` traits, so 🤷♂️
Add str::[r]split_once
This is useful for quick&dirty parsing of key: value config pairs. Used a bunch in Cargo and rust-analyzer:
* https://github.com/rust-lang/cargo/search?q=splitn%282&unscoped_q=splitn%282
* https://github.com/rust-analyzer/rust-analyzer/search?q=split_delim&unscoped_q=split_delim
In theory, once const-generics are done, this functionality could be achieved without a dedicated method with
```rust
match s.splitn(delimier, 2).collect_array::<2>() {
Some([prefix, suffix]) => todo!(),
None => todo!(),
}
```
Even in that world, having a dedicated method seems clearer on the intention.
I am not sure about naming -- this is something I've just came up with yesterday, I don't know off the top of my head analogs in other languages.
If T-libs thinks this is a reasonable API to have, I'll open a tracking issue and add more thorough tests.
Add #[inline] to RawWaker::new
`RawWaker::new` is used when creating a new waker or cloning an existing one,
for example as in code below. The `RawWakerVTable::new` can be const evaluated,
but `RawWaker::new` itself cannot since waker pointer is not known at compile
time. Add `#[inline]` to avoid overhead of a function call.
```rust
unsafe fn clone_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) -> RawWaker {
unsafe { Arc::incr_strong_count(waker as *const W) };
RawWaker::new(
waker as *const (),
&RawWakerVTable::new(clone_waker::<W>, wake::<W>, wake_by_ref::<W>, drop_waker::<W>),
)
}
```
This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.
Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.
For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.
This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.
Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.
* `object` - this crate is used to parse object file headers and
contents. Very low-level support is used from this crate and almost
all of it is disabled. Largely we're just using struct definitions as
well as convenience methods internally to read bytes and such.
* `addr2line` - this is the main meat of the implementation for
symbolication. This crate depends on `gimli` for DWARF parsing and
then provides interfaces needed by the `backtrace` crate to turn an
address into a filename / line number. This crate is actually pretty
small (fits in a single file almost!) and mirrors most of what
`dwarf.c` does for libbacktrace.
* `miniz_oxide` - the libbacktrace crate transparently handles
compressed debug information which is compressed with zlib. This crate
is used to decompress compressed debug sections.
* `gimli` - not actually used directly, but a dependency of `addr2line`.
* `adler32`- not used directly either, but a dependency of
`miniz_oxide`.
The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.
Some references for those interested are:
* Original addition of libbacktrace - #12602
* OOM with libbacktrace - #24231
* Backtrace failure due to use of uninitialized value - #28447
* Possibility to feed untrusted data to libbacktrace - #21889
* Soundness fix for libbacktrace - #33729
* Crash in libbacktrace - #39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - #29293, #37477
* Update procedure is quite complicated due to how many patches we
need to carry - #50955
* Libbacktrace doesn't work on MinGW with dynamic libs - #71060
* Segfault in libbacktrace on macOS - #71397
Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.
This commit updates the src/stdarch submodule primarily to include
rust-lang/stdarch#874 which updated and revamped WebAssembly SIMD
intrinsics and renamed WebAssembly atomics intrinsics. This is all
unstable surface area of the standard library so the changes should be
ok here. The SIMD updates also enable SIMD intrinsics to be used by any
program any any time, yay!
cc #74372, a tracking issue I've opened for the stabilization of SIMD
intrinsics
This has already been done for `SocketAddrV4`, `SocketAddrV6`,
`IpAddrV4` and `IpAddrV6`. I don't see a point to keep the rather bad
to read derived impl, especially when pretty printing:
V4(
127.0.0.1
)
From the `Display`, one can easily and unambiguously see if it's V4 or
V6. Using `Display` as `Debug` is very convenient for configuration
structs (e.g. for webservers) that often just have a `derive(Debug)`
and are printed that way to the user.
