As LLVM seems to be outperformed by the complexity of signed 128-bits
number compared to our Hacker's Delight implementation.[^1]
It doesn't seems like it's an improvement for the other sizes[^2], so we
let them with the wide implementation.
[^1]: https://rust.godbolt.org/z/ravE75EYj
[^2]: https://rust.godbolt.org/z/fzr171zKh
Rename macro `SmartPointer` to `CoercePointee`
As per resolution #129104 we will rename the macro to better reflect the technical specification of the feature and clarify the communication.
- `SmartPointer` is renamed to `CoerceReferent`
- `#[pointee]` attribute is renamed to `#[referent]`
- `#![feature(derive_smart_pointer)]` gate is renamed to `#![feature(derive_coerce_referent)]`.
- Any mention of `SmartPointer` in the file names are renamed accordingly.
r? `@compiler-errors`
cc `@nikomatsakis` `@Darksonn`
Round negative signed integer towards zero in `iN::midpoint`
This PR changes the implementation of `iN::midpoint` (the signed variants) to round negative signed integers **towards zero** *instead* of negative infinity as is currently the case.
This is done so that the obvious expectations[^1] of `midpoint(a, b) == midpoint(b, a)` and `midpoint(-a, -b) == -midpoint(a, b)` are true, which makes the even more obvious implementation `(a + b) / 2` always true.
The unsigned variants `uN::midpoint` (which are being [FCP-ed](https://github.com/rust-lang/rust/pull/131784#issuecomment-2417188117)) already rounds towards zero, so there is no consistency issue.
cc `@scottmcm`
r? `@dtolnay`
[^1]: https://github.com/rust-lang/rust/issues/110840#issuecomment-2336753931
Instead of towards negative infinity as is currently the case.
This done so that the obvious expectations of
`midpoint(a, b) == midpoint(b, a)` and
`midpoint(-a, -b) == -midpoint(a, b)` are true, which makes the even
more obvious implementation `(a + b) / 2` true.
https://github.com/rust-lang/rust/issues/110840#issuecomment-2336753931
Const stability checks v2
The const stability system has served us well ever since `const fn` were first stabilized. It's main feature is that it enforces *recursive* validity -- a stable const fn cannot internally make use of unstable const features without an explicit marker in the form of `#[rustc_allow_const_fn_unstable]`. This is done to make sure that we don't accidentally expose unstable const features on stable in a way that would be hard to take back. As part of this, it is enforced that a `#[rustc_const_stable]` can only call `#[rustc_const_stable]` functions. However, some problems have been coming up with increased usage:
- It is baffling that we have to mark private or even unstable functions as `#[rustc_const_stable]` when they are used as helpers in regular stable `const fn`, and often people will rather add `#[rustc_allow_const_fn_unstable]` instead which was not our intention.
- The system has several gaping holes: a private `const fn` without stability attributes whose inherited stability (walking up parent modules) is `#[stable]` is allowed to call *arbitrary* unstable const operations, but can itself be called from stable `const fn`. Similarly, `#[allow_internal_unstable]` on a macro completely bypasses the recursive nature of the check.
Fundamentally, the problem is that we have *three* disjoint categories of functions, and not enough attributes to distinguish them:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
Functions in the first two categories cannot use unstable const features and they can only call functions from the first two categories.
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, all the holes mentioned above have been closed. There's still one potential hole that is hard to avoid, which is when MIR building automatically inserts calls to a particular function in stable functions -- which happens in the panic machinery. Those need to be manually marked `#[rustc_const_stable_indirect]` to be sure they follow recursive const stability. But that's a fairly rare and special case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be constified simply by marking it as `const fn`, and it will then be const-callable from stable `const fn` and subject to recursive const stability requirements. If it is publicly reachable (which implies it cannot be unmarked), it will be const-unstable under the same feature gate. Only if the function ever becomes `#[stable]` does it need a `#[rustc_const_unstable]` or `#[rustc_const_stable]` marker to decide if this should also imply const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to use unstable const lang features (including intrinsics), or (b) `#[stable]` functions that are not yet intended to be const-stable. Adding `#[rustc_const_stable]` is only needed for functions that are actually meant to be directly callable from stable const code. `#[rustc_const_stable_indirect]` is used to mark intrinsics as const-callable and for `#[rustc_const_unstable]` functions that are actually called from other, exposed-on-stable `const fn`. No other attributes are required.
Also see the updated dev-guide at https://github.com/rust-lang/rustc-dev-guide/pull/2098.
I think in the future we may want to tweak this further, so that in the hopefully common case where a public function's const-stability just exactly mirrors its regular stability, we never have to add any attribute. But right now, once the function is stable this requires `#[rustc_const_stable]`.
### Open question
There is one point I could see we might want to do differently, and that is putting `#[rustc_const_unstable]` functions (but not intrinsics) in category 2 by default, and requiring an extra attribute for `#[rustc_const_not_exposed_on_stable]` or so. This would require a bunch of extra annotations, but would have the advantage that turning a `#[rustc_const_unstable]` into `#[rustc_const_stable]` will never change the way the function is const-checked. Currently, we often discover in the const stabilization PR that a function needs some other unstable const things, and then we rush to quickly deal with that. In this alternative universe, we'd work towards getting rid of the `rustc_const_not_exposed_on_stable` before stabilization, and once that is done stabilization becomes a trivial matter. `#[rustc_const_stable_indirect]` would then only be used for intrinsics.
I think I like this idea, but might want to do it in a follow-up PR, as it will need a whole bunch of annotations in the standard library. Also, we probably want to convert all const intrinsics to the "new" form (`#[rustc_intrinsic]` instead of an `extern` block) before doing this to avoid having to deal with two different ways of declaring intrinsics.
Cc `@rust-lang/wg-const-eval` `@rust-lang/libs-api`
Part of https://github.com/rust-lang/rust/issues/129815 (but not finished since this is not yet sufficient to safely let us expose `const fn` from hashbrown)
Fixes https://github.com/rust-lang/rust/issues/131073 by making it so that const-stable functions are always stable
try-job: test-various
library: consistently use American spelling for 'behavior'
We use "behavior" a lot more often than "behaviour", but some "behaviour" have even snuck into user-facing docs. This makes the spelling consistent.
Fundamentally, we have *three* disjoint categories of functions:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, several holes in recursive const stability checking are being closed.
There's still one potential hole that is hard to avoid, which is when MIR
building automatically inserts calls to a particular function in stable
functions -- which happens in the panic machinery. Those need to *not* be
`rustc_const_unstable` (or manually get a `rustc_const_stable_indirect`) to be
sure they follow recursive const stability. But that's a fairly rare and special
case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be
constified simply by marking it as `const fn`, and it will then be
const-callable from stable `const fn` and subject to recursive const stability
requirements. If it is publicly reachable (which implies it cannot be unmarked),
it will be const-unstable under the same feature gate. Only if the function ever
becomes `#[stable]` does it need a `#[rustc_const_unstable]` or
`#[rustc_const_stable]` marker to decide if this should also imply
const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to
use unstable const lang features (including intrinsics), or (b) `#[stable]`
functions that are not yet intended to be const-stable. Adding
`#[rustc_const_stable]` is only needed for functions that are actually meant to
be directly callable from stable const code. `#[rustc_const_stable_indirect]` is
used to mark intrinsics as const-callable and for `#[rustc_const_unstable]`
functions that are actually called from other, exposed-on-stable `const fn`. No
other attributes are required.
This commit contains a new Receiver trait, which is the basis for the
Arbitrary Self Types v2 RFC. This allows smart pointers to be method
receivers even if they're not Deref.
This is currently unused by the compiler - a subsequent PR will start to
use this for method resolution if the arbitrary_self_types feature gate
is enabled. This is being landed first simply to make review
simpler: if people feel this should all be in an atomic PR let me know.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
Expand `ptr::fn_addr_eq()` documentation.
* Describe more clearly what is (not) guaranteed, and de-emphasize the description of rustc implementation details.
* Explain what you *can* reliably use it for.
Tracking issue for `ptr_fn_addr_eq`: #129322
The motivation for this PR is that I just learned that `ptr::fn_addr_eq()` exists, read the documentation, and thought: “*I* know what this means, but someone not already familiar with how `rustc` works could be left wondering whether this is even good for anything.” Fixing that seems especially important if we’re going to recommend people use it instead of `==` (as per #118833).
Rollup of 6 pull requests
Successful merges:
- #131851 ([musl] use posix_spawn if a directory change was requested)
- #132048 (AIX: use /dev/urandom for random implementation )
- #132093 (compiletest: suppress Windows Error Reporting (WER) for `run-make` tests)
- #132101 (Avoid using imports in thread_local_inner! in static)
- #132113 (Provide a default impl for Pattern::as_utf8_pattern)
- #132115 (rustdoc: Extend fake_variadic to "wrapped" tuples)
r? `@ghost`
`@rustbot` modify labels: rollup
Provide a default impl for Pattern::as_utf8_pattern
Newly added ```Pattern::as_utf8_pattern()``` causes needless breakage for crates that implement Pattern. This provides a default implementation instead.
r? `@BurntSushi`
Avoid using imports in thread_local_inner! in static
Fixes#131863 for wasm targets
All other macros were done in #131866, but this sub module is missed.
r? `@jieyouxu`
AIX: use /dev/urandom for random implementation
On AIX, we can poll `/dev/urandom` for cryptographically secure random output to implement `fill_bytes` because we don't have equivalent syscalls like other platforms. https://www.ibm.com/docs/en/aix/7.3?topic=files-random-urandom-devices
[musl] use posix_spawn if a directory change was requested
Currently, not all libcs have the `posix_spawn_file_actions_addchdir_np` symbol available to them. So we attempt to do a weak symbol lookup for that function. But that only works if libc is a dynamic library -- with statically linked musl binaries the symbol lookup would never work, so we would never be able to use it even if the musl in use supported the symbol.
Now that Rust has a minimum musl version of 1.2.3, all supported musl versions now include this symbol, so we can unconditionally expect it to be there. This symbol was added to libc in https://github.com/rust-lang/libc/pull/3949 -- use it here.
I couldn't find any tests for whether the posix_spawn path is used, but I've verified with cargo-nextest that this change works. This is a substantial improvement to nextest's performance with musl. On my workstation with a Ryzen 7950x, against https://github.com/clap-rs/clap at
61f5ee514f8f60ed8f04c6494bdf36c19e7a8126:
Before:
```
Summary [ 1.071s] 879 tests run: 879 passed, 0 skipped
```
After:
```
Summary [ 0.392s] 879 tests run: 879 passed, 0 skipped
```
Fixes#99740.
try-job: dist-various-1
try-job: dist-various-2
Document textual format of SocketAddrV{4,6}
This commit adds new "Textual representation" documentation sections to SocketAddrV4 and SocketAddrV6, by analogy to the existing "textual representation" sections of Ipv4Addr and Ipv6Addr.
Rationale: Without documentation about which formats are actually accepted, it's hard for a programmer to be sure that their code will actually behave as expected when implementing protocols that require support (or rejection) for particular representations. This lack of clarity can in turn can lead to ambiguities and security problems like those discussed in RFC 6942.
(I've tried to describe the governing RFCs or standards where I could, but it's possible that the actual implementers had something else in mind. I could not find any standards that corresponded _exactly_ to the one implemented in SocketAddrv6, but I have linked the relevant documents that I could find.)
Represent trait constness as a distinct predicate
cc `@rust-lang/project-const-traits`
r? `@ghost` for now
Also mirrored everything that is written below on this hackmd here: https://hackmd.io/`@compiler-errors/r12zoixg1l`
# Tl;dr:
* This PR removes the bulk of the old effect desugaring.
* This PR reimplements most of the effect desugaring as a new predicate and set of a couple queries. I believe it majorly simplifies the implementation and allows us to move forward more easily on its implementation.
I'm putting this up both as a request for comments and a vibe-check, but also as a legitimate implementation that I'd like to see land (though no rush of course on that last part).
## Background
### Early days
Once upon a time, we represented trait constness in the param-env and in `TraitPredicate`. This was very difficult to implement correctly; it had bugs and was also incomplete; I don't think this was anyone's fault though, it was just the limit of experimental knowledge we had at that point.
Dealing with `~const` within predicates themselves meant dealing with constness all throughout the trait solver. This was difficult to keep track of, and afaict was not handled well with all the corners of candidate assembly.
Specifically, we had to (in various places) remap constness according to the param-env constness:
574b64a97f/compiler/rustc_trait_selection/src/traits/select/mod.rs (L1498)
This was annoying and manual and also error prone.
### Beginning of the effects desugaring
Later on, #113210 reimplemented a new desugaring for const traits via a `<const HOST: bool>` predicate. This essentially "reified" the const checking and separated it from any of the remapping or separate tracking in param-envs. For example, if I was in a const-if-const environment, but I wanted to call a trait that was non-const, this reification would turn the constness mismatch into a simple *type* mismatch of the effect parameter.
While this was a monumental step towards straightening out const trait checking in the trait system, it had its own issues, since that meant that the constness of a trait (or any item within it, like an associated type) was *early-bound*. This essentially meant that `<T as Trait>::Assoc` was *distinct* from `<T as ~const Trait>::Assoc`, which was bad.
### Associated-type bound based effects desugaring
After this, #120639 implemented a new effects desugaring. This used an associated type to more clearly represent the fact that the constness is not an input parameter of a trait, but a property that could be computed of a impl. The write-up linked in that PR explains it better than I could.
However, I feel like it really reached the limits of what can comfortably be expressed in terms of associated type and trait calculus. Also, `<const HOST: bool>` remains a synthetic const parameter, which is observable in nested items like RPITs and closures, and comes with tons of its own hacks in the astconv and middle layer.
For example, there are pieces of unintuitive code that are needed to represent semantics like elaboration, and eventually will be needed to make error reporting intuitive, and hopefully in the future assist us in implementing built-in traits (eventually we'll want something like `~const Fn` trait bounds!).
elaboration hack: 8069f8d17a/compiler/rustc_type_ir/src/elaborate.rs (L133-L195)
trait bound remapping hack for diagnostics: 8069f8d17a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs (L2370-L2413)
I want to be clear that I don't think this is a issue of implementation quality or anything like that; I think it's simply a very clear sign that we're using types and traits in a way that they're not fundamentally supposed to be used, especially given that constness deserves to be represented as a first-class concept.
### What now?
This PR implements a new desugaring for const traits. Specifically, it introduces a `HostEffect` predicate to represent the obligation an impl is const, rather than using associated type bounds and the compat trait that exists for effects today.
### `HostEffect` predicate
A `HostEffect` clause has two parts -- the `TraitRef` we're trying to prove, and a `HostPolarity::{Maybe, Const}`.
`HostPolarity::Const` corresponds to `T: const Trait` bounds, which must *always* be proven as const, and which can be written in any context. These are lowered directly into the predicates of an item, since they're not "context-specific".
On the other hand, `HostPolarity::Maybe` corresponds to `T: ~const Trait` bounds which must only exist in a conditionally-const context like a method in a `#[const_trait]`, or a `const fn` free function. We do not lower these immediately into the predicates of an item; instead, we collect them into a new query called the **`const_conditions`**. These are the set of trait refs that we need to prove have const implementations for an item to be const.
Notably, they're represented as bare (poly) trait refs because they are meant to be paired back together with a `HostPolarity` when they're being registered in typeck (see next section).
For example, given:
```rust
const fn foo<T: ~const A + const B>() {}
```
`foo`'s const conditions would contain `T: A`, but not `T: B`. On the flip side, foo's predicates (`predicates_of`) query would contain `HostEffect(T: B, HostPolarity::Const)` but not `HostEffect(T: A, HostPolarity::Maybe)` since we don't need to prove that predicate in a non-const environment (and it's not even the right predicate to prove in an unconditionally const environment).
### Type checking const bodies
When type checking bodies in HIR, when we encounter a call expression, we additionally register the callee item's const conditions with the `HostPolarity` from the body we're typechecking (`Const` for unconditionally const things like `const`/`static` items, and `Maybe` for conditionally const things like const fns; and we don't register `HostPolarity` predicates for non-const bodies).
When type-checking a conditionally const body, we augment its param-env with `HostEffect(..., Maybe)` predicates.
### Checking that const impls are WF
We extend the logic in `compare_method_predicate_entailment` to also check the const-conditions of the impl method, to make sure that we error for:
```rust
#[const_trait] Bar {}
#[const_trait] trait Foo {
fn method<T: Bar>();
}
impl Foo for () {
fn method<T: ~const Bar>() {} // stronger assumption!
}
```
We also extend the WF check for impls to register the const conditions of the trait that is being implemented. This is to make sure we error for:
```rust
#[const_trait] trait Bar {}
#[const_trait] trait Foo<T> where T: ~const Bar {}
impl<T> const Foo<T> for () {}
//~^ `T: ~const Bar` is missing!
```
### Proving a `HostEffect` predicate
We have several ways of proving a `HostEffect` predicate:
1. Matching a `HostEffect` predicate from the param-env
2. From an impl - we do impl selection very similar to confirming a trait goal, except we filter for only const impls, and we additionally register the impl's const conditions (i.e. the impl's `~const` where clauses).
Later I expect that we will add more built-in implementations for things like `Fn`.
## What next?
After this PR, I'd like to split out the work more so it can proceed in parallel and probably amongst others that are not me.
* Register `HostEffect` goal for places in HIR typeck that correspond to call terminators, like autoderef.
* Make traits in libstd const again.
* Probably need to impl host effect preds in old solver.
* Implement built-in `HostEffect` rules for traits like `Fn`.
* Rip out const checking from MIR altogether.
## So what?
This ends up being super convenient basically everywhere in the compiler. Due to the design of the new trait solver, we end up having an almost parallel structure to the existing trait and projection predicates for assembling `HostEffect` predicates; adding new candidates and especially new built-in implementations is now basically trivial, and it's quite straightforward to understand the confirmation logic for these predicates.
Same with diagnostics reporting; since we have predicates which represent the obligation to prove an impl is const, we can simplify and make these diagnostics richer without having to write a ton of logic to intercept and rewrite the existing `Compat` trait errors.
Finally, it gives us a much more straightforward path for supporting the const effect on the old trait solver. I'm personally quite passionate about getting const trait support into the hands of users without having to wait until the new solver lands[^1], so I think after this PR lands we can begin to gauge how difficult it would be to implement constness in the old trait solver too. This PR will not do this yet.
[^1]: Though this is not a prerequisite or by any means the only justification for this PR.
Remove the `Arc` rt::init allocation for thread info
Removes an allocation pre-main by just not storing anything in std:🧵:Thread for the main thread.
- The thread name can just be a hard coded literal, as was done in #123433.
- Storing ThreadId and Parker in a static that is initialized once at startup. This uses SyncUnsafeCell and MaybeUninit as this is quite performance critical and we don't need synchronization or to store a tag value and possibly leave in a panic.
This commit adds new "Textual representation" documentation sections to
SocketAddrV4 and SocketAddrV6, by analogy to the existing
"textual representation" sections of Ipv4Addr and Ipv6Addr.
Rationale: Without documentation about which formats are actually
accepted, it's hard for a programmer to be sure that their code
will actually behave as expected when implementing protocols that
require support (or rejection) for particular representations.
This lack of clarity can in turn can lead to ambiguities and
security problems like those discussed in RFC 6942.
(I've tried to describe the governing RFCs or standards where I
could, but it's possible that the actual implementers had something
else in mind. I could not find any standards that corresponded
_exactly_ to the one implemented in SocketAddrv6, but I have linked
the relevant documents that I could find.)
Currently, not all libcs have the `posix_spawn_file_actions_addchdir_np` symbol
available to them. So we attempt to do a weak symbol lookup for that function.
But that only works if libc is a dynamic library -- with statically linked musl
binaries the symbol lookup would never work, so we would never be able to use it
even if the musl in use supported the symbol.
Now that Rust has a minimum musl version of 1.2.3, all supported musl versions
now include this symbol, so we can unconditionally expect it to be there. This
symbol was added to libc in https://github.com/rust-lang/libc/pull/3949 -- use
it here.
I couldn't find any tests for whether the posix_spawn path is used, but I've
verified with cargo-nextest that this change works. This is a substantial
improvement to nextest's performance with musl. On my workstation with a Ryzen
7950x, against https://github.com/clap-rs/clap at
61f5ee514f8f60ed8f04c6494bdf36c19e7a8126:
Before:
```
Summary [ 1.071s] 879 tests run: 879 passed, 0 skipped
```
After:
```
Summary [ 0.392s] 879 tests run: 879 passed, 0 skipped
```
Fixes#99740.
Rename Receiver -> LegacyReceiver
As part of the "arbitrary self types v2" project, we are going to replace the current `Receiver` trait with a new mechanism based on a new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard. Options considered included:
* HardCodedReceiver (because it should only be used for things in the standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary. Assuming the new mechanism proceeds to stabilization as intended, the legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library, we suspect it may be in use elsehwere, so we're landing this change separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? `@wesleywiser`
"innermost", "outermost", "leftmost", and "rightmost" don't need hyphens
These are all standard dictionary words and don't require hyphenation.
-----
Encountered an instance of this in error messages and it bugged me, so I
figured I'd fix it across the entire codebase.
Optimize `Rc<T>::default`
The missing piece of https://github.com/rust-lang/rust/pull/131460.
Also refactored `Arc<T>::default` by using a safe `NonNull::from(Box::leak(_))` to replace the unnecessarily unsafe call to `NonNull::new_unchecked(Box::into_raw(_))`. The remaining unsafety is coming from `[Rc|Arc]::from_inner`, which is safe from the construction of `[Rc|Arc]Inner`.
Run most `core::num` tests in const context too
This adds some infrastructure for something I was going to use in #131566, but it felt worthwhile enough on its own to merge/discuss separately.
Essentially, right now we tend to rely on UI tests to ensure that things work in const context, rather than just using library tests. This uses a few simple macro tricks to make it *relatively* painless to execute tests in both runtime and compile-time context. And this only applies to the numeric tests, and not anything else.
Recommended to review without whitespace in the diff.
cc `@RalfJung`
better default capacity for str::replace
Adds smarter capacity for str::replace in cases where we know that the output will be at least as long as the original string.
As part of the "arbitrary self types v2" project, we are going to
replace the current `Receiver` trait with a new mechanism based on a
new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard.
Options considered included:
* HardCodedReceiver (because it should only be used for things in the
standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary.
Assuming the new mechanism proceeds to stabilization as intended, the
legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library,
we suspect it may be in use elsehwere, so we're landing this change
separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a
patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
update ABI compatibility docs for new option-like rules
Documents the rules decided [here](https://github.com/rust-lang/rust/pull/130628#issuecomment-2402761599) for our ABI compatibility rules.
Long-term this should be moved to the reference, but for now this is what we got.
Cc `@rust-lang/lang` `@rust-lang/opsem`
stabilize Strict Provenance and Exposed Provenance APIs
Given that [RFC 3559](https://rust-lang.github.io/rfcs/3559-rust-has-provenance.html) has been accepted, t-lang has approved the concept of provenance to exist in the language. So I think it's time that we stabilize the strict provenance and exposed provenance APIs, and discuss provenance explicitly in the docs:
```rust
// core::ptr
pub const fn without_provenance<T>(addr: usize) -> *const T;
pub const fn dangling<T>() -> *const T;
pub const fn without_provenance_mut<T>(addr: usize) -> *mut T;
pub const fn dangling_mut<T>() -> *mut T;
pub fn with_exposed_provenance<T>(addr: usize) -> *const T;
pub fn with_exposed_provenance_mut<T>(addr: usize) -> *mut T;
impl<T: ?Sized> *const T {
pub fn addr(self) -> usize;
pub fn expose_provenance(self) -> usize;
pub fn with_addr(self, addr: usize) -> Self;
pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}
impl<T: ?Sized> *mut T {
pub fn addr(self) -> usize;
pub fn expose_provenance(self) -> usize;
pub fn with_addr(self, addr: usize) -> Self;
pub fn map_addr(self, f: impl FnOnce(usize) -> usize) -> Self;
}
impl<T: ?Sized> NonNull<T> {
pub fn addr(self) -> NonZero<usize>;
pub fn with_addr(self, addr: NonZero<usize>) -> Self;
pub fn map_addr(self, f: impl FnOnce(NonZero<usize>) -> NonZero<usize>) -> Self;
}
```
I also did a pass over the docs to adjust them, because this is no longer an "experiment". The `ptr` docs now discuss the concept of provenance in general, and then they go into the two families of APIs for dealing with provenance: Strict Provenance and Exposed Provenance. I removed the discussion of how pointers also have an associated "address space" -- that is not actually tracked in the pointer value, it is tracked in the type, so IMO it just distracts from the core point of provenance. I also adjusted the docs for `with_exposed_provenance` to make it clear that we cannot guarantee much about this function, it's all best-effort.
There are two unstable lints associated with the strict_provenance feature gate; I moved them to a new [strict_provenance_lints](https://github.com/rust-lang/rust/issues/130351) feature since I didn't want this PR to have an even bigger FCP. ;)
`@rust-lang/opsem` Would be great to get some feedback on the docs here. :)
Nominating for `@rust-lang/libs-api.`
Part of https://github.com/rust-lang/rust/issues/95228.
[FCP comment](https://github.com/rust-lang/rust/pull/130350#issuecomment-2395114536)
replace STATX_ALL with (STATX_BASIC_STATS | STATX_BTIME) as former is deprecated
STATX_ALL was deprecated in 581701b7ef and suggested to use equivalent (STATX_BASIC_STATS | STATX_BTIME) combination, to prevent future surprises.
zero-sized accesses are fine on null pointers
We entirely forgot to update all the function docs when changing the central docs. That's the problem with helpfully repeating shared definitions in tons of places...
Update `use` keyword docs to describe precise capturing
I noticed that the standard library keyword docs for the `use` keyword haven't been updated yet to describe the new precise capturing syntax.
Make `profiler_builtins` an optional dependency of sysroot, not std
This avoids unnecessary rebuilds of std (and the compiler) when `build.profiler` is toggled off or on.
Fixes#131812.
---
Background: The `profiler_builtins` crate has been an optional dependency of std (behind a cargo feature) ever since it was added back in #42433. But as far as I can tell that has only ever been a convenient way to force the crate to be built, not a genuine dependency.
The side-effect of this false dependency is that toggling `build.profiler` causes a rebuild of std and the compiler, which shouldn't be necessary. This PR therefore makes `profiler_builtins` an optional dependency of the dummy sysroot crate (#108865), rather than a dependency of std.
What makes this change so small is that all of the necessary infrastructure already exists. Previously, bootstrap would enable the `profiler` feature on the sysroot crate, which would forward that feature to std. Now, enabling that feature directly enables sysroot's `profiler_builtins` dependency instead.
---
I believe this is more of a bootstrap change than a libs change, so tentatively:
r? bootstrap
- Since in almost all cases, there will only be 1 UEFI shell, share the
shell handle between all functions that require it.
Signed-off-by: Ayush Singh <ayush@beagleboard.org>
Rollup of 3 pull requests
Successful merges:
- #126207 (std::unix::stack_overflow::drop_handler addressing todo through libc …)
- #131864 (Never emit `vptr` for empty/auto traits)
- #131870 (compiletest: Store test collection context/state in two structs)
r? `@ghost`
`@rustbot` modify labels: rollup
Abstract the state type for futexes
In the same way that we expose `SmallAtomic` and `SmallPrimitive` to allow Windows to use a value other than an `AtomicU32` for its futex state, switch the primary futex state type from `AtomicU32` to `futex::Futex`. The `futex::Futex` type should be usable as an atomic value with underlying primitive type equal to `futex::Primitive`. (`SmallAtomic` is also renamed to `SmallFutex`).
This allows supporting the futex API on systems where the underlying kernel futex implementation requires more user state than simply an `AtomicU32`.
All in-tree futex implementations simply define {`Futex`,`Primitive`} directly as {`AtomicU32`,`u32`}.
Avoid use imports in `thread_local_inner!`
Previously, the use imports in `thread_local_inner!` can shadow user-provided types or type aliases of the names `Storage`, `EagerStorage`, `LocalStorage` and `LocalKey`. This PR fixes that by dropping the use imports and instead refer to the std-internal types via fully qualified paths. A basic test is added to ensure `thread_local!`s with static decls with type names that match the aforementioned std-internal type names can successfully compile.
Fixes#131863.
Remove outdated documentation for `repeat_n`
After #106943, which made `Take<Repeat<I>>` implement `ExactSizeIterator`, part of documentation about difference from `repeat(x).take(n)` is no longer valid.
````@rustbot```` labels: +A-docs, +A-iterators
Fix predicate signatures in retain_mut docs
This is my first PR here so let me know if I'm doing anything wrong.
The docs for `retain_mut` in `LinkedList` and `VecDeque` say the predicate takes `&e`, but it should be `&mut e` to match the actual signature. `Vec` [has it documented](https://doc.rust-lang.org/std/vec/struct.Vec.html#method.retain_mut) correctly already.
Add getentropy for RTEMS
RTEMS provides the `getentropy` function.
Use this for providing random data.
This PR enables the `getentropy` function for the RTEMS operating system to get random data.
It is exposed via libc (see https://github.com/rust-lang/libc/pull/3975).
Bump libc to 0.2.161
Bumps libc to the latest release version 0.2.161 which
- includes libc support for the tier 3 RTEMS target
- fixes segfaults on 32-bit FreeBSD targets
- gets musl's `posix_spawn_file_actions_addchdir_np` for some spawn opts
Various fixes for Xous
This patchset includes several fixes for Xous that have crept in over the last few months:
* The `adjust_process()` syscall was incorrect
* Warnings have started appearing in `alloc` -- adopt the same approach as wasm, until wasm figures out a workaround
* Dead code warnings have appeared in the networking code. Add `allow(dead_code)` as these structs are used as IPC values
* Add support for `args` and `env`, which have been useful for running tests
* Update `unwinding` to `0.2.3` which fixes the recent regression due to changes in `asm!()` code
Avoid superfluous UB checks in `IndexRange`
`IndexRange::len` is justified as an overall invariant, and
`take_prefix` and `take_suffix` are justified by local branch
conditions. A few more UB-checked calls remain in cases that are only
supported locally by `debug_assert!`, which won't do anything in
distributed builds, so those UB checks may still be useful.
We generally expect core's `#![rustc_preserve_ub_checks]` to optimize
away in user's release builds, but the mere presence of that extra code
can sometimes inhibit optimization, as seen in #131563.
In the same way that we expose SmallAtomic and SmallPrimitive to allow
Windows to use a value other than an AtomicU32 for its futex state, this
patch switches the primary futex state type from AtomicU32 to
futex::Atomic. The futex::Atomic type should be usable as an atomic
value with underlying primitive type equal to futex::Primitive.
This allows supporting the futex API on systems where the underlying
kernel futex implementation requires more state than simply an
AtomicU32.
All in-tree futex implementations simply define {Atomic,Primitive}
directly as {AtomicU32,u32}.
Add `must_use` to `CommandExt::exec`
[CommandExt::exec](https://fburl.com/0qhpo7nu) returns a `std::io::Error` in the case exec fails, but its not currently marked as `must_use` making it easy to accidentally ignore it.
This PR adds the `must_use` attributed here as i think it fits the definition in the guide of [When to add #[must_use]](https://std-dev-guide.rust-lang.org/policy/must-use.html#when-to-add-must_use)
optimize str.replace
Adds a fast path for str.replace for the ascii to ascii case. This allows for autovectorizing the code. Also should this instead be done with specialization? This way we could remove one branch. I think it is the kind of branch that is easy to predict though.
Benchmark for the fast path (replace all "a" with "b" in the rust wikipedia article, using criterion) :
| N | Speedup | Time New (ns) | Time Old (ns) |
|----------|---------|---------------|---------------|
| 2 | 2.03 | 13.567 | 27.576 |
| 8 | 1.73 | 17.478 | 30.259 |
| 11 | 2.46 | 18.296 | 45.055 |
| 16 | 2.71 | 17.181 | 46.526 |
| 37 | 4.43 | 18.526 | 81.997 |
| 64 | 8.54 | 18.670 | 159.470 |
| 200 | 9.82 | 29.634 | 291.010 |
| 2000 | 24.34 | 81.114 | 1974.300 |
| 20000 | 30.61 | 598.520 | 18318.000 |
| 1000000 | 29.31 | 33458.000 | 980540.000 |
Refactor some `core::fmt` macros
While looking at the macros in `core::fmt`, find that the macros are not well organized. So I created a patch to fix it.
[`core/src/fmt/num.rs`](https://github.com/rust-lang/rust/blob/master/library/core/src/fmt/num.rs)
* `impl_int!` and `impl_uint!` macro are **completly** same. It would be better to combine for readability
* `impl_int!` has a problem that the indenting is not uniform. It has unified into 4 spaces
* `debug` macro in `num` renamed to `impl_Debug`, And it was moved to a position close to the `impl_Display`.
[`core/src/fmt/float.rs`](https://github.com/rust-lang/rust/blob/master/library/core/src/fmt/float.rs)
[`core/src/fmt/nofloat.rs`](https://github.com/rust-lang/rust/blob/master/library/core/src/fmt/nofloat.rs)
* `floating` macro now receive multiple idents at once. It makes the code cleaner.
* Modified the panic message more clearly in fallback function of `cfg(no_fp_fmt_parse)`
Add `from_ref` and `from_mut` constructors to `core::ptr::NonNull`.
Relevant tracking issue: #130823
The `core::ptr::NonNull` type should have the convenience constructors `from_ref` and `from_mut` for parity with `core::ptr::from_ref` and `core::ptr::from_mut`.
Although the type in question already implements `From<&T>` and `From<&mut T>`, these new functions also carry the ability to be used in constant expressions (due to not being behind a trait).
Mark the unstable LazyCell::into_inner const
Other cell `into_inner` functions are const and there shouldn't be any problem here. Make the unstable `LazyCell::into_inner` const under the same gate as its stability (`lazy_cell_into_inner`).
Tracking issue: https://github.com/rust-lang/rust/issues/125623
uefi: Implement getcwd and chdir
- Using EFI Shell Protocol. These functions do not make much sense unless a shell is present.
- Return the exe dir in case shell protocol is missing.
r? `@joboet`
Rollup of 9 pull requests
Successful merges:
- #122670 (Fix bug where `option_env!` would return `None` when env var is present but not valid Unicode)
- #131095 (Use environment variables instead of command line arguments for merged doctests)
- #131339 (Expand set_ptr_value / with_metadata_of docs)
- #131652 (Move polarity into `PolyTraitRef` rather than storing it on the side)
- #131675 (Update lint message for ABI not supported)
- #131681 (Fix up-to-date checking for run-make tests)
- #131702 (Suppress import errors for traits that couldve applied for method lookup error)
- #131703 (Resolved python deprecation warning in publish_toolstate.py)
- #131710 (Remove `'apostrophes'` from `rustc_parse_format`)
r? `@ghost`
`@rustbot` modify labels: rollup
Some float methods are now `const fn` under the `const_float_methods` feature gate.
In order to support `min`, `max`, `abs` and `copysign`, the implementation of some intrinsics had to be moved from Miri to rustc_const_eval.
Stabilise `const_make_ascii`.
Closes: #130698
This PR stabilises the `const_make_ascii` feature gate (i.e. marking the `make_ascii_uppercase` and `make_ascii_lowercase` methods in `char`, `u8`, `[u8]`, and `str` as const).
Implemented `FromStr` for `CString` and `TryFrom<CString>` for `String`
The motivation of this change is making it possible to use `CString` in generic methods with `FromStr` and `TryInto<String>` trait bounds. The same traits are already implemented for `OsString` which is an FFI type too.
Expand set_ptr_value / with_metadata_of docs
In preparation of a potential FCP, intends to clean up and expand the documentation of this operation.
Rewrite these blobs to explicitly mention the case of a sized operand. The previous made that seem wrong instead of emphasizing it is nothing but a simple cast. Instead, the explanation now emphasizes that the address portion of the argument, together with its provenance, is discarded which previously had to be inferred by the reader. Then an example demonstrates a simple line of incorrect usage based on this idea of provenance.
Tracking issue: https://github.com/rust-lang/rust/issues/75091
Fix bug where `option_env!` would return `None` when env var is present but not valid Unicode
Fixes#122669 by making `option_env!` emit an error when the value of the environment variable is not valid Unicode.
Autodiff Upstreaming - enzyme frontend
This is an upstream PR for the `autodiff` rustc_builtin_macro that is part of the autodiff feature.
For the full implementation, see: https://github.com/rust-lang/rust/pull/129175
**Content:**
It contains a new `#[autodiff(<args>)]` rustc_builtin_macro, as well as a `#[rustc_autodiff]` builtin attribute.
The autodiff macro is applied on function `f` and will expand to a second function `df` (name given by user).
It will add a dummy body to `df` to make sure it type-checks. The body will later be replaced by enzyme on llvm-ir level,
we therefore don't really care about the content. Most of the changes (700 from 1.2k) are in `compiler/rustc_builtin_macros/src/autodiff.rs`, which expand the macro. Nothing except expansion is implemented for now.
I have a fallback implementation for relevant functions in case that rustc should be build without autodiff support. The default for now will be off, although we want to flip it later (once everything landed) to on for nightly. For the sake of CI, I have flipped the defaults, I'll revert this before merging.
**Dummy function Body:**
The first line is an `inline_asm` nop to make inlining less likely (I have additional checks to prevent this in the middle end of rustc. If `f` gets inlined too early, we can't pass it to enzyme and thus can't differentiate it.
If `df` gets inlined too early, the call site will just compute this dummy code instead of the derivatives, a correctness issue. The following black_box lines make sure that none of the input arguments is getting optimized away before we replace the body.
**Motivation:**
The user facing autodiff macro can verify the user input. Then I write it as args to the rustc_attribute, so from here on I can know that these values should be sensible. A rustc_attribute also turned out to be quite nice to attach this information to the corresponding function and carry it till the backend.
This is also just an experiment, I expect to adjust the user facing autodiff macro based on user feedback, to improve usability.
As a simple example of what this will do, we can see this expansion:
From:
```
#[autodiff(df, Reverse, Duplicated, Const, Active)]
pub fn f1(x: &[f64], y: f64) -> f64 {
unimplemented!()
}
```
to
```
#[rustc_autodiff]
#[inline(never)]
pub fn f1(x: &[f64], y: f64) -> f64 {
::core::panicking::panic("not implemented")
}
#[rustc_autodiff(Reverse, Duplicated, Const, Active,)]
#[inline(never)]
pub fn df(x: &[f64], dx: &mut [f64], y: f64, dret: f64) -> f64 {
unsafe { asm!("NOP"); };
::core::hint::black_box(f1(x, y));
::core::hint::black_box((dx, dret));
::core::hint::black_box(f1(x, y))
}
```
I will add a few more tests once I figured out why rustc rebuilds every time I touch a test.
Tracking:
- https://github.com/rust-lang/rust/issues/124509
try-job: dist-x86_64-msvc
Other cell `into_inner` functions are const and there shouldn't be any
problem here. Make the unstable `LazyCell::into_inner` const under the
same gate as its stability (`lazy_cell_into_inner`).
Tracking issue: https://github.com/rust-lang/rust/issues/125623
Update precondition tests (especially for zero-size access to null)
I don't much like the current way I've updated the precondition check helpers, but I couldn't come up with anything better. Ideas welcome.
I've organized `tests/ui/precondition-checks` mostly with one file per function that has `assert_unsafe_precondition` in it, with revisions that check each precondition. The important new test is `tests/ui/precondition-checks/zero-size-null.rs`.
Stabilize `Pin::as_deref_mut()`
Tracking issue: closes#86918
Stabilizing the following API:
```rust
impl<Ptr: DerefMut> Pin<Ptr> {
pub fn as_deref_mut(self: Pin<&mut Pin<Ptr>>) -> Pin<&mut Ptr::Target>;
}
```
I know that an FCP has not been started yet, but this isn't a very complex stabilization, and I'm hoping this can motivate an FCP to *get* started - this has been pending for a while and it's a very useful function when writing Future impls.
r? ``@jonhoo``
- Using EFI Shell Protocol. These functions do not make much sense
unless a shell is present.
- Return the exe dir in case shell protocol is missing.
Signed-off-by: Ayush Singh <ayush@beagleboard.org>
merge const_ipv4 / const_ipv6 feature gate into 'ip' feature gate
https://github.com/rust-lang/rust/issues/76205 has been closed a while ago, but there are still some functions that reference it. Those functions are all unstable *and* const-unstable. There's no good reason to use a separate feature gate for their const-stability, so this PR moves their const-stability under the same gate as their regular stability, and therefore removes the remaining references to https://github.com/rust-lang/rust/issues/76205.
core/net: add Ipv[46]Addr::from_octets, Ipv6Addr::from_segments.
Adds:
- `Ipv4Address::from_octets([u8;4])`
- `Ipv6Address::from_octets([u8;16])`
- `Ipv6Address::from_segments([u16;8])`
equivalent to the existing `From` impls.
Advantages:
- Consistent with `to_bits, from_bits`.
- More discoverable than the `From` impls.
- Helps with type inference: it's common to want to convert byte slices to IP addrs. If you try this
```rust
fn foo(x: &[u8]) -> Ipv4Addr {
Ipv4Addr::from(foo.try_into().unwrap())
}
```
it [doesn't work](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=0e2873312de275a58fa6e33d1b213bec). You have to write `Ipv4Addr::from(<[u8;4]>::try_from(x).unwrap())` instead, which is not great. With `from_octets` it is able to infer the right types.
Found this while porting [smoltcp](https://github.com/smoltcp-rs/smoltcp/) from its own IP address types to the `core::net` types.
~~Tracking issues #27709 #76205~~
Tracking issue: https://github.com/rust-lang/rust/issues/131360
std::fs::get_path freebsd update.
what matters is we re doing the right things as doing sizeof, rather than passing KINFO_FILE_SIZE (only defined on intel architectures), the kernel
making sure it matches the expectation in its side.
Rollup of 8 pull requests
Successful merges:
- #130356 (don't warn about a missing change-id in CI)
- #130900 (Do not output () on empty description)
- #131066 (Add the Chinese translation entry to the RustByExample build process)
- #131067 (Fix std_detect links)
- #131644 (Clean up some Miri things in `sys/windows`)
- #131646 (sys/unix: add comments for some Miri fallbacks)
- #131653 (Remove const trait bound modifier hack)
- #131659 (enable `download_ci_llvm` test)
r? `@ghost`
`@rustbot` modify labels: rollup
Clean up some Miri things in `sys/windows`
- remove miri hack that is only needed for win7 (we don't support win7 as a target in Miri)
- remove outdated comment now that Miri is on CI
The allocator on Xous is now throwing warnings because the allocator
needs to be mutable, and allocators hand out mutable pointers, which
the `static_mut_refs` lint now catches.
Give the same treatment to Xous as wasm, at least until a solution is
devised for fixing the warning on wasm.
Signed-off-by: Sean Cross <sean@xobs.io>
Process arguments and environment variables are both passed by way of
Application Parameters. These are a TLV format that gets passed in as
the second process argument.
This patch combines both as they are very similar in their decode.
Signed-off-by: Sean Cross <sean@osdyne.com>
Optimize `escape_ascii` using a lookup table
Based upon my suggestion here: https://github.com/rust-lang/rust/pull/125340#issuecomment-2130441817
Effectively, we can take advantage of the fact that ASCII only needs 7 bits to make the eighth bit store whether the value should be escaped or not. This adds a 256-byte lookup table, but 256 bytes *should* be small enough that very few people will mind, according to my probably not incontrovertible opinion.
The generated assembly isn't clearly better (although has fewer branches), so, I decided to benchmark on three inputs: first on a random 200KiB, then on `/bin/cat`, then on `Cargo.toml` for this repo. In all cases, the generated code ran faster on my machine. (an old i7-8700)
But, if you want to try my benchmarking code for yourself:
<details><summary>Criterion code below. Replace <code>/home/ltdk/rustsrc</code> with the appropriate directory.</summary>
```rust
#![feature(ascii_char)]
#![feature(ascii_char_variants)]
#![feature(const_option)]
#![feature(let_chains)]
use core::ascii;
use core::ops::Range;
use criterion::{criterion_group, criterion_main, Criterion};
use rand::{thread_rng, Rng};
const HEX_DIGITS: [ascii::Char; 16] = *b"0123456789abcdef".as_ascii().unwrap();
#[inline]
const fn backslash<const N: usize>(a: ascii::Char) -> ([ascii::Char; N], Range<u8>) {
const { assert!(N >= 2) };
let mut output = [ascii::Char::Null; N];
output[0] = ascii::Char::ReverseSolidus;
output[1] = a;
(output, 0..2)
}
#[inline]
const fn hex_escape<const N: usize>(byte: u8) -> ([ascii::Char; N], Range<u8>) {
const { assert!(N >= 4) };
let mut output = [ascii::Char::Null; N];
let hi = HEX_DIGITS[(byte >> 4) as usize];
let lo = HEX_DIGITS[(byte & 0xf) as usize];
output[0] = ascii::Char::ReverseSolidus;
output[1] = ascii::Char::SmallX;
output[2] = hi;
output[3] = lo;
(output, 0..4)
}
#[inline]
const fn verbatim<const N: usize>(a: ascii::Char) -> ([ascii::Char; N], Range<u8>) {
const { assert!(N >= 1) };
let mut output = [ascii::Char::Null; N];
output[0] = a;
(output, 0..1)
}
/// Escapes an ASCII character.
///
/// Returns a buffer and the length of the escaped representation.
const fn escape_ascii_old<const N: usize>(byte: u8) -> ([ascii::Char; N], Range<u8>) {
const { assert!(N >= 4) };
match byte {
b'\t' => backslash(ascii::Char::SmallT),
b'\r' => backslash(ascii::Char::SmallR),
b'\n' => backslash(ascii::Char::SmallN),
b'\\' => backslash(ascii::Char::ReverseSolidus),
b'\'' => backslash(ascii::Char::Apostrophe),
b'\"' => backslash(ascii::Char::QuotationMark),
0x00..=0x1F => hex_escape(byte),
_ => match ascii::Char::from_u8(byte) {
Some(a) => verbatim(a),
None => hex_escape(byte),
},
}
}
/// Escapes an ASCII character.
///
/// Returns a buffer and the length of the escaped representation.
const fn escape_ascii_new<const N: usize>(byte: u8) -> ([ascii::Char; N], Range<u8>) {
/// Lookup table helps us determine how to display character.
///
/// Since ASCII characters will always be 7 bits, we can exploit this to store the 8th bit to
/// indicate whether the result is escaped or unescaped.
///
/// We additionally use 0x80 (escaped NUL character) to indicate hex-escaped bytes, since
/// escaped NUL will not occur.
const LOOKUP: [u8; 256] = {
let mut arr = [0; 256];
let mut idx = 0;
loop {
arr[idx as usize] = match idx {
// use 8th bit to indicate escaped
b'\t' => 0x80 | b't',
b'\r' => 0x80 | b'r',
b'\n' => 0x80 | b'n',
b'\\' => 0x80 | b'\\',
b'\'' => 0x80 | b'\'',
b'"' => 0x80 | b'"',
// use NUL to indicate hex-escaped
0x00..=0x1F | 0x7F..=0xFF => 0x80 | b'\0',
_ => idx,
};
if idx == 255 {
break;
}
idx += 1;
}
arr
};
let lookup = LOOKUP[byte as usize];
// 8th bit indicates escape
let lookup_escaped = lookup & 0x80 != 0;
// SAFETY: We explicitly mask out the eighth bit to get a 7-bit ASCII character.
let lookup_ascii = unsafe { ascii::Char::from_u8_unchecked(lookup & 0x7F) };
if lookup_escaped {
// NUL indicates hex-escaped
if matches!(lookup_ascii, ascii::Char::Null) {
hex_escape(byte)
} else {
backslash(lookup_ascii)
}
} else {
verbatim(lookup_ascii)
}
}
fn escape_bytes(bytes: &[u8], f: impl Fn(u8) -> ([ascii::Char; 4], Range<u8>)) -> Vec<ascii::Char> {
let mut vec = Vec::new();
for b in bytes {
let (buf, range) = f(*b);
vec.extend_from_slice(&buf[range.start as usize..range.end as usize]);
}
vec
}
pub fn criterion_benchmark(c: &mut Criterion) {
let mut group = c.benchmark_group("escape_ascii");
group.sample_size(1000);
let rand_200k = &mut [0; 200 * 1024];
thread_rng().fill(&mut rand_200k[..]);
let cat = include_bytes!("/bin/cat");
let cargo_toml = include_bytes!("/home/ltdk/rustsrc/Cargo.toml");
group.bench_function("old_rand", |b| {
b.iter(|| escape_bytes(rand_200k, escape_ascii_old));
});
group.bench_function("new_rand", |b| {
b.iter(|| escape_bytes(rand_200k, escape_ascii_new));
});
group.bench_function("old_bin", |b| {
b.iter(|| escape_bytes(cat, escape_ascii_old));
});
group.bench_function("new_bin", |b| {
b.iter(|| escape_bytes(cat, escape_ascii_new));
});
group.bench_function("old_cargo_toml", |b| {
b.iter(|| escape_bytes(cargo_toml, escape_ascii_old));
});
group.bench_function("new_cargo_toml", |b| {
b.iter(|| escape_bytes(cargo_toml, escape_ascii_new));
});
group.finish();
}
criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);
```
</details>
My benchmark results:
```
escape_ascii/old_rand time: [1.6965 ms 1.7006 ms 1.7053 ms]
Found 22 outliers among 1000 measurements (2.20%)
4 (0.40%) high mild
18 (1.80%) high severe
escape_ascii/new_rand time: [1.6749 ms 1.6953 ms 1.7158 ms]
Found 38 outliers among 1000 measurements (3.80%)
38 (3.80%) high mild
escape_ascii/old_bin time: [224.59 µs 225.40 µs 226.33 µs]
Found 39 outliers among 1000 measurements (3.90%)
17 (1.70%) high mild
22 (2.20%) high severe
escape_ascii/new_bin time: [164.86 µs 165.63 µs 166.58 µs]
Found 107 outliers among 1000 measurements (10.70%)
43 (4.30%) high mild
64 (6.40%) high severe
escape_ascii/old_cargo_toml
time: [23.397 µs 23.699 µs 24.014 µs]
Found 204 outliers among 1000 measurements (20.40%)
21 (2.10%) high mild
183 (18.30%) high severe
escape_ascii/new_cargo_toml
time: [16.404 µs 16.438 µs 16.483 µs]
Found 88 outliers among 1000 measurements (8.80%)
56 (5.60%) high mild
32 (3.20%) high severe
```
Random: 1.7006ms => 1.6953ms (<1% speedup)
Binary: 225.40µs => 165.63µs (26% speedup)
Text: 23.699µs => 16.438µs (30% speedup)
The recent changes to naked `asm!()` macros made this unbuildable
on Xous. The upstream package maintainer released 0.2.3 to fix support
on newer nightly toolchains.
Update the dependency to 0.2.3, which is the oldest version that works
with the current nightly compiler.
This closes#131602 and fixes the build on xous.
Signed-off-by: Sean Cross <sean@xobs.io>
Use throw intrinsic from stdarch in wasm libunwind
Tracking issue: #118168
This is a very belated followup to #121438; now that rust-lang/stdarch#1542 is merged, we can use the intrinsic exported from `core::arch` instead of defining it inline. I also cleaned up the cfgs a bit and added a more detailed comment.
remove const_cow_is_borrowed feature gate
The two functions guarded by this are still unstable, and there's no reason to require a separate feature gate for their const-ness -- we can just have `cow_is_borrowed` cover both kinds of stability.
Cc #65143
std: fix stdout-before-main
Fixes#130210.
Since #124881, `ReentrantLock` uses `ThreadId` to identify threads. This has the unfortunate consequence of breaking uses of `Stdout` before main: Locking the `ReentrantLock` that synchronizes the output will initialize the thread ID before the handle for the main thread is set in `rt::init`. But since that would overwrite the current thread ID, `thread::set_current` triggers an abort.
This PR fixes the problem by using the already initialized thread ID for constructing the main thread handle and allowing `set_current` calls that do not change the thread's ID.
Stabilize const `ptr::write*` and `mem::replace`
Since `const_mut_refs` and `const_refs_to_cell` have been stabilized, we may now also stabilize the ability to write to places during const evaluation inside our library API. So, we now propose the `const fn` version of `ptr::write` and its variants. This allows us to also stabilize `mem::replace` and `ptr::replace`.
- const `mem::replace`: https://github.com/rust-lang/rust/issues/83164#issuecomment-2338660862
- const `ptr::write{,_bytes,_unaligned}`: https://github.com/rust-lang/rust/issues/86302#issuecomment-2330275266
Their implementation requires an additional internal stabilization of `const_intrinsic_forget`, which is required for `*::write*` and thus `*::replace`. Thus we const-stabilize the internal intrinsics `forget`, `write_bytes`, and `write_via_move`.
Fixes#130210.
Since #124881, `ReentrantLock` uses `ThreadId` to identify threads. This has the unfortunate consequence of breaking uses of `Stdout` before main: Locking the `ReentrantLock` that synchronizes the output will initialize the thread ID before the handle for the main thread is set in `rt::init`. But since that would overwrite the current thread ID, `thread::set_current` triggers an abort.
This PR fixes the problem by using the already initialized thread ID for constructing the main thread handle and allowing `set_current` calls that do not change the thread's ID.
Migrate lib's `&Option<T>` into `Option<&T>`
Trying out my new lint https://github.com/rust-lang/rust-clippy/pull/13336 - according to the [video](https://www.youtube.com/watch?v=6c7pZYP_iIE), this could lead to some performance and memory optimizations.
Basic thoughts expressed in the video that seem to make sense:
* `&Option<T>` in an API breaks encapsulation:
* caller must own T and move it into an Option to call with it
* if returned, the owner must store it as Option<T> internally in order to return it
* Performance is subject to compiler optimization, but at the basics, `&Option<T>` points to memory that has `presence` flag + value, whereas `Option<&T>` by specification is always optimized to a single pointer.
intrinsics fmuladdf{32,64}: expose llvm.fmuladd.* semantics
Add intrinsics `fmuladd{f32,f64}`. This computes `(a * b) + c`, to be fused if the code generator determines that (i) the target instruction set has support for a fused operation, and (ii) that the fused operation is more efficient than the equivalent, separate pair of `mul` and `add` instructions.
https://llvm.org/docs/LangRef.html#llvm-fmuladd-intrinsic
The codegen_cranelift uses the `fma` function from libc, which is a correct implementation, but without the desired performance semantic. I think this requires an update to cranelift to expose a suitable instruction in its IR.
I have not tested with codegen_gcc, but it should behave the same way (using `fma` from libc).
---
This topic has been discussed a few times on Zulip and was suggested, for example, by `@workingjubilee` in [Effect of fma disabled](https://rust-lang.zulipchat.com/#narrow/stream/122651-general/topic/Effect.20of.20fma.20disabled/near/274179331).
`IndexRange::len` is justified as an overall invariant, and
`take_prefix` and `take_suffix` are justified by local branch
conditions. A few more UB-checked calls remain in cases that are only
supported locally by `debug_assert!`, which won't do anything in
distributed builds, so those UB checks may still be useful.
We generally expect core's `#![rustc_preserve_ub_checks]` to optimize
away in user's release builds, but the mere presence of that extra code
can sometimes inhibit optimization, as seen in #131563.
Stabilise `const_char_encode_utf8`.
Closes: #130512
This PR stabilises the `const_char_encode_utf8` feature gate (i.e. support for `char::encode_utf8` in const scenarios).
Note that the linked tracking issue is currently awaiting FCP.
Port sort-research-rs test suite to Rust stdlib tests
This PR is a followup to https://github.com/rust-lang/rust/pull/124032. It replaces the tests that test the various sort functions in the standard library with a test-suite developed as part of https://github.com/Voultapher/sort-research-rs. The current tests suffer a couple of problems:
- They don't cover important real world patterns that the implementations take advantage of and execute special code for.
- The input lengths tested miss out on code paths. For example, important safety property tests never reach the quicksort part of the implementation.
- The miri side is often limited to `len <= 20` which means it very thoroughly tests the insertion sort, which accounts for 19 out of 1.5k LoC.
- They are split into to core and alloc, causing code duplication and uneven coverage.
- ~~The randomness is tied to a caller location, wasting the space exploration capabilities of randomized testing.~~ The randomness is not repeatable, as it relies on `std:#️⃣:RandomState::new().build_hasher()`.
Most of these issues existed before https://github.com/rust-lang/rust/pull/124032, but they are intensified by it. One thing that is new and requires additional testing, is that the new sort implementations specialize based on type properties. For example `Freeze` and non `Freeze` execute different code paths.
Effectively there are three dimensions that matter:
- Input type
- Input length
- Input pattern
The ported test-suite tests various properties along all three dimensions, greatly improving test coverage. It side-steps the miri issue by preferring sampled approaches. For example the test that checks if after a panic the set of elements is still the original one, doesn't do so for every single possible panic opportunity but rather it picks one at random, and performs this test across a range of input length, which varies the panic point across them. This allows regular execution to easily test inputs of length 10k, and miri execution up to 100 which covers significantly more code. The randomness used is tied to a fixed - but random per process execution - seed. This allows for fully repeatable tests and fuzzer like exploration across multiple runs.
Structure wise, the tests are previously found in the core integration tests for `sort_unstable` and alloc unit tests for `sort`. The new test-suite was developed to be a purely black-box approach, which makes integration testing the better place, because it can't accidentally rely on internal access. Because unwinding support is required the tests can't be in core, even if the implementation is, so they are now part of the alloc integration tests. Are there architectures that can only build and test core and not alloc? If so, do such platforms require sort testing? For what it's worth the current implementation state passes miri `--target mips64-unknown-linux-gnuabi64` which is big endian.
The test-suite also contains tests for properties that were and are given by the current and previous implementations, and likely relied upon by users but weren't tested. For example `self_cmp` tests that the two parameters `a` and `b` passed into the comparison function are never references to the same object, which if the user is sorting for example a `&mut [Mutex<i32>]` could lead to a deadlock.
Instead of using the hashed caller location as rand seed, it uses seconds since unix epoch / 10, which given timestamps in the CI should be reasonably easy to reproduce, but also allows fuzzer like space exploration.
---
Test run-time changes:
Setup:
```
Linux 6.10
rustc 1.83.0-nightly (f79a912d9 2024-09-18)
AMD Ryzen 9 5900X 12-Core Processor (Zen 3 micro-architecture)
CPU boost enabled.
```
master: e9df22f
Before core integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/coretests-219cbd0308a49e2f
Time (mean ± σ): 869.6 ms ± 21.1 ms [User: 1327.6 ms, System: 95.1 ms]
Range (min … max): 845.4 ms … 917.0 ms 10 runs
# MIRIFLAGS="-Zmiri-disable-isolation" to get real time
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/core
finished in 738.44s
```
After core integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/coretests-219cbd0308a49e2f
Time (mean ± σ): 865.1 ms ± 14.7 ms [User: 1283.5 ms, System: 88.4 ms]
Range (min … max): 836.2 ms … 885.7 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/core
finished in 752.35s
```
Before alloc unit tests:
```
LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloc-19c15e6e8565aa54
Time (mean ± σ): 295.0 ms ± 9.9 ms [User: 719.6 ms, System: 35.3 ms]
Range (min … max): 284.9 ms … 319.3 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 322.75s
```
After alloc unit tests:
```
LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloc-19c15e6e8565aa54
Time (mean ± σ): 97.4 ms ± 4.1 ms [User: 297.7 ms, System: 28.6 ms]
Range (min … max): 92.3 ms … 109.2 ms 27 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 309.18s
```
Before alloc integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloctests-439e7300c61a8046
Time (mean ± σ): 103.2 ms ± 1.7 ms [User: 135.7 ms, System: 39.4 ms]
Range (min … max): 99.7 ms … 107.3 ms 28 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 231.35s
```
After alloc integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloctests-439e7300c61a8046
Time (mean ± σ): 379.8 ms ± 4.7 ms [User: 4620.5 ms, System: 1157.2 ms]
Range (min … max): 373.6 ms … 386.9 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 449.24s
```
In my opinion the results don't change iterative library development or CI execution in meaningful ways. For example currently the library doc-tests take ~66s and incremental compilation takes 10+ seconds. However I only have limited knowledge of the various local development workflows that exist, and might be missing one that is significantly impacted by this change.
Add intrinsics `fmuladd{f16,f32,f64,f128}`. This computes `(a * b) +
c`, to be fused if the code generator determines that (i) the target
instruction set has support for a fused operation, and (ii) that the
fused operation is more efficient than the equivalent, separate pair
of `mul` and `add` instructions.
https://llvm.org/docs/LangRef.html#llvm-fmuladd-intrinsic
MIRI support is included for f32 and f64.
The codegen_cranelift uses the `fma` function from libc, which is a
correct implementation, but without the desired performance semantic. I
think this requires an update to cranelift to expose a suitable
instruction in its IR.
I have not tested with codegen_gcc, but it should behave the same
way (using `fma` from libc).
rustc_target: Add sme-b16b16 as an explicit aarch64 target feature
LLVM 20 split out what used to be called b16b16 and correspond to aarch64
FEAT_SVE_B16B16 into sve-b16b16 and sme-b16b16.
Add sme-b16b16 as an explicit feature and update the codegen accordingly.
Resolves https://github.com/rust-lang/rust/pull/129894.
Stabilize const `{slice,array}::from_mut`
This PR stabilizes the following APIs as const stable as of rust `1.83`:
```rs
// core::array
pub const fn from_mut<T>(s: &mut T) -> &mut [T; 1];
// core::slice
pub const fn from_mut<T>(s: &mut T) -> &mut [T];
```
This is made possible by `const_mut_refs` being stabilized (yay).
Tracking issue: #90206
The `Box<T: Default>` impl currently calls `T::default()` before allocating
the `Box`.
Most `Default` impls are trivial, which should in theory allow
LLVM to construct `T: Default` directly in the `Box` allocation when calling
`<Box<T>>::default()`.
However, the allocation may fail, which necessitates calling `T's` destructor if it has one.
If the destructor is non-trivial, then LLVM has a hard time proving that it's
sound to elide, which makes it construct `T` on the stack first, and then copy it into the allocation.
Create an uninit `Box` first, and then write `T::default` into it, so that LLVM now only needs to prove
that the `T::default` can't panic, which should be trivial for most `Default` impls.
LLVM 20 split out what used to be called b16b16 and correspond to aarch64
FEAT_SVE_B16B16 into sve-b16b16 and sme-b16b16.
Add sme-b16b16 as an explicit feature and update the codegen accordingly.
Decouple WASIp2 sockets from WasiFd
This is a follow up to #129638, decoupling WASIp2's socket implementation from WASIp1's `WasiFd` as discussed with `@alexcrichton.`
Quite a few trait implementations in `std::os::fd` rely on the fact that there is an additional layer of abstraction between `Socket` and `OwnedFd`. I thus had to add a thin `WasiSocket` wrapper struct that just "forwards" to `OwnedFd`. Alternatively, I could have added a lot of conditional compilation to `std::os::fd`, which feels even worse.
Since `WasiFd::sock_accept` is no longer accessible from `TcpListener` and since WASIp2 has proper support for accepting sockets through `Socket::accept`, the `std::os::wasi::net` module has been removed from WASIp2, which only contains a single `TcpListenerExt` trait with a `sock_accept` method as well as an implementation for `TcpListener`. Let me know if this is an acceptable solution.
liballoc: introduce String, Vec const-slicing
This change `const`-qualifies many methods on `Vec` and `String`, notably `as_slice`, `as_str`, `len`. These changes are made behind the unstable feature flag `const_vec_string_slice`.
## Motivation
This is to support simultaneous variance over ownership and constness. I have an enum type that may contain either `String` or `&str`, and I want to produce a `&str` from it in a possibly-`const` context.
```rust
enum StrOrString<'s> {
Str(&'s str),
String(String),
}
impl<'s> StrOrString<'s> {
const fn as_str(&self) -> &str {
match self {
// In a const-context, I really only expect to see this variant, but I can't switch the implementation
// in some mode like #[cfg(const)] -- there has to be a single body
Self::Str(s) => s,
// so this is a problem, since it's not `const`
Self::String(s) => s.as_str(),
}
}
}
```
Currently `String` and `Vec` don't support this, but can without functional changes. Similar logic applies for `len`, `capacity`, `is_empty`.
## Changes
The essential thing enabling this change is that `Unique::as_ptr` is `const`. This lets us convert `RawVec::ptr` -> `Vec::as_ptr` -> `Vec::as_slice` -> `String::as_str`.
I had to move the `Deref` implementations into `as_{str,slice}` because `Deref` isn't `#[const_trait]`, but I would expect this change to be invisible up to inlining. I moved the `DerefMut` implementations as well for uniformity.
This change `const`-qualifies many methods on Vec and String, notably
`as_slice`, `as_str`, `len`. These changes are made behind the unstable
feature flag `const_vec_string_slice` with the following tracking issue:
https://github.com/rust-lang/rust/issues/129041
Rewrite these blobs to explicitly mention the case of a sized operand.
The previous made that seem wrong instead of emphasizing it is nothing
but a simple cast. Instead, the explanation now emphasizes that the
address portion of the argument, together with its provenance, is
discarded which previously had to be inferred by the reader. Then an
example demonstrates a simple line of incorrect usage based on this
idea of provenance.
Android: Debug assertion after setting thread name
While `prctl` cannot fail if it points to a valid buffer, it's still better to assert the result as it's done for other places.
make Cell unstably const
Now that we can do interior mutability in `const`, most of the Cell API can be `const fn`. :) The main exception is `set`, because it drops the old value. So from const context one has to use `replace`, which delegates the responsibility for dropping to the caller.
Tracking issue: https://github.com/rust-lang/rust/issues/131283
`as_array_of_cells` is itself still unstable to I added the const-ness to the feature gate for that function and not to `const_cell`, Cc #88248.
r? libs-api
