Emit future-incompatibility lint when calling/declaring functions with vectors that require missing target feature
On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)
As discussed in https://github.com/rust-lang/lang-team/issues/235, this turns out to very easily lead to unsound code.
This commit makes it a post-monomorphization error to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.
See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187) for more discussion.
r? RalfJung
Part of https://github.com/rust-lang/rust/issues/116558
ci: aarch64-gnu-debug job
- Adds a new CI job which checks that the compiler builds with `--enable-debug` and tests that `needs-force-clang-based-tests` pass (where cross-language LTO is tested).
- Add a test confirming that `-Zbranch-protection=pac-ret` and cross-language LTO work together.
r? `@Mark-Simulacrum`
try-job: aarch64-gnu-debug
On some architectures, vector types may have a different ABI when
relevant target features are enabled.
As discussed in https://github.com/rust-lang/lang-team/issues/235, this
turns out to very easily lead to unsound code.
This commit makes it an error to declare or call functions using those
vector types in a context in which the corresponding target features are
disabled, if using an ABI for which the difference is relevant.
coverage: Emit LLVM intrinsics using the normal helper method
Codegen already has convenient ways to declare and emit LLVM intrinsics, so there's no need for coverage instrumentation to jump through hoops to emit them manually.
Add support for `~const` item bounds
Supports the only missing capability of `~const` associated types that I can think of now (this is obviously excluding `~const` opaques, which I see as an extension to this; I'll probably do that next).
r? ``@lcnr`` mostly b/c it changes candidate assembly, or reassign
cc ``@fee1-dead``
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).
[rustdoc] Do not consider nested functions as main function even if named `main` in doctests
Fixes#131893.
If a nested function is called `main`, it is not considered as the entry point of the program. Therefore, doctests should not consider such functions as such either.
r? `@notriddle`
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`
compiletest: suppress Windows Error Reporting (WER) for `run-make` tests
WER by default will show a *bunch* of error dialogues for missing DLLs on Windows for `run-make` tests. We address that by:
1. Guarding `run-make` test process spawning with `disable_error_reporting`.
2. Fixing `disable_error_reporting` to also add the [`SEM_FAILCRITICALERRORS` flag to `SetErrorMode`][SetErrorMode]. Just `SEM_NOGPFAULTERRORBOX` was not sufficient to suppress error dialogues for e.g. missing DLLs.
Fixes#132092. In particular, refer to that issue for the necessary conditions to observe these dialogues from popping up in the first place.
I was only able to manually test this locally in my "native" Windows msvc environment and it prevents the WER dialogues from popping up, I don't think it's possible to really test this automatically.
[SetErrorMode]: https://learn.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-seterrormode?redirectedfrom=MSDN#parameters
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
Remove visit_expr_post from ast Visitor
`visit_expr_post` is only present in the immutable version of ast Visitors and its default implementation is a noop.
Given that its only implementer is on `rustc_lint/src/early.rs` and its name follows the same naming convention as some other lints (`_post`), it seems that `visit_expr_post` being in `Visitor` was a little mistake.
r? `@petrochenkov`
related to #128974
Stabilize shorter-tail-lifetimes
Close#131445
Tracked by #123739
We found a test case `tests/ui/drop/drop_order.rs` that had not been covered by the change. The test fixture is fixed now with the correct expectation.
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.
Adds a new CI job which checks that the compiler builds with
`--enable-debug` and tests that `needs-force-clang-based-tests` pass
(where cross-language LTO is tested).
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.)
Rollup of 5 pull requests
Successful merges:
- #129248 (Taking a raw ref (`&raw (const|mut)`) of a deref of pointer (`*ptr`) is always safe)
- #131906 (rustdoc: adjust spacing and typography in header)
- #132084 (Consider param-env candidates even if they have errors)
- #132096 (Replace an FTP link in comments with an equivalent HTTPS link)
- #132098 (rustc_feature::Features: explain what that 'Option<Symbol>' is about)
r? `@ghost`
`@rustbot` modify labels: rollup
Replace an FTP link in comments with an equivalent HTTPS link
Modern browsers and editors often don't support following FTP links, so using an ordinary web link gives the same result in a more convenient way.
Consider param-env candidates even if they have errors
I added this logic in https://github.com/rust-lang/rust/pull/106309, but frankly I don't know why -- the logic was a very large hammer. It seems like recent changes to error tainting has made that no longer necessary.
Ideally we'd rework the way we handle error reporting in all of candidate assembly to be a bit more responsible; we're just suppressing candidates all willy-nilly and it leads to mysterious *other* errors cropping up, like the one that #132082 originally wanted to fix.
**N.B.** This has the side-effect of turning a failed resolution like `where Missing: Sized` into a trivial where clause that matches all types, but also I don't think it really matters?
I'm putting this up as an alternative to #132082, since that PR doesn't address the case when one desugars the APIT into a regular type param.
r? lcnr vibeck
