Automatic Rustup #4169
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Fix deduplication mismatches in vtables leading to upcasting unsoundness
We currently have two cases where subtleties in supertraits can trigger disagreements in the vtable layout, e.g. leading to a different vtable layout being accessed at a callsite compared to what was prepared during unsizing. Namely:
### #135315
In this example, we were not normalizing supertraits when preparing vtables. In the example,
```
trait Supertrait<T> {
fn _print_numbers(&self, mem: &[usize; 100]) {
println!("{mem:?}");
}
}
impl<T> Supertrait<T> for () {}
trait Identity {
type Selff;
}
impl<Selff> Identity for Selff {
type Selff = Selff;
}
trait Middle<T>: Supertrait<()> + Supertrait<T> {
fn say_hello(&self, _: &usize) {
println!("Hello!");
}
}
impl<T> Middle<T> for () {}
trait Trait: Middle<<() as Identity>::Selff> {}
impl Trait for () {}
fn main() {
(&() as &dyn Trait as &dyn Middle<()>).say_hello(&0);
}
```
When we prepare `dyn Trait`, we see a supertrait of `Middle<<() as Identity>::Selff>`, which itself has two supertraits `Supertrait<()>` and `Supertrait<<() as Identity>::Selff>`. These two supertraits are identical, but they are not duplicated because we were using structural equality and *not* considering normalization. This leads to a vtable layout with two trait pointers.
When we upcast to `dyn Middle<()>`, those two supertraits are now the same, leading to a vtable layout with only one trait pointer. This leads to an offset error, and we call the wrong method.
### #135316
This one is a bit more interesting, and is the bulk of the changes in this PR. It's a bit similar, except it uses binder equality instead of normalization to make the compiler get confused about two vtable layouts. In the example,
```
trait Supertrait<T> {
fn _print_numbers(&self, mem: &[usize; 100]) {
println!("{mem:?}");
}
}
impl<T> Supertrait<T> for () {}
trait Trait<T, U>: Supertrait<T> + Supertrait<U> {
fn say_hello(&self, _: &usize) {
println!("Hello!");
}
}
impl<T, U> Trait<T, U> for () {}
fn main() {
(&() as &'static dyn for<'a> Trait<&'static (), &'a ()>
as &'static dyn Trait<&'static (), &'static ()>)
.say_hello(&0);
}
```
When we prepare the vtable for `dyn for<'a> Trait<&'static (), &'a ()>`, we currently consider the PolyTraitRef of the vtable as the key for a supertrait. This leads two two supertraits -- `Supertrait<&'static ()>` and `for<'a> Supertrait<&'a ()>`.
However, we can upcast[^up] without offsetting the vtable from `dyn for<'a> Trait<&'static (), &'a ()>` to `dyn Trait<&'static (), &'static ()>`. This is just instantiating the principal trait ref for a specific `'a = 'static`. However, when considering those supertraits, we now have only one distinct supertrait -- `Supertrait<&'static ()>` (which is deduplicated since there are two supertraits with the same substitutions). This leads to similar offsetting issues, leading to the wrong method being called.
[^up]: I say upcast but this is a cast that is allowed on stable, since it's not changing the vtable at all, just instantiating the binder of the principal trait ref for some lifetime.
The solution here is to recognize that a vtable isn't really meaningfully higher ranked, and to just treat a vtable as corresponding to a `TraitRef` so we can do this deduplication more faithfully. That is to say, the vtable for `dyn for<'a> Tr<'a>` and `dyn Tr<'x>` are always identical, since they both would correspond to a set of free regions on an impl... Do note that `Tr<for<'a> fn(&'a ())>` and `Tr<fn(&'static ())>` are still distinct.
----
There's a bit more that can be cleaned up. In codegen, we can stop using `PolyExistentialTraitRef` basically everywhere. We can also fix SMIR to stop storing `PolyExistentialTraitRef` in its vtable allocations.
As for testing, it's difficult to actually turn this into something that can be tested with `rustc_dump_vtable`, since having multiple supertraits that are identical is a recipe for ambiguity errors. Maybe someone else is more creative with getting that attr to work, since the tests I added being run-pass tests is a bit unsatisfying. Miri also doesn't help here, since it doesn't really generate vtables that are offset by an index in the same way as codegen.
r? `@lcnr` for the vibe check? Or reassign, idk. Maybe let's talk about whether this makes sense.
<sup>(I guess an alternative would also be to not do any deduplication of vtable supertraits (or only a really conservative subset) rather than trying to normalize and deduplicate more faithfully here. Not sure if that works and is sufficient tho.)</sup>
cc `@steffahn` -- ty for the minimizations
cc `@WaffleLapkin` -- since you're overseeing the feature stabilization :3
Fixes #135315
Fixes #135316
Stabilize `const_black_box` This has been unstably const since #92226, but a tracking issue was never created. Per [discussion on Zulip][zulip], there should not be any blockers to making this const-stable. The function does not provide any functionality at compile time but does allow code reuse between const- and non-const functions, so stabilize it here. [zulip]: https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/const_black_box
ci: use windows 2025 for i686-mingw try-job: i686-mingw
rustdoc: rename `issue-\d+.rs` tests to have meaningful names (part 11) Follow up * rust-lang/rust#134053 * rust-lang/rust#130287 et al As always, it's easier to review the commits one at a time. Don't use the Files Changed tab. It's confusing.
Remove `NamedVarMap`. `NamedVarMap` is extremely similar to `ResolveBoundVars`. The former contains two `UnordMap<ItemLocalId, T>` fields (obscured behind `ItemLocalMap` typedefs). The latter contains two `SortedMap<ItemLocalId, T>` fields. We construct a `NamedVarMap` and then convert it into a `ResolveBoundVars` by sorting the `UnordMap`s, which is unnecessary busywork. This commit removes `NamedVarMap` and constructs a `ResolveBoundVars` directly. `SortedMap` and `NamedVarMap` have slightly different perf characteristics during construction (e.g. speed of insertion) but this code isn't hot enough for that to matter. A few details to note. - A `FIXME` comment is removed. - The detailed comments on the fields of `NamedVarMap` are copied to `ResolveBoundVars` (which has a single, incorrect comment). - `BoundVarContext::map` is renamed. - `ResolveBoundVars` gets a derived `Default` impl. r? `@jackh726`
…asper add constraint graph to polonius MIR dump Another easy one while I work on diagnostics. This PR adds a mermaid visualization of the polonius constraint graph to the polonius MIR dump. Adding kills is left to a future PR (until they're encoded in edges directly or I set up recording debugging info in and out of the analysis), because right now they're only computed during traversal. [Here's](https://gistpreview.github.io/?096b0131e8258f9a3125c55c7ac369bc) how that looks. r? `@matthewjasper` but as always feel free to reroll.
LLVM changed the nocapture attribute to captures(none) This updates RustWrapper.cpp and tests after llvm/llvm-project#123181
some test suite cleanups found while checking `compare-mode next-solver` r? `@oli-obk` <sub> [lcnr](https://github.com/rust-lang/rust/commits?author=lcnr) authored and JJ_EMPTY_STRING committed </sub>
float::min/max: mention the non-determinism around signed 0 Turns out this can actually produce different results on different machines [in practice](rust-lang/rust#83984 (comment)); that seems worth documenting. I assume LLVM will happily const-fold these operations so so there could be different results for the same input even on the same machine, depending on whether things get const-folded or not. `@nikic` I remember there was an LLVM soundness fix regarding scalar evolution for loops that had to recognize certain operations as non-deterministic... it seems to me that pass would also have to avoid predicting the result of `llvm.{min,max}num`, for the same reason? r? `@tgross35` Cc `@rust-lang/libs-api` If this lands we should also make Miri non-deterministic here. Fixes rust-lang/rust#83984
…er-errors
When encountering unexpected closure return type, point at return type/expression
```
error[E0271]: expected `{[email protected]:18:40}` to be a closure that returns `()`, but it returns `!`
--> $DIR/fallback-closure-wrap.rs:19:9
|
LL | let error = Closure::wrap(Box::new(move || {
| -------
LL | panic!("Can't connect to server.");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!`
|
= note: expected unit type `()`
found type `!`
= note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>`
```
```
error[E0271]: expected `{[email protected]:6:10}` to be a closure that returns `bool`, but it returns `Option<()>`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16
|
LL | call(|| -> Option<()> {
| ---- ------^^^^^^^^^^
| | |
| | expected `bool`, found `Option<()>`
| required by a bound introduced by this call
|
= note: expected type `bool`
found enum `Option<()>`
note: required by a bound in `call`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:3:25
|
LL | fn call(_: impl Fn() -> bool) {}
| ^^^^ required by this bound in `call`
```
```
error[E0271]: expected `{[email protected]:28:13}` to be a closure that returns `Result<(), _>`, but it returns `!`
--> f670.rs:28:20
|
28 | let c = |e| -> ! {
| -------^
| |
| expected `Result<(), _>`, found `!`
...
32 | f().or_else(c);
| ------- required by a bound introduced by this call
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs:1433:28
|
= note: expected enum `Result<(), _>`
found type `!`
note: required by a bound in `Result::<T, E>::or_else`
--> /home/gh-estebank/rust/library/core/src/result.rs:1406:39
|
1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
| ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else`
```
CC #111539.
Autodiff Upstreaming - rustc_codegen_ssa, rustc_middle This PR should not be merged until the rustc_codegen_llvm part is merged. I will also alter it a little based on what get's shaved off from the cg_llvm PR, and address some of the feedback I received in the other PR (including cleanups). I am putting it already up to 1) Discuss with `@jieyouxu` if there is more work needed to add tests to this and 2) Pray that there is someone reviewing who can tell me why some of my autodiff invocations get lost. Re 1: My test require fat-lto. I also modify the compilation pipeline. So if there are any other llvm-ir tests in the same compilation unit then I will likely break them. Luckily there are two groups who currently have the same fat-lto requirement for their GPU code which I have for my autodiff code and both groups have some plans to enable support for thin-lto. Once either that work pans out, I'll copy it over for this feature. I will also work on not changing the optimization pipeline for functions not differentiated, but that will require some thoughts and engineering, so I think it would be good to be able to run the autodiff tests isolated from the rest for now. Can you guide me here please? For context, here are some of my tests in the samples folder: https://github.com/EnzymeAD/rustbook Re 2: This is a pretty serious issue, since it effectively prevents publishing libraries making use of autodiff: EnzymeAD/rust#173. For some reason my dummy code persists till the end, so the code which calls autodiff, deletes the dummy, and inserts the code to compute the derivative never gets executed. To me it looks like the rustc_autodiff attribute just get's dropped, but I don't know WHY? Any help would be super appreciated, as rustc queries look a bit voodoo to me. Tracking: - rust-lang/rust#124509 r? `@jieyouxu`
`rustc_hir_analysis` cleanups Just some improvements I found while looking through this code. r? `@lcnr`
Fix a typo in profile-guided-optimization.md It's either "profile-guided" or "profiled-guided" and I think it'sw the former. :)
atomic: extend compare_and_swap migration docs Fixes rust-lang/rust#80486
normalize `*.long-type.txt` paths for compare-mode tests When using a compare mode, the name of the test + compare-mode is embedded in some of rustc's output, like the location where a long type `bla.long-type(-some-hash)?.txt` is written to. That generally makes these tests fail under all compare-modes. This PR fixes this by normalizing the compare-mode suffix away in the stderr output. We can also see some remnants of the long-removed `nll` compare mode being normalized away ^^. I did this to fix some failures with `--compare-mode next-solver` (but it also fixes them with e.g. `--compare-mode polonius` of course): - it makes 9 new tests pass with the new solver - however, 3 tests I changed here still don't pass with the new solver (IIRC there were 2 ICEs, and some duplicate errors for the 3rd one) (There was also one that triggered slowness in the new solver while triggering the long type failure, I'll mention this on zulip. )
…4, r=ytmimi Disable `overflow_delimited_expr` in edition 2024 This reverts the style guide changes and sets the default to "false" in rustfmt for style edition 2024. r? `@ytmimi` cc `@rust-lang/style` `@rust-lang/rustfmt`
Filter out RPITITs when suggesting unconstrained assoc type on too many generics Fixes #136233
Fix a typo in conventions.md Introduced in #135950
Rollup of 8 pull requests Successful merges: - #135414 (Stabilize `const_black_box`) - #136150 (ci: use windows 2025 for i686-mingw) - #136258 (rustdoc: rename `issue-\d+.rs` tests to have meaningful names (part 11)) - #136270 (Remove `NamedVarMap`.) - #136278 (add constraint graph to polonius MIR dump) - #136287 (LLVM changed the nocapture attribute to captures(none)) - #136291 (some test suite cleanups) - #136296 (float::min/max: mention the non-determinism around signed 0) r? `@ghost` `@rustbot` modify labels: rollup
Rollup of 9 pull requests Successful merges: - #132156 (When encountering unexpected closure return type, point at return type/expression) - #133429 (Autodiff Upstreaming - rustc_codegen_ssa, rustc_middle) - #136281 (`rustc_hir_analysis` cleanups) - #136297 (Fix a typo in profile-guided-optimization.md) - #136300 (atomic: extend compare_and_swap migration docs) - #136310 (normalize `*.long-type.txt` paths for compare-mode tests) - #136312 (Disable `overflow_delimited_expr` in edition 2024) - #136313 (Filter out RPITITs when suggesting unconstrained assoc type on too many generics) - #136323 (Fix a typo in conventions.md) r? `@ghost` `@rustbot` modify labels: rollup
… enabled Similar to how the alignment is already checked, this adds a check for null pointer dereferences in debug mode. It is implemented similarly to the alignment check as a MirPass. This is related to a 2025H1 project goal for better UB checks in debug mode: rust-lang/rust-project-goals#177.
…e,aDotInTheVoid [rustdoc] Add `--extract-doctests` command-line flag Part of rust-lang/rust#134529. It was discussed with the Rust-for-Linux project recently that they needed a way to extract doctests so they can modify them and then run them more easily (look for "a way to extract doctests" [here](Rust-for-Linux/linux#2)). For now, I output most of `ScrapedDoctest` fields in JSON format with `serde_json`. So it outputs the following information: * filename * line * langstr * text cc `@ojeda` r? `@notriddle`
…r=jieyouxu Compiler: Finalize dyn compatibility renaming Update the Reference link to use the new URL fragment from rust-lang/reference#1666 (this change has finally hit stable). Fixes a FIXME. Follow-up to #130826. Part of #130852. ~~Blocking it on #133372.~~ (merged) r? ghost
Improve documentation when adding a new target rust-lang/rust#133631 (comment) shows that it can be a bit difficult process-wise to add a new target. I've added a bit of text to the docs, suggesting that users add the target defintion/spec first, and later work on `std` support. I also found that we have two places where we document how to add a new target. I've linked these for now, but they should probably be merged somehow in the future. `@rustbot` label A-docs r? compiler CC `@workingjubilee` who's worked a lot on target specs IIRC.
Support clobber_abi in BPF inline assembly This supports [`clobber_abi`](https://doc.rust-lang.org/nightly/reference/inline-assembly.html#abi-clobbers) which is one of the requirements of stabilization mentioned in the tracking Issue for `asm_experimental_arch` (#93335). Refs: [Section 1.1 "Registers and calling convention" in BPF ABI Recommended Conventions and Guidelines v1.0](https://github.com/torvalds/linux/blob/v6.13/Documentation/bpf/standardization/abi.rst#11registers-and-calling-convention) > R0 - R5 are scratch registers and BPF programs needs to spill/fill them if necessary across calls. cc `@alessandrod` `@dave-tucker` `@tamird` `@vadorovsky` (target maintainers mentioned in platform support document which will be added by rust-lang/rust#135107) r? `@Amanieu` `@rustbot` label +O-eBPF +A-inline-assembly
Delay a bug when indexing unsized slices Fixes #136298 r? RalfJung or reassign
Replace our `LLVMRustDIBuilderRef` with LLVM-C's `LLVMDIBuilderRef` Inspired by trying to split #134009 into smaller steps that are easier to review individually. This makes it possible to start incrementally replacing our debuginfo bindings with the ones in the LLVM-C API, all of which operate on `LLVMDIBuilderRef`. There should be no change to compiler behaviour.
Remove unnecessary hooks Some hooks can be downgraded to vanilla functions. r? `@oli-obk`
…ieyouxu Overhaul `rustc_middle::util` It's an odd module with some odd stuff in it. r? `@Noratrieb`
Remove myself from vacation r? `@ghost`
Insert null checks for pointer dereferences when debug assertions are enabled
Similar to how the alignment is already checked, this adds a check
for null pointer dereferences in debug mode. It is implemented similarly
to the alignment check as a `MirPass`.
This inserts checks in the same places as the `CheckAlignment` pass and additionally
also inserts checks for `Borrows`, so code like
```rust
let ptr: *const u32 = std::ptr::null();
let val: &u32 = unsafe { &*ptr };
```
will have a check inserted on dereference. This is done because null references
are UB. The alignment check doesn't cover these places, because in `&(*ptr).field`,
the exact requirement is that the final reference must be aligned. This is something to
consider further enhancements of the alignment check.
For now this is implemented as a separate `MirPass`, to make it easy to disable
this check if necessary.
This is related to a 2025H1 project goal for better UB checks in debug
mode: rust-lang/rust-project-goals#177.
r? `@saethlin`
Rollup of 9 pull requests Successful merges: - #134531 ([rustdoc] Add `--extract-doctests` command-line flag) - #135860 (Compiler: Finalize dyn compatibility renaming) - #135992 (Improve documentation when adding a new target) - #136194 (Support clobber_abi in BPF inline assembly) - #136325 (Delay a bug when indexing unsized slices) - #136326 (Replace our `LLVMRustDIBuilderRef` with LLVM-C's `LLVMDIBuilderRef`) - #136330 (Remove unnecessary hooks) - #136336 (Overhaul `rustc_middle::util`) - #136341 (Remove myself from vacation) r? `@ghost` `@rustbot` modify labels: rollup
…ratrieb tests: Port `symbol-mangling-hashed` to rmake.rs Part of #121876. This PR supersedes #128567 and is co-authored with `@lolbinarycat.` ### Summary This PR ports `tests/run-make/symbol-mangling-hashed` to rmake.rs. Notable differences when compared to the Makefile version includes: - It's no longer limited to linux + x86_64 only. In particular, this now is exercised on darwin and windows (esp. msvc) too. - The test uses `object` crate to be more precise in the filtering, and avoids relying on parsing the human-readable `nm` output for *some* `nm` in the given environment (which isn't really a thing on msvc anyway, and `llvm-nm` doesn't handle msvc dylibs AFAICT). - Dump the symbols satisfying various criteria on test failure to make it hopefully less of a pain to debug if it ever fails in CI. ### Review advice - Best reviewed commit-by-commit. - I'm not *super* sure about the msvc logic, would benefit from a MSVC (PE/COFF) expert taking a look. --- try-job: x86_64-msvc-1 try-job: i686-msvc-1 try-job: i686-mingw try-job: x86_64-mingw-1 try-job: x86_64-apple-1 try-job: aarch64-apple try-job: test-various
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