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Use the type-level constant value `ty::Value` where needed
**Follow-up to #136180**
### Summary
This PR refactors functions to accept a single type-level constant value `ty::Value` instead of separate `ty::ValTree` and `ty::Ty` parameters:
- `valtree_to_const_value`: now takes `ty::Value`
- `pretty_print_const_valtree`: now takes `ty::Value`
- Uses `pretty_print_const_valtree` for formatting valtrees when `visit_const_operand`
- Moves `try_to_raw_bytes` from `ty::Valtree` to `ty::Value`
---
r? ``@lukas-code`` ``@oli-obk``
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Signed-off-by: FedericoBruzzone <federico.bruzzone.i@gmail.com>
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Remove hook calling via `TyCtxtAt`.
All hooks receive a `TyCtxtAt` argument.
Currently hooks can be called through `TyCtxtAt` or `TyCtxt`. In the latter case, a `TyCtxtAt` is constructed with a dummy span and passed to the hook.
However, in practice hooks are never called through `TyCtxtAt`, and always receive a dummy span. (I confirmed this via code inspection, and double-checked it by temporarily making the `TyCtxtAt` code path panic and running all the tests.)
This commit removes all the `TyCtxtAt` machinery for hooks. All hooks now receive `TyCtxt` instead of `TyCtxtAt`. There are two existing hooks that use `TyCtxtAt::span`: `const_caller_location_provider` and `try_destructure_mir_constant_for_user_output`. For both hooks the span is always a dummy span, probably unintentionally. This dummy span use is now explicit. If a non-dummy span is needed for these two hooks it would be easy to add it as an extra argument because hooks are less constrained than queries.
r? `@oli-obk`
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miri: improve error when offset_from preconditions are violated
Fixes https://github.com/rust-lang/miri/issues/4143
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All hooks receive a `TyCtxtAt` argument.
Currently hooks can be called through `TyCtxtAt` or `TyCtxt`. In the
latter case, a `TyCtxtAt` is constructed with a dummy span and passed to
the hook.
However, in practice hooks are never called through `TyCtxtAt`, and
always receive a dummy span. (I confirmed this via code inspection, and
double-checked it by temporarily making the `TyCtxtAt` code path panic
and running all the tests.)
This commit removes all the `TyCtxtAt` machinery for hooks. All hooks
now receive `TyCtxt` instead of `TyCtxtAt`. There are two existing hooks
that use `TyCtxtAt::span`: `const_caller_location_provider` and
`try_destructure_mir_constant_for_user_output`. For both hooks the span
is always a dummy span, probably unintentionally. This dummy span use is
now explicit. If a non-dummy span is needed for these two hooks it would
be easy to add it as an extra argument because hooks are less
constrained than queries.
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Implement MIR lowering for unsafe binders
This is the final bit of the unsafe binders puzzle. It implements MIR, CTFE, and codegen for unsafe binders, and enforces that (for now) they are `Copy`. Later on, I'll introduce a new trait that relaxes this requirement to being "is `Copy` or `ManuallyDrop<T>`" which more closely models how we treat union fields.
Namely, wrapping unsafe binders is now `Rvalue::WrapUnsafeBinder`, which acts much like an `Rvalue::Aggregate`. Unwrapping unsafe binders are implemented as a MIR projection `ProjectionElem::UnwrapUnsafeBinder`, which acts much like `ProjectionElem::Field`.
Tracking:
- https://github.com/rust-lang/rust/issues/130516
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miri: make float min/max non-deterministic
This makes Miri match the documentation that landed in https://github.com/rust-lang/rust/pull/136296.
r? ``@oli-obk``
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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
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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: https://github.com/rust-lang/rust-project-goals/pull/177.
r? `@saethlin`
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Delay a bug when indexing unsized slices
Fixes #136298
r? RalfJung or reassign
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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: https://github.com/rust-lang/rust-project-goals/pull/177.
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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
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Co-authored-by: FedericoBruzzone <federico.bruzzone.i@gmail.com>
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miri: optimize zeroed alloc
When allocating zero-initialized memory in MIR interpretation, rustc allocates zeroed memory, marks it as initialized and then re-zeroes it. Remove the last step.
I don't expect this to have much of an effect on performance normally, but in my case in which I'm creating a large allocation via mmap it gets in the way.
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interpret: is_alloc_live: check global allocs last
See https://github.com/rust-lang/rust/pull/136105#discussion_r1930609553.
(A perf run makes no sense as this is only used by Miri.)
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Rollup of 9 pull requests
Successful merges:
- #135869 (Make docs for AtomicUsize::from_mut platform-independent)
- #135892 (-Znext-solver: "normalize" signature before checking it mentions self in `deduce_closure_signature`)
- #136055 (Implement MIR const trait stability checks)
- #136066 (Pass spans to `perform_locally_in_new_solver`)
- #136071 ([Clippy] Add vec_reserve & vecdeque_reserve diagnostic items)
- #136124 (Arbitrary self types v2: explain test.)
- #136149 (Flip the `rustc-rayon`/`indexmap` dependency order)
- #136173 (Update comments and sort target_arch in c_char_definition)
- #136178 (Update username in build helper example)
r? `@ghost`
`@rustbot` modify labels: rollup
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Implement MIR const trait stability checks
Addresses https://github.com/rust-lang/project-const-traits/issues/16
cc ``@rust-lang/project-const-traits``
r? ``@RalfJung``
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Co-authored-by: Ralf Jung <post@ralfj.de>
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r=davidtwco,RalfJung"
This reverts commit 122a55bb442bd1995df9cf9b36e6f65ed3ef4a1d.
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- `check-pass` test for a MRE of #135020
- fail test for #135138
- switch to `TooGeneric` for checking CMSE fn signatures
- switch to `TooGeneric` for compute `SizeSkeleton` (for transmute)
- fix broken tests
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Provide structured suggestion for `#![feature(..)]` in more cases
Fix #81370.
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Temporarily bring back `Rvalue::Len`
r? `@compiler-errors` as requested in https://github.com/rust-lang/rust/issues/135671#issuecomment-2599580364
> However, in the mean time, I'd rather we not crunch trying to find and more importantly validate the soundness of a solution 🤔
Agreed. To fix the IMO P-critical #135671 for which we somehow didn't have test coverage, this PR temporarily reverts:
- https://github.com/rust-lang/rust/pull/133734
- its bugfix https://github.com/rust-lang/rust/pull/134371
- https://github.com/rust-lang/rust/pull/134330
cc `@scottmcm`
I added the few samples from that issue as a test, but we can add more in the future, in particular it seems `@steffahn` [will work on that](https://github.com/rust-lang/rust/issues/135671#issuecomment-2599714354).
Fixes #135671. And if we want to land this, it should also be nominated for beta backport.
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r=davidtwco,RalfJung"
This reverts commit b57d93d8b9525fa261404b4cd9c0670eeb1264b8, reversing
changes made to 0aeaa5eb22180fdf12a8489e63c4daa18da6f236.
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This reverts commit e108481f74ff123ad98a63bd107a18d13035b275, reversing
changes made to 303e8bd768526a5812bb1776e798e829ddb7d3ca.
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```
error: `size_of_val` is not yet stable as a const intrinsic
--> $DIR/const-unstable-intrinsic.rs:17:9
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LL | unstable_intrinsic::size_of_val(&x);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: add `#![feature(unstable)]` to the crate attributes to enable
help: add `#![feature(unstable)]` to the crate attributes to enable
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LL + #![feature("unstable")]
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```
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When encountering a call corresponding to an item marked as unstable behind a feature flag, provide a structured suggestion pointing at where in the crate the `#![feature(..)]` needs to be written.
```
error: `foobar` is not yet stable as a const fn
--> $DIR/const-stability-attribute-implies-no-feature.rs:12:5
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LL | foobar();
| ^^^^^^^^
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help: add `#![feature(const_foobar)]` to the crate attributes to enable
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LL + #![feature(const_foobar)]
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```
Fix #81370.
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conditionally const
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This should make it clearer that this bitset is dense, with the
advantages and disadvantages that it entails.
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