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`
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
Check ABI target compatibility for function pointers
Tracking issue: https://github.com/rust-lang/rust/issues/130260
Related tracking issue: #87678
Compatibility of an ABI for a target was previously only performed on function definitions and `extern` blocks. This PR adds it also to function pointers to be consistent.
This might have broken some of the `tests/ui/` depending on the platform, so a try run seems like a good idea.
Also this might break existing code, because we now emit extra errors. Does this require a crater run?
# Example
```rust
// build with: --target=x86_64-unknown-linux-gnu
// These raise E0570
extern "thiscall" fn foo() {}
extern "thiscall" { fn bar() }
// This did not raise any error
fn baz(f: extern "thiscall" fn()) { f() }
```
# Open Questions
* [x] Should this report a future incompatibility warning like #87678 ?
* [ ] Is this the best place to perform the check?
Move ZST ABI handling to `rustc_target`
Currently, target specific handling of ZST function call ABI (specifically passing them indirectly instead of ignoring them) is handled in `rustc_ty_utils`, whereas all other target specific function call ABI handling is located in `rustc_target`. This PR moves the ZST handling to `rustc_target` so that all the target-specific function call ABI handling is in one place. In the process of doing so, this PR fixes#125850 by ensuring that ZST arguments are always correctly ignored in the x86-64 `"sysv64"` ABI; any code which would be affected by this fix would have ICEd before this PR. Tests are also added using `#[rustc_abi(debug)]` to ensure this behaviour does not regress.
Fixes#125850
Use a multipart suggestion instead of a single whole-span replacement:
```
error[E0796]: creating a shared reference to a mutable static
--> $DIR/reference-to-mut-static-unsafe-fn.rs:10:18
|
LL | let _y = &X;
| ^^ shared reference to mutable static
|
= note: this shared reference has lifetime `'static`, but if the static ever gets mutated, or a mutable reference is created, then any further use of this shared reference is Undefined Behavior
help: use `addr_of!` instead to create a raw pointer
|
LL | let _y = addr_of!(X);
| ~~~~~~~~~ +
```
Ensure floats are returned losslessly by the Rust ABI on 32-bit x86
Solves #115567 for the (default) `"Rust"` ABI. When compiling for 32-bit x86, this PR changes the `"Rust"` ABI to return floats indirectly instead of in x87 registers (with the exception of single `f32`s, which this PR returns in general purpose registers as they are small enough to fit in one). No change is made to the `"C"` ABI as that ABI requires x87 register usage and therefore will need a different solution.
Remove extern "wasm" ABI
Remove the unstable `extern "wasm"` ABI (`wasm_abi` feature tracked in #83788).
As discussed in https://github.com/rust-lang/rust/pull/127513#issuecomment-2220410679 and following, this ABI is a failed experiment that did not end up being used for anything. Keeping support for this ABI in LLVM 19 would require us to switch wasm targets to the `experimental-mv` ABI, which we do not want to do.
It should be noted that `Abi::Wasm` was internally used for two things: The `-Z wasm-c-abi=legacy` ABI that is still used by default on some wasm targets, and the `extern "wasm"` ABI. Despite both being `Abi::Wasm` internally, they were not the same. An explicit `extern "wasm"` additionally enabled the `+multivalue` feature.
I've opted to remove `Abi::Wasm` in this patch entirely, instead of keeping it as an ABI with only internal usage. Both `-Z wasm-c-abi` variants are now treated as part of the normal C ABI, just with different different treatment in
adjust_for_foreign_abi.
Remove the unstable `extern "wasm"` ABI (`wasm_abi` feature tracked
in #83788).
As discussed in https://github.com/rust-lang/rust/pull/127513#issuecomment-2220410679
and following, this ABI is a failed experiment that did not end
up being used for anything. Keeping support for this ABI in LLVM 19
would require us to switch wasm targets to the `experimental-mv`
ABI, which we do not want to do.
It should be noted that `Abi::Wasm` was internally used for two
things: The `-Z wasm-c-abi=legacy` ABI that is still used by
default on some wasm targets, and the `extern "wasm"` ABI. Despite
both being `Abi::Wasm` internally, they were not the same. An
explicit `extern "wasm"` additionally enabled the `+multivalue`
feature.
I've opted to remove `Abi::Wasm` in this patch entirely, instead
of keeping it as an ABI with only internal usage. Both
`-Z wasm-c-abi` variants are now treated as part of the normal
C ABI, just with different different treatment in
adjust_for_foreign_abi.
Disable dead variant removal for `#[repr(C)]` enums.
This prevents removing dead branches from a `#[repr(C)]` enum (they now get discriminants allocated as if they were inhabited).
Implementation notes: ABI of something like
```rust
#[repr(C)]
enum Foo {
Foo(!),
}
```
is still `Uninhabited`, but its layout is now computed as if all the branches were inhabited.
This seemed to me like a proper way to do it, especially given that ABI sanity check explicitly asserts that type-level uninhabitedness implies ABI uninhabitedness.
This probably needs some sort of FCP (given that it changes `#[repr(C)]` layout, which is a stable guarantee), but I’m not sure how to call for one or which team is the most relevant.
See https://github.com/rust-lang/unsafe-code-guidelines/issues/500.
