Implement RFC 1861: Extern types
A few notes :
- Type parameters are not supported. This was an unresolved question from the RFC. It is not clear how useful this feature is, and how variance should be treated. This can be added in a future PR.
- `size_of_val` / `align_of_val` can be called with extern types, and respectively return 0 and 1. This differs from the RFC, which specified that they should panic, but after discussion with @eddyb on IRC this seems like a better solution.
If/when a `DynSized` trait is added, this will be disallowed statically.
- Auto traits are not implemented by default, since the contents of extern types is unknown. This means extern types are `!Sync`, `!Send` and `!Freeze`. This seems like the correct behaviour to me.
Manual `unsafe impl Sync for Foo` is still possible.
- This PR allows extern type to be used as the tail of a struct, as described by the RFC :
```rust
extern {
type OpaqueTail;
}
#[repr(C)]
struct FfiStruct {
data: u8,
more_data: u32,
tail: OpaqueTail,
}
```
However this is undesirable, as the alignment of `tail` is unknown (the current PR assumes an alignment of 1). Unfortunately we can't prevent it in the general case as the tail could be a type parameter :
```rust
#[repr(C)]
struct FfiStruct<T: ?Sized> {
data: u8,
more_data: u32,
tail: T,
}
```
Adding a `DynSized` trait would solve this as well, by requiring tail fields to be bound by it.
- Despite being unsized, pointers to extern types are thin and can be casted from/to integers. However it is not possible to write a `null<T>() -> *const T` function which works with extern types, as I've explained here : https://github.com/rust-lang/rust/issues/43467#issuecomment-321678621
- Trait objects cannot be built from extern types. I intend to support it eventually, although how this interacts with `DynSized`/`size_of_val` is still unclear.
- The definition of `c_void` is unmodified
Move Generics from MethodSig to TraitItem and ImplItem
As part of `rust-impl-period/WG-compiler-traits`, we want to "lift" `Generics` from `MethodSig` into `TraitItem` and `ImplItem`. This is in preparation for adding associated type generics. (https://github.com/rust-lang/rust/issues/44265#issuecomment-331172238)
Currently this change is only made in the AST. In the future, it may also impact the HIR. (Still discussing)
To understand this PR, it's probably best to start from the changes to `ast.rs` and then work your way to the other files to understand the far reaching effects of this change.
r? @nikomatsakis
rustdoc: add a primitive page for "unit"
In `src/libstd/primitive_docs.rs`, a `#[doc(primitive = "unit")]`
section has sat long neglected. This patch teaches rustdoc to recognize
"unit", and steals its trait implementations away from the tuple page.
Deprecate several flags in rustdoc
Part of #44136
cc @rust-lang/dev-tools @rust-lang/docs
This is a very basic PR to start deprecating some flags; `rustdoc` doesn't really have fancy output options like `rustc` does, so I went with `eprintln!`. Happy to change it if people feel that's not appropriate.
Also, I have no idea if we can or should write tests here, so I didn't try. If someone feels strongly about it, then let's do it, but given that the only outcome here is a side effect...
In `src/libstd/primitive_docs.rs`, a `#[doc(primitive = "unit")]`
section has sat long neglected. This patch teaches rustdoc to recognize
"unit", and steals its trait implementations away from the tuple page.
rustbuild: Support specifying archiver and linker explicitly
With this patch `x.py test` passes without toolchain being in `PATH` if `cc`, `cxx`, `ar`, `linker` and `gdb` are specified in `config.toml` (except for a few `run-make` tests using `nm`).
Fixes https://github.com/rust-lang/rust/issues/41821
r? @Mark-Simulacrum
some low-hanging rustdoc optimizations
There were a few discussions earlier today in #rust-internals about the syscall usage and overall performance of rustdoc. This PR is intended to pick some low-hanging fruit and try to rein in some of the performance issues of rustdoc.
Add x86_64-unknown-linux-gnux32 target
This adds X32 ABI support for Linux on X86_64. Let's package and dist it so we can star testing libc, libstd, etc.
Fixes https://github.com/rust-lang/rfcs/issues/1339
doc-test: In Markdown tests, Use all of `<h1>` to `<h6>` as the test name
This mainly simplifies debugging error index tests, as the error codes are `<h2>`s in the huge document containing all codes.
