add `extern "custom"` functions
tracking issue: rust-lang/rust#140829
previous discussion: https://github.com/rust-lang/rust/issues/140566
In short, an `extern "custom"` function is a function with a custom ABI, that rust does not know about. Therefore, such functions can only be defined with `#[unsafe(naked)]` and `naked_asm!`, or via an `extern "C" { /* ... */ }` block. These functions cannot be called using normal rust syntax: calling them can only be done from inline assembly.
The motivation is low-level scenarios where a custom calling convention is used. Currently, we often pick `extern "C"`, but that is a lie because the function does not actually respect the C calling convention.
At the moment `"custom"` seems to be the name with the most support. That name is not final, but we need to pick something to actually implement this.
r? `@traviscross`
cc `@tgross35`
try-job: x86_64-apple-2
Replace ad-hoc ABI "adjustments" with an `AbiMap` to `CanonAbi`
Our `conv_from_spec_abi`, `adjust_abi`, and `is_abi_supported` combine to give us a very confusing way of reasoning about what _actual_ calling convention we want to lower our code to and whether we want to compile the resulting code at all. Instead of leaving this code as a miniature adventure game in which someone tries to combine stateful mutations into a Rube Goldberg machine that will let them escape the maze and arrive at the promised land of codegen, we let `AbiMap` devour this complexity. Once you have an `AbiMap`, you can answer which `ExternAbi`s will lower to what `CanonAbi`s (and whether they will lower at all).
Removed:
- `conv_from_spec_abi` replaced by `AbiMap::canonize_abi`
- `adjust_abi` replaced by same
- `Conv::PreserveAll` as unused
- `Conv::Cold` as unused
- `enum Conv` replaced by `enum CanonAbi`
target-spec.json changes:
- If you have a target-spec.json then now your "entry-abi" key will be specified in terms of one of the `"{abi}"` strings Rust recognizes, e.g.
```json
"entry-abi": "C",
"entry-abi": "win64",
"entry-abi": "aapcs",
```
Rollup of 7 pull requests
Successful merges:
- #140056 (Fix a wrong error message in 2024 edition)
- #140220 (Fix detection of main function if there are expressions around it)
- #140249 (Remove `weak` alias terminology)
- #140316 (Introduce `BoxMarker` to improve pretty-printing correctness)
- #140347 (ci: clean more disk space in codebuild)
- #140349 (ci: use aws codebuild for the `dist-x86_64-linux` job)
- #140379 (rustc-dev-guide subtree update)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove `weak` alias terminology
I find the "weak" alias terminology to be quite confusing. It implies the existence of "strong" aliases (which do not exist) and I'm not really sure what about weak aliases is "weak". I much prefer "free alias" as the term. I think it's much more obvious what it means as "free function" is a well defined term that already exists in rust.
It's also a little confusing given "weak alias" is already a term in linker/codegen spaces which are part of the compiler too. Though I'm not particularly worried about that as it's usually very obvious if you're talking about the type system or not lol. I'm also currently trying to write documentation about aliases and it's somewhat awkward/confusing to be talking about *weak* aliases, when I'm not really sure what the basis for that as the term actually *is*.
I would also be happy to just find out there's a nice meaning behind calling them "weak" aliases :-)
r? `@oli-obk`
maybe we want a types MCP to decide on a specific naming here? or maybe we think its just too late to go back on this naming decision ^^'
StableMIR: Implement `CompilerInterface`
This PR implements part of [the document](https://hackmd.io/``@celinaval/H1lJBGse0).``
With `TablesWrapper` wrapped by `CompilerInterface`, the stable-mir's TLV stores a pointer to `CompilerInterface`, while the rustc-specific TLV stores a pointer to tables.
Pass `args` to `run` instead of storing it in a field. This avoids the
need to clone it within `run`.
Also, change `args` from `Vec<String>` to `&[String]`, avoiding the need
for some vecs and clones.
- With `Context` wrapped by `SmirInterface`, the stable-mir's TLV stores a pointer to `SmirInterface`, while the rustc-specific TLV stores a pointer to tables.
- This PR make the `rustc_smir` mod public.
Overhaul `AssocItem`
`AssocItem` has multiple fields that only make sense some of the time. E.g. the `name` can be empty if it's an RPITIT associated type. It's clearer and less error prone if these fields are moved to the relevant `kind` variants.
r? ``@fee1-dead``
To accurately reflect that RPITIT assoc items don't have a name. This
avoids the use of `kw::Empty` to mean "no name", which is error prone.
Helps with #137978.
`hir::AssocItem` currently has a boolean `fn_has_self_parameter` field,
which is misplaced, because it's only relevant for associated fns, not
for associated consts or types. This commit moves it (and renames it) to
the `AssocKind::Fn` variant, where it belongs.
This requires introducing a new C-style enum, `AssocTag`, which is like
`AssocKind` but without the fields. This is because `AssocKind` values
are passed to various functions like `find_by_ident_and_kind` to
indicate what kind of associated item should be searched for, and having
to specify `has_self` isn't relevant there.
New methods:
- Predicates `AssocItem::is_fn` and `AssocItem::is_method`.
- `AssocItem::as_tag` which converts `AssocItem::kind` to `AssocTag`.
Removed `find_by_name_and_kinds`, which is unused.
`AssocItem::descr` can now distinguish between methods and associated
functions, which slightly improves some error messages.
It's very useful. There are some false positives involving integration
tests in `rustc_pattern_analysis` and `rustc_serialize`. There is also a
false positive involving `rustc_driver_impl`'s
`rustc_randomized_layouts` feature. And I removed a `rustc_span` mention
in a doc comment in `rustc_log` because it wasn't integral to the
comment but caused a dev-dependency.
Continuing the work from #137350.
Removes the unused methods: `expect_variant`, `expect_field`,
`expect_foreign_item`.
Every method gains a `hir_` prefix.
Revert <https://github.com/rust-lang/rust/pull/138084> to buy time to
consider options that avoids breaking downstream usages of cargo on
distributed `rustc-src` artifacts, where such cargo invocations fail due
to inability to inherit `lints` from workspace root manifest's
`workspace.lints` (this is only valid for the source rust-lang/rust
workspace, but not really the distributed `rustc-src` artifacts).
This breakage was reported in
<https://github.com/rust-lang/rust/issues/138304>.
This reverts commit 48caf81484, reversing
changes made to c6662879b2.
By naming them in `[workspace.lints.rust]` in the top-level
`Cargo.toml`, and then making all `compiler/` crates inherit them with
`[lints] workspace = true`. (I omitted `rustc_codegen_{cranelift,gcc}`,
because they're a bit different.)
The advantages of this over the current approach:
- It uses a standard Cargo feature, rather than special handling in
bootstrap. So, easier to understand, and less likely to get
accidentally broken in the future.
- It works for proc macro crates.
It's a shame it doesn't work for rustc-specific lints, as the comments
explain.
