remove support for the (unstable) #[start] attribute
As explained by `@Noratrieb:`
`#[start]` should be deleted. It's nothing but an accidentally leaked implementation detail that's a not very useful mix between "portable" entrypoint logic and bad abstraction.
I think the way the stable user-facing entrypoint should work (and works today on stable) is pretty simple:
- `std`-using cross-platform programs should use `fn main()`. the compiler, together with `std`, will then ensure that code ends up at `main` (by having a platform-specific entrypoint that gets directed through `lang_start` in `std` to `main` - but that's just an implementation detail)
- `no_std` platform-specific programs should use `#![no_main]` and define their own platform-specific entrypoint symbol with `#[no_mangle]`, like `main`, `_start`, `WinMain` or `my_embedded_platform_wants_to_start_here`. most of them only support a single platform anyways, and need cfg for the different platform's ways of passing arguments or other things *anyways*
`#[start]` is in a super weird position of being neither of those two. It tries to pretend that it's cross-platform, but its signature is a total lie. Those arguments are just stubbed out to zero on ~~Windows~~ wasm, for example. It also only handles the platform-specific entrypoints for a few platforms that are supported by `std`, like Windows or Unix-likes. `my_embedded_platform_wants_to_start_here` can't use it, and neither could a libc-less Linux program.
So we have an attribute that only works in some cases anyways, that has a signature that's a total lie (and a signature that, as I might want to add, has changed recently, and that I definitely would not be comfortable giving *any* stability guarantees on), and where there's a pretty easy way to get things working without it in the first place.
Note that this feature has **not** been RFCed in the first place.
*This comment was posted [in May](https://github.com/rust-lang/rust/issues/29633#issuecomment-2088596042) and so far nobody spoke up in that issue with a usecase that would require keeping the attribute.*
Closes https://github.com/rust-lang/rust/issues/29633
try-job: x86_64-gnu-nopt
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
try-job: test-various
Subtree sync for rustc_codegen_cranelift
Nothing too exciting this time, but this includes a fix for a linker hang on Windows: https://github.com/rust-lang/rustc_codegen_cranelift/pull/1554
r? ``@ghost``
``@rustbot`` label +A-codegen +A-cranelift +T-compiler
Partial progress on #132735: Replace extern "rust-intrinsic" with #[rustc_intrinsic] across the codebase
Part of #132735: Replace `extern "rust-intrinsic"` with `#[rustc_intrinsic]` macro
- Updated all instances of `extern "rust-intrinsic"` to use the `#[rustc_intrinsic]` macro.
- Skipped `.md` files and test files to avoid unnecessary changes.
Add gpu-kernel calling convention
The amdgpu-kernel calling convention was reverted in commit f6b21e90d1 (#120495 and https://github.com/rust-lang/rust-analyzer/pull/16463) due to inactivity in the amdgpu target.
Introduce a `gpu-kernel` calling convention that translates to `ptx_kernel` or `amdgpu_kernel`, depending on the target that rust compiles for.
Tracking issue: #135467
amdgpu target tracking issue: #135024
The amdgpu-kernel calling convention was reverted in commit
f6b21e90d1 due to inactivity in the amdgpu
target.
Introduce a `gpu-kernel` calling convention that translates to
`ptx_kernel` or `amdgpu_kernel`, depending on the target that rust
compiles for.
Fuchsia explicitly builds rust and all rust targets with `-C
panic=abort` to minimize code generation size. However, when compiling a
proc-macro with this setting it can cause a warning to be emitted, which
breaks `tests/ui/invalid-compile-flags/crate-type-flag.rs`. This hasn't
been a problem in the past for us since we compile our proc macros on
host, rather than inside Fuchsia.
This attempts to fix the issue by explicitly requiring that we're using
the unwinder when compiling this test to avoid the warning being
emitted.
Fixes#135223
mod_bench is basically useless as test and hasn't been used as benchmark
for a long time. alloc_example doesn't test anything that isn't
already tested by std_example.
