Tracking Issue for `c_variadic_naked_functions`

[folkertdev]

The feature gate for the issue is #![feature(c_variadic_naked_functions)].

This feature allows naked c-variadic function definitions with any ABI that is supported for foreign c-variadic functions.

#![feature(c_variadic, c_variadic_naked_functions)]

#[unsafe(naked)]
unsafe extern "win64" fn variadic_win64(_: u32, _: ...) -> u32 {
    core::arch::naked_asm!(
        r#"
        push    rax
        mov     qword ptr [rsp + 40], r9
        mov     qword ptr [rsp + 24], rdx
        mov     qword ptr [rsp + 32], r8
        lea     rax, [rsp + 40]
        mov     qword ptr [rsp], rax
        lea     eax, [rdx + rcx]
        add     eax, r8d
        pop     rcx
        ret
    "#,
    )
}

About tracking issues

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They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.
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Steps

• Implement the feature implement feature(c_variadic_naked_functions) #148770
• Adjust documentation (see instructions on rustc-dev-guide)
• Style updates for any new syntax (nightly-style-procedure)
  • Style team decision on new formatting
  • Formatting for new syntax has been added to the Style Guide
  • (non-blocking) Formatting has been implemented in rustfmt
• Stabilization PR (see instructions on rustc-dev-guide)

Unresolved Questions

XXX --- list all the "unresolved questions" found in the RFC to ensure they are
not forgotten

Implementation history

• implement feature(c_variadic_naked_functions) #148770