Stabilize c-variadic function definitions

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -1,4 +1,4 @@
-use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
+use rustc_ast::visit::{self, AssocCtxt, FnKind, Visitor};
 use rustc_ast::{self as ast, AttrVec, GenericBound, NodeId, PatKind, attr, token};
 use rustc_attr_parsing::AttributeParser;
 use rustc_errors::msg;
@@ -382,7 +382,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_poly_trait_ref(self, t);
     }
 
-    fn visit_fn(&mut self, fn_kind: FnKind<'a>, _: &AttrVec, span: Span, _: NodeId) {
+    fn visit_fn(&mut self, fn_kind: FnKind<'a>, _: &AttrVec, _: Span, _: NodeId) {
         if let Some(_header) = fn_kind.header() {
             // Stability of const fn methods are covered in `visit_assoc_item` below.
         }
@@ -391,10 +391,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             self.check_late_bound_lifetime_defs(generic_params);
         }
 
-        if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
-            gate!(self, c_variadic, span, "C-variadic functions are unstable");
-        }
-
         visit::walk_fn(self, fn_kind)
     }
 

compiler/rustc_feature/src/accepted.rs

@@ -94,6 +94,8 @@ declare_features! (
     (accepted, c_str_literals, "1.77.0", Some(105723)),
     /// Allows `extern "C-unwind" fn` to enable unwinding across ABI boundaries and treat `extern "C" fn` as nounwind.
     (accepted, c_unwind, "1.81.0", Some(74990)),
+    /// Allows using C-variadics.
+    (accepted, c_variadic, "CURRENT_RUSTC_VERSION", Some(44930)),
     /// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
     (accepted, cfg_attr_multi, "1.33.0", Some(54881)),
     /// Allows the use of `#[cfg(<true/false>)]`.

compiler/rustc_feature/src/unstable.rs

@@ -424,8 +424,6 @@ declare_features! (
     (unstable, avx10_target_feature, "1.88.0", Some(138843)),
     /// Target features on bpf.
     (unstable, bpf_target_feature, "1.54.0", Some(150247)),
-    /// Allows using C-variadics.
-    (unstable, c_variadic, "1.34.0", Some(44930)),
     /// Allows defining c-variadic functions on targets where this feature has not yet
     /// undergone sufficient testing for stabilization.
     (unstable, c_variadic_experimental_arch, "1.97.0", Some(155973)),

library/core/src/ffi/mod.rs

@@ -24,11 +24,7 @@ use crate::fmt;
 pub mod c_str;
 
 mod va_list;
-#[unstable(
-    feature = "c_variadic",
-    issue = "44930",
-    reason = "the `c_variadic` feature has not been properly tested on all supported platforms"
-)]
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 pub use self::va_list::{VaArgSafe, VaList};
 
 mod primitives;

library/core/src/ffi/va_list.rs

@@ -2,12 +2,6 @@
 //!
 //! Better known as "varargs".
 
-#![unstable(
-    feature = "c_variadic",
-    issue = "44930",
-    reason = "the `c_variadic` feature has not been properly tested on all supported platforms"
-)]
-
 #[cfg(not(target_arch = "xtensa"))]
 use crate::ffi::c_void;
 use crate::fmt;
@@ -195,8 +189,6 @@ crate::cfg_select! {
 /// is automatically initialized (equivalent to calling `va_start` in C).
 ///
 /// ```
-/// #![feature(c_variadic)]
-///
 /// use std::ffi::VaList;
 ///
 /// /// # Safety
@@ -230,11 +222,13 @@ crate::cfg_select! {
 /// terms of layout and ABI.
 #[repr(transparent)]
 #[lang = "va_list"]
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 pub struct VaList<'a> {
     inner: VaListInner,
     _marker: PhantomCovariantLifetime<'a>,
 }
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 impl fmt::Debug for VaList<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // No need to include `_marker` in debug output.
@@ -249,6 +243,7 @@ impl VaList<'_> {
     }
 }
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_const_unstable(feature = "const_c_variadic", issue = "151787")]
 const impl<'f> Clone for VaList<'f> {
     /// Clone the [`VaList`], producing a second independent cursor into the variable argument list.
@@ -264,6 +259,7 @@ const impl<'f> Clone for VaList<'f> {
     }
 }
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_const_unstable(feature = "const_c_variadic", issue = "151787")]
 const impl<'f> Drop for VaList<'f> {
     /// Drop the [`VaList`].
@@ -316,6 +312,7 @@ const impl<'f> Drop for VaList<'f> {
 // types with a non-scalar layout. Inline assembly can be used to accept unsupported types in the
 // meantime.
 #[lang = "va_arg_safe"]
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 pub impl(self) unsafe trait VaArgSafe: Copy {}
 
 crate::cfg_select! {
@@ -324,7 +321,9 @@ crate::cfg_select! {
         //
         // - i8 is implicitly promoted to c_int in C, and cannot implement `VaArgSafe`.
         // - u8 is implicitly promoted to c_uint in C, and cannot implement `VaArgSafe`.
+        #[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
         unsafe impl VaArgSafe for i16 {}
+        #[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
         unsafe impl VaArgSafe for u16 {}
     }
     _ => {
@@ -338,6 +337,7 @@ crate::cfg_select! {
 crate::cfg_select! {
     target_arch = "avr" => {
         // c_double is f32 on this target.
+        #[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
         unsafe impl VaArgSafe for f32 {}
     }
     _ => {
@@ -347,12 +347,18 @@ crate::cfg_select! {
     }
 }
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for i32 {}
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for i64 {}
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for isize {}
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for u32 {}
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for u64 {}
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for usize {}
 
 // Implement `VaArgSafe` for 128-bit integers on targets where clang provides `__int128`.
@@ -400,19 +406,19 @@ cfg_select! {
     _ => {
         #[repr(transparent)]
         #[derive(Clone, Copy)]
-        struct S(i32);
-
         // When there are no actual implementations on i128, declare the c_variadic_int128 feature
         // on a private type so that the feature is defined on all targets.
         #[unstable(feature = "c_variadic_int128", issue = "155752")]
-        unsafe impl VaArgSafe for S {}
-
+        struct S(i32);
     }
 }
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl VaArgSafe for f64 {}
 
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl<T> VaArgSafe for *mut T {}
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 unsafe impl<T> VaArgSafe for *const T {}
 
 // Check that relevant `core::ffi` types implement `VaArgSafe`.
@@ -459,6 +465,7 @@ impl<'f> VaList<'f> {
     ///
     /// [`c_void`]: core::ffi::c_void
     #[inline] // Avoid codegen when not used to help backends that don't support VaList.
+    #[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
     #[rustc_const_unstable(feature = "const_c_variadic", issue = "151787")]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn next_arg<T: VaArgSafe>(&mut self) -> T {

library/std/src/ffi/mod.rs

@@ -166,12 +166,7 @@ pub mod c_str;
 
 #[stable(feature = "core_c_void", since = "1.30.0")]
 pub use core::ffi::c_void;
-#[unstable(
-    feature = "c_variadic",
-    reason = "the `c_variadic` feature has not been properly tested on \
-              all supported platforms",
-    issue = "44930"
-)]
+#[stable(feature = "c_variadic", since = "CURRENT_RUSTC_VERSION")]
 pub use core::ffi::{VaArgSafe, VaList};
 #[stable(feature = "core_ffi_c", since = "1.64.0")]
 pub use core::ffi::{

library/std/src/lib.rs

@@ -421,7 +421,6 @@
 // Only for re-exporting:
 // tidy-alphabetical-start
 #![feature(async_iterator)]
-#![feature(c_variadic)]
 #![feature(cfg_accessible)]
 #![feature(cfg_eval)]
 #![feature(concat_bytes)]

src/tools/miri/tests/fail/c-variadic-ignored-argument.rs

@@ -1,5 +1,3 @@
-#![feature(c_variadic)]
-
 // While 1-ZST are currently ignored on most ABIs, we don't guarantee that, and it's UB to
 // rely on it.
 

src/tools/miri/tests/fail/c-variadic-mismatch-count.rs

@@ -1,5 +1,3 @@
-#![feature(c_variadic)]
-
 unsafe extern "C" fn helper(_: i32, _: ...) {}
 
 fn main() {

src/tools/miri/tests/fail/c-variadic-mismatch.rs

@@ -1,5 +1,3 @@
-#![feature(c_variadic)]
-
 unsafe extern "C" fn helper(_: i32, _: ...) {}
 
 fn main() {

src/tools/miri/tests/fail/c-variadic.rs

@@ -1,5 +1,3 @@
-#![feature(c_variadic)]
-
 fn read_too_many() {
     unsafe extern "C" fn variadic(mut ap: ...) {
         ap.next_arg::<i32>(); //~ERROR: more C-variadic arguments read than were passed

src/tools/miri/tests/pass/both_borrows/c_variadics.rs

@@ -1,7 +1,6 @@
 //@revisions: stack tree tree_implicit_writes
 //@[tree_implicit_writes]compile-flags: -Zmiri-tree-borrows -Zmiri-tree-borrows-implicit-writes
 //@[tree]compile-flags: -Zmiri-tree-borrows
-#![feature(c_variadic)]
 
 fn main() {
     unsafe extern "C" fn write_with_first_arg(ptr_to_val: *mut i32, _hidden_mut_ref_to_val: ...) {

src/tools/miri/tests/pass/c-variadic.rs

@@ -1,5 +1,4 @@
 //@run-native
-#![feature(c_variadic)]
 
 use std::ffi::{CStr, VaList, c_char, c_double, c_int, c_long};
 

tests/assembly-llvm/c-variadic/aarch64.rs

@@ -12,7 +12,7 @@
 //@ [AARCH64_MSVC] needs-llvm-components: aarch64
 //@ [ARM64EC_MSVC] compile-flags: -Copt-level=3 --target arm64ec-pc-windows-msvc
 //@ [ARM64EC_MSVC] needs-llvm-components: aarch64
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/arm.rs

@@ -5,7 +5,6 @@
 //@ ignore-android
 #![no_std]
 #![crate_type = "lib"]
-#![feature(c_variadic)]
 
 // Check that the assembly that rustc generates matches what clang emits. This example in particular
 // is related to https://github.com/rust-lang/rust/pull/144549 and shows the effect of us correctly

tests/assembly-llvm/c-variadic/avr.rs

@@ -4,7 +4,7 @@
 //@ revisions: AVR
 //@ [AVR] compile-flags: -Copt-level=3 --target=avr-none -Ctarget-cpu=atmega328p
 //@ [AVR] needs-llvm-components: avr
-#![feature(c_variadic, c_variadic_experimental_arch, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(c_variadic_experimental_arch, no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/gpu.rs

@@ -7,7 +7,7 @@
 //@ [AMDGPU] needs-llvm-components: amdgpu
 //@ [NVPTX] compile-flags: --crate-type=rlib --target=nvptx64-nvidia-cuda
 //@ [NVPTX] needs-llvm-components: nvptx
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/mips.rs

@@ -6,7 +6,7 @@
 //@ [MIPS] compile-flags: -Copt-level=3 --target mips-unknown-linux-gnu
 //@ [MIPS64] compile-flags: -Copt-level=3 --target mipsisa64r6-unknown-linux-gnuabi64
 //@ [MIPS64EL] compile-flags: -Copt-level=3 --target mips64el-unknown-linux-gnuabi64
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs, asm_experimental_arch)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs, asm_experimental_arch)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/powerpc.rs

@@ -10,7 +10,7 @@
 //@ [POWERPC64LE] needs-llvm-components: powerpc
 //@ [AIX] compile-flags: -Copt-level=3 --target powerpc64-ibm-aix
 //@ [AIX] needs-llvm-components: powerpc
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/riscv.rs

@@ -6,7 +6,7 @@
 //@ [RISCV32] needs-llvm-components: riscv
 //@ [RISCV64] compile-flags: -Copt-level=3 --target riscv64gc-unknown-linux-gnu
 //@ [RISCV64] needs-llvm-components: riscv
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/s390x.rs

@@ -3,7 +3,7 @@
 //
 //@ compile-flags: -Copt-level=3 --target s390x-unknown-linux-gnu
 //@ needs-llvm-components: systemz
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/sparc.rs

@@ -6,7 +6,7 @@
 //@ [SPARC] needs-llvm-components: sparc
 //@ [SPARC64] compile-flags: -Copt-level=3 --target sparc64-unknown-linux-gnu
 //@ [SPARC64] needs-llvm-components: sparc
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs, asm_experimental_arch)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs, asm_experimental_arch)]
 #![cfg_attr(target_arch = "sparc", feature(c_variadic_experimental_arch))]
 #![no_core]
 #![crate_type = "lib"]

tests/assembly-llvm/c-variadic/wasm.rs

@@ -6,7 +6,7 @@
 //@ [WASM32] needs-llvm-components: webassembly
 //@ [WASM64] compile-flags: -Copt-level=3 -Zmerge-functions=disabled --target wasm64-unknown-unknown
 //@ [WASM64] needs-llvm-components: webassembly
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/x86-linux.rs

@@ -11,7 +11,7 @@
 //@ [I686] compile-flags: -Copt-level=3 -Cllvm-args=-x86-asm-syntax=intel
 //@ [I686] compile-flags: --target i686-unknown-linux-gnu
 //@ [I686] needs-llvm-components: x86
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/x86_64-windows.rs

@@ -8,7 +8,7 @@
 //@ [WINDOWS_MSVC] compile-flags: -Copt-level=3 -Cllvm-args=-x86-asm-syntax=intel
 //@ [WINDOWS_MSVC] compile-flags: --target x86_64-pc-windows-msvc
 //@ [WINDOWS_MSVC] needs-llvm-components: x86
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/assembly-llvm/c-variadic/xtensa.rs

@@ -5,7 +5,7 @@
 //@ revisions: XTENSA
 //@ [XTENSA] compile-flags: -Copt-level=3 --target xtensa-esp32-none-elf
 //@ [XTENSA] needs-llvm-components: xtensa
-#![feature(c_variadic, no_core, lang_items, intrinsics, rustc_attrs)]
+#![feature(no_core, lang_items, intrinsics, rustc_attrs)]
 #![no_core]
 #![crate_type = "lib"]
 

tests/codegen-llvm/c-variadic-lifetime.rs

@@ -1,6 +1,5 @@
 //@ add-minicore
 //@ compile-flags: -Copt-level=3
-#![feature(c_variadic)]
 #![crate_type = "lib"]
 
 // Check that `%args` explicitly has its lifetime start and end. Being explicit can improve