stabilize extern_system_varargs

compiler/rustc_abi/src/extern_abi.rs

@@ -269,10 +269,8 @@ impl ExternAbi {
             | Self::Aapcs { .. }
             | Self::Win64 { .. }
             | Self::SysV64 { .. }
-            | Self::EfiApi => CVariadicStatus::Stable,
-            Self::System { .. } => {
-                CVariadicStatus::Unstable { feature: rustc_span::sym::extern_system_varargs }
-            }
+            | Self::EfiApi
+            | Self::System { .. } => CVariadicStatus::Stable,
             _ => CVariadicStatus::NotSupported,
         }
     }

compiler/rustc_feature/src/accepted.rs

@@ -215,6 +215,8 @@ declare_features! (
     (accepted, extern_crate_self, "1.34.0", Some(56409)),
     /// Allows access to crate names passed via `--extern` through prelude.
     (accepted, extern_prelude, "1.30.0", Some(44660)),
+    /// Allows using `system` as a calling convention with varargs.
+    (accepted, extern_system_varargs, "CURRENT_RUSTC_VERSION", Some(136946)),
     /// Allows using F16C intrinsics from `core::arch::{x86, x86_64}`.
     (accepted, f16c_target_feature, "1.68.0", Some(44839)),
     /// Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.

compiler/rustc_feature/src/unstable.rs

@@ -498,8 +498,6 @@ declare_features! (
     (incomplete, explicit_tail_calls, "1.72.0", Some(112788)),
     /// Allows using `#[export_stable]` which indicates that an item is exportable.
     (incomplete, export_stable, "1.88.0", Some(139939)),
-    /// Allows using `system` as a calling convention with varargs.
-    (unstable, extern_system_varargs, "1.86.0", Some(136946)),
     /// Allows defining `extern type`s.
     (unstable, extern_types, "1.23.0", Some(43467)),
     /// Allow using 128-bit (quad precision) floating point numbers.

tests/codegen-llvm/cffi/c-variadic-ffi.rs

@@ -14,7 +14,6 @@
 //@[arm32] needs-llvm-components: arm
 #![crate_type = "lib"]
 #![feature(no_core)]
-#![feature(extern_system_varargs)]
 #![no_core]
 
 extern crate minicore;

tests/ui/feature-gates/feature-gate-extern_system_varargs.rs

@@ -1,7 +0,0 @@
-fn system(f: extern "system" fn(usize, ...)) {
-    //~^  ERROR unstable
-
-    f(22, 44);
-}
-
-fn main() {}

tests/ui/feature-gates/feature-gate-extern_system_varargs.stderr

@@ -1,13 +0,0 @@
-error[E0658]: C-variadic functions with the "system" calling convention are unstable
-  --> $DIR/feature-gate-extern_system_varargs.rs:1:14
-   |
-LL | fn system(f: extern "system" fn(usize, ...)) {
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #136946 <https://github.com/rust-lang/rust/issues/136946> for more information
-   = help: add `#![feature(extern_system_varargs)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0658`.