rust-lang · folkertdev · Jun 27, 2026
diff --git a/compiler/rustc_ast_lowering/src/stability.rs b/compiler/rustc_ast_lowering/src/stability.rs
@@ -70,6 +70,7 @@ pub fn extern_abi_stability(abi: ExternAbi) -> Result<(), UnstableAbi> {
         ExternAbi::Rust
         | ExternAbi::C { .. }
         | ExternAbi::Cdecl { .. }
+        | ExternAbi::Custom
         | ExternAbi::Stdcall { .. }
         | ExternAbi::Fastcall { .. }
         | ExternAbi::Thiscall { .. }
@@ -144,9 +145,6 @@ pub fn extern_abi_stability(abi: ExternAbi) -> Result<(), UnstableAbi> {
             feature: sym::cmse_nonsecure_entry,
             explain: GateReason::Experimental,
         }),
-        ExternAbi::Custom => {
-            Err(UnstableAbi { abi, feature: sym::abi_custom, explain: GateReason::Experimental })
-        }
         ExternAbi::Swift => {
             Err(UnstableAbi { abi, feature: sym::abi_swift, explain: GateReason::Experimental })
         }

diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
@@ -46,6 +46,8 @@ declare_features! (
 
     /// Allows `#[target_feature(...)]` on aarch64 platforms
     (accepted, aarch64_target_feature, "1.61.0", Some(44839)),
+    /// Allows `extern "custom" fn()`.
+    (accepted, abi_custom, "CURRENT_RUSTC_VERSION", Some(140829)),
     /// Allows using the `efiapi` ABI.
     (accepted, abi_efiapi, "1.68.0", Some(65815)),
     /// Allows the sysV64 ABI to be specified on all platforms

diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
@@ -372,8 +372,6 @@ declare_features! (
     (unstable, abi_avr_interrupt, "1.45.0", Some(69664)),
     /// Allows `extern "cmse-nonsecure-call" fn()`.
     (unstable, abi_cmse_nonsecure_call, "1.90.0", Some(81391)),
-    /// Allows `extern "custom" fn()`.
-    (unstable, abi_custom, "1.89.0", Some(140829)),
     /// Allows `extern "gpu-kernel" fn()`.
     (unstable, abi_gpu_kernel, "1.86.0", Some(135467)),
     /// Allows `extern "msp430-interrupt" fn()`.

diff --git a/library/compiler-builtins/compiler-builtins/src/lib.rs b/library/compiler-builtins/compiler-builtins/src/lib.rs
@@ -1,6 +1,5 @@
 #![cfg_attr(feature = "compiler-builtins", compiler_builtins)]
 #![cfg_attr(all(target_family = "wasm"), feature(wasm_numeric_instr))]
-#![feature(abi_custom)]
 #![feature(abi_unadjusted)]
 #![feature(asm_experimental_arch)]
 #![feature(cfg_target_has_atomic)]

diff --git a/src/doc/unstable-book/src/compiler-flags/instrument-mcount.md b/src/doc/unstable-book/src/compiler-flags/instrument-mcount.md
@@ -38,7 +38,6 @@ The following example can be compiled with `-Zinstrument-mcount=yes` or `-Zinstr
 
 ```rust
 #![feature(instrument_fn)]
-#![feature(abi_custom)]
 
 fn main() {
     // Ensure all the early startup occurs before attempting to call this trivial, single-threaded

diff --git a/tests/ui/abi/bad-custom.rs b/tests/ui/abi/bad-custom.rs
@@ -1,7 +1,6 @@
 //@ edition: 2021
 //@ check-fail
 //@ needs-asm-support
-#![feature(abi_custom)]
 
 #[unsafe(naked)]
 extern "custom" fn must_be_unsafe(a: i64) -> i64 {