Use rustc_std_internal_symbol instead of linkage = "weak"

Author: madsmtm

compiler/rustc_symbol_mangling/src/v0.rs

@@ -82,13 +82,16 @@ pub(super) fn mangle<'tcx>(
 }
 
 pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> String {
-    if item_name == "rust_eh_personality" {
+    match item_name {
         // rust_eh_personality must not be renamed as LLVM hard-codes the name
-        return "rust_eh_personality".to_owned();
-    } else if item_name == "__rust_no_alloc_shim_is_unstable" {
+        "rust_eh_personality" => return item_name.to_owned(),
         // Temporary back compat hack to give people the chance to migrate to
         // include #[rustc_std_internal_symbol].
-        return "__rust_no_alloc_shim_is_unstable".to_owned();
+        "__rust_no_alloc_shim_is_unstable" => return item_name.to_owned(),
+        // Apple availability symbols need to not be mangled to be usable by
+        // C/Objective-C code.
+        "__isPlatformVersionAtLeast" | "__isOSVersionAtLeast" => return item_name.to_owned(),
+        _ => {}
     }
 
     let prefix = "_R";

library/std/src/sys/platform_version/darwin/public_extern.rs

@@ -71,7 +71,10 @@ use super::{current_version, pack_u32_os_version};
 // SAFETY: The signature is the same as what Clang expects, and we export weakly to allow linking
 // both this and `libclang_rt.*.a`, similar to how `compiler-builtins` does it:
 // https://github.com/rust-lang/compiler-builtins/blob/0.1.113/src/macros.rs#L494
-#[cfg_attr(not(feature = "compiler-builtins-mangled-names"), unsafe(no_mangle), linkage = "weak")]
+//
+// NOTE: This symbol has a workaround in the compiler's symbol mangling to avoid mangling it, while
+// still not exposing it from non-cdylib (like `#[no_mangle]` would).
+#[rustc_std_internal_symbol]
 // extern "C" is correct, Clang assumes the function cannot unwind:
 // https://github.com/llvm/llvm-project/blob/llvmorg-20.1.0/clang/lib/CodeGen/CGObjC.cpp#L3980
 //
@@ -139,7 +142,7 @@ pub(super) extern "C" fn __isPlatformVersionAtLeast(
 
 /// Old entry point for availability. Used when compiling with older Clang versions.
 // SAFETY: Same as for `__isPlatformVersionAtLeast`.
-#[cfg_attr(not(feature = "compiler-builtins-mangled-names"), unsafe(no_mangle), linkage = "weak")]
+#[rustc_std_internal_symbol]
 pub(super) extern "C" fn __isOSVersionAtLeast(major: u32, minor: u32, subminor: u32) -> i32 {
     let version = pack_u32_os_version(major, minor, subminor);
     (version <= current_version()) as i32