From 8979b3d9f6906c51eeec82210aa07b755cb1c9bc Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Mon, 11 Nov 2024 10:27:44 -0800
Subject: [PATCH] Make unsafe extern conditional on compiler version

---
 impl/build.rs           | 6 ++++++
 impl/src/declaration.rs | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/impl/build.rs b/impl/build.rs
index 872296c..beeea10 100644
--- a/impl/build.rs
+++ b/impl/build.rs
@@ -12,6 +12,12 @@ fn main() {
 
     if rustc >= 80 {
         println!("cargo:rustc-check-cfg=cfg(exhaustive)");
+        println!("cargo:rustc-check-cfg=cfg(no_unsafe_extern_blocks)");
+    }
+
+    if rustc < 82 {
+        // https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#safe-items-with-unsafe-extern
+        println!("cargo:rustc-cfg=no_unsafe_extern_blocks");
     }
 }
 
diff --git a/impl/src/declaration.rs b/impl/src/declaration.rs
index 03c403a..e9117c4 100644
--- a/impl/src/declaration.rs
+++ b/impl/src/declaration.rs
@@ -113,6 +113,12 @@ pub fn expand(input: TokenStream) -> TokenStream {
     let link_section_macro_str = format!("_linkme_macro_{}", ident);
     let link_section_macro = Ident::new(&link_section_macro_str, call_site);
 
+    let unsafe_extern = if cfg!(no_unsafe_extern_blocks) {
+        None
+    } else {
+        Some(Token![unsafe](call_site))
+    };
+
     quote! {
         #(#attrs)*
         #vis static #ident: #linkme_path::DistributedSlice<#ty> = {
@@ -129,7 +135,7 @@ pub fn expand(input: TokenStream) -> TokenStream {
                 target_os = "openbsd",
                 target_os = "psp",
             ))]
-            unsafe extern "Rust" {
+            #unsafe_extern extern "Rust" {
                 #[cfg_attr(any(target_os = "none", target_os = "linux", target_os = "android", target_os = "fuchsia", target_os = "psp"), link_name = #linux_section_start)]
                 #[cfg_attr(any(target_os = "macos", target_os = "ios", target_os = "tvos"), link_name = #macho_section_start)]
                 #[cfg_attr(target_os = "illumos", link_name = #illumos_section_start)]