Rollup merge of #123967 - RalfJung:static_mut_refs, r=Nilstrieb

static_mut_refs: use raw pointers to remove the remaining FIXME Using `SyncUnsafeCell` would not make a lot of sense IMO.
rust-lang · Apr 20, 2024 · ccd9880 · ccd9880
2 parents e9e936c + b4a4645
commit ccd9880
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Showing 3 changed files with 15 additions and 11 deletions.
diff --git a/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs b/compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs
@@ -1,4 +1,13 @@
-#![feature(no_core, lang_items, never_type, linkage, extern_types, thread_local, repr_simd)]
+#![feature(
+    no_core,
+    lang_items,
+    never_type,
+    linkage,
+    extern_types,
+    thread_local,
+    repr_simd,
+    raw_ref_op
+)]
 #![no_core]
 #![allow(dead_code, non_camel_case_types, internal_features)]
 
@@ -112,9 +121,7 @@ fn start<T: Termination + 'static>(
 
 static mut NUM: u8 = 6 * 7;
 
-// FIXME: Use `SyncUnsafeCell` instead of allowing `static_mut_refs` lint
-#[allow(static_mut_refs)]
-static NUM_REF: &'static u8 = unsafe { &NUM };
+static NUM_REF: &'static u8 = unsafe { &*&raw const NUM };
 
 unsafe fn zeroed<T>() -> T {
     let mut uninit = MaybeUninit { uninit: () };

diff --git a/compiler/rustc_codegen_gcc/example/mini_core_hello_world.rs b/compiler/rustc_codegen_gcc/example/mini_core_hello_world.rs
@@ -2,7 +2,7 @@
 
 #![feature(
     no_core, unboxed_closures, start, lang_items, never_type, linkage,
-    extern_types, thread_local
+    extern_types, thread_local, raw_ref_op
 )]
 #![no_core]
 #![allow(dead_code, internal_features, non_camel_case_types)]
@@ -99,9 +99,7 @@ fn start<T: Termination + 'static>(
 
 static mut NUM: u8 = 6 * 7;
 
-// FIXME: Use `SyncUnsafeCell` instead of allowing `static_mut_refs` lint
-#[allow(static_mut_refs)]
-static NUM_REF: &'static u8 = unsafe { &NUM };
+static NUM_REF: &'static u8 = unsafe { &* &raw const NUM };
 
 macro_rules! assert {
     ($e:expr) => {

diff --git a/library/std/src/sys/thread_local/static_local.rs b/library/std/src/sys/thread_local/static_local.rs
@@ -11,8 +11,6 @@ pub macro thread_local_inner {
     (@key $t:ty, const $init:expr) => {{
         #[inline] // see comments below
         #[deny(unsafe_op_in_unsafe_fn)]
-        // FIXME: Use `SyncUnsafeCell` instead of allowing `static_mut_refs` lint
-        #[allow(static_mut_refs)]
         unsafe fn __getit(
             _init: $crate::option::Option<&mut $crate::option::Option<$t>>,
         ) -> $crate::option::Option<&'static $t> {
@@ -25,7 +23,8 @@ pub macro thread_local_inner {
             // FIXME(#84224) this should come after the `target_thread_local`
             // block.
             static mut VAL: $t = INIT_EXPR;
-            unsafe { $crate::option::Option::Some(&VAL) }
+            // SAFETY: we only ever create shared references, so there's no mutable aliasing.
+            unsafe { $crate::option::Option::Some(&*$crate::ptr::addr_of!(VAL)) }
         }
 
         unsafe {