Comments

objc2/src/macros.rs

@@ -76,6 +76,9 @@ macro_rules! sel {
             #[used]
             static _IMAGE_TAG: [u32; 2] = [0, 0];
 
+            // Marked with `unnamed_addr` in Objective-C's LLVM.
+            // See rust-lang/rust#18297
+            // Should only be an optimization (?)
             #[link_section = "__TEXT,__objc_methname,cstring_literals"]
             #[export_name = concat!("\x01L_OBJC_METH_VAR_NAME_", $crate::__proc_macros::hash_idents!($($idents)+))]
             static NAME: [u8; X.len()] = {
@@ -89,6 +92,8 @@ macro_rules! sel {
             };
 
             // Place the constant value in the correct section.
+            //
+            // Clang uses `no_dead_strip` here for some reason?
             #[link_section = "__DATA,__objc_selrefs,literal_pointers"]
             #[export_name = concat!("\x01L_OBJC_SELECTOR_REFERENCES_", $crate::__proc_macros::hash_idents!($($idents)+))]
             static mut REF: &[u8; X.len()] = &NAME;
@@ -97,6 +102,9 @@ macro_rules! sel {
             // loaded, so we need to use a volatile read to prevent the
             // optimizer from thinking it can circumvent the read through REF.
             //
+            // Clang avoids this by marking `REF` with LLVM's
+            // `externally_initialized`.
+            //
             // TODO: `::core` here could be replaced with some more
             // sophisticated logic so we don't rely on downstream users having
             // this setup.