std: allow weak in item position on Apple platforms

Author: joboet

library/std/src/sys/pal/unix/weak.rs

@@ -63,15 +63,16 @@ impl<F: Copy> ExternWeak<F> {
 }
 
 pub(crate) macro dlsym {
-    (fn $name:ident($($t:ty),*) -> $ret:ty) => (
-         dlsym!(fn $name($($t),*) -> $ret, stringify!($name));
+    ($v:vis fn $name:ident($($t:ty),*) -> $ret:ty) => (
+        dlsym!($v fn $name($($t),*) -> $ret, stringify!($name));
     ),
-    (fn $name:ident($($t:ty),*) -> $ret:ty, $sym:expr) => (
-        static DLSYM: DlsymWeak<unsafe extern "C" fn($($t),*) -> $ret> =
+    ($v:vis fn $name:ident($($t:ty),*) -> $ret:ty, $sym:expr) => (
+        #[allow(non_upper_case_globals)]
+        $v static $name: DlsymWeak<unsafe extern "C" fn($($t),*) -> $ret> =
             DlsymWeak::new(concat!($sym, '\0'));
-        let $name = &DLSYM;
     )
 }
+
 pub(crate) struct DlsymWeak<F> {
     name: &'static str,
     func: AtomicPtr<libc::c_void>,