std: allow weak in item position on Apple platforms

Author: joboet

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

@@ -284,9 +284,9 @@ impl FileDesc {
         super::weak::weak!(fn preadv(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
 
         match preadv.get() {
-            Some(preadv) => {
+            Some(read) => {
                 let ret = cvt(unsafe {
-                    preadv(
+                    read(
                         self.as_raw_fd(),
                         bufs.as_mut_ptr() as *mut libc::iovec as *const libc::iovec,
                         cmp::min(bufs.len(), max_iov()) as libc::c_int,
@@ -477,9 +477,9 @@ impl FileDesc {
         super::weak::weak!(fn pwritev(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
 
         match pwritev.get() {
-            Some(pwritev) => {
+            Some(read) => {
                 let ret = cvt(unsafe {
-                    pwritev(
+                    read(
                         self.as_raw_fd(),
                         bufs.as_ptr() as *const libc::iovec,
                         cmp::min(bufs.len(), max_iov()) as libc::c_int,

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

@@ -62,15 +62,16 @@ 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>,