Fix watchOS and visionOS for pread64 and pwrite64 calls

Author: simlay

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

@@ -208,6 +208,7 @@ impl FileDesc {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "watchos",
+        target_os = "visionos",
     )))]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
         io::default_read_vectored(|b| self.read_at(b, offset), bufs)
@@ -249,6 +250,7 @@ impl FileDesc {
         target_os = "tvos", // tvos 14.0
         target_os = "macos", // macos 11.0
         target_os = "watchos", // watchos 7.0
+        target_os = "visionos", // visionos 1.0
     ))]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
         super::weak::weak!(fn preadv64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);
@@ -367,6 +369,7 @@ impl FileDesc {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "watchos",
+        target_os = "visionos",
     )))]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
         io::default_write_vectored(|b| self.write_at(b, offset), bufs)
@@ -408,6 +411,7 @@ impl FileDesc {
         target_os = "tvos", // tvos 14.0
         target_os = "macos", // macos 11.0
         target_os = "watchos", // watchos 7.0
+        target_os = "visionos", // visionos 1.0
     ))]
     pub fn write_vectored_at(&self, bufs: &[IoSlice<'_>], offset: u64) -> io::Result<usize> {
         super::weak::weak!(fn pwritev64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);

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

@@ -28,7 +28,8 @@ use crate::ptr;
 use crate::sync::atomic::{self, AtomicPtr, Ordering};
 
 // We can use true weak linkage on ELF targets.
-#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "tvos")))]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos",
+            target_os = "visionos")))]
 pub(crate) macro weak {
     (fn $name:ident($($t:ty),*) -> $ret:ty) => (
         let ref $name: ExternWeak<unsafe extern "C" fn($($t),*) -> $ret> = {
@@ -43,7 +44,8 @@ pub(crate) macro weak {
 }
 
 // On non-ELF targets, use the dlsym approximation of weak linkage.
-#[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos"))]
+#[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos",
+        target_os = "visionos"))]
 pub(crate) use self::dlsym as weak;
 
 pub(crate) struct ExternWeak<F: Copy> {