Readd Macos x86-64 remove_dir_all() special case using dynamic symbols.

Author: hkratz

library/std/src/sys/unix/fs.rs

@@ -1475,11 +1475,7 @@ mod remove_dir_impl {
 }
 
 // Modern implementation using openat(), unlinkat() and fdopendir()
-#[cfg(not(any(
-    all(target_os = "macos", target_arch = "x86_64"),
-    target_os = "redox",
-    target_os = "espidf"
-)))]
+#[cfg(not(any(target_os = "redox", target_os = "espidf")))]
 mod remove_dir_impl {
     use super::{cstr, lstat, Dir, DirEntry, InnerReadDir, ReadDir};
     use crate::ffi::CStr;
@@ -1489,8 +1485,39 @@ mod remove_dir_impl {
     use crate::path::{Path, PathBuf};
     use crate::sync::Arc;
     use crate::sys::{cvt, cvt_r};
+
+    #[cfg(not(all(target_os = "macos", target_arch = "x86_64"),))]
     use libc::{fdopendir, openat, unlinkat};
 
+    #[cfg(all(target_os = "macos", target_arch = "x86_64"))]
+    mod macos_weak {
+        use crate::sys::weak::weak;
+        use libc::{c_char, c_int, DIR};
+
+        pub unsafe fn openat(dirfd: c_int, pathname: *const c_char, flags: c_int) -> c_int {
+            weak!(fn openat(c_int, *const c_char, c_int) -> c_int);
+            openat.get().unwrap()(dirfd, pathname, flags)
+        }
+
+        pub unsafe fn fdopendir(fd: c_int) -> *mut DIR {
+            weak!(fn fdopendir(c_int) -> *mut DIR, "fdopendir$INODE64");
+            fdopendir.get().unwrap()(fd)
+        }
+
+        pub unsafe fn unlinkat(dirfd: c_int, pathname: *const c_char, flags: c_int) -> c_int {
+            weak!(fn unlinkat(c_int, *const c_char, c_int) -> c_int);
+            unlinkat.get().unwrap()(dirfd, pathname, flags)
+        }
+
+        pub fn has_openat() -> bool {
+            weak!(fn openat(c_int, *const c_char, c_int) -> c_int);
+            openat.get().is_some()
+        }
+    }
+
+    #[cfg(all(target_os = "macos", target_arch = "x86_64"))]
+    use macos_weak::{fdopendir, openat, unlinkat};
+
     pub fn openat_nofollow_dironly(parent_fd: Option<RawFd>, p: &CStr) -> io::Result<OwnedFd> {
         let fd = cvt_r(|| unsafe {
             openat(
@@ -1629,7 +1656,7 @@ mod remove_dir_impl {
         }
     }
 
-    pub fn remove_dir_all(p: &Path) -> io::Result<()> {
+    fn remove_dir_all_modern(p: &Path) -> io::Result<()> {
         // We cannot just call remove_dir_all_loop() here because that would not delete a passed
         // symlink. No need to worry about races, because remove_dir_all_loop() does not descend
         // into symlinks.
@@ -1640,4 +1667,20 @@ mod remove_dir_impl {
             remove_dir_all_loop(p)
         }
     }
+
+    #[cfg(not(all(target_os = "macos", target_arch = "x86_64")))]
+    pub fn remove_dir_all(p: &Path) -> io::Result<()> {
+        remove_dir_all_modern(p)
+    }
+
+    #[cfg(all(target_os = "macos", target_arch = "x86_64"))]
+    pub fn remove_dir_all(p: &Path) -> io::Result<()> {
+        if macos_weak::has_openat() {
+            // openat() is available with macOS 10.10+, just like unlinkat() and fdopendir()
+            remove_dir_all_modern(p)
+        } else {
+            // fall back to classic implementation
+            crate::sys_common::fs::remove_dir_all(p)
+        }
+    }
 }