gh-157899: added iOS as supported platform for calling os.readlink with a FD referring to a symlink.

Also some code/test cleanup.

Author: OOTS

Doc/library/os.rst

@@ -2802,11 +2802,11 @@ features:
    This function can also support :ref:`paths relative to directory descriptors
    <dir_fd>`.
 
-   On Linux, Android and macOS, *path* can also be a file descriptor referring
+   On Linux, Android, macOS and iOS, *path* can also be a file descriptor referring
    to a symbolic link. In that case, *dir_fd* must be ``None``.
    (On Linux and Android, such a file descriptor must be obtained through
    :func:`os.open` with ``os.O_RDONLY | os.O_PATH | os.O_NOFOLLOW``.
-   On macOS, :func:`os.open` must be called with
+   On macOS and iOS, :func:`os.open` must be called with
    ``os.O_RDONLY | os.O_SYMLINK``.)
    On other operating systems, a ``NotImplementedError`` is raised if *path*
    is an integer.
@@ -2840,7 +2840,7 @@ features:
 
    .. versionchanged:: next
       Accepts file descriptors pointing to symbolic links as *path* on
-      Linux, Android and macOS.
+      Linux, Android, macOS and iOS.
 
 .. function:: remove(path, *, dir_fd=None)
 

Doc/whatsnew/3.16.rst

@@ -547,7 +547,7 @@ os
   (Contributed by Md Arif in :gh:`152936`.)
 
 * :func:`os.readlink` now accepts a file descriptor referring to a symlink on
-  Linux, Android and macOS.
+  Linux, Android, macOS and iOS.
   (Contributed by OOTS in :gh:`157899`.)
 
 

Lib/test/test_os/test_posix.py

@@ -1882,19 +1882,16 @@ def test_readlink_dir_fd(self):
             self.assertEqual(posix.readlink(name, dir_fd=dir_fd), 'symlink')
 
 
-    _support_readlink_with_fd = hasattr(os, 'readlink') and (
-        "HAVE_FREADLINK" in posix._have_functions  # macOS
-        or (
-            os.readlink in os.supports_dir_fd
-            and sys.platform in ["linux", "android"]
-        )
+    _support_readlink_with_fd = (
+        hasattr(os, 'readlink') \
+        and os.readlink in os.supports_fd
     )
 
     def _open_symlink_as_fd(self, path):
         open_flags = os.O_RDONLY
-        if hasattr(os, "O_SYMLINK"):  # macOS
+        if hasattr(os, "O_SYMLINK"):  # macOS/iOS
             open_flags |= os.O_SYMLINK
-        elif hasattr(os, "O_NOFOLLOW") and hasattr(os, "O_PATH"):  # Linux
+        elif hasattr(os, "O_NOFOLLOW") and hasattr(os, "O_PATH"):  # Linux/Android
             open_flags |= os.O_NOFOLLOW | os.O_PATH
         else:
             self.fail("lacking open flags for this test")
@@ -1947,9 +1944,10 @@ def test_readlink_with_fd_throws_not_implemented_error(self):
         with self.assertRaises(NotImplementedError):
             os.readlink(fd)
 
-    @unittest.skipUnless(hasattr(os, "readlink"), "needs os.readlink")
-    def test_readlink_is_in_supports_fd_on_supported_platforms(self):
-        self.assertEqual(os.readlink in os.supports_fd, self._support_readlink_with_fd)
+    @unittest.skipUnless(sys.platform in ["linux", "android", "darwin", "ios"],
+                         "feature not supported on this platform")
+    def test_readlink_is_marked_as_supports_fd(self):
+        self.assertIn(os.readlink, os.supports_fd)
 
     @unittest.skipUnless(os.rename in os.supports_dir_fd, "test needs dir_fd support in os.rename()")
     def test_rename_dir_fd(self):

Misc/NEWS.d/next/Library/2026-09-21-14-41-07.gh-issue-157899.s6vBQC.rst

@@ -1,2 +1,2 @@
 :func:`os.readlink` now accepts a file descriptor referring to a
-symlink on Linux, Android and macOS.
+symlink on Linux, Android, macOS and iOS.

Modules/clinic/posixmodule.c.h

@@ -505,7 +505,7 @@ static const unsigned int _Py_STATX_KNOWN = (STATX_BASIC_STATS | STATX_BTIME
 #  define HAVE_UNLINKAT_RUNTIME __builtin_available(macOS 10.10, iOS 8.0, *)
 #  define HAVE_OPENAT_RUNTIME __builtin_available(macOS 10.10, iOS 8.0, *)
 #  define HAVE_READLINKAT_RUNTIME __builtin_available(macOS 10.10, iOS 8.0, *)
-#  define HAVE_FREADLINK_RUNTIME __builtin_available(macOS 13.0, *)
+#  define HAVE_FREADLINK_RUNTIME __builtin_available(macOS 13.0, iOS 16.0, *)
 #  define HAVE_SYMLINKAT_RUNTIME __builtin_available(macOS 10.10, iOS 8.0, *)
 #  define HAVE_FUTIMENS_RUNTIME __builtin_available(macOS 10.13, iOS 11.0, tvOS 11.0, watchOS 4.0, *)
 #  define HAVE_UTIMENSAT_RUNTIME __builtin_available(macOS 10.13, iOS 11.0, tvOS 11.0, watchOS 4.0, *)
@@ -11009,22 +11009,13 @@ that directory.
 dir_fd may not be implemented on your platform.  If it is unavailable,
 using it will raise a NotImplementedError.
 
-On Linux, Android and macOS, path may be a file descriptor referring to
-a symlink. If it is, dir_fd must be None, and the return value will be a
-string object. (File descriptors for symlinks can be obtained with
-
-    os.open(..., os.O_RDONLY | os.O_PATH | os.O_NOFOLLOW)
-
-on Linux and Android, and:
-
-    os.open(..., os.O_RDONLY | os.O_SYMLINK)
-
-on macOS.)
+On Linux, Android, macOS and iOS, path may be a file descriptor
+referring to a symlink. If it is, dir_fd must be None.
 [clinic start generated code]*/
 
 static PyObject *
 os_readlink_impl(PyObject *module, path_t *path, int dir_fd)
-/*[clinic end generated code: output=d21b732a2e814030 input=14546747b3db62f6]*/
+/*[clinic end generated code: output=d21b732a2e814030 input=d90bddfeee86f673]*/
 {
 #if defined(HAVE_READLINK)
     char buffer[MAXPATHLEN+1];
@@ -11079,10 +11070,12 @@ os_readlink_impl(PyObject *module, path_t *path, int dir_fd)
     }
     buffer[length] = '\0';
 
-    if (path->is_fd || PyUnicode_Check(path->object))
+    if (path->is_fd || PyUnicode_Check(path->object)) {
         return PyUnicode_DecodeFSDefaultAndSize(buffer, length);
-    else
+    }
+    else {
         return PyBytes_FromStringAndSize(buffer, length);
+    }
 #elif defined(MS_WINDOWS)
     DWORD n_bytes_returned;
     DWORD io_result = 0;

Modules/posixmodule.c

@@ -5578,6 +5578,7 @@ AC_CHECK_FUNCS([ \
   wait wait3 wait4 waitid waitpid wcscoll wcsftime wcsxfrm wmemcmp writev \
 ])
 
+PY_CHECK_FUNC_PRIVATE([freadlink], [@%:@include <unistd.h>])
 PY_CHECK_FUNC_PRIVATE([strerror_r], [@%:@include <string.h>])
 
 
@@ -5600,7 +5601,6 @@ fi
 # raise an error if used at runtime. Force these symbols off.
 if test "$ac_sys_system" != "iOS" ; then
   AC_CHECK_FUNCS([dup3 getentropy getgroups pipe2 system])
-  PY_CHECK_FUNC_PRIVATE([freadlink], [@%:@include <unistd.h>])
 fi
 
 AC_CHECK_DECL([dirfd],