diff -r 69ecc87571ac Lib/test/test_posixpath.py
--- a/Lib/test/test_posixpath.py	Sun Mar 20 18:34:24 2011 +0100
+++ b/Lib/test/test_posixpath.py	Sun Mar 20 12:52:06 2011 -0700
@@ -309,6 +309,30 @@
                 safe_rmdir(ABSTFN + "/k")
                 safe_rmdir(ABSTFN)
 
+        def test_realpath_bug11397(self):
+            # Bug #11397: realpath() fails to return the correct real path of
+            # some tree of symlinks.
+            try:
+                old_path = abspath('.')
+                os.mkdir(ABSTFN)
+                os.chdir(ABSTFN)
+                os.mkdir(ABSTFN + '/a')
+                os.symlink('../a', 'a/blink')
+                os.makedirs(ABSTFN + '/a/c/d')
+                os.symlink('a/c/d/..', 'xlink')         # xlink -> /a/c
+                os.symlink('xlink/../blink', 'zlink')   # zlink -> /a/blink -> /a
+
+                self.assertEqual(realpath('zlink'), ABSTFN + '/a')
+            finally:
+                os.chdir(old_path)
+                test_support.unlink(ABSTFN + '/zlink')
+                test_support.unlink(ABSTFN + '/xlink')
+                test_support.unlink(ABSTFN + '/a/blink')
+                safe_rmdir(ABSTFN + '/a/c/d')
+                safe_rmdir(ABSTFN + '/a/c')
+                safe_rmdir(ABSTFN + '/a')
+                safe_rmdir(ABSTFN)
+
     def test_relpath(self):
         (real_getcwd, os.getcwd) = (os.getcwd, lambda: r"/home/user/bar")
         try: