Revert r88639 (the optimization changes behaviour and breaks buildbots)

Lib/ctypes/test/test_loading.py

@@ -102,12 +102,5 @@ class LoaderTest(unittest.TestCase):
             # This is the real test: call the function via 'call_function'
             self.assertEqual(0, call_function(proc, (None,)))
 
-    if os.name != "nt":
-        def test_libc_exists(self):
-            # A basic test that the libc is found by find_library()
-            # XXX Can this fail on some non-Windows systems?
-            self.assertTrue(libc_name)
-            self.assertTrue(os.path.exists(libc_name))
-
 if __name__ == "__main__":
     unittest.main()

Lib/ctypes/util.py

@@ -203,17 +203,13 @@ elif os.name == "posix":
             abi_type = mach_map.get(machine, 'libc6')
 
             # XXX assuming GLIBC's ldconfig (with option -p)
-            name = 'lib%s' % name
-            pat = re.compile('\s*(/[^\(\)\s]*%s\.[^\(\)\s]*)' % re.escape(name))
+            expr = r'(\S+)\s+\((%s(?:, OS ABI:[^\)]*)?)\)[^/]*(/[^\(\)\s]*lib%s\.[^\(\)\s]*)' \
+                   % (abi_type, re.escape(name))
             with contextlib.closing(os.popen('LC_ALL=C LANG=C /sbin/ldconfig -p 2>/dev/null')) as f:
-                for line in f:
-                    if not '=>' in line:
-                        continue
-                    path = line.rsplit('=>', 1)[1]
-                    if not name+'.' in path:
-                        continue
-                    res = pat.search(path)
-                    if res:
+                data = f.read()
+            res = re.search(expr, data)
+            if not res:
+                return None
             return res.group(1)
 
         def find_library(name):

Misc/ACKS

@@ -329,7 +329,6 @@ Dag Gruneau
 Michael Guravage
 Lars Gustäbel
 Thomas Güttler
-Jonas H.
 Barry Haddow
 Paul ten Hagen
 Rasmus Hahn

Misc/NEWS

@@ -35,9 +35,6 @@ Core and Builtins
 Library
 -------
 
-- Issue #11258: Speed up ctypes.util.find_library() under Linux a lot.  Patch
-  by Jonas H.
-
 - Issue #11297: Add collections.ChainMap().
 
 - Issue #10755: Add the posix.fdlistdir() function.  Patch by Ross Lagerwall.