gh-130567: Fix crash in locale.strxfrm() on macOS

Author: serhiy-storchaka

Lib/test/test_locale.py

@@ -351,8 +351,7 @@ def setUp(self):
         enc = codecs.lookup(locale.getencoding() or 'ascii').name
         if enc not in ('utf-8', 'iso8859-1', 'cp1252'):
             raise unittest.SkipTest('encoding not suitable')
-        if enc != 'iso8859-1' and (sys.platform == 'darwin' or is_android or
-                                   sys.platform.startswith('freebsd')):
+        if enc != 'iso8859-1' and is_android:
             raise unittest.SkipTest('wcscoll/wcsxfrm have known bugs')
         BaseLocalizedTest.setUp(self)
 
@@ -372,6 +371,21 @@ def test_strcoll_with_diacritic(self):
     def test_strxfrm_with_diacritic(self):
         self.assertLess(locale.strxfrm('à'), locale.strxfrm('b'))
 
+    # @unittest.skipUnless(sys.platform == 'darwin',
+    #                  "only macOS")
+    def test_xxx(self):
+        bad = []
+        for c in map(chr, range(1, 0x1000)):
+            if c.isprintable():
+                for n in range(8):
+                    x = 'a'*n + c
+                    s = locale.strxfrm(x)
+                    if '\1' in s and s.index('\1') < len(x):
+                        bad += c
+                        print(f'{x!r} {x!a} -> {s!a}')
+                        break
+        self.fail(repr(''.join(bad)))
+
 
 class NormalizeTest(unittest.TestCase):
     def check(self, localename, expected):

Modules/_localemodule.c

@@ -457,7 +457,7 @@ _locale_strxfrm_impl(PyObject *module, PyObject *str)
 
     /* assume no change in size, first */
     n1 = n1 + 1;
-    buf = PyMem_New(wchar_t, n1);
+    buf = PyMem_New(wchar_t, n1+1);
     if (!buf) {
         PyErr_NoMemory();
         goto exit;