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

Author: serhiy-storchaka

Lib/test/test_locale.py

@@ -372,6 +372,16 @@ def test_strcoll_with_diacritic(self):
     def test_strxfrm_with_diacritic(self):
         self.assertLess(locale.strxfrm('à'), locale.strxfrm('b'))
 
+    def test_xxx(self):
+        bad = []
+        for c in map(chr, range(1, 0x3000)):
+            if c.isprintable():
+                s = locale.strxfrm(c)
+                if '\1' in s:
+                    bad += c
+                    print(f'{c!r} {c!a} -> {s!a}')
+        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;