[3.13] gh-137273: Fix debug assertion failure in locale.setlocale() on Windows (GH-137300) (GH-137306)

It happened when there were at least 16 characters after dot in the
locale name.
(cherry picked from commit 718e0c89ba)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Modules/_localemodule.c

@@ -87,6 +87,41 @@ copy_grouping(const char* s)
     return result;
 }
 
+#if defined(MS_WINDOWS)
+
+// 16 is the number of elements in the szCodePage field
+// of the __crt_locale_strings structure.
+#define MAX_CP_LEN 15
+
+static int
+check_locale_name(const char *locale, const char *end)
+{
+    size_t len = end ? (size_t)(end - locale) : strlen(locale);
+    const char *dot = memchr(locale, '.', len);
+    if (dot && locale + len - dot - 1 > MAX_CP_LEN) {
+        return -1;
+    }
+    return 0;
+}
+
+static int
+check_locale_name_all(const char *locale)
+{
+    const char *start = locale;
+    while (1) {
+        const char *end = strchr(start, ';');
+        if (check_locale_name(start, end) < 0) {
+            return -1;
+        }
+        if (end == NULL) {
+            break;
+        }
+        start = end + 1;
+    }
+    return 0;
+}
+#endif
+
 /*[clinic input]
 _locale.setlocale
 
@@ -111,6 +146,18 @@ _locale_setlocale_impl(PyObject *module, int category, const char *locale)
                         "invalid locale category");
         return NULL;
     }
+    if (locale) {
+        if ((category == LC_ALL
+             ? check_locale_name_all(locale)
+             : check_locale_name(locale, NULL)) < 0)
+        {
+            /* Debug assertion failure on Windows.
+             * _Py_BEGIN_SUPPRESS_IPH/_Py_END_SUPPRESS_IPH do not help. */
+            PyErr_SetString(get_locale_state(module)->Error,
+                "unsupported locale setting");
+            return NULL;
+        }
+    }
 #endif
 
     if (locale) {