Issue #17928: Fix test_structmembers on 64-bit big-endian machines.

(_testcapi isn't Py_ssize_t-clean, the "s#" code should use an int for length)

Misc/NEWS

@@ -97,6 +97,8 @@ Library
 Tests
 -----
 
+- Issue #17928: Fix test_structmembers on 64-bit big-endian machines.
+
 - Issue #17883: Fix buildbot testing of Tkinter on Windows.
   Patch by Zachary Ware.
 

Modules/_testcapimodule.c

@@ -1813,7 +1813,7 @@ test_structmembers_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
         ;
     test_structmembers *ob;
     const char *s = NULL;
-    Py_ssize_t string_len = 0;
+    int string_len = 0;
     ob = PyObject_New(test_structmembers, type);
     if (ob == NULL)
         return NULL;