remove faulthandler._read_null()

Reading from NULL is an undefined behavior and `faulthandler`
should not check for low-level C about undefined behaviors.

Author: picnixz

Lib/test/test_faulthandler.py

@@ -166,29 +166,6 @@ def check_windows_exception(self, code, line_number, name_regex, **kw):
         fatal_error = 'Windows fatal exception: %s' % name_regex
         self.check_error(code, line_number, fatal_error, **kw)
 
-    @unittest.skipIf(sys.platform.startswith('aix'),
-                     "the first page of memory is a mapped read-only on AIX")
-    def test_read_null(self):
-        if not MS_WINDOWS:
-            self.check_fatal_error("""
-                import faulthandler
-                faulthandler.enable()
-                faulthandler._read_null()
-                """,
-                3,
-                # Issue #12700: Read NULL raises SIGILL on Mac OS X Lion
-                '(?:Segmentation fault'
-                    '|Bus error'
-                    '|Illegal instruction)')
-        else:
-            self.check_windows_exception("""
-                import faulthandler
-                faulthandler.enable()
-                faulthandler._read_null()
-                """,
-                3,
-                'access violation')
-
     @skip_segfault_on_android
     def test_sigsegv(self):
         self.check_fatal_error("""

Modules/faulthandler.c

@@ -1069,17 +1069,6 @@ faulthandler_suppress_crash_report(void)
 #endif
 }
 
-static PyObject*
-faulthandler_read_null(PyObject *self, PyObject *Py_UNUSED(args))
-{
-    volatile int *x;
-    volatile int y;
-
-    faulthandler_suppress_crash_report();
-    x = NULL;
-    y = *x;
-    return PyLong_FromLong(y);
-}
 
 static void
 faulthandler_raise_sigsegv(void)
@@ -1304,10 +1293,6 @@ static PyMethodDef module_methods[] = {
                "Unregister the handler of the signal "
                "'signum' registered by register().")},
 #endif
-    {"_read_null", faulthandler_read_null, METH_NOARGS,
-     PyDoc_STR("_read_null($module, /)\n--\n\n"
-               "Read from NULL, raise "
-               "a SIGSEGV or SIGBUS signal depending on the platform.")},
     {"_sigsegv", faulthandler_sigsegv, METH_VARARGS,
      PyDoc_STR("_sigsegv($module, release_gil=False, /)\n--\n\n"
                "Raise a SIGSEGV signal.")},