Address review

* Optimize also "P" format
* Test also "m != m"
* Handle native formats such as "@b"

Author: vstinner

Lib/test/test_memoryview.py

@@ -584,17 +584,20 @@ def test_compare_equal(self):
                 a = array.array(int_format, [1, 2, 3])
                 m = memoryview(a)
                 self.assertTrue(m == m)
+                self.assertFalse(m != m)
 
         for float_format in 'fd':
             with self.subTest(format=int_format):
                 a = array.array(float_format, [1.0, 2.0, float('nan')])
                 m = memoryview(a)
                 # nan is not equal to nan
                 self.assertFalse(m == m)
+                self.assertTrue(m != m)
 
                 a = array.array(float_format, [1.0, 2.0, 3.0])
                 m = memoryview(a)
                 self.assertTrue(m == m)
+                self.assertFalse(m != m)
 
 
 class BytesMemorySliceTest(unittest.TestCase,

Objects/memoryobject.c

@@ -3131,9 +3131,12 @@ memory_richcompare(PyObject *v, PyObject *w, int op)
         int can_compare_ptr;
         const char *format = vv->format;
         if (format != NULL) {
+            if (*format == '@') {
+                format++;
+            }
             // Include only formats known by struct, exclude formats "d" (double),
-            // "f" (float), "e" (16-bit float) and "P" (void*)
-            can_compare_ptr = (strchr("bBchHiIlLnNqQ?", format[0]) != NULL
+            // "f" (float), "e" (16-bit float)
+            can_compare_ptr = (strchr("bBchHiIlLnNPqQ?", format[0]) != NULL
                                && format[1] == 0);
         }
         else {