bpo-39943: Properly const the pointers in dictkeys_get_index (GH-19170)

Author: petdance

Objects/dictobject.c

@@ -331,27 +331,27 @@ dictkeys_decref(PyDictKeysObject *dk)
 
 /* lookup indices.  returns DKIX_EMPTY, DKIX_DUMMY, or ix >=0 */
 static inline Py_ssize_t
-dictkeys_get_index(PyDictKeysObject *keys, Py_ssize_t i)
+dictkeys_get_index(const PyDictKeysObject *keys, Py_ssize_t i)
 {
     Py_ssize_t s = DK_SIZE(keys);
     Py_ssize_t ix;
 
     if (s <= 0xff) {
-        int8_t *indices = (int8_t*)(keys->dk_indices);
+        const int8_t *indices = (const int8_t*)(keys->dk_indices);
         ix = indices[i];
     }
     else if (s <= 0xffff) {
-        int16_t *indices = (int16_t*)(keys->dk_indices);
+        const int16_t *indices = (const int16_t*)(keys->dk_indices);
         ix = indices[i];
     }
 #if SIZEOF_VOID_P > 4
     else if (s > 0xffffffff) {
-        int64_t *indices = (int64_t*)(keys->dk_indices);
+        const int64_t *indices = (const int64_t*)(keys->dk_indices);
         ix = indices[i];
     }
 #endif
     else {
-        int32_t *indices = (int32_t*)(keys->dk_indices);
+        const int32_t *indices = (const int32_t*)(keys->dk_indices);
         ix = indices[i];
     }
     assert(ix >= DKIX_DUMMY);