py: De-optimise some uses of mp_getiter, so they don't use the C stack.

In these cases the heap is anyway used to create a new object so no real
need to use the C stack for iterating.  It saves a few bytes of code size.

py/objarray.c

@@ -141,8 +141,7 @@ STATIC mp_obj_t array_construct(char typecode, mp_obj_t initializer) {
 
     mp_obj_array_t *array = array_new(typecode, len);
 
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iterable = mp_getiter(initializer, &iter_buf);
+    mp_obj_t iterable = mp_getiter(initializer, NULL);
     mp_obj_t item;
     size_t i = 0;
     while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {

py/objdict.c

@@ -250,8 +250,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(dict_copy_obj, dict_copy);
 
 // this is a classmethod
 STATIC mp_obj_t dict_fromkeys(size_t n_args, const mp_obj_t *args) {
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iter = mp_getiter(args[1], &iter_buf);
+    mp_obj_t iter = mp_getiter(args[1], NULL);
     mp_obj_t value = mp_const_none;
     mp_obj_t next = MP_OBJ_NULL;
 
@@ -377,12 +376,10 @@ STATIC mp_obj_t dict_update(size_t n_args, const mp_obj_t *args, mp_map_t *kwarg
             }
         } else {
             // update from a generic iterable of pairs
-            mp_obj_iter_buf_t iter_buf;
-            mp_obj_t iter = mp_getiter(args[1], &iter_buf);
+            mp_obj_t iter = mp_getiter(args[1], NULL);
             mp_obj_t next = MP_OBJ_NULL;
             while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
-                mp_obj_iter_buf_t inner_iter_buf;
-                mp_obj_t inneriter = mp_getiter(next, &inner_iter_buf);
+                mp_obj_t inneriter = mp_getiter(next, NULL);
                 mp_obj_t key = mp_iternext(inneriter);
                 mp_obj_t value = mp_iternext(inneriter);
                 mp_obj_t stop = mp_iternext(inneriter);

py/objlist.c

@@ -60,8 +60,7 @@ STATIC void list_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t k
 }
 
 STATIC mp_obj_t list_extend_from_iter(mp_obj_t list, mp_obj_t iterable) {
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iter = mp_getiter(iterable, &iter_buf);
+    mp_obj_t iter = mp_getiter(iterable, NULL);
     mp_obj_t item;
     while ((item = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
         mp_obj_list_append(list, item);

py/objset.c

@@ -129,8 +129,7 @@ STATIC mp_obj_t set_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_
         default: { // can only be 0 or 1 arg
             // 1 argument, an iterable from which we make a new set
             mp_obj_t set = mp_obj_new_set(0, NULL);
-            mp_obj_iter_buf_t iter_buf;
-            mp_obj_t iterable = mp_getiter(args[0], &iter_buf);
+            mp_obj_t iterable = mp_getiter(args[0], NULL);
             mp_obj_t item;
             while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
                 mp_obj_set_store(set, item);
@@ -235,8 +234,7 @@ STATIC mp_obj_t set_diff_int(size_t n_args, const mp_obj_t *args, bool update) {
         if (self == other) {
             set_clear(self);
         } else {
-            mp_obj_iter_buf_t iter_buf;
-            mp_obj_t iter = mp_getiter(other, &iter_buf);
+            mp_obj_t iter = mp_getiter(other, NULL);
             mp_obj_t next;
             while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
                 set_discard(self, next);
@@ -273,8 +271,7 @@ STATIC mp_obj_t set_intersect_int(mp_obj_t self_in, mp_obj_t other, bool update)
     mp_obj_set_t *self = MP_OBJ_TO_PTR(self_in);
     mp_obj_set_t *out = MP_OBJ_TO_PTR(mp_obj_new_set(0, NULL));
 
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iter = mp_getiter(other, &iter_buf);
+    mp_obj_t iter = mp_getiter(other, NULL);
     mp_obj_t next;
     while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
         if (mp_set_lookup(&self->set, next, MP_MAP_LOOKUP)) {
@@ -414,8 +411,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_2(set_remove_obj, set_remove);
 STATIC mp_obj_t set_symmetric_difference_update(mp_obj_t self_in, mp_obj_t other_in) {
     check_set(self_in);
     mp_obj_set_t *self = MP_OBJ_TO_PTR(self_in);
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iter = mp_getiter(other_in, &iter_buf);
+    mp_obj_t iter = mp_getiter(other_in, NULL);
     mp_obj_t next;
     while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
         mp_set_lookup(&self->set, next, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND_OR_REMOVE_IF_FOUND);
@@ -434,8 +430,7 @@ STATIC mp_obj_t set_symmetric_difference(mp_obj_t self_in, mp_obj_t other_in) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(set_symmetric_difference_obj, set_symmetric_difference);
 
 STATIC void set_update_int(mp_obj_set_t *self, mp_obj_t other_in) {
-    mp_obj_iter_buf_t iter_buf;
-    mp_obj_t iter = mp_getiter(other_in, &iter_buf);
+    mp_obj_t iter = mp_getiter(other_in, NULL);
     mp_obj_t next;
     while ((next = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
         mp_set_lookup(&self->set, next, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);

py/objtuple.c

@@ -82,8 +82,7 @@ STATIC mp_obj_t mp_obj_tuple_make_new(const mp_obj_type_t *type_in, size_t n_arg
             size_t len = 0;
             mp_obj_t *items = m_new(mp_obj_t, alloc);
 
-            mp_obj_iter_buf_t iter_buf;
-            mp_obj_t iterable = mp_getiter(args[0], &iter_buf);
+            mp_obj_t iterable = mp_getiter(args[0], NULL);
             mp_obj_t item;
             while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
                 if (len >= alloc) {

py/runtime.c

@@ -745,8 +745,7 @@ void mp_call_prepare_args_n_kw_var(bool have_self, size_t n_args_n_kw, const mp_
         // get the keys iterable
         mp_obj_t dest[3];
         mp_load_method(kw_dict, MP_QSTR_keys, dest);
-        mp_obj_iter_buf_t iter_buf;
-        mp_obj_t iterable = mp_getiter(mp_call_method_n_kw(0, 0, dest), &iter_buf);
+        mp_obj_t iterable = mp_getiter(mp_call_method_n_kw(0, 0, dest), NULL);
 
         mp_obj_t key;
         while ((key = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
@@ -877,8 +876,7 @@ void mp_unpack_ex(mp_obj_t seq_in, size_t num_in, mp_obj_t *items) {
         // items destination array, then the rest to a dynamically created list.  Once the
         // iterable is exhausted, we take from this list for the right part of the items.
         // TODO Improve to waste less memory in the dynamically created list.
-        mp_obj_iter_buf_t iter_buf;
-        mp_obj_t iterable = mp_getiter(seq_in, &iter_buf);
+        mp_obj_t iterable = mp_getiter(seq_in, NULL);
         mp_obj_t item;
         for (seq_len = 0; seq_len < num_left; seq_len++) {
             item = mp_iternext(iterable);