import uctypes

# Find the size corresponding to a pointer
ptr_size = uctypes.sizeof((uctypes.PTR, uctypes.INT8))
assert ptr_size in (4, 8)
UINTPTR = uctypes.UINT64 if ptr_size == 8 else uctypes.UINT32

# This descriptor lets us store an address via val then dereference it via ptr
descr = {
    'ptr': (uctypes.PTR | 0, uctypes.INT8),
    'val': UINTPTR | 0
}

# Build the data. `x.ptr` points at b2.
b1 = bytearray(uctypes.sizeof(descr))
b2 = bytearray(8)
x = uctypes.struct(uctypes.addressof(b1), descr)
x.val = uctypes.addressof(b2)

# Optimization: avoid rebuilding the `x.ptr` struct object
# (this has no influence over the bug)
ptr = x.ptr

# Access the data...
print("Setting via uctypes ptr, reading via bytearray")
for i in range(8):
    ptr[i] = i
for i in range(8):
    print(b2[i], end=" ")
    #assert ptr[i] == i ## Assertion fails!
print()

print("Setting via bytearray, reading via ptr")
for i in range(8):
    b2[i] = 10 + i
for i in range(8):
    print(ptr[i], end=" ")
    assert ptr[i] == 10 + i
print()

         } else if (agg_type == PTR) {
             byte *p = *(void **)self->addr;
             if (mp_obj_is_small_int(t->items[1])) {
                 uint val_type = GET_TYPE(MP_OBJ_SMALL_INT_VALUE(t->items[1]), VAL_TYPE_BITS);
-                return get_aligned(val_type, p, index);
+                if (value == MP_OBJ_SENTINEL) {
+                    return get_aligned(val_type, p, index);
+                } else {
+                    set_aligned(val_type, p, index, value);
+                    return value; // just !MP_OBJ_NULL
+                }