After some playing with gdb I found that in printtup() there is a non null
attribute with typeinfo->attrs[i]->atttypid = 0 (invalid oid). Unfortunately
attibutes with invalid type are neither printed nor marked as null, and this
explains why psql doesn't get all the expected data.
So I made this patch to printtup():
Marc G. Fournier
3067ac8e77