let new_sz = new_size.checked_add(cur_sz.unwrap());
if new_sz == None { return Err(AllocatorError::TooLargeDimensions); }
new_size = new_sz.unwrap();
let new_sz = new_size.checked_add(cur_sz.unwrap());
if new_sz == None { return Err(AllocatorError::TooLargeDimensions); }
new_size = new_sz.unwrap();