getarg.patch fixes STORE_SIZE macro used in convertsimple(). If the input size is bigger than INT_MAX, it raises an OverflowError("size does not fit in an int") and calls converterr() which expected="".

The value of expected is useless because converterr() is only used to notice that an error occured. I think that return msgbuf instead of calling converterr() would be enough, but I don't know this code very well and so i copied the code used to raise an OverflowError for the 'b' format.