decoding the illegal string 'GGW' does not throw an exception

[euneuber]

The string 'GGW' contains only valid chars but cannot be decoded. This should also throw an exception and not return an empty string.

[chris-baumann-at]

The string "GGW" is not "illegal", as it consists of chars of the charset. And it decodes to two chr(0x00).
So it works as designed/defined.
But it possibly is senseless to decode a string which will never be the result of an encoding.