that is bug?

[kdevel]

On Saturday, 7 April 2018 at 10:25:19 UTC, bauss wrote:
> On Saturday, 7 April 2018 at 09:07:48 UTC, sdvcn wrote:
>>
>>         true?stt="AA":stt="BB";    <<<<-----///Out:BB
>
> It's an UB.
>
> Not a bug.

Why UB? stt is only modified once.