Yes, that is a perfect example of buggy compiler handling of undefined behaviour. A non-buggy compiler would either behave in a manner chacteristic of the environment (ie read address array+i), ignore the situation entirely (which also results in reading array+i), or (preferably) issue a error to the effect of "possible array access out of bounds, suggest 'assert(i<10);' here".
Yes, that is a perfect example of buggy compiler handling of undefined behaviour. A non-buggy compiler would either behave in a manner chacteristic of the environment (ie read address array+i), ignore the situation entirely (which also results in reading array+i), or (preferably) issue a error to the effect of "possible array access out of bounds, suggest 'assert(i<10);' here".