Empty QBitArray behaves badly.

QBitArray a;
a.resize (0);
qDebug () << a.count () << a.count (true) << a.count (false);

void QBitArray::resize(int size)
{
    if (!size) {
        d.resize(0); /* QByteArray is resized to 0 */
....
}

int QBitArray::count(bool on) const
{
    int numBits = 0;
    int len = size();
    const quint8 *bits = reinterpret_cast<const quint8 *>(d.data()) + 1;  
   /* bits now points past the end of allocated memory */
.......

    while (len >= 0) {
        if (bits[len / 8] & (1 << ((len - 1) & 7)))  /* here we access some unknown memory */
            ++numBits;
        --len;
    }

    return on ? numBits : size() - numBits;
}