Question

I is possible that QBuffer::open(OpenMode mode) ever returns false? Here is implementation:

bool QBuffer::open(OpenMode flags)
{
    Q_D(QBuffer);

    if ((flags & Append) == Append)
        flags |= WriteOnly;
    setOpenMode(flags);
    if (!(isReadable() || isWritable())) {
        qWarning("QFile::open: File access not specified");
        return false;
    }

    if ((flags & QIODevice::Truncate) == QIODevice::Truncate) {
        d->buf->resize(o);
    }
    if ((flags & QIODevice::Append) == QIODevice::Append) // append to end of buffer
        seek(d->buf->size());
    else
        seek(o);

    return true;
}

bool QIODevice::isReadable() const
{
    return (openMode() & ReadOnly) != 0;
}

bool QIODevice::isWritable() const
{
    return (openMode() & WriteOnly) != 0;
}

I would say no. I am making this research so my flexLint code analysis won’t create new kind of warning.

Answer 1

It can return false if you don’t give it the right flags. Calling QBuffer::open(QIODevice::Text), for example, would fail since that does not specify read or write mode. Apart from that, it will always return true.