Question

I have the following code:

bool operator==(const Inc::CReminderItem& Item1, const Inc::CReminderItem& Item2)
{
    bool bDate = false, bDesc = false, bInfo = false, bWeekday = false;

    if(Item1.m_Date == Item2.m_Date)
        bDate = true;
    if(Item1.m_strDescription == Item2.m_strDescription)
        bDesc = true;
    if(Item1.m_strInfoShort == Item2.m_strInfoShort)
        bInfo = true;
    if(Item1.m_nWeekday == Item2.m_nWeekday)
        bWeekday = true;

    return(bDate && bDesc && bInfo && bWeekday);
}

bool operator!=(const Inc::CReminderItem& Item1, const Inc::CReminderItem& Item2)
{
    return !(Item1 == Item2);    // <<--- ambiguous here!
}

both operators are declared as friend operators in the class.

the error is:

error C2593: ‘operator ==’ is
ambiguous

I am not sure, why it is ambiguous O_o and how to fix this.
Any help is greatly appreciated:)

Answer 1

First, if it is “ambiguous”, I would expect other operator== to be
present somewhere. But it’s hard to say what any particular compiler is
really trying to tell you with it’s error messages.

Second, you really don’t show enough code for anyone to say what is
wrong. There are a number of possible errors: the class where the
friend is declared and these definitions are in different namespaces,
the signature of the friend is subtly different, etc. If Inc is
a namespace, these operators must be in Inc as well. Otherwise,
you’ve declared an operator== in Inc in the friend declaration, and
an operator== in global namespace here. Both are considered, which
results in an ambiguity.

(The way I usually handle this is to define a member function,
isEqual, and have both operator== and operator!= call it. That
way, there’s no need for the friend declaration.)