Re: operator==

From:

"Daniel T." <daniel_t@earthlink.net>

Newsgroups:

comp.lang.c++

Date:

Tue, 14 Dec 2010 07:46:29 -0500

Message-ID:

<daniel_t-C0E0F1.07462914122010@70-3-168-216.pools.spcsdns.net>

Andrea Crotti <andrea.crotti.0@gmail.com> wrote:

Is it possible in theory to force the subclasses to have an operator==?

Yes. If the base class doesn't have an op== or that op== is otherwise
inaccessible, then in order for users of the derived classes to compare
objects, an op== will need to be defined.

It is not possible to force them to have an op== if one is not needed
however.

Now I wanted to define a generic == operator, and supposing Packet is
the superclass and fields:
std::vector<Serializable *> fields;

In serializable I also have defined
virtual bool operator==(const Serializable& other) { return false; }

So here it is

An important note, assuming that "Packet" is a subclass of
"Serializable," the function below is not an override of the function
above.

bool Packet::operator==(const Packet& other) const
{
    for (size_t i=0; i < fields.size(); ++i) {
        if (! ((*fields[i]) == (*other.fields[i]))) {
            return false;
        }
    }
    return true;
}

and it doesn't work unfortunately.
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ba6830 in Packet::operator== (this=0x7fffffffd070, other=...) at
src/Packet.cpp:22
22 if (! ((*fields[i]) == (*other.fields[i]))) {

the fields of the other object should be also set to correct memory
addresses, and thus it should be fine.
What could be wrong in this?

You likely have an invalid dereference going on. The problem with your
code is probably not in the above function.