What is the name of this C++ functionality?

Question

I was writing some C++ code and mistakenly omitted the name of a function WSASocket. However, my compiler did not raise an error and associated my SOCKET with the integer value 1 instead of a valid socket.

The code in question should have looked like this:

this->listener = WSASocket(address->ai_family, address->ai_socktype, address->ai_protocol, NULL, NULL, WSA_FLAG_OVERLAPPED); 

But instead, it looked like this:

this->listener = (address->ai_family, address->ai_socktype, address->ai_protocol, NULL, NULL, WSA_FLAG_OVERLAPPED); 

Coming from other languages, this looks like it may be some kind of anonymous type. What is the name of the feature, in the case it is really a feature?

What is its purpose?

It's difficult to search for it, when you don't know where to begin.

Answer 1

The comma operator† evaluates the left hand side, discards its value, and as a result yields the right hand side. WSA_FLAG_OVERLAPPED is 1, and that is the result of the expression; all the other values are discarded. No socket is ever created.

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† Unless overloaded. Yes, it can be overloaded. No, you should not overload it. Step away from the keyboard, right now!

Answer 2

The comma operator is making sense of your code.

You are effectively setting this->listener = WSA_FLAG_OVERLAPPED; which just happens to be syntatically valid.