C / C++ / MFC

George_George wrote:

This question is what I learned that swap could be used to design and implement an exception safe assignment operator.

George_George wrote:

I think you are well known about how to use swap to implement exception safe assignment opeator from your replies. Could you help to correct my code please?

George_George wrote:

Let us wait for other MVP's reply.

A temp;
temp = a;
a = *this;
*this = temp;

toxcct wrote:

that's how swap is normally designed.

toxcct wrote:

however, there's a lack in this design, because having a A::operator=() calling a A::swap() function, which itself calls A::operator=() 3 more times is recursive for sure, with no possibility to stop the loop.

so I think swap is not coded like this in B. Stroustrup's example...

George_George wrote:

I agree that there is some issue in my code.

George_George wrote:

It is appreciated if you could provide some pseudo code to correct my code to implement the using swap technique to implement a exception safe assignment operator.

A& A::operator=(const A& other)
{
	A temp(other);
	swap(temp);
	return *this;
}

toxcct wrote:

hey, you want an exception safe copy ?

backup your object,

toxcct wrote:

Yes. but I believe that the state of the parameter only may throw an exception, if its state is corrupted.

toxcct wrote:

so if a is OK, then swapping it with this would be OK too...

George_George wrote:

We are talking about the state of current object instance (this object), why you are talking about the state of parameter?

toxcct wrote:

1) because : if the state of the parameter is corrupted, the state of the current object could have been corrupted too. but as long as we're assigning a temporary object first, the current object's assignment is exception-safe !