C++ Primer Plus

Smart Pointer Considerations

Why three smart pointers? (Actually, there are four, but we won’t discuss weak_ptr.) And why is auto_ptr being deprecated?

Begin by considering assignment:

auto_ptr<string> ps (new string("I reigned lonely as a cloud."));auto_ptr<string> vocation;vocation = ps;

What should the assignment statement accomplish? If ps and vocation were ordinary pointers, the result would be two pointers pointing to the same string object. That is not acceptable here because the program would wind up attempting to delete the same object twice—once when ps expires, and once when vocation expires. There are ways to avoid this problem:

• Define the assignment operator so that it makes a deep copy. This results in two pointers pointing to ...