Resource lifetime management can be problematic. Martin Janzen reminds us how important destructors are and when to be mindful of their limitations.

Live and Let Die

By Martin Janzen

From the article:

Most experienced C++ programmers will agree that one of the best properties of our language is the ability to manage object lifecycles using constructors and destructors.

Bjarne Stroustrup [Stroustrup19] has described ctor/dtor pairs as one of C++’s most elegant features, giving us the ability to create clean types which tidy up after themselves, with predictable performance, minimal overhead, and no need for garbage collection.

In this year’s ACCU Conference Lightning Talks, Nico Josuttis singled out destructors as (spoiler alert!) “the most important C++ feature” [Josuttis23]; and Wiktor Klonowski told a sad tale of time wasted debugging a .NET program that kept running out of ports, a fate which could have been avoided by the use of dtors [Klonowski23].

At the same conference, as well as at the recent C++ On Sea, numerous speakers talked about C++ and safety, a subject that’s been very much in the news recently [NSA22], with C++ predictably receiving a lot of flak for the ease with which one can write code containing buffer overflows, memory leaks, and of course a rich and varied choice of ways to introduce undefined behaviour (UB).

In its favour, though, C++ also provides at least one way in which we can improve safety, and reliability, greatly, by use of the powerful RAII (Resource Acquisition is Initialisation) idiom: taking ownership of a resource in the ctor, then releasing it in the dtor.