Marc Mutz wrote in his recent article about the properties of default constructed object as required by Elements of Programming.

Stepanov-Regularity and Partially-Formed Objects vs. C++ Value Types

by Marc Mutz

From the article:

In this article, I will take a look at one of the fundamental concepts introduced in Alex Stepanov and Paul McJones’ seminal book “Elements of Programming” (EoP for short) — that of a (Semi-)Regular Type and Partially-Formed State.

Using these, I shall try to derive rules for C++ implementations of what are commonly called “value types”, focusing on the bare essentials, as I feel they have not been addressed in sufficient depth up to now: Special Member Functions.