# cppcoreguidelines-special-member-functions¶

The check finds classes where some but not all of the special member functions are defined.

By default the compiler defines a copy constructor, copy assignment operator, move constructor, move assignment operator and destructor. The default can be suppressed by explicit user-definitions. The relationship between which functions will be suppressed by definitions of other functions is complicated and it is advised that all five are defaulted or explicitly defined.

Note that defining a function with = delete is considered to be a definition.

This rule is part of the “Constructors, assignments, and destructors” profile of the C++ Core Guidelines, corresponding to rule C.21. See

## Options¶

AllowSoleDefaultDtor

When set to 1 (default is 0), this check doesn’t flag classes with a sole, explicitly defaulted destructor. An example for such a class is:

struct A {
virtual ~A() = default;
};

AllowMissingMoveFunctions

When set to 1 (default is 0), this check doesn’t flag classes which define no move operations at all. It still flags classes which define only one of either move constructor or move assignment operator. With this option enabled, the following class won’t be flagged:

struct A {
A(const A&);
A& operator=(const A&);
~A();
}