Deleted copy constructor results in deleted default constructor

c++, c++11, deleted-functions

Solution

C++11 §12.1/5 states:

A default constructor for a class `X` is a constructor of class `X` that can be called without an argument. If there is no user-declared constructor for class `X`, a constructor having no parameters is implicitly declared as defaulted (8.4).

Your `Base(const Base&) = delete;` counts as a user-declared constructor, so it suppresses generation of the implicit default constructor. The workaround is of course to declare it:

Base() = default;

Problem

This code will not compile with gcc 4.7.0: ``` class Base { public: Base(const Base&) = delete; }; class Derived : Base { public: Derived(int i) : m_i(i) {} int m_i; }; ``` The error is: ``` c.cpp: In constructor `Derived::Derived(int)´: c.cpp:10:24: error: no matching function for call to `Base::Base()´ c.cpp:10:24: note: candidate is: c.cpp:4:2: note: Base::Base(const Base&) <deleted> c.cpp:4:2: note: candidate expects 1 argument, 0 provided ``` In other words, the compiler does not generate a default constructor for the base class, and instead tries to call the deleted copy constructor as the only available overload. Is that normal behavior?

Original source