Closes #1446

CppCoreGuidelines.md

@@ -1,6 +1,6 @@
 # <a name="main"></a>C++ Core Guidelines
 
-May 2, 2019
+June 16, 2019
 
 
 Editors:
@@ -6305,6 +6305,7 @@ Worse, a direct or indirect call to an unimplemented pure virtual function from
         virtual void f() = 0;   // not implemented
         virtual void g();       // implemented with Base version
         virtual void h();       // implemented with Base version
+        virtual ~Base();        // implemented with Base version
     };
 
     class Derived : public Base {
@@ -6977,8 +6978,6 @@ It's simple and clear:
 * `override` means exactly and only "this is a non-final overrider."
 * `final` means exactly and only "this is a final overrider."
 
-If a base class destructor is declared `virtual`, one should avoid declaring derived class destructors  `virtual` or `override`. Some code base and tools might insist on `override` for destructors, but that is not the recommendation of these guidelines.
-
 ##### Example, bad
 
     struct B {
@@ -7260,7 +7259,7 @@ Copying a polymorphic class is discouraged due to the slicing problem, see [C.67
     class B {
     public:
         virtual owner<B*> clone() = 0;
-        virtual ~B() = 0;
+        virtual ~B() = default;
 
         B(const B&) = delete;
         B& operator=(const B&) = delete;
@@ -7269,7 +7268,7 @@ Copying a polymorphic class is discouraged due to the slicing problem, see [C.67
     class D : public B {
     public:
         owner<D*> clone() override;
-        virtual ~D() override;
+        ~D() override;
     };
 
 Generally, it is recommended to use smart pointers to represent ownership (see [R.20](#Rr-owner)). However, because of language rules, the covariant return type cannot be a smart pointer: `D::clone` can't return a `unique_ptr<D>` while `B::clone` returns `unique_ptr<B>`. Therefore, you either need to consistently return `unique_ptr<B>` in all overrides, or use `owner<>` utility from the [Guidelines Support Library](#SS-views).
@@ -7545,6 +7544,7 @@ Without a using declaration, member functions in the derived class hide the enti
     public:
         virtual int f(int i) { std::cout << "f(int): "; return i; }
         virtual double f(double d) { std::cout << "f(double): "; return d; }
+        virtual ~B() = default;
     };
     class D: public B {
     public:
@@ -7632,6 +7632,7 @@ That can cause confusion: An overrider does not inherit default arguments.
     class Base {
     public:
         virtual int multiply(int value, int factor = 2) = 0;
+        virtual ~Base() = default;
     };
 
     class Derived : public Base {
@@ -7659,7 +7660,7 @@ If you have a class with a virtual function, you don't (in general) know which c
 
 ##### Example
 
-    struct B { int a; virtual int f(); };
+    struct B { int a; virtual int f(); virtual ~B() = default };
     struct D : B { int b; int f() override; };
 
     void use(B b)
@@ -7702,6 +7703,7 @@ Flag all slicing.
     struct B {   // an interface
         virtual void f();
         virtual void g();
+        virtual ~B();
     };
 
     struct D : B {   // a wider interface
@@ -21507,6 +21509,8 @@ Here is an example of the last option:
             p->post_initialize();
             return p;
         }
+
+        // ...
     };