Address items called out in Issue 1424 (#1539)

* Address items called out in Issue 1424

* Fix issues caught by CI

* Updates based on PR review

CppCoreGuidelines.md

@@ -4512,6 +4512,7 @@ Other default operations rules:
 * [C.86: Make `==` symmetric with respect of operand types and `noexcept`](#Rc-eq)
 * [C.87: Beware of `==` on base classes](#Rc-eq-base)
 * [C.89: Make a `hash` `noexcept`](#Rc-hash)
+* [C.90: Rely on constructors and assignment operators, not memset and memcpy](#Rc-memset)
 
 ## <a name="SS-defop"></a>C.defop: Default Operations
 
@@ -6539,6 +6540,37 @@ That tends to work better than "cleverness" for non-specialists.
 
 * Flag throwing `hash`es.
 
+### <a name="Rc-memset"></a>C.90: Rely on constructors and assignment operators, not `memset` and `memcpy`
+
+##### Reason
+
+The standard C++ mechanism to construct an instance of a type is to call its constructor. As specified in guideline [C.41](#Rc-complete): a constructor should create a fully initialized object. No additional initialization, such as by `memcpy`, should be required.
+A type will provide a copy constructor and/or copy assignment operator to appropriately make a copy of the class, preserving the type's invariants.  Using memcpy to copy a non-trivially copyable type has undefined behavior.  Frequently this results in slicing, or data corruption.
+
+##### Example, bad
+
+    struct base
+    {
+        virtual void update() = 0;
+        std::shared_ptr<int> sp;
+    };
+
+    struct derived : public base
+    {
+        void update() override {}
+    };
+
+    void init(derived& a)
+    {
+        memset(&a, 0, sizeof(derived));
+    }
+
+    void copy(derived& a, derived& b)
+    {
+        memcpy(&a, &b, sizeof(derived));
+    }
+
+
 ## <a name="SS-containers"></a>C.con: Containers and other resource handles
 
 A container is an object holding a sequence of objects of some type; `std::vector` is the archetypical container.

scripts/hunspell/isocpp.dic

@@ -301,6 +301,7 @@ md
 memberinit
 members'
 memcmp
+memcpy
 memmove
 memoization
 memoized