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.
@@ -18904,7 +18936,7 @@ Doing so takes away an `#include`r's ability to effectively disambiguate and to
 ##### Note
 
 An exception is `using namespace std::literals;`. This is necessary to use string literals
-in header files and given [the rules](http://eel.is/c++draft/over.literal) - users are required 
+in header files and given [the rules](http://eel.is/c++draft/over.literal) - users are required
 to name their own UDLs `operator""_x` - they will not collide with the standard library.
 
 ##### Enforcement
@@ -20087,12 +20119,12 @@ and errors (when we didn't deal correctly with semi-constructed objects consiste
             my = y;
             data = nullptr;
         }
-    
+
         ~Picture()
         {
             Cleanup();
         }
-    
+
         bool Init()
         {
             // invariant checks
@@ -20105,14 +20137,14 @@ and errors (when we didn't deal correctly with semi-constructed objects consiste
             data = (char*) malloc(mx*my*sizeof(int));
             return data != nullptr;
         }
-    
+
         void Cleanup()
         {
             if (data) free(data);
             data = nullptr;
         }
     };
-    
+
     Picture picture(100, 0); // not ready-to-use picture here
     // this will fail..
     if (!picture.Init()) {
@@ -20127,14 +20159,14 @@ and errors (when we didn't deal correctly with semi-constructed objects consiste
         size_t mx;
         size_t my;
         vector<char> data;
-    
+
         static size_t check_size(size_t s)
         {
             // invariant check
             Expects(s > 0);
             return s;
         }
-    
+
     public:
         // even more better would be a class for a 2D Size as one single parameter
         Picture(size_t x, size_t y)
@@ -20147,10 +20179,10 @@ and errors (when we didn't deal correctly with semi-constructed objects consiste
         }
         // compiler generated dtor does the job. (also see C.21)
     };
-    
+
     Picture picture1(100, 100);
     // picture is ready-to-use here...
-    
+
     // not a valid size for y,
     // default contract violation behavior will call std::terminate then
     Picture picture2(100, 0);

scripts/hunspell/isocpp.dic

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