doc: cleanup and references in C++ guide

PR-URL: #23650
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

CPP_STYLE_GUIDE.md

@@ -192,40 +192,39 @@ class FancyContainer {
 
 ### Use `nullptr` instead of `NULL` or `0`
 
-What it says in the title.
+Further reading in the [C++ Core Guidelines][ES.47].
 
 ### Ownership and Smart Pointers
 
-"Smart" pointers are classes that act like pointers, e.g.
-by overloading the `*` and `->` operators. Some smart pointer types can be
-used to automate ownership bookkeeping, to ensure these responsibilities are
-met. `std::unique_ptr` is a smart pointer type introduced in C++11, which
-expresses exclusive ownership of a dynamically allocated object; the object
-is deleted when the `std::unique_ptr` goes out of scope. It cannot be
-copied, but can be moved to represent ownership transfer.
-`std::shared_ptr` is a smart pointer type that expresses shared ownership of a
-dynamically allocated object. `std::shared_ptr`s can be copied; ownership
-of the object is shared among all copies, and the object
-is deleted when the last `std::shared_ptr` is destroyed.
-
-Prefer to use `std::unique_ptr` to make ownership
-transfer explicit. For example:
+* [R.20]: Use `std::unique_ptr` or `std::shared_ptr` to represent ownership
+* [R.21]: Prefer `unique_ptr` over `shared_ptr` unless you need to share
+  ownership
+
+Use `std::unique_ptr` to make ownership transfer explicit. For example:
 
 ```cpp
 std::unique_ptr<Foo> FooFactory();
 void FooConsumer(std::unique_ptr<Foo> ptr);
 ```
 
-Never use `std::auto_ptr`. Instead, use `std::unique_ptr`.
+Since `std::unique_ptr` has only move semantics, passing one by value transfers
+ownership to the callee and invalidates the caller's instance.
+
+Don't use `std::auto_ptr`, it is deprecated ([Reference][cppref_auto_ptr]).
 
 ## Others
 
 ### Type casting
 
-- Always avoid C-style casts (`(type)value`)
-- `dynamic_cast` does not work because RTTI is not enabled
-- Use `static_cast` for casting whenever it works
-- `reinterpret_cast` is okay if `static_cast` is not appropriate
+- Use `static_cast<T>` if casting is required, and it is valid
+- Use `reinterpret_cast` only when it is necessary
+- Avoid C-style casts (`(type)value`)
+- `dynamic_cast` does not work because Node.js is built without
+  [Run Time Type Information][]
+
+Further reading:
+* [ES.48]: Avoid casts
+* [ES.49]: If you must use a cast, use a named cast
 
 ### Using `auto`
 
@@ -316,13 +315,25 @@ exports.foo = function(str) {
 
 #### Avoid throwing JavaScript errors in nested C++ methods
 
-When you have to throw the errors from C++, try to do it at the top level and
-not inside of nested calls.
+When you need to throw a JavaScript exception from C++ (i.e.
+`isolate()->ThrowException()`) prefer to do it as close to the return to JS as
+possible, and not inside of nested C++ calls. Since this changes the JS
+execution state doing it closest to where it is consumed reduces the chances of
+side effects.
 
-Using C++ `throw` is not allowed.
+Node.js is built [without C++ exception handling][], so code using `throw` or
+even `try` and `catch` **will** break.
 
 
 [C++ Core Guidelines]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines
 [Google C++ Style Guide]: https://google.github.io/styleguide/cppguide.html
 [Google’s `cpplint`]: https://github.com/google/styleguide
 [errors]: https://github.com/nodejs/node/blob/master/doc/guides/using-internal-errors.md
+[ES.47]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Res-nullptr
+[ES.48]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Res-casts
+[ES.49]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Res-casts-named
+[R.20]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rr-owner
+[R.21]: http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rr-unique
+[Run Time Type Information]: https://en.wikipedia.org/wiki/Run-time_type_information
+[cppref_auto_ptr]: https://en.cppreference.com/w/cpp/memory/auto_ptr
+[without C++ exception handling]: https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_exceptions.html#intro.using.exception.no