From a968af59d0be0047a2fcf7f6697e0cad8e8b9b8e Mon Sep 17 00:00:00 2001
From: Sergey Zubkov <cubbi@cubbi.com>
Date: Sun, 18 Dec 2016 14:46:11 -0500
Subject: [PATCH] C.138 initial content
---
CppCoreGuidelines.md | 44 +++++++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)
diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index 8df991e..f861b15 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -6561,11 +6561,49 @@ This a relatively rare use because implementation can often be organized into a
##### Reason
-???
+Without a using declaration, member functions in the derived class hide the entire inherited overload sets.
-##### Example
+##### Example, bad
- ???
+ #include <iostream>
+ class B {
+ public:
+ virtual int f(int i) { std::cout << "f(int): "; return i; }
+ virtual double f(double d) { std::cout << "f(double): "; return d; }
+ };
+ class D: public B {
+ public:
+ int f(int i) override { std::cout << "f(int): "; return i+1; }
+ };
+ int main()
+ {
+ D d;
+ std::cout << d.f(2) << '\n'; // prints "f(int): 3"
+ std::cout << d.f(2.3) << '\n'; // prints "f(int): 3"
+ }
+
+##### Example, good
+
+ class D: public B {
+ public:
+ int f(int i) override { std::cout << "f(int): "; return i+1; }
+ using B::f; // exposes f(double)
+ };
+
+##### Note
+
+This issue affects both virtual and non-virtual member functions
+
+For variadic bases, C++17 introduced a variadic form of the using-declaration,
+
+ template <class... Ts>
+ struct Overloader : Ts... {
+ using Ts::operator()...; // exposes operator() from every base
+ };
+
+##### Enforcement
+
+Diagnose name hiding
### <a name="Rh-final"></a>C.139: Use `final` sparingly