diff --git a/CppCoreGuidelines.md b/CppCoreGuidelines.md
index 3bf4366..43a2a1b 100644
--- a/CppCoreGuidelines.md
+++ b/CppCoreGuidelines.md
@@ -1,6 +1,6 @@
# C++ Core Guidelines
-December 12, 2016
+February 1, 2017
Editors:
@@ -6388,7 +6388,7 @@ A trivial getter or setter adds no semantic value; the data item could just as w
##### Example
- class Point {
+ class Point { // Bad: verbose
int x;
int y;
public:
@@ -6403,10 +6403,12 @@ A trivial getter or setter adds no semantic value; the data item could just as w
Consider making such a class a `struct` -- that is, a behaviorless bunch of variables, all public data and no member functions.
struct Point {
- int x = 0;
- int y = 0;
+ int x {0};
+ int y {0};
};
+Note that we can put default initializers on member variables: [C.49: Prefer initialization to assignment in constructors](#Rc-initialize).
+
##### Note
A getter or a setter that converts from an internal type to an interface type is not trivial (it provides a form of information hiding).
@@ -6560,11 +6562,49 @@ 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
+ 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
+ struct Overloader : Ts... {
+ using Ts::operator()...; // exposes operator() from every base
+ };
+
+##### Enforcement
+
+Diagnose name hiding
### C.139: Use `final` sparingly
@@ -9316,7 +9356,7 @@ Assuming that there is a logical connection between `i` and `j`, that connection
Obviously, what we really would like is a construct that initialized n variables from a `tuple`. For example:
- auto {i, j} = make_related_widgets(cond); // Not C++14
+ auto [i,j] = make_related_widgets(cond); // C++17, not C++14
Today, we might approximate that using `tie()`:
@@ -9613,7 +9653,7 @@ not. Unfortunately, it may be impossible to detect when a non-`const` was not
##### Reason
-Readability.
+Readability and safety.
##### Example, bad
@@ -9624,6 +9664,26 @@ Readability.
for (i = 0; i < 200; ++i) { /* ... */ } // bad: i recycled
}
+##### Note
+
+As an optimization, you may want to reuse a buffer as a scratchpad, but even then prefer to limit the variables's scope as much as possible and be careful not to cause bugs from data left in a recycled buffer as this is a common source of security bugs.
+
+ {
+ std::string buffer; // to avoid reallocations on every loop iteration
+ for (auto& o : objects)
+ {
+ // First part of the work.
+ generateFirstString(buffer, o);
+ writeToFile(buffer);
+
+ // Second part of the work.
+ generateSecondString(buffer, o);
+ writeToFile(buffer);
+
+ // etc...
+ }
+ }
+
##### Enforcement
Flag recycled variables.
@@ -13762,7 +13822,28 @@ This gives a more precise statement of design intent, better readability, more e
##### Note
-[Do not cast away `const`](#Res-casts-const).
+It is not inherently bad to pass a pointer or reference to non-const,
+but that should be done only when the called function is supposed to modify the object.
+A reader of code must assume that a funtion that takes a "plain" `T*` or `T&` will modify the object referred to.
+If it doesn't now, it might do so later without forcing recompilation.
+
+##### Note
+
+There are code/libraries that are offer functions that declare a`T*` even though
+those function do not modify that `T`.
+This is a problem for people modernizing code.
+You can
+
+* update the library to be `const`-correct; preferred long-term solution
+* "cast away `const`"; [best avoided](#Res-casts-const).
+* provide a wrapper function; for example
+
+ void f(int* p); // old code: f() does not mpdify `*p`
+ void f(const int* p) { f(const_cast(p); } // wrapper
+
+Note that this wrapper solution is a patch that should be used only when the declaration of `f()` cannot be be modified,
+e.g. because it is in a library that you cannot modify.
+
##### Enforcement
@@ -16068,8 +16149,8 @@ Source file rule summary:
* [SF.3: Use `.h` files for all declarations used in multiple source files](#Rs-declaration-header)
* [SF.4: Include `.h` files before other declarations in a file](#Rs-include-order)
* [SF.5: A `.cpp` file must include the `.h` file(s) that defines its interface](#Rs-consistency)
-* [SF.6: Use `using`-directives for transition, for foundation libraries (such as `std`), or within a local scope](#Rs-using)
-* [SF.7: Don't put a `using`-directive in a header file](#Rs-using-directive)
+* [SF.6: Use `using namespace` directives for transition, for foundation libraries (such as `std`), or within a local scope](#Rs-using)
+* [SF.7: Don't write `using namespace` in a header file](#Rs-using-directive)
* [SF.8: Use `#include` guards for all `.h` files](#Rs-guards)
* [SF.9: Avoid cyclic dependencies among source files](#Rs-cycles)
@@ -16271,7 +16352,7 @@ The argument-type error for `bar` cannot be caught until link time because of th
???
-### SF.6: Use `using`-directives for transition, for foundation libraries (such as `std`), or within a local scope
+### SF.6: Use `using namespace` directives for transition, for foundation libraries (such as `std`), or within a local scope
##### Reason
@@ -16285,7 +16366,7 @@ The argument-type error for `bar` cannot be caught until link time because of th
???
-### SF.7: Don't put a `using`-directive in a header file
+### SF.7: Don't write `using namespace` in a header file
##### Reason
@@ -16293,11 +16374,22 @@ Doing so takes away an `#include`r's ability to effectively disambiguate and to
##### Example
- ???
+ // bad.h
+ #include
+ using namespace std; // bad
+
+ // user.cpp
+ #include "bad.h"
+
+ bool copy( /*... some parameters ...*/); // some function that happens to be named copy
+
+ int main() {
+ copy( /*...*/ ); // now overloads local ::copy and std::copy, could be ambiguous
+ }
##### Enforcement
-???
+Flag `using namespace` at global scope in a header file.
### SF.8: Use `#include` guards for all `.h` files
@@ -19121,10 +19213,11 @@ A relatively informal definition of terms used in the guidelines
This is our to-do list.
Eventually, the entries will become rules or parts of rules.
Alternatively, we will decide that no change is needed and delete the entry.
-
* No long-distance friendship
* Should physical design (what's in a file) and large-scale design (libraries, groups of libraries) be addressed?
* Namespaces
+* Don't place using directives in headers
+* Avoid using directives in the global scope (except for std, and other "fundamental" namespaces (e.g. experimental))
* How granular should namespaces be? All classes/functions designed to work together and released together (as defined in Sutter/Alexandrescu) or something narrower or wider?
* Should there be inline namespaces (à la `std::literals::*_literals`)?
* Avoid implicit conversions