Autosar Guidelines C++14, example code compile list(164)Rule A18-9-2  Forwarding values to other functions

Guidelines for the use of the C++14 language in critical and
safety-related systems Sample code compile list(164)
https://www.autosar.org/fileadmin/user_upload/standards/adaptive/17-03/AUTOSAR_RS_CPP14Guidelines.pdf
Autosar Guidelines C++14 example code compile list(1-169)
https://qiita.com/kaizen_nagoya/items/8ccbf6675c3494d57a76
#目的(purpose)
AutosarのC++ GuidelineをOS, 制御のプログラムで利用するにあたって、以下を検討する。
(1)hosted, freestandingのどちらを基本にすべきか。(2)C++2014,C++2017, C++202aのどれを用いると良いか。
(3)どの処理系を併用すると良いか。
-std=c++14, -std=c++17, -std=c++2aの3種類で、複数のコンパイラでコンパイルすることにより、誤(error)、警告(warning)、関数・変数連携(link)、出力(output)、にどのような影響があるかを確認する。
#成果(outcome)
複数の処理系の特徴が明確になる。
各標準段階の違いを明確にする。
hostedまたはfreestandingの特徴と課題を明確にする。


#A18-9-2.cpp
##算譜(source code)

```c++:A18-9-2.cpp
//Guidelines for the use of the C++14 language in critical and safety-related systems
const char* msg="Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp";
//https://www.autosar.org/fileadmin/user_upload/standards/adaptive/17-03/AUTOSAR_RS_CPP14Guidelines.pdf
// There is no description about Autosar declear hosted or freestanding.
// If the Autosar intended both depending on the cases, autosar.h can choose one.
// Compile with -DHOSTED work as  hosted environment, -DFREESTANDING work as freestanding.

#include "autosar.h"/// @line add header file https://qiita.com/kaizen_nagoya/items/4bde8f21ab059b96cf2a

using namespace std;/// @line add using

/// @ start AUTOSAR: From here to the "///end AUTOSAR" are from the AUTOSAR code without some code having /// comment in line.
// $Id: A18-9-2.cpp 271927 2017-03-24 12:01:35Z piotr.tanski $
#include <cstdint>
#include <string>
#include <utility>
class A
{
public:
  explicit A(std::string&& s)
    : str(std::move(s)) // Compliant - forwarding rvalue reference
  {
  }

private:
  std::string str;
};
class B
{
};
void fn1(const B& lval)
{
}
void fn1(B&& rval)
{
}
template <typename T>
void fn2(T&& param)
{
  fn1(std::forward<T>(param)); // Compliant - forwarding forwarding reference
}
template <typename T>
void fn3(T&& param)
{
  fn1(std::move(param)); // Non-compliant - forwarding forwarding reference
// via std::move
}
void fn4() noexcept
{
  B b1;
  B& b2 = b1;
  fn2(b2); // fn1(const B&) is called
  fn2(std::move(b1)); // fn1(B&&) is called
  fn3(b2); // fn1(B&&) is called
  fn3(std::move(b1)); // fn1(B&&) is called
}
/// @ end AUTOSAR
int start() { /// @{} for start
  B b;
  const B& lval=b;
  fn1(lval);
  fn4();
  cout<< msg << endl;
  ShutdownOS()  EXIT_SUCCESS;
/// Autosar OS 3.1.1, 2009: 7.1.2.2 Undefined Behaviour in OSEK OS
/// OS425 If ShutdownOS is called and ShutdownHook() returns then the operating system shall disable all interrupts and enter an endless loop.
}
```
##編纂・実行結果(compile and go)

```shell-session:cpa.sh
$ ../cpa.sh a18-9-2
$ clang++ a18-9-2.cpp -I./ -std=c++14 -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp
$ clang++ a18-9-2.cpp  -I./ -std=c++17 -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp
$ clang++ a18-9-2.cpp  -I./ -std=c++2a -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp

$ g++-8 a18-9-2.cpp  -I./ -std=c++14  -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp
$ g++-8 a18-9-2.cpp  -I./ -std=c++17  -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp
$ g++-8 a18-9-2.cpp  -I./ -std=c++2a  -Wall
Rule A18-9-2 (required, implementation, automated) Forwarding values to other functions shall be done via: (1) std::move if the value is an rvalue reference, (2) std::forward if the value is forwarding reference.(164)A18-9-2.cpp
```

#検討事項(agenda)
###1. 自律(freestanding)環境. 接待(hosted)環境

C++N4606 1.4 Implementation compliance p.4

###2. 対応OSの水準、対応通信規約、応用機能による分類
freestanding用の関数、ライブラリ等
###3. C++2014, C++2017, C++202aの比較項目
本件なし
###4. clang++, g++の比較検討項目
本件なし

###5.  template <typename T>
void fn2(T&& param)
の引数の渡し方

###6. 役立つまたは意味のある出力

#参考文献(reference)
###C++N4741 2018
Working Draft, Standard for Programming Language C++
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/n4741.pdf

C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list
https://qiita.com/kaizen_nagoya/items/3294c014044550896010

###C++N4606 2016
Working Draft, Standard for Programming Language C++
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf

C++N4606, 2016符号断片編纂一覧(example code compile list)
 Working Draft 2016, ISO/IEC 14882(1)
https://qiita.com/kaizen_nagoya/items/df5d62c35bd6ed1c3d43/

# 文書履歴(document history)
ver 0.10 初稿 20180612
ver 0.11 一覧追記 20180614

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