Autosar Guidelines C++14, example code compile list(71)Rule A8-2-1 When declaring function templates, the trailing return type syntax shall be used

Guidelines for the use of the C++14 language in critical and
safety-related systems Sample code compile list(71)
https://www.autosar.org/fileadmin/user_upload/standards/adaptive/17-03/AUTOSAR_RS_CPP14Guidelines.pdf
Autosar Guidelines C++14, example code compile list(
#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、(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を検討するため、-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とともに、各標準段階, hosted, freestandingの特徴と課題を明確にする。


#A8-2-1.cpp
##算譜(source code)

```c++:A8-2-1.cpp
//Guidelines for the use of the C++14 language in critical and safety-related systems
const char* msg="Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.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" is from AUTOSAR without code having /// comment in line.
// $Id: A8-2-1.cpp 271687 2017-03-23 08:57:35Z piotr.tanski $
#include <cstdint>
template <typename T>
class A
{
public:
  using Type = std::int32_t;

  Type f(T const&) noexcept;
  Type g(T const&) noexcept;
};
template <typename T>
typename A<T>::Type A<T>::f(T const&) noexcept // Non-compliant
{
// Implementation
}
template <typename T>
auto A<T>::g(T const&) noexcept -> Type // Compliant
{
// Implementation
}
///end AUTOSAR
int start() { /// @{} for start
  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 a8-2-1
$ clang++ a8-2-1.cpp -I./ -std=c++14 -Wall
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.cpp
$ clang++ a8-2-1.cpp  -I./ -std=c++17 -Wall
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.cpp
$ clang++ a8-2-1.cpp  -I./ -std=c++2a -Wall
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.cpp

$ g++-8 a8-2-1.cpp  -I./ -std=c++14  -Wall
a8-2-1.cpp: In member function 'A<T>::Type A<T>::f(const T&)':
a8-2-1.cpp:28:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
a8-2-1.cpp: In member function 'A<T>::Type A<T>::g(const T&)':
a8-2-1.cpp:33:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.cpp
$ g++-8 a8-2-1.cpp  -I./ -std=c++17  -Wall
a8-2-1.cpp: In member function 'A<T>::Type A<T>::f(const T&)':
a8-2-1.cpp:28:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
a8-2-1.cpp: In member function 'A<T>::Type A<T>::g(const T&)':
a8-2-1.cpp:33:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.cpp
$ g++-8 a8-2-1.cpp  -I./ -std=c++2a  -Wall
a8-2-1.cpp: In member function 'A<T>::Type A<T>::f(const T&)':
a8-2-1.cpp:28:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
a8-2-1.cpp: In member function 'A<T>::Type A<T>::g(const T&)':
a8-2-1.cpp:33:2: warning: no return statement in function returning non-void [-Wreturn-type]
  }
  ^
Rule A8-2-1 (required, implementation, automated)When declaring function templates, the trailing return type syntax shall be used if the return type depends on the type of parameters.(71)A8-2-1.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
clang++警告なし, g++警告あり

###5 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/2017/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
ver 0.10 初稿 20180611