Autosar Guidelines C++14, example code compile list(60)Rule A7-1-5 The auto specifier 

Guidelines for the use of the C++14 language in critical and
safety-related systems Sample code compile list(60)
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。


#A7-1-5.cpp
##算譜(source code)

```c++:A7-1-5.cpp
//Guidelines for the use of the C++14 language in critical and safety-related systems
const char* msg="Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.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
#include <cstdint>


using namespace std;/// @line add using

///start AUTOSAR: From here to the "///end AUTOSAR" is from AUTOSAR without code having /// comment in line.
// $Id: A7-1-5.cpp 272338 2017-03-28 08:15:01Z piotr.tanski $
#include <cstdint>
#include <vector>

class A
{
};
void f1() noexcept
{
  auto x1 = 5; // Non-compliant - initializer is of fundamental type
  auto x2 = 0.3F; // Non-compliant - initializer is of fundamental type
  auto x3 = {8}; // Non-compliant - initializer is of fundamental type

  std::vector<std::int32_t> v;
  auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
// is returned from v.size() method

  auto a = A{}; // Compliant with case (2)

  auto lambda1 = []() -> std::uint16_t {
    return 5U;
  }; // Compliant with case (2) - lambda1 is of non-fundamental lambda
// expression type
  auto x5 = lambda1(); // Compliant with case (1) - x5 is of
// std::uint16_t type
  cout <<"x1="<<x1<<" x2="<<x2<<endl;
}
void f2() noexcept
{
  auto lambda1 = [](auto x, auto y) -> decltype(x + y) {
    return (x + y);
  }; // Compliant with cases (2) and (3)
  auto y1 = lambda1(5.0, 10); // Compliant with case (1)
  cout <<"y1="<<y1<<endl;
}
template <typename T, typename U>
auto f3(T t, U u) noexcept -> decltype(t + u) // Compliant with case (4)
{
  return (t + u);
}
template <typename T>
class B
{
public:
  T fn(T t);
};
template <typename T>
auto B<T>::fn(T t) -> T // Compliant with case (4)
{
// ...
  return t;
}
///end AUTOSAR
int start() { /// @{} for start
  f1();
  f2();
  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 a7-1-5
$ clang++ a7-1-5.cpp -I./ -std=c++14 -Wall
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
 auto x5 = lambda1(); // Compliant with case (1) - x5 is of
      ^
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
 auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
      ^
a7-1-5.cpp:32:7: warning: unused variable 'a' [-Wunused-variable]
 auto a = A{}; // Compliant with case (2)
      ^
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
 auto x3 = {8}; // Non-compliant - initializer is of fundamental type
      ^
4 warnings generated.
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.cpp
$ clang++ a7-1-5.cpp  -I./ -std=c++17 -Wall
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
 auto x5 = lambda1(); // Compliant with case (1) - x5 is of
      ^
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
 auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
      ^
a7-1-5.cpp:32:7: warning: unused variable 'a' [-Wunused-variable]
 auto a = A{}; // Compliant with case (2)
      ^
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
 auto x3 = {8}; // Non-compliant - initializer is of fundamental type
      ^
4 warnings generated.
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.cpp
$ clang++ a7-1-5.cpp  -I./ -std=c++2a -Wall
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
 auto x3 = {8}; // Non-compliant - initializer is of fundamental type
      ^
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
 auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
      ^
a7-1-5.cpp:32:7: warning: unused variable 'a' [-Wunused-variable]
 auto a = A{}; // Compliant with case (2)
      ^
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
 auto x5 = lambda1(); // Compliant with case (1) - x5 is of
      ^
4 warnings generated.
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.cpp

$ g++-8 a7-1-5.cpp  -I./ -std=c++14  -Wall
a7-1-5.cpp: In function 'void f1()':
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
  auto x3 = {8}; // Non-compliant - initializer is of fundamental type
       ^~
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
  auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
       ^~
a7-1-5.cpp:32:7: warning: variable 'a' set but not used [-Wunused-but-set-variable]
  auto a = A{}; // Compliant with case (2)
       ^
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
  auto x5 = lambda1(); // Compliant with case (1) - x5 is of
       ^~
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.cpp
$ g++-8 a7-1-5.cpp  -I./ -std=c++17  -Wall
a7-1-5.cpp: In function 'void f1()':
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
  auto x3 = {8}; // Non-compliant - initializer is of fundamental type
       ^~
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
  auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
       ^~
a7-1-5.cpp:32:7: warning: variable 'a' set but not used [-Wunused-but-set-variable]
  auto a = A{}; // Compliant with case (2)
       ^
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
  auto x5 = lambda1(); // Compliant with case (1) - x5 is of
       ^~
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.cpp
$ g++-8 a7-1-5.cpp  -I./ -std=c++2a  -Wall
a7-1-5.cpp: In function 'void f1()':
a7-1-5.cpp:26:7: warning: unused variable 'x3' [-Wunused-variable]
  auto x3 = {8}; // Non-compliant - initializer is of fundamental type
       ^~
a7-1-5.cpp:29:7: warning: unused variable 'x4' [-Wunused-variable]
  auto x4 = v.size(); // Compliant with case (1) - x4 is of size_t type that
       ^~
a7-1-5.cpp:32:7: warning: variable 'a' set but not used [-Wunused-but-set-variable]
  auto a = A{}; // Compliant with case (2)
       ^
a7-1-5.cpp:38:7: warning: unused variable 'x5' [-Wunused-variable]
  auto x5 = lambda1(); // Compliant with case (1) - x5 is of
       ^~
x1=5 x2=0.3
y1=15
Rule A7-1-5 (required, implementation, automated) The auto specifier shall not be used apart from following cases: (1) to declare that a variable has the same type as return type of a function call, (2) to declare that a variable has the same type as initializer of non-fundamental type, (3) to declare parameters of a generic lambda expression, (4) to declare a function template using trailing return type syntax.(60)A7-1-5.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 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