C++N4606(258) 25.2.3 Effect of execution policies on algorithm execution [algorithms.parallel.exec] p1006


#はじめに(Introduction)
C++N4606 Working Draft, Standard for Programming Language C++
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/#mailing2016-11
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf

C++N4606は、ISO/IEC JTC1 SC22 WG21の作業原案(Working Draft)です。
公式のISO/IEC 14882原本ではありません。
ISO/IEC JTC1 SC22 WG21では、可能な限り作業文書を公開し、幅広い意見を求めています。
一連の記事はコード断片をコンパイルできる形にする方法を検討してコンパイル、リンク、実行して、規格案の原文と処理系(g++, Clang++)との違いを確認し、技術内容を検討し、ISO/IEC JTC1 SC22 WG21にフィードバックするために用います。
また、CERT C++, MISRA C++等のコーディング標準のコード断片をコンパイルする際の参考にさせていただこうと考えています。CERT C++, MISRA C++が標準化の動きとの時間的なずれがあれば確認できれば幸いです。また、boostライブラリとの関連、Linux OS, TOPPERSカーネル、g++(GCC), clang++(LLVM）との関係も調査中です。
何か、抜け漏れ、耳より情報がありましたらおしらせくださると幸いです。

##作業方針(sequence)
１）コンパイルエラーを収集する。
２）コンパイルエラーをなくす方法を検討する。
コンパイルエラーになる例を示すだけが目的のコードは、コンパイルエラーをなくすのではなく、コンパイルエラーの種類を収集するだけにする。
文法を示すのが目的のコード場合に、コンパイルエラーをなくすのに手間がかかる場合は、順次作業します。
３）リンクエラーをなくす方法を検討する。
文法を示すのが目的のコード場合に、リンクエラーをなくすのに手間がかかる場合は、順次作業します。
４）意味のある出力を作る。
コンパイル、リンクが通っても、意味のある出力を示そうとすると、コンパイル・リンクエラーが出て収拾できそうにない場合がある。順次作業します。

１）だけのものから４）まで進んだものと色々ある状態です。一歩でも前に進むご助言をお待ちしています。「検討事項」の欄に現状を記録するようにしています。

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


## 編纂器(Compiler)
###clang++ --version
clang version 6.0.0 (tags/RELEASE_600/final)
Target: x86_64-apple-darwin17.4.0

###g++-7 --version
g++-7 (Homebrew GCC 7.3.0_1) 7.3.0
Copyright (C) 2017 Free Software Foundation, Inc.

#(258) 25.2.3 Effect of execution policies on algorithm execution [algorithms.parallel.exec] p1006

##算譜(source code)

```c++:p1006.cpp
// C++N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf
#define msg "C++N4606(258) 25.2.3 Effect of execution policies on algorithm execution [algorithms.parallel.exec] p1006.cpp"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <cstdlib>
#include <numeric>
#include <iostream>
#include <array>
#include <iterator>

using namespace std; /// add from compiler errors

int main() {
  {
    int a[] = {0,1};
    std::vector<int> v;
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
      v.push_back(i*2+1); // incorrect: data race
      std::cout<< "i="<<i << std::endl;
    });
  }
  {
    std::atomic<int> x{0};
    int a[] = {1,2};
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
      x.fetch_add(1, std::memory_order_relaxed);
// spin wait for another iteration to change the value of x
      while (x.load(std::memory_order_relaxed) == 1) { } // incorrect: assumes execution order
    });
    std::cout<< "x="<<x << std::endl;

  }
  {
    int x = 0;
    std::mutex m;
    int a[] = {1,2};
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
      std::lock_guard<mutex> guard(m);
      ++x;
    });
    std::cout<< "x="<<x << std::endl;

  }
  {
    int x = 0;
    std::mutex m;
    int a[] = {1,2};
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
      std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
      ++x;
    });
    std::cout<< "x="<<x << std::endl;
  }
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

```
##編纂・実行結果(compile and go)

```shell_session:cppall.sh
$ ./cppall.sh p1006
$ clang++ p1006.cpp -std=c++03 -Wall
p1006.cpp:15:22: error: implicit instantiation of undefined template 'std::__1::vector<int,
      std::__1::allocator<int> >'
    std::vector<int> v;
                     ^
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/iosfwd:200:28: note: template is declared here
class _LIBCPP_TEMPLATE_VIS vector;
                           ^
p1006.cpp:16:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:16:68: error: expected expression
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                                                                   ^
p1006.cpp:16:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:22:23: error: expected ';' at end of declaration
    std::atomic<int> x{0};
                      ^
                      ;
p1006.cpp:24:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:24:68: error: expected expression
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                                   ^
p1006.cpp:24:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:36:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:36:68: error: expected expression
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                                   ^
p1006.cpp:36:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:47:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:47:74: error: expected expression
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                                                                         ^
p1006.cpp:47:35: error: no member named 'par_unseq' in 'std::exception'
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
14 errors generated.
$ clang++ p1006.cpp -std=c++11 -Wall
p1006.cpp:15:22: error: implicit instantiation of undefined template 'std::__1::vector<int,
      std::__1::allocator<int> >'
    std::vector<int> v;
                     ^
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/iosfwd:200:28: note: template is declared here
class _LIBCPP_TEMPLATE_VIS vector;
                           ^
p1006.cpp:16:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:16:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:24:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:24:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:36:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:36:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:47:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:47:35: error: no member named 'par_unseq' in 'std::exception'
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
9 errors generated.
$ clang++ p1006.cpp -std=c++17 -Wall
p1006.cpp:15:22: error: implicit instantiation of undefined template 'std::__1::vector<int,
      std::__1::allocator<int> >'
    std::vector<int> v;
                     ^
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/iosfwd:200:28: note: template is declared here
class _LIBCPP_TEMPLATE_VIS vector;
                           ^
p1006.cpp:16:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:16:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:24:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:24:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:36:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:36:35: error: no member named 'par' in 'std::exception'
    std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
p1006.cpp:47:24: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~^~~~~~~~~
                       exception
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/exception:97:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
p1006.cpp:47:35: error: no member named 'par_unseq' in 'std::exception'
    std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                  ~~~~~~~~~~~~~~~~^
9 errors generated.

$ g++-7 p1006.cpp -std=c++03  -Wall
p1006.cpp: In function 'int main()':
p1006.cpp:15:10: error: 'vector' is not a member of 'std'
     std::vector<int> v;
          ^~~~~~
p1006.cpp:15:17: error: expected primary-expression before 'int'
     std::vector<int> v;
                 ^~~
p1006.cpp:16:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
          ^~~~~~~~
p1006.cpp:16:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                        ^~~~~~~~~
p1006.cpp:16:45: error: 'begin' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                                             ^~~~~
p1006.cpp:16:60: error: 'end' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                                                            ^~~
p1006.cpp:16:60: note: suggested alternative: 'ends'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                                                            ^~~
                                                            ends
p1006.cpp: In lambda function:
p1006.cpp:17:7: error: 'v' was not declared in this scope
       v.push_back(i*2+1); // incorrect: data race
       ^
p1006.cpp: In function 'int main()':
p1006.cpp:19:5: warning: lambda expressions only available with -std=c++11 or -std=gnu++11
     });
     ^
p1006.cpp:22:10: error: 'atomic' is not a member of 'std'
     std::atomic<int> x{0};
          ^~~~~~
p1006.cpp:22:17: error: expected primary-expression before 'int'
     std::atomic<int> x{0};
                 ^~~
p1006.cpp:24:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:24:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp:24:45: error: 'begin' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                             ^~~~~
p1006.cpp:24:60: error: 'end' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                            ^~~
p1006.cpp:24:60: note: suggested alternative: 'ends'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                            ^~~
                                                            ends
p1006.cpp: In lambda function:
p1006.cpp:25:7: error: 'x' was not declared in this scope
       x.fetch_add(1, std::memory_order_relaxed);
       ^
p1006.cpp:25:27: error: 'memory_order_relaxed' is not a member of 'std'
       x.fetch_add(1, std::memory_order_relaxed);
                           ^~~~~~~~~~~~~~~~~~~~
p1006.cpp:27:26: error: 'memory_order_relaxed' is not a member of 'std'
       while (x.load(std::memory_order_relaxed) == 1) { } // incorrect: assumes execution order
                          ^~~~~~~~~~~~~~~~~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:28:5: warning: lambda expressions only available with -std=c++11 or -std=gnu++11
     });
     ^
p1006.cpp:29:23: error: 'x' was not declared in this scope
     std::cout<< "x="<<x << std::endl;
                       ^
p1006.cpp:34:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:36:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:36:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp:36:45: error: 'begin' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                             ^~~~~
p1006.cpp:36:60: error: 'end' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                            ^~~
p1006.cpp:36:60: note: suggested alternative: 'ends'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                                                            ^~~
                                                            ends
p1006.cpp: In lambda function:
p1006.cpp:37:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m);
            ^~~~~~~~~~
p1006.cpp:37:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                       ^~~~~
p1006.cpp:37:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                                    ^
p1006.cpp:37:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                              ^~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:39:5: warning: lambda expressions only available with -std=c++11 or -std=gnu++11
     });
     ^
p1006.cpp:45:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:47:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:47:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp:47:51: error: 'begin' is not a member of 'std'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                                                   ^~~~~
p1006.cpp:47:66: error: 'end' is not a member of 'std'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                                                                  ^~~
p1006.cpp:47:66: note: suggested alternative: 'ends'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                                                                  ^~~
                                                                  ends
p1006.cpp: In lambda function:
p1006.cpp:48:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
            ^~~~~~~~~~
p1006.cpp:48:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                       ^~~~~
p1006.cpp:48:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                                    ^
p1006.cpp:48:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                              ^~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:50:5: warning: lambda expressions only available with -std=c++11 or -std=gnu++11
     });
     ^

$ g++-7 p1006.cpp -std=c++11  -Wall
p1006.cpp: In function 'int main()':
p1006.cpp:15:10: error: 'vector' is not a member of 'std'
     std::vector<int> v;
          ^~~~~~
p1006.cpp:15:17: error: expected primary-expression before 'int'
     std::vector<int> v;
                 ^~~
p1006.cpp:16:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
          ^~~~~~~~
p1006.cpp:16:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
          ^~~~~~~~
          forward
p1006.cpp:16:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:17:7: error: 'v' was not declared in this scope
       v.push_back(i*2+1); // incorrect: data race
       ^
p1006.cpp: In function 'int main()':
p1006.cpp:22:10: error: 'atomic' is not a member of 'std'
     std::atomic<int> x{0};
          ^~~~~~
p1006.cpp:22:17: error: expected primary-expression before 'int'
     std::atomic<int> x{0};
                 ^~~
p1006.cpp:24:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:24:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:24:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:25:7: error: 'x' was not declared in this scope
       x.fetch_add(1, std::memory_order_relaxed);
       ^
p1006.cpp:25:27: error: 'memory_order_relaxed' is not a member of 'std'
       x.fetch_add(1, std::memory_order_relaxed);
                           ^~~~~~~~~~~~~~~~~~~~
p1006.cpp:27:26: error: 'memory_order_relaxed' is not a member of 'std'
       while (x.load(std::memory_order_relaxed) == 1) { } // incorrect: assumes execution order
                          ^~~~~~~~~~~~~~~~~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:29:23: error: 'x' was not declared in this scope
     std::cout<< "x="<<x << std::endl;
                       ^
p1006.cpp:34:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:36:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:36:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:36:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:37:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m);
            ^~~~~~~~~~
p1006.cpp:37:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                       ^~~~~
p1006.cpp:37:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                                    ^
p1006.cpp:37:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                              ^~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:45:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:47:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:47:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:47:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:48:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
            ^~~~~~~~~~
p1006.cpp:48:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                       ^~~~~
p1006.cpp:48:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                                    ^
p1006.cpp:48:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                              ^~~~~

$ g++-7 p1006.cpp -std=c++17  -Wall
p1006.cpp: In function 'int main()':
p1006.cpp:15:10: error: 'vector' is not a member of 'std'
     std::vector<int> v;
          ^~~~~~
p1006.cpp:15:17: error: expected primary-expression before 'int'
     std::vector<int> v;
                 ^~~
p1006.cpp:16:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
          ^~~~~~~~
p1006.cpp:16:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
          ^~~~~~~~
          forward
p1006.cpp:16:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int i) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:17:7: error: 'v' was not declared in this scope
       v.push_back(i*2+1); // incorrect: data race
       ^
p1006.cpp: In function 'int main()':
p1006.cpp:22:10: error: 'atomic' is not a member of 'std'
     std::atomic<int> x{0};
          ^~~~~~
p1006.cpp:22:17: error: expected primary-expression before 'int'
     std::atomic<int> x{0};
                 ^~~
p1006.cpp:24:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:24:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:24:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:25:7: error: 'x' was not declared in this scope
       x.fetch_add(1, std::memory_order_relaxed);
       ^
p1006.cpp:25:27: error: 'memory_order_relaxed' is not a member of 'std'
       x.fetch_add(1, std::memory_order_relaxed);
                           ^~~~~~~~~~~~~~~~~~~~
p1006.cpp:27:26: error: 'memory_order_relaxed' is not a member of 'std'
       while (x.load(std::memory_order_relaxed) == 1) { } // incorrect: assumes execution order
                          ^~~~~~~~~~~~~~~~~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:29:23: error: 'x' was not declared in this scope
     std::cout<< "x="<<x << std::endl;
                       ^
p1006.cpp:34:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:36:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:36:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:36:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:37:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m);
            ^~~~~~~~~~
p1006.cpp:37:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                       ^~~~~
p1006.cpp:37:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                                    ^
p1006.cpp:37:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m);
                              ^~~~~
p1006.cpp: In function 'int main()':
p1006.cpp:45:10: error: 'mutex' is not a member of 'std'
     std::mutex m;
          ^~~~~
p1006.cpp:47:10: error: 'for_each' is not a member of 'std'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
p1006.cpp:47:10: note: suggested alternative: 'forward'
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
          ^~~~~~~~
          forward
p1006.cpp:47:24: error: 'std::execution' has not been declared
     std::for_each(std::execution::par_unseq, std::begin(a), std::end(a), [&](int) {
                        ^~~~~~~~~
p1006.cpp: In lambda function:
p1006.cpp:48:12: error: 'lock_guard' is not a member of 'std'
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
            ^~~~~~~~~~
p1006.cpp:48:23: error: 'mutex' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                       ^~~~~
p1006.cpp:48:36: error: 'm' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                                    ^
p1006.cpp:48:30: error: 'guard' was not declared in this scope
       std::lock_guard<mutex> guard(m); // incorrect: lock_guard constructor calls m.lock()
                              ^~~~~
```


#検討事項(agenda)
executionヘッダファイルがclang++, g++ともincludeできない理由。
役に立つまたは意味のある出力

#参考資料(reference)

docker gnu(gcc/g++) and llvm(clang/clang++)
https://qiita.com/drafts/059874ea39c4de64c0f7

C++N4606 Working Draft 2016, ISO/IEC 14882, C++ standardのコード断片をコンパイルするためにしていること
https://qiita.com/kaizen_nagoya/items/a8d7ee2f2e29e76c19c1

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)
https://qiita.com/kaizen_nagoya/items/74220c0577a512c2d7da

Clang/Clang++(LLVM) gcc/g++(GNU) コンパイラ警告等比較
https://qiita.com/kaizen_nagoya/items/9a82b958cc3aeef0403f

C++2003とC++2017でコンパイルエラーになるならない事例集
https://qiita.com/kaizen_nagoya/items/a13ea3823441c430edff

Qiitaに投稿するCのStyle例(暫定)
https://qiita.com/kaizen_nagoya/items/946df1528a6a1ef2bc0d

cpprefjpのdecltypeをコンパイル試験
https://qiita.com/kaizen_nagoya/items/090909af702f0d5d8a67

MISRA C++ 5-0-16
https://qiita.com/kaizen_nagoya/items/7df2d4e05db724752a74

C++ Templates Part1 BASICS Chapter 3. Class Templates 3.2 Use of Class Template Stack stack1test.cpp
https://qiita.com/kaizen_nagoya/items/cd5fc49106fad5a4e9ed

ISO/IEC TS 17961:2013 C Secure Coding Rules(1) All list(to be confirmed)
https://qiita.com/kaizen_nagoya/items/54e056195c4f11b850a1

C言語（C++)に対する誤解、曲解、無理解、爽快。
https://qiita.com/kaizen_nagoya/items/3f3992c9722c1cee2e3a

C Puzzle Bookの有り難み5つ、C言語規格及びCコンパイラの特性を認識
https://qiita.com/kaizen_nagoya/items/d89a48c1536a02ecdec9

'wchar.h' file not found で困った clang++ macOS
https://qiita.com/kaizen_nagoya/items/de15cd46d657517fac11

Open POSIX Test Suiteの使い方を調べはじめました
https://qiita.com/kaizen_nagoya/items/644d5e407f5faf96e6dc

MISRA-C 2012 Referenceに掲載している文献の入手可能性を確認
https://qiita.com/kaizen_nagoya/items/96dc8b125e462d5575bb

どうやって MISRA Example Suiteをコンパイルするか
https://qiita.com/kaizen_nagoya/items/fbdbff5ff696e2ca7f00

MISRA C まとめ #include <misra_c.h>
https://qiita.com/kaizen_nagoya/items/f1a79a7cbd281607c7c9

「C++完全理解ガイド」の同意できること上位10
https://qiita.com/kaizen_nagoya/items/aa5744e0c4a8618c7671

#文書履歴(document history)
ver. 0.10 初稿 20180501