C++N4606(249) 20.11.2.2 Class template shared_ptr [util.smartptr.shared]p622


#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.

#(249) 20.11.2.2 Class template shared_ptr [util.smartptr.shared]p622
##算譜(source code)

```c++:p622.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(249) 20.11.2.2 Class template shared_ptr [util.smartptr.shared]p622.cpp"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <iostream>
#include <cstdlib>

int main() {
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
    // do something with px
    std::cout << "px="<< px << 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 p622
$ clang++ p622.cpp -std=c++03 -Wall
p622.cpp:10:7: error: no template named 'shared_ptr'; did you mean 'std::shared_ptr'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
      ^~~~~~~~~~
      std::shared_ptr
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:3686:28: note: 'std::shared_ptr' declared here
class _LIBCPP_TEMPLATE_VIS shared_ptr
                           ^
p622.cpp:10:18: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                 ^
p622.cpp:10:21: error: type name requires a specifier or qualifier
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                    ^
p622.cpp:10:26: error: no template named 'dynamic_pointer_cast'; did you mean 'std::dynamic_pointer_cast'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                         ^~~~~~~~~~~~~~~~~~~~
                         std::dynamic_pointer_cast
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:4911:1: note: 'std::dynamic_pointer_cast' declared here
dynamic_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
^
p622.cpp:10:47: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                              ^
5 errors generated.
$ clang++ p622.cpp -std=c++11 -Wall
p622.cpp:10:7: error: no template named 'shared_ptr'; did you mean 'std::shared_ptr'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
      ^~~~~~~~~~
      std::shared_ptr
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:3686:28: note: 'std::shared_ptr' declared here
class _LIBCPP_TEMPLATE_VIS shared_ptr
                           ^
p622.cpp:10:18: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                 ^
p622.cpp:10:21: error: type name requires a specifier or qualifier
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                    ^
p622.cpp:10:26: error: no template named 'dynamic_pointer_cast'; did you mean 'std::dynamic_pointer_cast'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                         ^~~~~~~~~~~~~~~~~~~~
                         std::dynamic_pointer_cast
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:4911:1: note: 'std::dynamic_pointer_cast' declared here
dynamic_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
^
p622.cpp:10:47: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                              ^
5 errors generated.
$ clang++ p622.cpp -std=c++17 -Wall
p622.cpp:10:7: error: no template named 'shared_ptr'; did you mean 'std::shared_ptr'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
      ^~~~~~~~~~
      std::shared_ptr
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:3686:28: note: 'std::shared_ptr' declared here
class _LIBCPP_TEMPLATE_VIS shared_ptr
                           ^
p622.cpp:10:18: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                 ^
p622.cpp:10:21: error: type name requires a specifier or qualifier
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                    ^
p622.cpp:10:26: error: no template named 'dynamic_pointer_cast'; did you mean 'std::dynamic_pointer_cast'?
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                         ^~~~~~~~~~~~~~~~~~~~
                         std::dynamic_pointer_cast
/usr/local/Cellar/llvm/6.0.0/include/c++/v1/memory:4911:1: note: 'std::dynamic_pointer_cast' declared here
dynamic_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
^
p622.cpp:10:47: error: use of undeclared identifier 'X'
  if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                              ^
5 errors generated.

$ g++-7 p622.cpp -std=c++03  -Wall
p622.cpp: In function 'int main()':
p622.cpp:10:7: error: 'shared_ptr' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
       ^~~~~~~~~~
p622.cpp:10:18: error: 'X' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                  ^
p622.cpp:10:21: error: 'px' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                     ^~
p622.cpp:10:26: error: 'dynamic_pointer_cast' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                          ^~~~~~~~~~~~~~~~~~~~
p622.cpp:10:50: error: 'py' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                                  ^~

$ g++-7 p622.cpp -std=c++11  -Wall
p622.cpp: In function 'int main()':
p622.cpp:10:7: error: 'shared_ptr' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
       ^~~~~~~~~~
p622.cpp:10:7: note: suggested alternative: 'char16_t'
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
       ^~~~~~~~~~
       char16_t
p622.cpp:10:18: error: 'X' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                  ^
p622.cpp:10:21: error: 'px' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                     ^~
p622.cpp:10:26: error: 'dynamic_pointer_cast' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                          ^~~~~~~~~~~~~~~~~~~~
p622.cpp:10:50: error: 'py' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                                  ^~

$ g++-7 p622.cpp -std=c++17  -Wall
p622.cpp: In function 'int main()':
p622.cpp:10:7: error: 'shared_ptr' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
       ^~~~~~~~~~
p622.cpp:10:7: note: suggested alternative: 'char16_t'
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
       ^~~~~~~~~~
       char16_t
p622.cpp:10:18: error: 'X' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                  ^
p622.cpp:10:21: error: 'px' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                     ^~
p622.cpp:10:26: error: 'dynamic_pointer_cast' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                          ^~~~~~~~~~~~~~~~~~~~
p622.cpp:10:50: error: 'py' was not declared in this scope
   if (shared_ptr<X> px = dynamic_pointer_cast<X>(py)) {
                                                  ^~
```
## std::をつける。Xの宣言。
###算譜(source code)

```c++:p622a.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(249) 20.11.2.2 Class template shared_ptr [util.smartptr.shared]p622a.cpp"
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.

#include <iostream>
#include <cstdlib>

struct X { // from p537
  X();
  X(const X&); // copies from lvalues
  X(X&&); // moves from rvalues
};

int main() {
  if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
    // do something with px
    std::cout << "px="<< px << 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 p622a
$ clang++ p622a.cpp -std=c++03 -Wall
p622a.cpp:12:6: warning: rvalue references are a C++11 extension [-Wc++11-extensions]
  X(X&&); // moves from rvalues
     ^
p622a.cpp:16:60: error: use of undeclared identifier 'py'
  if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                           ^
1 warning and 1 error generated.
$ clang++ p622a.cpp -std=c++11 -Wall
p622a.cpp:16:60: error: use of undeclared identifier 'py'
  if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                           ^
1 error generated.
$ clang++ p622a.cpp -std=c++17 -Wall
p622a.cpp:16:60: error: use of undeclared identifier 'py'
  if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                           ^
1 error generated.

$ g++-7 p622a.cpp -std=c++03  -Wall
p622a.cpp:12:6: error: expected ',' or '...' before '&&' token
   X(X&&); // moves from rvalues
      ^~
p622a.cpp:12:8: error: invalid constructor; you probably meant 'X (const X&)'
   X(X&&); // moves from rvalues
        ^
p622a.cpp: In function 'int main()':
p622a.cpp:16:12: error: 'shared_ptr' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
            ^~~~~~~~~~
p622a.cpp:16:24: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                        ^
p622a.cpp:16:26: error: 'px' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                          ^~
p622a.cpp:16:36: error: 'dynamic_pointer_cast' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                    ^~~~~~~~~~~~~~~~~~~~
p622a.cpp:16:58: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                          ^
p622a.cpp:16:60: error: 'py' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                            ^~

$ g++-7 p622a.cpp -std=c++11  -Wall
p622a.cpp: In function 'int main()':
p622a.cpp:16:12: error: 'shared_ptr' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
            ^~~~~~~~~~
p622a.cpp:16:24: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                        ^
p622a.cpp:16:26: error: 'px' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                          ^~
p622a.cpp:16:36: error: 'dynamic_pointer_cast' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                    ^~~~~~~~~~~~~~~~~~~~
p622a.cpp:16:58: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                          ^
p622a.cpp:16:60: error: 'py' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                            ^~

$ g++-7 p622a.cpp -std=c++17  -Wall
p622a.cpp: In function 'int main()':
p622a.cpp:16:12: error: 'shared_ptr' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
            ^~~~~~~~~~
p622a.cpp:16:24: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                        ^
p622a.cpp:16:26: error: 'px' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                          ^~
p622a.cpp:16:36: error: 'dynamic_pointer_cast' is not a member of 'std'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                    ^~~~~~~~~~~~~~~~~~~~
p622a.cpp:16:36: note: suggested alternative: 'add_pointer_t'
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                    ^~~~~~~~~~~~~~~~~~~~
                                    add_pointer_t
p622a.cpp:16:58: error: expected primary-expression before '>' token
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                          ^
p622a.cpp:16:60: error: 'py' was not declared in this scope
   if (std::shared_ptr<X> px = std::dynamic_pointer_cast<X>(py)) {
                                                            ^~

```
#検討事項(agenda)
エラー３つ取れない。
役に立つまたは意味のある出力

#参考資料(reference)

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 20180430