C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp

#はじめに(Introduction)
C++N3242, 2011, Working Draft, Standard for Programming Language C++
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf

C++N3242は、ISO/IEC JTC1 SC22 WG21の作業文書(N number Document)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）との関係を調査中です。

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)
下記4）までの過程はhosted環境で行います。
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。
５hosted環境とfreestnding環境の違いによる影響、課題を洗い出し、freestanding環境での実行結果の作成を試みます。

１）だけのものから５）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++N3242符号断片編纂一覧(example code compile list)
C++N3242, 2011, ISO/IEC 14882, C++ standard(1) Example code compile list
https://qiita.com/kaizen_nagoya/items/685b5c1a2c17c1bf1318

https://researchmap.jp/jodlit3dy-1797580/#_1797580

### 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/

### C++N4741符号断片編纂一覧(example code compile list)
C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list
https://qiita.com/kaizen_nagoya/items/3294c014044550896010


# (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
https://researchmap.jp/jopenwtte-1797580/#_1797580
## 編纂器(Compiler)
###clang++ --version
clang version 6.0.0 (tags/RELEASE_600/final)
Target: x86_64-apple-darwin17.4.0

###g++-8 --version
g++-8 (Homebrew GCC 8.1.0) 8.1.0
Copyright (C) 2018 Free Software Foundation, Inc.

##算譜(source code)

```c++:p57.cpp
// 1 filename:p57.cpp
// ver 0.1 June.10, 2014
// ver 0.2 July.7, 2018
// 2 original examples and/or notes:
// (c) ISO/IEC JTC1 SC22 WG21 N3242, April 12, 2011
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
const char* msg= "C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp";
//
// 3 compile and output mechanism:
// (c) Ogawa Kiyoshi, kaizen @ wh.commufa.jp
//
// 4 compile errors and/or wornings:
// 4.1(c) Apple LLVM
// 4.1.1 ver.0.10
// version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
// Target: x86_64-apple-darwin13.2.0,  Thread model: posix
// Command/Options: c++ -std=c++11 -stdlib=libc++ -Wall cpp2011-2-5.cpp
// (c) LLVM 2003-2009 University of Illinois at Urbana-Champaign.
// 4.1.2 ver.0.20
// clang version 6.0.0 (tags/RELEASE_600/final)
// Target: x86_64-apple-darwin17.4.0
// 4.2. g++-4.9 (GCC) 4.9.0 20131229 (experimental)
// Copyright (C) 2013 Free Software Foundation, Inc.
// This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// http://gcc.gnu.org/onlinedocs/gcc/Standards.html
// 4.2.1 ver. 0.1
// Command/Options: g++-4.9  -std=c++11  -Wall cpp2011-2-5.cpp
// g++-4.9: error: unrecognized command line option '-stdlib=libc++'
// Configuration:brew install gcc49
// 4.2.2 ver. 0.2
// g++-8 (Homebrew GCC 8.1.0) 8.1.0
// Copyright (C) 2018 Free Software Foundation, Inc.
// 4.3. Visual Studio Express 2013,
// (c) Microsoft http://www.visualstudio.com/
// SPEC:
// Windows 7, .NET Framework
// (c) VMware, Inc.
// VMWare fusion 6
///
// 5. Hardware:  MacBook Pro,
// 5.1 ver. 0.10
//(c) Intel http://ark.intel.com/products/37006/
// Core 2 Duo 2.53GHz, 8GB, 1067MHz DDR3
// 5.2 ver. 0.20
// intel Corei5, 2.6GHz, 16GB, 166MHz DDR
//
// 6. Special Thanks: Upper organizatios and
// ITSCJ/IPSJ http://www.itscj.ipsj.or.jp/itscj_english/index.html
// NPO SESSAME project, http://www.sessame.jp/workinggroup/WorkingGroup3/
// Toyo Corporation, http://www.toyo.co.jp/English/
// Japan Standard Association, http://bit.ly/1lzykg1
// NPO TOPPERS project, https://www.toppers.jp/asp-d-download.html
// Daido Universcity, http://www.daido-it.ac.jp/gakubugakka/computer/index.html
// WITZ Co.Ltd., http://www.witz-inc.co.jp/products/solution/solution.html
// SevenWise.co., http://www.7ws.co.jp/index.html
// TOYOTA Motor Corporation, http://toyota.jp/
// IT planning Inc., http://www.itpl.co.jp/en/index.html
// DENSO Corporation, http://www.globaldenso.com/en/
// Aisin Seiki co. Ltd., http://www.aisin.com/
// Spancion Inc., http://www.spansion.com/
// Yazaki Corporation, http://www.yazaki-group.com/global/
// Pananosic Corporation, http://www.panasonic.net/
// SWEST: Summer Workshop on Embedded System Technologies , http://swest.toppers.jp
// CEST: Consortium for Embedded System Technology, http://www.ertl.jp/CEST/
// JUSE: Union of Japanese Scientists and Engineers, http://www.juse.or.jp/e/
// OSC:Open Source Conference, http://www.ospn.jp/

#include <iostream>
#include <cstdlib>

using namespace std;

namespace N {
  int i = 4; /// add for compile error
}

/// from here, on the  N3242 without /// lines

struct Node {
  struct Node* Next; // OK: Refers to Node at global scope
  struct Data* Data; // OK: Declares type Data
// at global scope and member Data
};
struct Data {
  struct Node* Node; // OK: Refers to Node at global scope
// friend struct ::Glob; // error: Glob is not declared
// cannot introduce a qualified type (7.1.6.3)
  friend struct Glob; // OK: Refers to (as yet) undeclared Glob
// at global scope.
  /* ... */
};
struct Base {
  struct Data; // OK: Declares nested Data
  struct ::Data* thatData; // OK: Refers to ::Data
  struct Base::Data* thisData; // OK: Refers to nested Data
  friend class ::Data; // OK: global Data is a friend
  friend class Data; // OK: nested Data is a friend
  struct Data { /* ... */
  }; // Defines nested Data
};
struct Data; // OK: Redeclares Data at global scope
// struct ::Data; // error: cannot introduce a qualified type (7.1.6.3)
// struct Base::Data; // error: cannot introduce a qualified type (7.1.6.3)
// struct Base::Datum; // error: Datum undefined
struct Base::Data* pBase; // OK: refers to nested Data

/// to here, on the  N3242 without /// lines
int main() {
  cout << pBase <<  std::endl;
  cout << msg <<endl;
  return EXIT_SUCCESS;
}
```
##編纂・実行結果(compile and go)

```shell_session:cppall.sh
$ ../cppall.sh p57
$ clang++ p57.cpp -std=c++03 -Wall
p57.cpp:96:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class ::Data; // OK: global Data is a friend
       ^
p57.cpp:84:8: note: previous use is here
struct Data {
       ^
p57.cpp:96:8: note: did you mean struct here?
friend class ::Data; // OK: global Data is a friend
       ^~~~~
       struct
p57.cpp:97:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class Data; // OK: nested Data is a friend
       ^
p57.cpp:93:8: note: previous use is here
struct Data; // OK: Declares nested Data
       ^
2 warnings generated.
0x0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ clang++ p57.cpp -std=c++11 -Wall
p57.cpp:96:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class ::Data; // OK: global Data is a friend
       ^
p57.cpp:84:8: note: previous use is here
struct Data {
       ^
p57.cpp:96:8: note: did you mean struct here?
friend class ::Data; // OK: global Data is a friend
       ^~~~~
       struct
p57.cpp:97:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class Data; // OK: nested Data is a friend
       ^
p57.cpp:93:8: note: previous use is here
struct Data; // OK: Declares nested Data
       ^
2 warnings generated.
0x0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ clang++ p57.cpp -std=c++14 -Wall
p57.cpp:96:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class ::Data; // OK: global Data is a friend
       ^
p57.cpp:84:8: note: previous use is here
struct Data {
       ^
p57.cpp:96:8: note: did you mean struct here?
friend class ::Data; // OK: global Data is a friend
       ^~~~~
       struct
p57.cpp:97:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class Data; // OK: nested Data is a friend
       ^
p57.cpp:93:8: note: previous use is here
struct Data; // OK: Declares nested Data
       ^
2 warnings generated.
0x0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ clang++ p57.cpp -std=c++17 -Wall
p57.cpp:96:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class ::Data; // OK: global Data is a friend
       ^
p57.cpp:84:8: note: previous use is here
struct Data {
       ^
p57.cpp:96:8: note: did you mean struct here?
friend class ::Data; // OK: global Data is a friend
       ^~~~~
       struct
p57.cpp:97:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class Data; // OK: nested Data is a friend
       ^
p57.cpp:93:8: note: previous use is here
struct Data; // OK: Declares nested Data
       ^
2 warnings generated.
0x0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ clang++ p57.cpp -std=c++2a -Wall
p57.cpp:96:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class ::Data; // OK: global Data is a friend
       ^
p57.cpp:84:8: note: previous use is here
struct Data {
       ^
p57.cpp:96:8: note: did you mean struct here?
friend class ::Data; // OK: global Data is a friend
       ^~~~~
       struct
p57.cpp:97:8: warning: class 'Data' was previously declared as a struct
      [-Wmismatched-tags]
friend class Data; // OK: nested Data is a friend
       ^
p57.cpp:93:8: note: previous use is here
struct Data; // OK: Declares nested Data
       ^
2 warnings generated.
0x0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp

$ g++-8 p57.cpp -std=c++03  -Wall
0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ g++-8 p57.cpp -std=c++11  -Wall
0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ g++-8 p57.cpp -std=c++14  -Wall
0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ g++-8 p57.cpp -std=c++17  -Wall
0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
$ g++-8 p57.cpp -std=c++2a  -Wall
0
C++N3242, 2011 (20)3.4.4 Elaborated type specifiers [basic.lookup.elab] p57.cpp
```

#検討事項(agenda)
1. clang++警告あり、g++警告なしの背景

2.  役に立つまたは意味のある出力

#参考資料(reference)
###プログラミング言語教育のXYZ

https://qiita.com/kaizen_nagoya/items/1950c5810fb5c0b07be4
プログラミング言語教育のXYZ(youtube)
https://www.youtube.com/watch?v=He1_tg4px-w&t=486s
###Autosar Guidelines C++14
Autosar Guidelines C++14 example code compile list(1-169)
https://qiita.com/kaizen_nagoya/items/8ccbf6675c3494d57a76
###C++N4741 2018
C++N4741 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
C++N4606 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/

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

### others
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

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


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

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. 0.20 初稿 20180707
ver. 0.21 参考文献整理 20180708