Effective C++ Third version, sample code compile list(10) unctions during construcion or destruction

Effective C++:  55 Specific Ways to Improve Your Programs and DesignsThird version by Scott Mayers
https://www.informit.com/store/effective-c-plus-plus-55-specific-ways-to-improve-your-9780321334879
https://www.amazon.com/dp/0321334876

Sample code from
Yuzhen11/Effective_CPP
https://github.com/Yuzhen11/Effective_CPP
 
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 ＜この記事は個人の過去の経験に基づく個人の感想です。現在所属する組織、業務とは関係がありません。＞

#算譜(source code)

```c++:ec10.cpp
///Effective C++:  55 Specific Ways to Improve Your Programs and DesignsThird version by Scott Mayers
///https://www.informit.com/store/effective-c-plus-plus-55-specific-ways-to-improve-your-9780321334879
#include <iostream>
#include <cstdlib>
#include <vector>
using namespace std;

const char * msg ="Item 10: Have assignment operators return a reference to *this";

/// From here "Effective C++

void f() {
  int x,y,z;
  x = y = z = 15;
  x = (y = (x = 15));  // the same
}

class Widget {
public:
  Widget& operator+=(const Widget& rhs) {
///        ...
    return *this;
  }
  Widget& operator=(int rhs) {
///        ...
    return *this;
  }
};
//Things to Remember

//Have assignment operators return a reference to *this

/// to here from "Effective C++"

int main() {
  f();
  cout << msg << endl;
  return EXIT_SUCCESS;
}
```
#編纂・実行結果(compile and go)

```shell-session:cpa.sh
$ ../cpa.sh ec10
$ clang++ ec10.cpp -I./ -std=c++14 -Wall
Item 10: Have assignment operators return a reference to *this
$ clang++ ec10.cpp  -I./ -std=c++17 -Wall
Item 10: Have assignment operators return a reference to *this
$ clang++ ec10.cpp  -I./ -std=c++2a -Wall
Item 10: Have assignment operators return a reference to *this

$ g++-8 ec10.cpp  -I./ -std=c++14  -Wall
ec10.cpp: In function 'void f()':
ec10.cpp:15:3: warning: operation on 'x' may be undefined [-Wsequence-point]
 x = (y = (x = 15));  // the same
 ~~^~~~~~~~~~~~~~~~
Item 10: Have assignment operators return a reference to *this
$ g++-8 ec10.cpp  -I./ -std=c++17  -Wall
ec10.cpp: In function 'void f()':
ec10.cpp:15:3: warning: operation on 'x' may be undefined [-Wsequence-point]
 x = (y = (x = 15));  // the same
 ~~^~~~~~~~~~~~~~~~
Item 10: Have assignment operators return a reference to *this
$ g++-8 ec10.cpp  -I./ -std=c++2a  -Wall
ec10.cpp: In function 'void f()':
ec10.cpp:15:3: warning: operation on 'x' may be undefined [-Wsequence-point]
 x = (y = (x = 15));  // the same
 ~~^~~~~~~~~~~~~~~~
Item 10: Have assignment operators return a reference to *this

```
#課題(agenda)
1) g++とclang++と警告有無の背景

2)役に立つまたは意味のある出力

3)役に立つまたは意味のある関数、クラスの呼び出し方

#参考資料(reference)

docker gnu(gcc/g++) and llvm(clang/clang++)
https://qiita.com/drafts/059874ea39c4de64c0f7
[C][C++]の国際規格案の例題をコンパイルするときの課題７つ。
https://qiita.com/kaizen_nagoya/items/5f4b155030259497c4de
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 
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
C++参考資料一覧
https://researchmap.jp/joub9b3my-1797580/#_1797580


 ＜この記事は個人の過去の経験に基づく個人の感想です。現在所属する組織、業務とは関係がありません。＞

#文書履歴(document history)

ver. 0.10 初稿 20180622