Effective C++ Third version, sample code compile list(15) Provide access to raw resources in resource-managin classes

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
 
 <この項は書きかけです。順次追記します。>


#算譜(source code)

```c++:ec13.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 15: Provide access to raw resources in resource-managin classes";

typedef int  FontHandle;

int releaseFont(FontHandle) {};

/// From here "Effective C++

//Having an explicit get function like shared_ptr

class Font {
public:
  explicit Font(FontHandle fh):f(fh) {}
  ~Font() {
    releaseFont(f);
  }
  FontHandle get() const {
    return f;  // explicit conversion function
  }
private:
  FontHandle f;  // the raw font resource
};

void g() {
  changeFontSize(f.get(), newFontSize);
//Or implicity conversion
}

namespace B {

  class Font {
  public:
    operator FontHandle() const {
      return f;  // implicit conversion
    }
  };
}

void h() {
  changeFontSize(f, newFontSize);

  Font f1(getFont());
  FontHandle f2 = f1;  // oops
}

//Things to Remember

//APIs often require access to raw resources, so each RAII class should offer a way to get at the resource it manages.
//Access may be via explicit conversion or implicit conversion. In general, explicit conversion is safer, but implicit conversion is more convenient for clients.

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

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

```shell-session:cpa.sh
$ ../c1.sh ec15
$ clang++ ec15.cpp  -std=c++2a -Wall
ec15.cpp:12:29: warning: control reaches end of non-void function [-Wreturn-type]
int releaseFont(FontHandle){};
                            ^
ec15.cpp:28:16: error: use of undeclared identifier 'f'
changeFontSize(f.get(), newFontSize);
               ^
ec15.cpp:28:25: error: use of undeclared identifier 'newFontSize'
changeFontSize(f.get(), newFontSize);
                        ^
ec15.cpp:36:42: error: use of undeclared identifier 'f'
    operator FontHandle() const { return f; }  // implicit conversion
                                         ^
ec15.cpp:41:16: error: use of undeclared identifier 'f'
changeFontSize(f, newFontSize);
               ^
ec15.cpp:41:19: error: use of undeclared identifier 'newFontSize'
changeFontSize(f, newFontSize);
                  ^
ec15.cpp:43:9: error: use of undeclared identifier 'getFont'
Font f1(getFont());
        ^
ec15.cpp:44:12: error: no viable conversion from 'Font' to 'FontHandle' (aka 'int')
FontHandle f2 = f1;  // oops
           ^    ~~
1 warning and 7 errors generated.
```
#課題(agenda)
1)役に立つまたは意味のあるコンパイルエラーを取る方法

2)役に立つまたは意味のある関数、クラスの呼び出し方

3)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][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