算譜(source code)

ec14.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 <mutex>
#define Mutex mutex

using namespace std;

const char * msg ="Item 14: Think carefully about copying behavior in resource-managing classes";

/// From here "Effective C++

//In previous item, we see that heap-based resources can be managed using shared_ptr. Not all resources are heap-based.

//C API:

void lock(Mutex* pm);   // lock mutex pointed to by pm
void unlock(Mutex* pm);  // unlock the mutex
//RAII: Resources are acquired during construction and released during destruction.

class Lock {
public:
  explicit Lock(Mutex* pm): mutexPtr(pm) {
    lock(mutexPtr);  // acquire resource
  }
  ~Lock() {
    unlock(mutexPtr); // release resource
  }
private:
  Mutex* mutexPtr;
};

void f() {
  Mutex m;
  {
    Lock ml(&m);
  }

//What about the copying behavior?

  Lock ml1(&m);
  Lock ml2(&ml1);  // copy ml1 to ml2, what should happen here?
}
//Prohibit copying

namespace A {
  class Lock : private Uncopyable {  // see Item 6
  public:
//    ...
  };
//reference-count the underlying resource Copying the RAII object should increment the count of the number of objects.
//deleter should be defined
}

namespace B {
  class Lock {
  public:
    explicit Lock(Mutex* pm): mutexPtr(pm, unlock)  // deleter added
    {
      lock(mutexPtr.get());
    }
  private:
    std::shared_ptr<Mutex> mutexPtr;
  };
//Copying the underlying resource
//Make sure a deep copy. For example, STL.
}

//Transfer ownership of the underlying resource
//Example: auto_ptr

//Things to Remember

//Copying an RAII object entails copying the resource it manages, so the copying behavior of the resource determines the copying behavior of the RAII object.
//Common RAII class copying behaviors are disallowing copying and performing reference counting, but other behaviors are possible.

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

int main() {
  f();
  cout << msg << endl;
  return EXIT_SUCCESS;
}

編纂・実行結果(compile and go)

cpa.sh

$ ../c1.sh ec14
$ clang++ ec14.cpp  -std=c++2a -Wall
ec14.cpp:39:6: error: no matching constructor for initialization of 'Lock'
Lock ml2(&ml1);  // copy ml1 to ml2, what should happen here?
     ^   ~~~~
ec14.cpp:22:7: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from
      'Lock *' to 'const Lock' for 1st argument; remove &
class Lock {
      ^
ec14.cpp:24:14: note: candidate constructor not viable: no known conversion from 'Lock *' to 'std::__1::mutex *'
      for 1st argument
    explicit Lock(Mutex* pm): mutexPtr(pm) { lock(mutexPtr); }  // acquire resource
             ^
ec14.cpp:44:22: error: expected class name
class Lock : private Uncopyable {  // see Item 6
                     ^
2 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

文書履歴(document history)

ver. 0.10 初稿 20180622

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Effective C++ Third version, sample code compile list(14)Think carefully about copying behavior in resource-managing classes