🚡 🌫️ 🚫 新規および削除なしのC ++ 🧘🏻 😔 🍤

, !

, Align Technology. ++.

, . , ++ . , — .

. new

delete

. , . , ++ new

delete

.

, , . , . , .

, , - .

behappy.me

: new

delete

. , . , .

:

.
,
- c delete
  
  ;
- new
  
  make
  
  -;
- new
  
  .
.

, new

delete

STL boost.

`new`

`delete`

?

new

delete

++ .

, . , . thread-local , . . storage duration.

, . , , . .

. ( ). :

struct A
{
  std::string str;  //  ,     A (  
                    // ).    -   (*),   
                    //    std::string,       A. 
  // (*)      ,   Small String Optimization  
  //     .
};

void foo()
{
  std::vector<int> v;  //  ,      .
  v.push_back(10);  //   -   (),     
                    // ,        .

  A a;  //    ,      .

  A* pa = new A;  //  pa -  ,      ,
                  //        ,      .
  delete pa;  //    .

  auto upa =  //   upa -  ,      , 
    std::make_unique<A>();  //        ,    
                            //    .
}

, . , . upa->str

, .. — *upa

. .. / , .

/ , , .. , ^*). a

*pa

, , — .

++ new

, delete

. : , ! , . .

, , .

^* , / . , .

`new`

`delete`

?

new

delete

. delete

:

delete

( , memory leak).
delete

( ).
delete

( , double delete).
: delete

delete[]

( , undefined behavior).
delete

(dangling pointer).

, .

delete

, . new

, , , , . , make

-.

new

delete

. , , , new

delete

.

— .

— , . , , , , .

++ new

delete

: new[]

delete[]

. , :

void DoWork(int* buffer, size_t bufSize);

API ^*. , . , .. delete

, .

void Call(size_t n)
{
  int* p = new int[n];
  DoWork(p, n);
  delete[] p;  // !
}

, ++ std::vector

^**. . , , . :

void Call(size_t n)
{
  std::vector<int> v(n);  // .
  DoWork(v.data(), v.size());
}

, delete

, +, .

new

delete

. . , .

^* ++ span<int>

. STL- , ( ).

^** ++, , - : «! std::vector

(!) , int*

— . ! !». ++ Why C++ Sails When the Vasa Sank. , std::unique_ptr<int[]>

, dynarray

.

, - . , ^*, (. ). .

, - , : , , , - . , , — .

^**, . , , . , .

, , Qt. , . , .. QObject

. , , boost::intrusive_ptr

.

, . . . , QObject

setParent()

children()

, boost::intrusive_ptr

intrusive_ptr_add_ref

intrusive_ptr_release

.

, , . , , , .

. , , new

delete

, — .

^* : pimpl;

(, ).

^** std::locale::facet

(. ).

. ++, , .

, , , . . ++ : std::shared_ptr

std::unique_ptr

. std::weak_ptr

, .. std::shared_ptr

.

std::auto_ptr

, ++ ++17. !

, .. . , std::make_shared

std::make_unique

, .

.. :

std::unique_ptr<Cookie> cookie(new Cookie(dough, sugar, cinnamon));

auto cookie = std::make_unique<Cookie>(dough, sugar, cinnamon);

make

- GotW #89 Effective Modern C++, Item 21. , :

make

-:
- .
- .
std::make_shared

:
- , .. , . We Know Where You Live.

make- , :

make

-:
- deleter
  
  . , .. make
  
  - new
  
  .
- braced initializer
  
  , , perfect forwarding (. Effective Modern C++, Item 30).
std::make_shared

:
- (std::weak_pointer
  
  ).
- new
  
  delete
  
  .
- (false sharing) (. StackOverflow).

. , delete

, make

- new

. , new

, delete

.

, make

- (a.k.a. STL). Don’t Help the Compiler:

. , (reference counting) - (parent to child relationship).

new

delete

. - , - .

, . OpenSceneGraph. 3D-, ++ OpenGL.

osg::Referenced

, . ref()

, unref()

, .

osg::ref_ptr<T>

, T::ref()

T::unref()

. boost::intrusive_ptr

, ref()

unref()

.

, OpenSceneGraph 3.0: Beginner's guide:

osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array;
// ... 
osg::ref_ptr<osg::Vec3Array> normals = new osg::Vec3Array;
// ... 
osg::ref_ptr<osg::Geometry> geom = new osg::Geometry;
geom->setVertexArray(vertices.get());
geom->setNormalArray(normals.get());
// ...

osg::ref_ptr<T> p = new T

. , std::make_unique

std::make_shared

std::unique_ptr

std::shared_ptr

, osg::make_ref

osg::ref_ptr

. , std::make_unique

:

namespace osg
{
  template<typename T, typename... Args>
  osg::ref_ptr<T> make_ref(Args&&... args)
  {
    return new T(std::forward<Args>(args)...);
  }
}

auto vertices = osg::make_ref<osg::Vec3Array>();  
// ... 
auto normals = osg::make_ref<osg::Vec3Array>();  
// ... 
auto geom = osg::make_ref<osg::Geometry>();
geom->setVertexArray(vertices.get());
geom->setNormalArray(normals.get());
// ...

. ^*, .

delete

osg::Referenced::unref()

, new

osg::make_ref

. new

delete

.

^* , , .

MFC

, MFC. ++ Windows API. GUI Windows.

, Microsoft . .. , , . CDialog::PostNcDestroy()

. WM_NCDESTROY

— , .

CMainFrame::OnBnClickedCreate()

CMyDialog::PostNcDestroy()

.

void CMainFrame::OnBnClickedCreate()
{
  auto* pDialog = new CMyDialog(this);
  pDialog->ShowWindow(SW_SHOW);
}

class CMyDialog : public CDialog
{
public:
  CMyDialog(CWnd* pParent)
  {
    Create(IDD_MY_DIALOG, pParent);
  }

protected:
  void PostNcDestroy() override
  {
    CDialog::PostNcDestroy();
    delete this;
  }
};

new

, delete

. — . , PostNcDestroy()

, . new

, delete

, . , .

new

delete

CModelessDialog

CreateModelessDialog

, :

class CModelessDialog : public CDialog
{
public:
  CModelessDialog(UINT nIDTemplate, CWnd* pParent)
  {
    Create(nIDTemplate, pParent);
  }

protected:
  void PostNcDestroy() override
  {
    CDialog::PostNcDestroy();
    delete this;
  }
};

//     
template<class Derived, typename... Args>
Derived* CreateModelessDialog(Args&&... args)
{
  //  static_assert   ,   std::enable_if   ,     SFINAE. 
  //  ..       ,        .
  static_assert(std::is_base_of<CModelessDialog, Derived>::value, 
                "CreateModelessDialog should be called for descendants of CModelessDialog");
  auto* pDialog = new Derived(std::forward<Args>(args)...);
  pDialog->ShowWindow(SW_SHOW);
  return pDialog;
}

PostNcDestroy()

, delete

, , new

. :

void CMainFrame::OnBnClickedCreate()
{
  CreateModelessDialog<CMyDialog>(this);
}

class CMyDialog : public CModelessDialog
{
public:
  CMyDialog(CWnd* pParent) : CModelessDialog(IDD_MY_DIALOG, pParent) {}
};

, . , . , . CModelessDialog

. , , CMyDialog

, , . .

, . new

delete

.

-

, GUI. Qt — UI.

QObject

. , . ( ) .

, new

delete

. , . , (. Qt mailing list).

, new delete Qt.

`std::locale::facet`

++ std::locale

. (facet), . , .

, , , new (. Notes std::locale)

:

std::locale default;
std::locale myLocale(default, new std::codecvt_utf8<wchar_t>);

.

, , new

. , , .

, , . new

delete

make

- .

, , new

delete

. , .

, , . , , new

delete

, , . , , .

:

new

delete

. .
.
make

- , .
.

- new

delete

. , , , .

, , , .

C++ Russia. : , , , . , , , , , , .

PS , , : «» «». , «», . , «». , : «». -. , «», .

Herb Sutter, GotW #89 Solution: Smart Pointers.
Scott Meyers, Effective Modern C++, Item 21, p. 139.
Stephan T. Lavavej, Don’t Help the Compiler.
Bjarne Stroustrup, The C++ Programming Language, 11.2.1, p. 281.
Five Popular Myths about C++., Part 2
Mikhail Matrosov, C++ without new and delete.

新規および削除なしのC ++

MFC

-

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