• operator new/delete 預定義的內存
• • operator new/delete 語法格式
  • 舉例說明

operator new/delete 預定義的內存

適用于極個別情況需要定制的時候才用的到。一般很少用，比如定制內存。

operator new/delete 語法格式

void * operator new(size_t); void operator delete(void *); void * operator new[](size_t); void operator delete[](void *);

舉例說明

使用：void * operator new(size_t);

#include <iostream> #include <memory> using namespace std;class A { public:A(){}~A(){cout << "~A()" << endl;}void func(){cout << x <<" " << y << endl;}void* operator new(size_t size){cout << "void* operator new(size_t)" << endl;cout << size << endl;void* p = malloc(size);((A*)p)->x = 100;//底層提前初始化 寫死((A*)p)->y = 200;//底層提前初始化 寫死return p;} private:int x;int y; };int main() {A* pa = new A;pa->func();return 0; }

運行結果：

上面代碼有問題，只有malloc申請內存，沒有free釋放內存，通過引入void operator delete(void *);進行說明：

#include <iostream> #include <memory> using namespace std;class A { public:A(){}~A(){cout << "~A()" << endl;}void func(){cout << x <<" " << y << endl;}void* operator new(size_t size){cout << "void* operator new(size_t)" << endl;cout << size << endl;void* p = malloc(size);((A*)p)->x = 100;//底層初始化 寫死((A*)p)->y = 200;//底層初始化 寫死cout << p << endl;return p;}void operator delete(void* p){cout << "operator delete(void* p)" << endl;cout << p << endl;free(p);}private:int x;int y; };int main() {A* pa = new A;pa->func();delete pa;return 0; }

運行結果：

使用void * operator new[](size_t);

#include <iostream> #include <memory> using namespace std;class A { public:A(){cout << "A()" << endl;}~A(){cout << "~A()" << endl;}void func(){cout << x <<" " << y << endl;}void* operator new(size_t size){cout << "void* operator new(size_t)" << endl;cout << size << endl;void* p = malloc(size);((A*)p)->x = 100;//底層初始化 寫死((A*)p)->y = 200;//底層初始化 寫死cout << p << endl;return p;}void operator delete(void* p){cout << "operator delete(void* p)" << endl;cout << p << endl;free(p);}void* operator new[](size_t size){cout << "void* operator new[](size_t size)" << endl;cout << size << endl;void* p = malloc(size);return p;}private:int x;int y; };int main() {A* pa = new A[10];return 0; }

運行結果：

多出來的4字節用于記錄 A* pa = new A[10];中的10。

使用void operator delete[](void*);

#include <iostream> #include <memory> using namespace std;class A { public:A(){cout << "A()" << endl;}~A(){cout << "~A()" << endl;}void func(){cout << x <<" " << y << endl;}void* operator new(size_t size){cout << "void* operator new(size_t)" << endl;cout << size << endl;void* p = malloc(size);((A*)p)->x = 100;//底層初始化 寫死((A*)p)->y = 200;//底層初始化 寫死cout << p << endl;return p;}void operator delete(void* p){cout << "operator delete(void* p)" << endl;cout << p << endl;free(p);}void* operator new[](size_t size){cout << "void* operator new[](size_t size)" << endl;cout << size << endl;void* p = malloc(size);cout << p << endl;return p;}void operator delete[](void *p){cout << "void operator delete[](void *p)" << endl;cout << p << endl;free(p);}private:int x;int y; };int main() {A* pa = new A[10];delete []pa;return 0; }

運行結果：

總結

以上是生活随笔為你收集整理的operator new/delete，operator-＞ / *【C++运算符重载】的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。