1,基类析构函数不为虚函数 #include " pch.h " #include iostream class CBase{ public : CBase() { m_one = 0 ; printf( " this is CBase construct\n " ); } ~ CBase() { printf( " this is ~CBase deconstruct\n " ); } void setNumOne( int
1,基类析构函数不为虚函数
#include "pch.h" #include <iostream> class CBase { public: CBase() { m_one = 0; printf("this is CBase construct\n"); } ~CBase() { printf("this is ~CBase deconstruct\n"); } void setNumOne(int n) { m_one = n; } int getNumOne() { return m_one; } private: int m_one; }; class CDrived:public CBase { public: CDrived() { m_two = 0; printf("this is CDrived construct\n"); } ~CDrived() { printf("this is ~CDrived deconstruct\n"); } void setNumTwo(int n) { m_two = n; } int getNumTwo() { return m_two; } private: int m_two; }; int main() { CBase *p = new CDrived; delete p; std::cout << "Hello World!\n"; }
输出:
this is CBase construct this is CDrived construct this is ~CBase deconstruct Hello World!
可以发现继承类析构函数没有调用,若继承类中有一些资源需要释放,则不能释放,故需要将基类析构函数声明为虚函数。
#include "pch.h" #include <iostream> class CBase { public: CBase() { m_one = 0; printf("this is CBase construct\n"); } virtual ~CBase() { printf("this is ~CBase deconstruct\n"); } void setNumOne(int n) { m_one = n; } int getNumOne() { return m_one; } private: int m_one; }; class CDrived:public CBase { public: CDrived() { m_two = 0; printf("this is CDrived construct\n"); } ~CDrived() { printf("this is ~CDrived deconstruct\n"); } void setNumTwo(int n) { m_two = n; } int getNumTwo() { return m_two; } private: int m_two; }; int main() { CBase *p = new CDrived; delete p; std::cout << "Hello World!\n"; }
输出:
this is CBase construct this is CDrived construct this is ~CDrived deconstruct this is ~CBase deconstruct Hello World!
2,
#include "pch.h" #include <iostream> class CBase { public: CBase() { m_one = 0; printf("this is CBase construct\n"); } virtual ~CBase() { printf("this is ~CBase deconstruct\n"); } virtual void setNumOne(int n) { m_one = n; } virtual int getNumOne() { return m_one; } private: int m_one; }; class CDrived:public CBase { public: CDrived() { m_two = 0; printf("this is CDrived construct\n"); } ~CDrived() { printf("this is ~CDrived deconstruct\n"); } void setNumTwo(int n) { m_two = n; } int getNumTwo() { return m_two; } private: int m_two; }; int main() { CDrived *p = new CDrived; printf("sizeof(CDrived) = %d\n", sizeof(CDrived)); // 12 delete p; std::cout << "Hello World!\n"; }