[C++应用程序性能优化]单继承

转载于 2012-12-30 14:58:28 发布 · 307 阅读

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本文通过一个C++示例介绍了基类和派生类的概念。代码中定义了一个简单的基类simpleClass，并在此基础上创建了派生类dsimpleClass。通过对对象地址及成员变量地址的打印，展示了类继承中的内存布局。

class simpleClass
{
public:
 static int n_count;
 int n_value;
 char c;
 simpleClass() { printf("Create base class.\n"); }
 virtual ~simpleClass() { printf("Destroy base class.\n"); }
 int get_value(void);
 virtual void foo(void) { printf("foo in base class.\n"); }
 static void add_count();
};

class dsimpleClass : public simpleClass
{
public:
 int n_sub_value;
 dsimpleClass() { printf("create derived class.\n\n"); }
 ~dsimpleClass() { printf("destroy derived class.\n"); }
 virtual void foo() { printf("foo in derived class.\n"); }
};

#include <stdlib.h>
#include <stdio.h>
#include "gtest.h"

int simpleClass::n_count = 0;
int main()
{
 dsimpleClass asimple;
 printf("Object start address: %x\n", &asimple);
 printf("n_value address: %x\n", &asimple.n_value);
 printf("c address: %x\n", &asimple.c);
 printf("n_subvalue address: %x\n", &asimple.n_sub_value);
 printf("base class size: %d ; derived class size: %d\n\n", sizeof(simpleClass), sizeof(dsimpleClass));
 system("pause");
 return 0;
}