类数据默认初始化 [英] Class data default initialization

问题描述

我有以下代码:

#include <iostream>
using namespace std;

class Base
{
private:
    int i;
    char ch;
public:
    void showdata()
    {
        cout<<"Int:"<<i<<endl;
        cout<<"Char:"<<ch<<endl;
    }
    //int pub_data ;
} ;

int main()
{
    Base ob;
    ob.showdata() ;
    //cout<<"Public Data:"<<ob.pub_data<<endl;
    return 0;
}

该程序可以编译并正常运行.输出显示i初始化为0，ch初始化为'\ 0'.
如果您注意到我在该程序中已注释掉2条语句.首先是公共数据pub_data的声明，其次在主行中打印该公共数据.
现在的问题是，如果我取消注释这两行，则类(即i，ch，pub_data)的数据成员似乎未初始化，并且在打印时它们将显示垃圾值. 所以我的问题是公共数据在这里有什么不同?
我正在使用g ++ 3.4.6

This program compiles and runs fine. The output shows that i is initialized with 0 and ch is initialized with '\0'.
If you notice i have commented out 2 statements in this program. First the declaration of public data pub_data and second the line inside main printing this public data.
Now here the problem is, if i uncomment these two lines, the data members of class i.e. i, ch, pub_data do not seem to be initialized and when printed, they display junk values.
So my question is what difference public data makes here?
I'm using g++ 3.4.6

推荐答案

int和char都不会自动初始化为0.它发生的事实只是运气.

Neither int's nor char's are automatically initialized to 0. The fact that it happened is just luck.

您需要添加一个执行初始化的构造函数:

You need to add a constructor that does the initialization:

Base() : i(0), ch(0) {}

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