C / C ++未初始化数组的结果 [英] C/C++ the result of the uninitialized array

问题描述

这可能是一个无聊的问题！谢谢！

It might be a boring question! thanks!

这是代码：

#include <iostream>
#include <cstring>
using namespace std;

int main()
{
        int a[5] = {0};
        int b[5];
        cout << a << endl;
        cout << b << endl;
        for (int i = 0; i < 5; i++)
        {
                cout << a[i] << " ";
        }
        cout << endl;
        for (int i = 0; i < 5; i++)
        {
                cout << b[i] << " ";
        }
        cout << endl;
        return 0;
}

在Ubuntu中：g ++ a.cpp

in Ubuntu: g++ a.cpp

在装有DEV C ++的Windows中，MinGW GCC 4.7.2：
< a href = https://i.stack.imgur.com/QoNZw.png rel = nofollow noreferrer>

In windows with DEV C++ ,MinGW GCC 4.7.2:

因此，问题集中在数组b上：

So the question is focused on the array b:

>我知道我还没有初始化数组b。

I know I haven't initialized the array b.

数组b充满了垃圾值，但是为什么总是在固定位置使用 0，例如 X 0 X 0 X ??

Array b is full of garbage values, but why there is always having '0' with the fixed position like "X 0 X 0 X"??

里面发生了什么？？？
只是一种保护机制？

What happens inside?? Just a protection mechanism?

推荐答案

这是未定义的行为。如果存在这些零，则不能保证只是偶然。

That is undefined behavior. There is no guarantee, if these zeros are there, that just accidentally is true.

解释是，由于某种随机原因，在内存中的这些位置存储了0。在将其重新用于您的目的之前。由于您是在堆栈上分配数组，因此这些零可能来自先前的函数调用，并且可能有些填充。编译器将按照他的意愿进行操作。

The explanation is, that for some random reason at these places in memory a 0 was stored before it was reused for your purpose here. Since you allocate your arrays on the stack, these zeroes are probably from a prior function call and might be some padding. The compiler will do that as he pleases.

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