数组大小小于No。存储在其中的元素的数量 [英] Array size less than the no. of elements stored in it

问题描述

是否可以声明一个大小为1的数组并能够在其中存储5个元素然后检索它们？

Is it possible to declare an array of size 1 and be able to store 5 elements in it and then retrieve them?

我尝试一个这样的代码，在其中声明了数组 arr [1] ，然后将5个元素存储到其中。实际上可以存储5个元素！

I try one such code where I declared an array arr[1] and then stored 5 elements into it. It was actually possible to store 5 elements! How was it?

推荐答案

如果是C（或C ++），则可以轻松存储比数组大小更多的元素

If this is C (or C++), you can quite easily store more elements than the array is sized for:

#include <stdio.h>

int main (void) {
    int x = 0;
    int a[1];    // so that a[0] is the only valid element
    a[1] = 7;    // write beyond end of array

    printf ("x=%d, &a[0]=%p, &a[1]=%p, &x=%p\n", x, &(a[0]), &(a[1]), &x);
    return 1;
}

但是，这样做会导致行为不确定，可能会覆盖某些其他信息，并不是一个好主意。

Doing so, however, leads to undefined behaviour, probably overwriting some other piece of information, and is not really a good idea.

在我的系统上，上面的代码打印出来：

On my system, that code above prints:

x=7, &a[0]=0xbf9bb638, &a[1]=0xbf9bb63c, &x=0xbf9bb63c

尽管我将 x 设置为零，但从未明确更改它。这是因为超出数组末尾的写入已对其产生影响（如您从 a [1] 和 x ）。

despite the fact I set x to zero and never explicitly changed it. That's because writing beyond the end of the array has affected it (as you can see from the two identical addresses for a[1] and x).

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