数组元素值超出数组的大小数组c设置 [英] C array setting of array element value beyond size of array

问题描述

我有这款C code段

  INT号码[4] = {1};号码[0] = 1;号[1] = 2;数[3] = 3;数[10] = 4;
的printf（数字：％D％D％D \\ n，数字[0]，数字[1]，数字[3]，数字[6]，数字[10]，数字[5] ）;
 

这个片段中，输出端产生：

 数字：1 2 3 4 963180397 0
 

好吧，我有几个问题

1. 设置不会号码[10]给出一个错误的数组只是大小4如果没有的话，为什么（因为它没有给出任何错误）

的


2. 为什么印数[6]给出的垃圾值，而数字[5]给出0值？应该不是也有一个垃圾值。




3. 什么样的​​影响呢设定号码[10]有我知道它不会增加数组的大小，但又有什么怎么办呢？

在此先感谢。 PS我用GCC编译code！

解决方案

1. 这不会给一个错误，你的数组声明堆栈上有啥数[10]的确是在ADRESS数+（10 * sizeof的INT）编写并覆盖任何东西会在那里。


2. 作为Xymostech说0可以像963180397.印数[6]将打印的内容被存储在地址号码+（6 * sizeof的INT），所以它取决于你的程序的编译方式，如果你已经声明为多垃圾局部变量前的数字后，等等。
的

3. 请参阅回答1。

你可以做的是这样的：

  INT空[100];
INT号[4] = {1};
INT empty2 [100];memset的（空的0xCC，sizeof的空）;
memset的（empty2，0xDD，sizeof的empty2）;号码[0] = 1;数字[1] = 2;数字[3] = 3;数字[10] = 4;
的printf（数字：％D％D％D \\ n，数字[0]，数字[1]，数字[3]，数字[6]，数字[10]，数字[5] ）;
 

现在你能理解你的号码数组访问外出时要覆盖哪些

I Have this C code snippet

int numbers[4]={1};

numbers[0]=1; numbers[1]=2; numbers[3]=3; numbers[10]=4;
printf("numbers: %d %d %d %d %d %d\n",numbers[0],numbers[1],numbers[3],numbers[6],numbers[10],  numbers[5]) ;

The Output for this snippet produces :

    numbers: 1 2 3 963180397 4 0

Well I have couple of questions

1. wont setting numbers[10] give an error as array is just of size 4 if not then why ( as it didn't give any error )

2. why printing numbers[6] gives garbage value whereas numbers[5] gives value of 0 ? shouldn't it also be a garbage value.

3. what effect does setting numbers[10] has i know it does not increases size of array but what does it do then?

Thanks in advance . PS i used GCC to compile the code!!

解决方案

1. This won't give an error, your array is declared on the stack so what number[10] does is write at the adress number + (10*sizeof int) and overwrites anything that would be there.
2. As Xymostech said 0 can be as much garbage as 963180397. Printing numbers[6] will print what is stored at the address numbers + (6*sizeof int) so it depends on how your program is compiled, if you have declared local variables before of after numbers, etc.
3. See answer 1.

What you can do is this :

int empty[100];
int numbers[4]={1};
int empty2[100];

memset(empty, 0xCC, sizeof empty);
memset(empty2, 0xDD, sizeof empty2);

numbers[0]=1;numbers[1]=2;numbers[3]=3;numbers[10]=4;
printf("numbers: %d %d %d %d %d %d\n",numbers[0],numbers[1],numbers[3],numbers[6],numbers[10],  numbers[5]) ;

Now you can understand what you are overwriting when accessing out of your numbers array

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