c/c ++指针(系统中的内存分配) [英] c/c++ Pointers (Memory allocation in the system)

问题描述

大家好，

我对Pointer非常怀疑.

我已经声明了这样的变量

Hi to everyone,

I have very basic doubt in Pointer.

I have declared a variable like this

int **value;

书籍定义:

Book Definition:

value = &anotherpointer;

但是我使用相同的双指针将数据存储在二维数组中.

我在下面给出了示例代码:

But I have used the same double pointer for storing data in two dimensional array.

I have given a sample code below:

value = (int **) malloc(sizeof(int)*2);
value[0] = (int *)malloc(sizeof(int) *2);
value[1]= (int *)malloc(sizeof(int)*2);

上面的语法在我的程序中工作正常.

基本上，我尝试创建大小为(2X2)的动态二维数组.

创建动态数组的上述语法对于所有用户定义和内置数据类型均适用.

如果让我尝试创建动态结构指针或其他大小大小的数据类型(示例10)，请让我知道如何分配内存.

请让我知道我是否正确使用了指针?

让我知道原因.期待您的答复....

This above syntax is working fine with my program.

Basically, i have tried to create a dynamic two dimensional array of size (2X2).

The above syntax of creating dynamic array works fine for all user defined and built-in data types.

Please let me know how memory will be allocated if i tried to create a dynamic structure pointer or other data types of size (example 10).

Please let me know whether i have used the pointer correctly or not?

And let me know the reason. Looking forward for your replies....

推荐答案

是的，您可以使用双指针存储另一个指针的地址，以及创建矩阵(编译器)不会抱怨. :-)

您将要使用的内存实际上取决于malloc语句.

便笺:

Yes, you may use a double pointer to store the address of another pointer as well for creating a matrix, the compiler won''t complain. :-)

The memory you are going to use does actually depend on the malloc statements.

Plaese note:

balasubramaniyan94写道:

balasubramaniyan94 wrote:

value =(int **)malloc(sizeof(int)* 2);

value = (int **) malloc(sizeof(int)*2);

上一行是错误的，应该是

The above line is wrong, it should be

value = (int **) malloc(sizeof(int *) * 2);

(如果经常出现sizeof(int) == sizeof(int *)，您会很幸运.)

(You are lucky if, as often happens, sizeof(int) == sizeof(int *)).

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