我需要在C语言中使用动态内存中的指针创建一个矩阵，填充它们以随机数，然后打印出来。
这是大学作业的一部分（我必须为矩阵编写一整套函数），但是就帖子的目的而言，我认为我成功地找到并隔离了有问题的部分。以下是代码：
```c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>
int main()
{
    int rows = 2;
    int cols = 3;
    int **matrix = malloc(sizeof(int*) * rows); //声明和分配矩阵的动态内存
    for(int i=0;i<rows;i++)
        *(matrix+i) = malloc(sizeof(int) * cols);
    //生成矩阵的随机数：
    srand(time(NULL));
    for(int i=0;i<rows;i++)
        for(int j=0;j<cols;j++)
            *(*(matrix+j)+i) = rand() % 20;
    //打印矩阵：
    printf("{\t");
    for(int i=0;i<rows;i++)
    {
        int j;
        if(i>0)
            printf("\t");
        printf("{\t");
        for(j=0;j<cols;j++)
            printf("%d\t",*(*(matrix + j) + i));
        printf("}");
        if(i<rows-1)
            printf("\n");
    }
    printf("\t}\n\n");
    //销毁矩阵
    for(int i=0;i<rows;i++)
        free(matrix[i]);
    free(matrix);
    matrix = NULL;
    return 0;
}

{       {       5       17      3       }
        {       1       8       11      }       }

i = 0
j = 2
**(matrix + 2)（即 matrix[0][2]）= 无法访问地址为 0xabababababababab 的内存

<details>
<summary>英文:</summary>
I have to create a matrix with pointers in dynamic memory in C, fill it with random numbers then print it.
This is part of a larger assignment from college (I had to do a whole library of functions for matrixes) but for the purposes of the post, I think I managed to track down and isolate the problematic bits. Here&#39;s the code:

for(int i=0;i<rows;i++)
*(matrix+i) = malloc(sizeof(int) * cols);
//generating random numbers for the matrix:
srand(time(NULL));
for(int i=0;i<rows;i++)
for(int j=0;j<cols;j++)
*(*(matrix+j)+i) = rand() % 20;
//printing matrix:
printf("{\t");
for(int i=0;i<rows;i++)
{
int j;
if(i>0)
printf("\t");
printf("{\t");
for(j=0;j<cols;j++)
printf("%d\t",*(*(matrix + j) + i));
printf("}");
if(i<rows-1)
printf("\n");
}
printf("\t}\n\n");
//destroying the matrix
for(int i=0;i<rows;i++)
free(matrix[i]);
free(matrix);
matrix = NULL;
return 0;

The debugger stops here:
`*(*(matrix+j)+i) = rand() % 20;`
Apparently, when trying to generate a random number for the first column of the second row (i.e. when it first changes rows) the debugger "cannot access memory" for that position, then the program crashes.
I tried changing the amount of rows and columns and I found it only crashes when row size is less than column size, which is weird because when it's equal or more, it works just fine.
I'm trying with 2 rows by 3 columns. Expectation:

What actually happens:
`Process returned -1073741819 (0xC0000005)`
Values of the variables when the debugger stops (at generating random numbers):

At first I suspected I messed up when allocating memory for the matrix, but as I said when the matrix is square it does work fine, so I really don't know what's the issue here. I know the stackOverflow community doesn't like when someone posts "I don't know what I did wrong please help" kind of thing but I've really been a long time trying and couldn't get to the root of the problem.
Can someone please shed some light on this for me?
</details>
# 答案1
**得分**: 2
These nested for loops contain a bug
这些嵌套的for循环包含一个错误
```c
for(int i=0;i<rows;i++)
for(int j=0;j<cols;j++)
*(*(matrix+i)+j) = rand() % 20;

*(*(matrix+i)+j) = rand() % 20;

*(*(matrix+j)+i) = rand() % 20;

printf("%d\t",*(*(matrix + j) + i));

printf("%d\t",*(*(matrix + i) + j));

( *( matrix + i ) )[j]

*( *( matrix + i ) + j )

*( matrix[i] + j )

*( *( matrix + i ) + j )

T a[M][N];

a[i][j]
i[a][j]
j[a[i]]
j[i[a]]
*( *( a + i ) + j )
*( a[i] + j )
*( i[a] + j )
( *( a + i ) )[j]
j[*( a + i ) ]