C程序：尝试填充动态创建的数组时出现分段错误

Question

I am working on a homework assignment that requires the creation of a dynamically allocated array which is to be populated with strings from a text file. I then need to print the array to standard output, shuffle the array, and then print it again.

My current issue is that I cannot seem to populate the array with anything without getting a segmentation fault. I tested the program with a static array and everything worked, so I know there isn't an issue with any of the other code.

Here is a section of my program.

void alloc2dArray(char ***source, int dim1, int dim2)
{
    int i = 0;

    source = malloc(sizeof(char *) * dim1);

    if(source == NULL) 
    { 
        printf("Memory full!");
        exit(EXIT_FAILURE);
    }
    for(i = 0; i < dim1; i++)
    {
            source[i] = malloc(sizeof(char) * (dim2 + 1));
            if(source[i] == NULL) 
        { 
            printf("Memory full!"); 
            exit(EXIT_FAILURE);
        }
    }
}

---

EDIT:

In an effort to avoid being a Three Star Programmer I changed my code to the below snippet. As luck would have it, that fixed my issue. So thanks to Kniggug for posting the link to something I had no idea about before.

char** alloc2dArray(int dim1, int dim2)
{
        int i = 0;

        char **twoDArray = malloc(sizeof(char *) * dim1);

        if(twoDArray == NULL)
        {
                printf("Memory full!");
                exit(EXIT_FAILURE);
        }
        for(i = 0; i < dim1; i++)
        {
                (twoDArray[i]) = malloc(sizeof(char) * (dim2 + 1));
                if(twoDArray[i] == NULL)
                {
                        printf("Memory full!");
                        exit(EXIT_FAILURE);
                }
        }

        return twoDArray;
}

Thank you.

Answer 1

Void alloc2dArray(char ***source, int dim1, int dim2)
{
    int i = 0;

    source = malloc(sizeof(char *) * dim1);

The assignment above has no effect outside this function, apart from leaking memory. You mean to do:

    *source = malloc(sizeof(char *) * dim1);

similarly:

(*source)[i] = malloc(sizeof(char) * (dim2 + 1));

Answer 2

Change source to (*source) in alloc2dArray

Void alloc2dArray(char ***source, int dim1, int dim2)
{
    int i = 0;

    *source = malloc(sizeof(char *) * dim1);

    if(*source == NULL)
    {
        printf("Memory full!");
        exit(EXIT_FAILURE);
    }
    for(i = 0; i < dim1; i++)
    {
        (*source)[i] = malloc(sizeof(char) * (dim2 + 1));
        if((*source)[i] == NULL)
        {
                printf("Memory full!");
                exit(EXIT_FAILURE);
        }
    }
}