Question

Suppose I have the following code:

typedef struct
{
    char **p;
} STRUCT;

int main()
{
    STRUCT s;
    *(s.p) = "hello";
    printf("%s\n", *(s.p));

    return 0;
}

which obviously doesn’t work, but it should show what I want to do. How would I go about initialising, accessing, printing, etc the array of strings in the structure?

Answer 1

You have two * where you want just one, I think. Try:

typedef struct
{
    char *p;
} STRUCT;

int main()
{
    STRUCT s;
    s.p = "hello";
    printf("%s\n", s.p);

    return 0;
}

If you do really want to have the double indirection, you need to allocate some space for the pointer you’re dereferencing. *(s.p) in your original program dereferences an uninitialized pointer. In this case:

typedef struct
{
    char **p;
} STRUCT;

int main()
{
    STRUCT s;
    s.p = malloc(sizeof(char *));
    *(s.p) = "hello";
    printf("%s\n", *(s.p));
    free(s.p);
    return 0;
}

This second program allocates space for just one string pointer; if you want an array, just allocate the appropriate amount of space.