allocating memory for structure via double pointer

Question

HI I need help in allocating memory for a structure which is part of 2nd structure and 2nd structure is having double pointer as deceleration.

struct ant{ 
int stu;
int clas;
char *name;
};

struct cat{
int a;
int b;
struct ant *c;
};

int main()
{
   struct cat **sample;
   struct ant *info;

   info = calloc(1, sizeof(*info));

   <here i had allocated memory for **info** which is of type **ant**>
   <now i need to assig this **info** to the pointer which is there in **cat** structure>
   <how we can achive this> ?
}

Answer 1

Your cat struct has a member c that can hold a pointer to an ant struct. Just assign the pointer to your ant struct to the c member. If you have a double pointer to a cat struct, you first have to dereference it.

struct cat *some_cat_p;
some_cat_p = calloc(1, sizeof(*some_cat_p));

struct cat **some_cat_pp;
some_cat_pp = &some_cat_p;

struct ant *some_ant_p;
some_ant_p = calloc(1, sizeof(*some_ant_p));


(*some_cat_pp)->c = some_ant_p; 

Note: You may also want to check the return value of calloc and friends, it may return NULL if it fails to allocate memory.