Question

consider the fallowing code:

typedef struct port * pport;

struct port
{
  int a;
  int b;
  pport next;
  pport prev;
  char * port;
};

void addNewport(pport head)
{
  pport newPort = (pport)malloc(sizeof(pport*));
  newPort->prev=temp;
  head->next=newPort;
}

int main()
{
  pport head = (pport)malloc(sizeof(pport*));
  addNewport(head);
}

This will result in seg fault if try to add a new port via a subroutine, but if I perform it the main, no seg fault will appear. Why is that?

Answer 1

Replace

 malloc(sizeof(pport*))

with

 malloc(sizeof(struct port))

because you don’t want to allocate memory for a pointer, rather for the struct.