how to find the new size of array of pointer to string

Question

In the main method , i am creating an array of pointers to string in the add method i am reallocating the array size and adding x elements which i dont know while coming back to main how can i know the new size of the array , i mean the number of elements int the array ?

Here is my code .. (it has some bugs)

#include <stdio.h>

void add(char ***x);

int main()
{
  char **s;
  s = (char **) malloc(sizeof(char *));
  int i;
  add(&s);

  for( i=1;i<=?????(**find the new size of the array** );i++)
    puts(*s[i]);

  return 0;
}

void add(char ***x)
{

  - ** // alter arry add x random datas to the array of string pointer**

  /*
   s[1]="Hello";
   s[2]="Need";
   s[3]="a help";
   s[4]="and help";
   s[5]="for the  help";
   */

  char **data;
  int i = 0;
  for (i = 1; i <= 5; i++)
  {
    data = (char **) realloc(*x, 1 * sizeof(char *));
    data[i] = (char *) malloc(i * sizeof(char *));
    strcpy(data[i], "first");
  }

}

can some one please point and fix the bug in the code..

Answer 1

(Sidenote:

can some one please point and fix the bug in the code..

hey, isn't that what debuggers are for?)

Long story short, keep track of it manually:

char **func_that_reallocs(char **ptr, size_t *sz)
{
    char **tmp = realloc(ptr, new_size * sizeof(*ptr));
    *sz = new_size;
    return tmp;
}

And please do not cast the return value of malloc()!

Answer 2

Always add one entry more to the array as needed and set this additional last entry to NULL.

Then write a function which scans the array until it find this NULL-pointer and return the number of entries counted up until then and you are done.

It's the same concept as for a C-"string", with the only difference of using a NULL instead of '\0' as (array-)terminator.

Some people call this last element also the "stopper"-element.

The positive thing about this approach is, one does not have to keep the array's size in a different variable, which might get out of sync with the real size of the array: The size is implicitly given by the array itself.