convert_to_decimal (mpn_t a, size_t extra_zeroes)
{
  mp_limb_t *a_ptr = a.limbs;
   size_t a_len = a.nlimbs;
   /* 0.03345 is slightly larger than log(2)/(9*log(10)).  */
   size_t c_len = 9 * ((size_t)(a_len * (GMP_LIMB_BITS * 0.03345f)) + 1);
  char *c_ptr = (char *) malloc (xsum (c_len, extra_zeroes));
   if (c_ptr != NULL)
     {
       char *d_ptr = c_ptr;
      for (; extra_zeroes > 0; extra_zeroes--)
        *d_ptr++ = '0';
      while (a_len > 0)
        {
          /* Divide a by 10^9, in-place.  */
          mp_limb_t remainder = 0;
          mp_limb_t *ptr = a_ptr + a_len;
          size_t count;
          for (count = a_len; count > 0; count--)
            {
              mp_twolimb_t num =
                ((mp_twolimb_t) remainder << GMP_LIMB_BITS) | *--ptr;
              *ptr = num / 1000000000;
              remainder = num % 1000000000;
            }
          /* Store the remainder as 9 decimal digits.  */
          for (count = 9; count > 0; count--)
            {
              *d_ptr++ = '0' + (remainder % 10);
              remainder = remainder / 10;
            }
          /* Normalize a.  */
          if (a_ptr[a_len - 1] == 0)
            a_len--;
        }
      /* Remove leading zeroes.  */
      while (d_ptr > c_ptr && d_ptr[-1] == '0')
        d_ptr--;
      /* But keep at least one zero.  */
      if (d_ptr == c_ptr)
        *d_ptr++ = '0';
      /* Terminate the string.  */
      *d_ptr = '\0';
    }
  return c_ptr;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.