macroevolution

struct HEX
{
   KakoiToTip *member;
};

void do_something(HEX *hex)
{
   KakoiToTip tmp;
   hex->member= &tmp;
   ...
   //forget clear hex->member
}

void do_something2(HEX *hex)
{
   if (hex->member)
      printf("%s", hex->member->name());
}

void main()
{
   HEX hex;
   do_something(&hex);
   do_something2(&hex); //ups!
}