1. It can point to an object.
2. It can point to the location just immediately past the end of an object.
3. It can be a null pointer, indicating that it is not bound to any object.
4. It can be invalid; values other than the preceding three are invalid.
c ++ pointer lawful in three ways:
1. point to an object
2. The end of the next target point to a location of a byte
exp. for(vector<int>::iterator iter = vecInt.begin(); iter != vecInt.end(); ++iter)
3. Point null pointer
Otherwise, it is invalid pointer
Illegal pointer scenarios generated:
The non-null pointer to an object pointer pointing to the end of the life cycle of 1
class A
{
int i1 = 0;
double d1 = 0;
char *ch = nullptr;
public:
A()
{
i1 = 1;
d1 = 1;
ch = (char *)malloc(4);
strcpy_s(ch,3,"vi");
}
void showch()
{
cout << ch << endl;
}
void showi()
{
cout << i1 << endl;
}
~A()
{
free(ch);
}
};
int main()
{
double dval = 2.03;
A **pp = nullptr;
for (int i = 0; i < 1;i++)
{
A a11;
a11.showch();
a11.showi();
A *p= &a11;
pp = &p;
}
// point to objects that have been recovered, the compiler will not complain
(** pp) .showi (); // build-in type memory contents not yet erased or overwritten
(** pp) .showch (); // dynamically allocated memory that has been erased content
}
result：
2. Dynamic allocation space class members unimplemented copy constructor
class Message
{
private:
char* pmessage;
public:
void ShowIt() const
{
cout <<endl <<pmessage;
}
Message(const char* text = "Defaut message")
{
pmessage = new char[strlen(test) + 1];
strcpy_s(pmessage,strlen(text) + 1,text);
}
~CMessage()
{
delete[] pmessage;
}
};
int main ()
{
The Message motto1 ( "Fallout4.");
The Message motto2 (motto1); // if motto1 or motto2 wherein the other end of a life cycle will generate an illegal pointer, copy constructor should realize that the two different pointing object
}