C++堆栈类的子类出错。
/************************************************* stack_test -- Test the use of the classes *
* stack and safe_stack. *
************************************************/
#include <iostream>
// The largest stack we can use
// (private to class stack and safe_stack)
const int STACK_MAX = 100;
/************************************************
* stack -- Class to provide a classic stack. *
* *
* Member functions: *
* push -- Push data on to the stack. *
* pop -- Return the top item from the *
* stack. *
* *
* Warning: There are no checks to make sure *
* that stack limits are not exceeded. *
************************************************/
class stack {
protected:
int count; // Number of items in the stack
int *data; // The stack data
public:
// Initialize the stack
stack(void): count(0)
{
data = new int;
}
// Destructor
virtual ~stack(void) {
delete data;
data = NULL;
}
private:
// No copy constructor
stack(const stack &);
// No assignment operator
stack & operator = (const stack &);
public:
// Push an item on the stack
void push(
const int item // Item to push
) {
data = item;
++count;
}
// Remove the an item from the stack
int pop(void) {
--count;
return (data);
}
// Function to count things in
// an array of stacks
friend void stack_counter(
stack stack_array[],
const int n_stacks
);
};
/***********************************************
* safe_stack -- Like stack, but checks for *
* errors. *
* *
* Member functions: push and pop *
* (just like stack) *
***********************************************/
class safe_stack : public stack {
public:
const int max;// Limit of the stack
public:
safe_stack(void): max(STACK_MAX) {};
// Destructor defaults
private:
// No copy constructor
safe_stack(const safe_stack &);
// No assignment operator
safe_stack & operator =
(const safe_stack &);
public:
// Push an item on the stack
void push(
// Data to push on the stack
const int data
) {
if (count >= (STACK_MAX-1)) {
std::cout << "Stack push error\n";
exit (8);
}
stack::push(data);
}
// Pop an item off the stack
int pop(void) {
if (count <= 0) {
std::cout << "Stack pop error\n";
exit (8);
}
return (stack::pop());
}
};
/************************************************
* stack_counter -- Display the count of the *
* number of items in an array of stacks.*
************************************************/
void stack_counter(
// Array of stacks to check
stack *stack_array,
// Number of stacks to check
const int n_stacks
)
{
int i;
for (i = 0; i < n_stacks; ++i)
{
std::cout << "Stack " << i << " has " <<
stack_array.count << " elements\n";
}
}
// A set of very safe stacks for testing
static safe_stack stack_array;
int main()
{
stack_array.push(0);
stack_array.push(0);
stack_array.push(1);
stack_array.push(0);
stack_array.push(1);
stack_array.push(2);
stack_array.push(0);
stack_array.push(1);
stack_array.push(2);
stack_array.push(3);
stack_array.push(0);
stack_array.push(1);
stack_array.push(2);
stack_array.push(3);
stack_array.push(4);
stack_counter(stack_array, 5);
return (0);
}上面的代码大家可以看看，编译一下，就知道了。safe_stack不安全，哈哈。求解决办法。
StackOverflow和Yahoo Ask上面的答案已经把我搞蒙了。书上的解释也好乱。求大神。
下面是书上的解释：
We have an array of a derived class called safe stack. In C++, you can use a base class pointer (stack*) to point to a derived class (safe_stack). The system will see only the base part of the object, but you can still point to it.
Now a pointer can point to a single instance of a class or an array of objects.
So we have the following two rules:
[*]A base pointer can point to a derived object.
[*]An object pointer can point to an array of objects.
From this, we can conclude:
[*]A base pointer can point to an array of derived objects.
That's wrong.The problem is that an array of derived objects is not the same as an array of base objects.
So if we take a base pointer and point it a derived array, the memory layout will be wrong.好啦，请注意！！！我需要一个解决方案。建议使用dynamic_cast或者reinterpret_cast，不可以告诉我使用STL。如果是要使用auto_ptr或者share_ptr一类的能解决也行。多谢多谢。
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