Thread: no can compile

this is so wierd...there must be invisible characters on my screen that keeps dev-cpp from compiling it:

Here's the code that comes with the book that DID compile:

Code:

//  Programming with C++, Second Edition, by John R. Hubbard
//  Copyright McGraw-Hill 2000
//  Example 12.12, page 285
//  Memory Leaks

#include <iostream>
#include <cstdlib>

using namespace std;

class X
{
public:
  X() { p = new int[2]; cout << "X().  "; }
  ~X() { delete [] p; cout << "~X().\n"; }
private:
  int* p;
};

class Y : public X
{
public:
  Y() { q = new int[1023]; cout << "Y():T::q = " << q << ".  "; }
  ~Y() { delete [] q; cout << "~Y().  "; }
private:
  int* q;
};

int main()
{
  for (int i = 0; i < 8; i++)
    {
      X* r = new Y;
      delete r;
    }
  
  system("pause");
  return 0;
    
}

... and here's the code i typed in myself directly from the book with added comments that DID NOT COMPILE:

Code:

// Virtual Destructors and Memory Leaks
// an explicit destructor may be defined to be virtual
// the following example illustrates the value in defining
// a virtual destructor
//
// since r is declared to be a pointer to X objects, only
// the X destructor is invoked, deallocating only 8 bytes
// so on each iteration 4029 bytes are lost!

#include <iostream>
#include <cstdlib>

using namespace std;

class X
{ public:
    X() { p = new int[2];  cout << "X().  "; }
    ~X() { delete [] p;  cout << "~X().\n"; }
  private:
    int* p;
};

class Y
{ public:
    Y() { q = new int[1023];  cout << "Y(): Y::q = " << q << ".  "; }
    ~Y() { delete [] q;  cout << "~Y().  "; }
  private:
    int* q;
};

int main()
{ for (int i=0; i<8; i++)
  { X* r = new Y;
    delete r;
  }

  system("pause");
  return 0;
}

and here's the error msg the compiler spits out:


Compiler: Default compiler
Executing g++.exe...
g++.exe "C:\C\Code\MemLeak.cpp" -o "C:\C\Code\MemLeak.exe" -Wall -I"C:\DEVCPP\include\c++" -I"C:\DEVCPP\include\c++\mingw32" -I"C:\DEVCPP\include\c++\backward" -I"C:\DEVCPP\include" -L"C:\DEVCPP\lib"
C:/C/Code/MemLeak.cpp: In function `int main()':
C:/C/Code/MemLeak.cpp:33: cannot convert `Y*' to `X*' in initialization

Execution terminated


I'm not crazy, right?

Swaine777

Your version of the program is not deriving Y from X.

Working...

Code:

class Y : public X

... yours...

Code:

class Y

... so you cannot use a base class pointer because there is no base class.