[C++] Templates and inheritance

From: Pedro Graca (hexkid_at_hotpop.com)
Date: 09/28/04 

Date: 28 Sep 2004 14:48:59 GMT

What am I missing?
[apart from the C++ books or a mentor :) -- books are in transit]

I'm trying to learn C++ and wanted to make a special stack that only
allows pushing values smaller than the current stack top.

My code compiles with

$ g++ -Wall ss.cpp -o ss

but gives a segmentation fault when run.

If it matters:
$ echo; g++ --version

g++ (GCC) 3.3.4 (Debian 1:3.3.4-12)
Copyright (C) 2003 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

#include <iostream>
#include <exception>
#include <stack>
using namespace std;

template <class T>
class InheritedStack : public std::stack<T> {
  public:
    void my_push(const T& x) {
      if (top() > x) {
        push(x);
      } else throw "Invalid push value";
    }
};

/* ********* */

int main() {
  stack<int> NS;
  cout << "Normal stack: "; /* ********* */
  NS.push(6); /* */
  NS.push(9); /* STL stack */
  NS.push(2); /* */
  while (!NS.empty()) { /* works ok! */
    cout << NS.top() << " "; /* */
    NS.pop(); /* */
  } /* ********* */
  cout << endl;
  cout << endl;
  cout << endl;

  /* ********* */

  try {
    InheritedStack<int> IS;
    cout << "Inherited stack: ";
    try {
      IS.my_push(6);
      IS.my_push(9); // error! -- change to 4
      IS.my_push(2);
    }
    catch (char * msg) {
      cerr << "Exception caught: " << msg << endl;
    }
    while (!IS.empty()) {
      cout << IS.top() << " ";
      IS.pop();
    }
  }
  catch (std::exception& e) {
    cerr << "Exception: " << e.what() << endl;
  }
  cout << endl;
} 

-- 
USENET would be a better place if everybody read:   | to email me: use |
http://www.catb.org/~esr/faqs/smart-questions.html  | my name in "To:" |
http://www.netmeister.org/news/learn2quote2.html    | header, textonly |
http://www.expita.com/nomime.html                   | no attachments.  |

Relevant Pages