Re: why it seems that std::list::erase() doesnt free objects in a list, if the latter holds pointers to them?

From: Rob Williscroft (rtw_at_freenet.co.uk)
Date: 04/11/04 

Date: 11 Apr 2004 15:08:57 GMT

jimjim wrote in news:Y3dec.1164$FT7.11504891@news-text.cableinet.net in
comp.lang.c++:

> I would appreciate helping me understand why erase doesnt delete the
> object when I store a pointer to the object.
>
> Thanks in advance
>
>

#include <iostream>
#include <ostream>
#include <list>

using namespace std;

class X
{
public:
  X(){ cout << "X constructor\n"; }
  ~X() { cout << "X destructor\n"; }
  X( X const & ) { cout << "X copy constructor\n"; }

};

int main()
{
  X x;
  list<X>lists;
  lists.push_back(x);
  lists.erase(lists.begin());
}

output:

            X constructor
            X copy constructor
            X destructor
            X destructor

Note 2 constructors followed by 2 destructors:

The 1st ctor is for local 'x'.
The 2nd ctor is for the *copy* that is pushed into 'lists'.
The first dtor is for the X erased by erase( lists.begin() ).
The last dtor is for local 'x'.

Rob. 

-- 
http://www.victim-prime.dsl.pipex.com/

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