iterator problem

Unregistered · 03-22-2002

Hi all,

I have a list of pointers to objects and I am trying to delete the objects before clearing the list. Here's the code:

.................................................. .............................................

1: for (iter = addrlist.begin(); iter != addrlist.end(); iter++)
2: {
3: delete iter;
4: }
5:
6: this->addrlist.clear();

.................................................. ...............................................

I tried de-referencing iter but it kept crapping out on line 3. In line 3, iter points to a cell in the list that holds a pointer to an object. I want to delete the object first, how do I do that? TIA

BTW, here's how I am populating the list:
.................................................. ................................................

1: Addresse* add = new Addresse();
2: add->setID(LastRecordId++);
3: this->addrlist.push_back(*add);

.................................................. ................................................

**Sorensen** · 03-22-2002

As you have a list of pointers to Addresse objects, then the iterator will be a pointer to a pointer to an Addresse object. So de-referencing iter before deleting should work.

Are you doing any memory management in your Addresse destructor?

**SilentStrike** · 03-22-2002

Code:

 template <class container> void freeDynamicContainer(container& c) {
  for (typename container::iterator i = c.begin(); i != c.end(); i++) {
   delete (*i);
  }
  c.clear();
 }

Unregistered · 03-22-2002

Originally posted by Sorensen

Are you doing any memory management in your Addresse destructor?

Yes, I am trying to free memory in my destructor before exiting program.

**Sorensen** · 03-22-2002

Then if you were de-referencing iter, as per SilentStrikes example, and get the crash then it's likely that the error is in your destructor not your list deleting code.

**ginoitalo** · 03-22-2002

...To add on to Sorensen's post,

you may be deleting the data twice.

p.s.

When the std::list goes out of scope, can you overload it's destructor (if it has one ??) so that it does the memory management ?

**SilentStrike** · 03-23-2002

std::list (or any of the standard containers) doesn't have a virtual destructor... so you can't really do it. I was suprised g++ even let me compile this without warning (despite deriving from class with non-virtual destructor)

Code:

#include <list>
#include <iostream>

class check {
public:
 check() { count++;}
 ~check() {count--;}
 static int getCount() { return count; }
private:
 static int count;
};

int check::count=0;

template <class T> class ptrList: public std::list<T*> {
public:
 ptrList() { }
 ~ptrList() {
  for (std::list<T*>::iterator i = begin(); i != end(); i++) {
   delete *i;
  }
 }
};

int main() {
 std::list<check*>* blah = new ptrList<check>;
 blah->push_back(new check);
 blah->push_back(new check);
 delete blah;  // doesn't call ~ptrList() because of non-vrituality of ~std::list()
 std::cout << check::getCount() << std::endl; // would be 0 if they were deleted..
 return 0;
}

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