shared_ptr and unique_ptr related question

Newsgroup: comp.lang.c++

Subject: shared_ptr and unique_ptr related question

From: somenath <somenathpal@...>

Date: Fri, 21 Feb 2014 17:28:19 -0800 (PST)



To get some understanding of shared_ptr and unique_ptr I wrote the following naive implementation of linked list.



#include<memory>

using namespace std;



template <class T>

class List {

private:

class ListItem {

public:

ListItem( T Val );

shared_ptr <ListItem > Next;

T Data;



};



shared_ptr< ListItem >Head;



public:

int CreateNode();

List() {

Head.reset();

}

void PushBack(T Val);

void Dump();

};





template<class T>

List<T>::ListItem::ListItem( T Val):Data(Val) {

Next.reset();





}

template<class T>

void List<T>::PushBack( T val)

{

unique_ptr<ListItem > NewItem (new ListItem(val));

if (!Head ) {

Head = move(NewItem);

}

else {

shared_ptr<ListItem> Curr(Head);

shared_ptr<ListItem> Prev(Head);

while( (Curr) ) {

Prev = Curr;

Curr = Curr->Next;

}

Prev->Next = move(NewItem);

}

}



template<class T>

void List<T>::Dump() {

shared_ptr<ListItem > Curr(Head);

while ( Curr) {

cout<<"Val = "<<Curr->Data<<endl;;

Curr = Curr->Next;

}

}



But I am not very clear of the correct uses of shared_ptr and auto_ptr yet. Could you please comment on the uses of smart pointers in the context of my linked list code. According to my understanding where I do not need to assign smart pointers to other one I use unique_ptr . Is this understanding correct?



Also I am not able to get convinced the benefit of shared_ptr and unique_ptr in the context of my code. I could have used even raw pointers to implement the same without losing much benefit . Is it not the case here?



I can use the above code as



int main(int argc,char *argv[] )

{

unique_ptr< List <int> > ilst (new List<int>());



ilst->PushBack(5);

ilst->PushBack(15);

ilst->PushBack(25);

ilst->Dump();



return 0;

}



Is the benefit of using smart pointers is, ilst need to be freed manually?



Please point me to some real code where smart pointers has been heavily used.



--

Somenath

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