C++ list STL

jlynch

Hi,

I have a few questions on how memory is managed in a linked list in the C++ STL

Each list element has 3 fields, a time_t, int and string. In C I would use a struct. Is a class the best thing to use for c++?

Should I allocate memory using the new operator for the elements that I add to the linked list or when i call the push_back() function is a copy of the object placed on the linked list? The elements are added to the list inside a function in a class.

If elements were dynamically allocated do i need to iterate through the linked list in the destructor and use the delete operator for each element.

Is the destructor called when the progam ends or do I need to call the clear() function of the list to call the destructor?

Tobias Greeshman

jlynch wrote: »

Each list element has 3 fields, a time_t, int and string. In C I would use a struct. Is a class the best thing to use for c++?

The only difference in C++ between a struct and a class, is that a struct has public access by default. So I'd go with a struct unless you explicitly need to use encapsulation.

jlynch wrote: »

Should I allocate memory using the new operator for the elements that I add to the linked list or when i call the push_back() function is a copy of the object placed on the linked list? The elements are added to the list inside a function in a class.

Overriding the new() operator sounds like a lot of over-kill, unless you plan on doing custom allocation of memory. From what I can remember using the push_back() method will cause a copy of the element to be put into the linked list.

Webmonkey

Yeah as far as I remember, the pus_back method makes a copy thus you need to provide a copy constructor.

Jiri

Tobias Greeshman wrote: »

The only difference in C++ between a struct and a class, is that a struct has public access by default. So I'd go with a struct unless you explicitly need to use encapsulation.


Overriding the new() operator sounds like a lot of over-kill, unless you plan on doing custom allocation of memory. From what I can remember using the push_back() method will cause a copy of the element to be put into the linked list.

I guess he meant not overriding new operator, but just dynamically alocate each item in list.
class A
{
int a;
double b;
};

int main()
{
std::list<A*> mList;
A* item;

item = new A;
item.a = 1;
mList.push_back(item);


item = new A;
item.a = 2;
mList.push_back(item);

...

... and finally dealocate...

std::list<A*>::iterator it = mList.begin();
while (it!=mList.end()) {
delete (*it);
}

Tobias Greeshman

Jiri wrote: »

I guess he meant not overriding new operator, but just dynamically alocate each item in list.

On re-reading that there, I'd say you're correct.

Really shouldn't be replying to programming posts so late on a Sunday night!