C++ STL List implementation

[harsh.murari]

I wanted to know how the C++ STL list is implemented. Specifically, I
wanted to understand the memory usage by the list objects.

I have the following code snippet:

std::list <intL;

L.push_back(10);
L.push_back(20);

printf("List size %d\n", sizeof(L));

This is returning the object size of L to be 4 bytes. How is this
possible? What data members does the list object contain? Where are
previous pointer, next pointer etc stored? Any insights would be
appreciated.

[sebastian]

>This is returning the object size of L to be 4 bytes. How is this possible?

char * buffer = new char[ 1024 ];
cout << sizeof( buffer ) << endl;

obviously, sizeof( ) isn't very useful when applied to pointers. ;)

>What data members does the list object contain? Where are previous pointer, next pointer etc stored?

who knows? the standard doesn't dictate the actual implementation
details.

>Any insights would be appreciated.

SGI's implementation is fairly straightforward and quite readable:
http://www.sgi.com/tech/stl/. or simply browse the code that came with
your compiler.

[Juha Nieminen]

ha**********@gmail.com wrote:

I wanted to know how the C++ STL list is implemented. Specifically, I
wanted to understand the memory usage by the list objects.

I have the following code snippet:

std::list <intL;

L.push_back(10);
L.push_back(20);

printf("List size %d\n", sizeof(L));

This is returning the object size of L to be 4 bytes. How is this
possible?

In your compiler std::list is most probably a class which has one
pointer as member variable (a pointer to the actual data).

What data members does the list object contain? Where are
previous pointer, next pointer etc stored?

A list object has no "prev" and "next" pointers. List *nodes* have
them, not the list itself. List nodes are allocated separately and do
not affect the size of the list object in any way.