C++ iterators & loop optimization

Question

I see a lot of c++ code that looks like this:

for( const_iterator it = list.begin(),
     const_iterator ite = list.end();
     it != ite; ++it)

<

Answer 1

Consider this example:

for (const_iterator it = list.begin(); it != list.end(); ++list)
{
    if (moonFull())
        it = insert_stuff(list);
    else
        it = erase_stuff(list);
}

in this case, you NEED to call list.end() in the loop, and the compiler isn't going to optimize that away.

Other cases where the compiler can prove that end() is always returning the same value, optimization can take place.

If we are talking about STL containers, than i think any good compiler can optimize away multiple end() calls when multiple end() calls is not needed for the programming logic. However, if you have a custom container and implementation of end() is not in the same translation unit, than optimization will have to happen at link time. I know very little about link time optimization, but i'll bet most linkers will not do such optimization.