Is end() required to be constant in an STL map/set?

Question

§23.1.2.8 in the standard states that insertion/deletion operations on a set/map will not invalidate any iterators to those objects (except iterators pointing to a deleted eleme

Answer 1

Iterators in (multi)sets and (multi)maps won't be invalidated in insertions and deletions and thus comparing .end() against previous stored values of .end() will always yield true.

Take as an example GNU libstdc++ implementation where .end() in maps returns the default intialized value of Rb_tree_node

From stl_tree.h:

  _M_initialize()
  {
    this->_M_header._M_color = _S_red;
    this->_M_header._M_parent = 0;
    this->_M_header._M_left = &this->_M_header;
    this->_M_header._M_right = &this->_M_header;
  }