Is &*vector::end() undefined behavior?

Question

I thought &*vector::end() was undefined behavior... until I saw some post refer to Stroustrup\'s code:

void vector_pointer_test(element_t* first         


        

Answer 1

It's not necessarily undefined behavior, but it depends on the specific implementation of the iterator:

C++03 24.1/5 Iterator requirements

Just as a regular pointer to an array guarantees that there is a pointer value pointing past the last element of the array, so for any iterator type there is an iterator value that points past the last element of a corresponding container. These values are called past-the-end values. Values of an iterator i for which the expression *i is defined are called dereferenceable. The library never assumes that past-the-end values are dereferenceable.

The code in question has undefined behavior if container.end() is not dereferenceable. Many times a vector's iterator will simply be a pointer - in those cases there's no undefined behavior.