C++ Primer, Fifth Edition

The free Member

The free member must destroy the elements and then deallocate the space this StrVec allocated. The for loop calls the allocator member destroy in reverse order, starting with the last constructed element and finishing with the first:

void StrVec::free() {     // may not pass deallocate a 0 pointer; if elements is 0, there's no work to do     if (elements) {         // destroy the old elements in reverse order         for (auto p = first_free; p != elements; /* empty */)             alloc.destroy(--p);         alloc.deallocate(elements, cap - elements);     } }

The destroy function runs the string destructor. The string destructor frees whatever storage was allocated by the strings themselves.

Once the elements have been destroyed, ...