16.59.txt

// s is an std::string

svec.emplace_back(s)

// emplace_back takes zero or more rvalue references to template types
// s is an lvalue
// the function- and template parameter pack will have a size of 1
// the first and only template parameter will have a type of std::string &
// the function parameter will be std::string& &&
// through reference collapsing, the overall type of the parameter will be an std::string &

// chk_n_alloc function is called to ensure there is enough space for at least one more elements

// the std::allocator<string>::construct member constructs a new element to raw, uninitialized memory
// std::forward is called for each (now only for one) passed parameters in the pack
// std::forward<Args>(args)... is expanded to std::forward<string &>(s) to ensure we keep the original type
// construct is called with an lvalue reference to s
// construct calls std::string's constructor that takes an std::string, AKA the copy constructor
// a copy of s is constructed as a new element in the back of the StrVec