Who is responsible for deleting the facet?

Question

I have a function that uses the Boost.DateTime library for generating the current GMT/UTC date and time string (live example).

std::string get_curr_date() {
         


        

Answer 1

Am I required to delete the time_facet or is the std::locale object responsible for deleteing the it?

You're not required to delete the time_facet so long as time_facet derives from std::locale::facet, which it should. The std::locale::facet is a base class that all facets should derive from that implement a form of reference counting. The standard says this:

§ 22.3.1.6

Once a facet reference is obtained from a locale object by calling use_facet<>, that reference remains usable, and the results from member functions of it may be cached and re-used, as long as some locale object refers to that facet.

Once all references of the facet are not being used, the destructor of std::locale will manage and delete references to the facet if its ref count is 0.

This is all specified in §22.3.1.1.2 in the C++11 standard. Where it states:

The refs argument to the constructor is used for lifetime management.

— For refs == 0, the implementation performs delete static_cast<locale::facet*>(f) (where f is a pointer to the facet) when the last locale object containing the facet is destroyed; for refs == 1, the implementation never destroys the facet.

Answer 2

The locale is responsible for deleting the facet.

Answer 3

Not answering your question as others have already done it. But, it's really not required to construct the locale everytime.

std::string get_curr_date_time() {
    namespace bpt = boost::posix_time;
    namespace bdt = boost::date_time;
    std::ostringstream os;
    auto date = bdt::second_clock<bpt::ptime>::universal_time();
    const static std::locale currlocale (os.getloc(), new bpt::time_facet("%Y%m%d%H%M%S"));
    boost::posix_time::time_facet* facet = new boost::posix_time::time_facet("%a, %d %b %Y %H:%M:%S GMT");

    os.imbue(currlocale);
    os << date;
    return os.str();
}