Ownership/delete'ing the facet in a locale (st

问题:

I wrote the following function to get a date/time string using boost.date_time.

namespace bpt = boost::posix_time;

string
get_date_time_string(bpt::ptime time)
{
  bpt::time_facet * facet(new bpt::time_facet);
  facet->format("%Y%m%d%H%M%S");

  stringstream return_value;
  return_value.imbue(std::locale(std::locale::classic(), facet));
  return_value << time;

  return return_value.str();
}

I had a quick question about the ownership/delete'ing of the facet object. std::locale's constructor is not explicit on the ownership/delete'ing of the facet. Tried using shared_ptr-wrapped and stack allocated versions of facet - both of which caused seg-faults. Also, running the above function through valgrind didn't show any leaks(which probably implies that the locale or stream is taking care of delete'ing), but I just wanted to be clear that I am doing the right thing here. Thanks.

回答1:

According to Stroustrup, a 0 argument passed to the constructor tells the facet that the locale will handle destruction, and the both constructors of bpt::time_facet default to 0 when it isn't supplied. A non-zero value, though, implies that the programmer must explicitly handle the destruction of the facet.