template<class Allocator> void swap(basic_stacktrace<Allocator>& a, basic_stacktrace<Allocator>& b) noexcept(noexcept(a.swap(b));
string to_string(const stacktrace_entry& f);
template<class Allocator> string to_string(const basic_stacktrace<Allocator>& st);
ostream& operator<(ostream& os, const stacktrace_entry& f);
template<class Allocator> ostream& operator<(ostream& os, const basic_stacktrace<Allocator>& st);