"Has virtual functions but non-virtual destructor" build failure(s) — clang 6.0

PackageVersionSupposed error messageFull log Bug report
belr 0.1.3-2new_allocator.h:140:22: error: destructor called on non-final 'belr::ParserContext >' that has virtual functions but non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor] Log
cpp-hocon 0.1.6-1new_allocator.h:140:22: error: destructor called on non-final 'hocon::config_string' that has virtual functions but non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor] Log
cpprest 2.10.2-6new_allocator.h:140:22: error: destructor called on non-final 'pplx::details::linux_scheduler' that has virtual functions but non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor] Log
facter 3.11.0-1unique_ptr.h:78:2: error: delete called on 'facter::facts::external::resolver' that is abstract but has non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor] Log
pegtl 1.3.1-1new_allocator.h:140:22: error: destructor called on non-final 'examples::string_json' that has virtual functions but non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor] Log

5 errors