function 'value_etc' should be marked [[nodiscard]] 

function 'key_sid' should be marked [[nodiscard]] 

function 'value_etc' should be marked [[nodiscard]] 

function 'key_sid' should be marked [[nodiscard]] 

class 'sorting_context' defines a move constructor but does not define a destructor, a copy constructor, a copy assignment operator or a move assignment operator 

member variable 'sortdb' has public visibility 

member variable 'mtx_clear_storage' has public visibility 

member variable 'clear_storage' has public visibility 

an exception may be thrown in function 'sorting_context' which should not throw exceptions 

move constructors should be marked noexcept 

use '= default' to define a trivial default constructor