validation_error implicit copy/move constructor

Start in errors.hpp at validation_error and inspect how its destructor and special member functions interact with BOOST_DEFAULTED_FUNCTION. Then trace the copy construction in throw_exception.hpp and the call path in detail/value_semantic.hpp. Done means the reported deprecated-copy-with-dtor error is addressed without the caller needing diagnostic suppression.

We had a number of program options , most uint*_t and one additional that is a vector<string> using mutlitoken ) that began erroring. This was working, but post updates to boost 1.88.0 (prior 1.75.0) + clang 19.1.7, it now produces an error. We have opted to throw some push/pops around this in our code right now to suppress the issue but would like to address it with a more appropriate fix. Included below is the warning for one of the numeric options. We did not investigate these as much as we did the arguments_map ( https://github.com/boostorg/program_options/issues/146 ), but would believe this one is better handled by adding default constructors (this might even be a case where BOOST_DEFAULTED_FUNCTION should be updated) as nothing jumps out as being a pointer where special handling may be required but would like those with more knowledge of the library to weigh in.

In file included from /home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options.hpp:15:
In file included from /home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/options_description.hpp:12:
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/errors.hpp:383:34: error: definition of implicit copy constructor for 'validation_error' is deprecated because it has a user-declared destructor [-Werror,-Wdeprecated-copy-with-dtor]
  383 |         BOOST_DEFAULTED_FUNCTION(~validation_error() BOOST_NOEXCEPT_OR_NOTHROW, {})
      |                                  ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/throw_exception/include/boost/throw_exception.hpp:97:41: note: in implicit copy constructor for 'boost::program_options::validation_error' first required here
   97 |     explicit wrapexcept( E const & e ): E( e )
      |                                         ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/throw_exception/include/boost/throw_exception.hpp:165:11: note: in instantiation of member function 'boost::wrapexcept<boost::program_options::validation_error>::wrapexcept' requested here
  165 |     throw wrapexcept<E>( e );
      |           ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/detail/value_semantic.hpp:62:24: note: in instantiation of function template specialization 'boost::throw_exception<boost::program_options::validation_error>' requested here
   62 |                 boost::throw_exception(validation_error(validation_error::multiple_values_not_allowed));
      |                        ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/detail/value_semantic.hpp:90:48: note: in instantiation of function template specialization 'boost::program_options::validators::get_single_string<char>' requested here
   90 |         std::basic_string<charT> s(validators::get_single_string(xs));
      |                                                ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/detail/value_semantic.hpp:184:13: note: in instantiation of function template specialization 'boost::program_options::validate<unsigned short, char>' requested here
  184 |             validate(value_store, new_tokens, static_cast<T*>(nullptr), 0);
      |             ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/value_semantic.hpp:189:9: note: in instantiation of member function 'boost::program_options::typed_value<unsigned short>::xparse' requested here
  189 |         typed_value(T* store_to) 
      |         ^
/home/user/bitbucket/app/build/_deps/boost-src/libs/program_options/include/boost/program_options/detail/value_semantic.hpp:199:33: note: in instantiation of member function 'boost::program_options::typed_value<unsigned short>::typed_value' requested here
  199 |         typed_value<T>* r = new typed_value<T>(v);
      |                                 ^
/home/user/bitbucket/app/apps/app_name/src/main.cpp:111:49: note: in instantiation of function template specialization 'boost::program_options::value<unsigned short>' requested here
  111 |         ("listen_port", boost::program_options::value<uint16_t>(&opt_listen_port)->value_name("LISTEN_PORT")->required(),"Port to listen on")
      |                                                 ^

https://quuxplusone.github.io/blog/2023/05/05/deprecated-copy-with-dtor/
https://stackoverflow.com/a/51864979