I'm trying to use Boost.serialize. It appears to work fine, but I'm getting warnings when I turn on -Wextra and -Wall warnings with g++ (Version 10.2.0).
It ran fine, and compiled fine when I switch off the warnings. However I'd like to be able to get rid of them properly. I've been trying for hours but cannot find a solution. I found some examples of similar warnings, but those were cases when default constructors were not defined.
I have created a minimal example below:
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
struct minimal {
minimal()=default;
minimal(int in)
: x {in}
{}
template <typename Archive>
void serialize(Archive & ar, const unsigned vers){
ar & x;
}
int x;
};
int main()
{
std::stringstream ss;
boost::archive::text_oarchive oa {ss};
minimal M {10} ;
oa << M;
return 0;
}
The output when I compile is
g++ -Wextra -Wall minimal.cc -lboost_serialization
minimal.cc: In instantiation of 'void minimal::serialize(Archive&, unsigned int) [with Archive = boost::archive::text_oarchive]':
/usr/include/boost/serialization/access.hpp:116:20: required from 'static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = minimal]'
/usr/include/boost/serialization/serialization.hpp:59:22: required from 'void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = minimal]'
/usr/include/boost/serialization/serialization.hpp:109:14: required from 'void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::text_oarchive; T = minimal]'
/usr/include/boost/archive/detail/oserializer.hpp:153:40: required from 'void boost::archive::detail::oserializer<Archive, T>::save_object_data(boost::archive::detail::basic_oarchive&, const void*) const [with Archive = boost::archive::text_oarchive; T = minimal]'
/usr/include/boost/archive/detail/oserializer.hpp:106:1: [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/usr/include/boost/archive/detail/oserializer.hpp:315:22: required from 'static void boost::archive::detail::save_non_pointer_type<Archive>::invoke(Archive&, const T&) [with T = minimal; Archive = boost::archive::text_oarchive]'
/usr/include/boost/archive/detail/oserializer.hpp:539:18: required from 'void boost::archive::save(Archive&, T&) [with Archive = boost::archive::text_oarchive; T = const minimal]'
/usr/include/boost/archive/detail/common_oarchive.hpp:71:22: required from 'void boost::archive::detail::common_oarchive<Archive>::save_override(T&) [with T = const minimal; Archive = boost::archive::text_oarchive]'
/usr/include/boost/archive/basic_text_oarchive.hpp:83:52: required from 'void boost::archive::basic_text_oarchive<Archive>::save_override(T&) [with T = const minimal; Archive = boost::archive::text_oarchive]'
/usr/include/boost/archive/detail/interface_oarchive.hpp:70:36: required from 'Archive& boost::archive::detail::interface_oarchive<Archive>::operator<<(const T&) [with T = minimal; Archive = boost::archive::text_oarchive]'
minimal.cc:24:11: required from here
minimal.cc:11:46: warning: unused parameter 'vers' [-Wunused-parameter]
11 | void serialize(Archive & ar, const unsigned vers){
| ~~~~~~~~~~~~~~~^~~~
'''
It's easy to fix, just remove the unused argument's name, or comment out its name.
struct minimal {
minimal()=default;
minimal(int in)
: x {in}
{}
template <typename Archive>
void serialize(Archive & ar, unsigned /*vers*/){
ar & x;
}
int x;
};
With C++17 you have [[maybe_unused]] attribute specifier, like:
struct minimal {
minimal()=default;
minimal(int in)
: x {in}
{}
template <typename Archive>
void serialize(Archive & ar,[[maybe_unused]] unsigned ver){
ar & x;
}
int x;
};
See this question for further reading: