Compilation problems with greg_serialize.hpp

[yunior-peralta-gonzalez]

I noticed that the following code doesn't compile:

#include <sstream>
#include <iostream>

#include <boost/date_time/gregorian/greg_serialize.hpp>
#include <boost/archive/text_oarchive.hpp>

int main()
{
    boost::gregorian::date d(2021, boost::date_time::Feb, 14);

    std::ostringstream oss;
    boost::archive::text_oarchive oa(oss);
    oa & d;

    std::cout << oss.str() << std::endl;
    return 0;
}

it throws the following error:

boost/date_time/gregorian/greg_serialize.hpp:34:15: error: ‘split_free’ was not declared in this scope, and no declarations were found by argument-dependent lookup at the point of instantiation [-fpermissive]

And if we invert the order of the two boost inclusion headers (putting first text_oarchive.hpp and then greg_serialize.hpp) then it compiles but doesn't link:

main.cpp:(.text._ZN5boost13serialization4saveINS_7archive13text_oarchiveEEEvRT_RKNS_9gregorian4dateEj[_ZN5boost13serialization4saveINS_7archive13text_oarchiveEEEvRT_RKNS_9gregorian4dateEj]+0x36): undefined reference to `boost::gregorian::to_iso_string[abi:cxx11](boost::gregorian::date const&)'

In order to get it linked I added a new header: #include <boost/date_time/gregorian/gregorian.hpp>

So it seems that the header boost/date_time/gregorian/greg_serialize.hpp has missing dependencies, right? I didn't see any special consideration in the documentation of the library about using this header in a specific order.

[JeffGarland]

So I think this is a similar report as this one https://github.com/boostorg/date_time/issues/176 - which even has a stack overflow question.

Documentation is certainly in order if the code isn't going to be changed -- which was the answer above since we're trying to uncouple the dependencies. Right now I don't know a better way to fix things.

[yunior-peralta-gonzalez]

Thanks @JeffGarland, but I don't think the documentation is in order because I followed the doc and I had several compilation issues, I had to look at the code of the boost library to solve them. Maybe adding some notes here https://www.boost.org/doc/libs/1_75_0/doc/html/date_time/serialization.html would help.

What about having a new library date_time_serialization (for greg_serialize and time_serialize) that depends on date_time and serialization? This would be modular, the code wouldn't be duplicated just to avoid dependencies on another library and it wouldn't have the include ordering problem.