This code generates an xml file that cannot be read by deserialization:
#include<fstream>
#include <boost/serialization/nvp.hpp>
#include<boost/archive/polymorphic_xml_oarchive.hpp>
int main(){
int i = 5;
{
std::ofstream ofs{"file.xml"};
boost::archive::polymorphic_oarchive* poa = new boost::archive::polymorphic_xml_oarchive(ofs);
(*poa) << i;
delete poa;
}
}file.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<!DOCTYPE boost_serialization>
<boost_serialization signature="serialization::archive" version="16">
5</boost_serialization>
Of course the problem is that I "forgot" to add the named value pair. For non-polymorphic archives this would produce a compilation error, but fails silently in the polymorphic case. I think a more correct behavior would be either 1) to make a runtime-time check that the passed object is a named-value pair when passing to an actual XML archive, or 2) force polymorphic archives to only accept named-value pairs.
In this case is obvious but in the case were many runtime cases are considered (including other archives format that do not require named-value-pair), this is difficult to spot. The error only happens when trying to load the file.
For reference, the workaround is to do this:
(*poa) << boost::serialization::make_nvp("i", i);with the output:
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<!DOCTYPE boost_serialization>
<boost_serialization signature="serialization::archive" version="16">
<i>5</i>
</boost_serialization>
Any how I think this points out to another possibility that could make the XML archive more powerful, and that is that if no named-value pair is passed to it, the archive should generate unique names, (possibly based partially on the type information + some uuid or fixed string, e.g. "unnamed").
This code generates an xml file that cannot be read by deserialization:
file.xml
Of course the problem is that I "forgot" to add the named value pair. For non-polymorphic archives this would produce a compilation error, but fails silently in the polymorphic case. I think a more correct behavior would be either 1) to make a runtime-time check that the passed object is a named-value pair when passing to an actual XML archive, or 2) force polymorphic archives to only accept named-value pairs.
In this case is obvious but in the case were many runtime cases are considered (including other archives format that do not require named-value-pair), this is difficult to spot. The error only happens when trying to load the file.
For reference, the workaround is to do this:
(*poa) << boost::serialization::make_nvp("i", i);with the output:
Any how I think this points out to another possibility that could make the XML archive more powerful, and that is that if no named-value pair is passed to it, the archive should generate unique names, (possibly based partially on the type information + some uuid or fixed string, e.g. "unnamed").