Re: [Boost-users] errors serializing pointers on Fedora Core 5

Dan Bikel wrote:

The following tiny program generates two compiler errors on FC 5 (which comes with g++ 4.1.1 and boost 1.33.1):

#include <iostream> #include <fstream> #include <string> #include #include #include

using namespace std; using namespace boost;

int main(int argc, char **argv) { string * pFoo = new string("foo"); ofstream ofs("strfile"); { archive::text_oarchive oa(ofs); oa << pFoo; } }

Error No. 1: /usr/include/boost/archive/detail/oserializer.hpp:567: error: invalid application of -1òøsizeofòù to incomplete type òøboost::STATIC_ASSERTION_FAILURE<false>

Error No. 2: /usr/include/boost/serialization/access.hpp:109: error: -1òøstruct std::basic_string

...

òù has no member named òøserializeòù

Error No. 1 can be fixed by making pFoo a const pointer type, i.e., by changing the declaration/assignment statement to be string *const pFoo = new string("foo");

I cannot figure out why such a change is necessary, as the serialization library documentation does not indicate that it is necessary to make pointers const in order to serialize them (as is borne out by the demo.cpp code).

This is explained in the "Rationale" section of the documentation.

Also, I cannot figure out how to fix Error No. 2.

Any help would be much appreciated!

The following program compiles. The problem is that std::string is marked with a "primitive" serialization trait. It's the only non built-in type so marked. Pointers to primitive types cannot be serialized. The standard advice is to use BOOST_STRONG_TYPEDEF to make a divferently named version of the same type. This doesn't work for string - so I made the same thing in this example. There are other ways to do this - e.g. casting - but this should give you the idea #include <iostream> #include <fstream> #include #include #include using namespace std; using namespace boost; class serializable_string : public string { friend class serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version){ ar & static_cast(*this); } public: serializable_string(const char * s) : string(s) { } }; int main(int argc, char **argv) { serializable_string * const pFoo = new serializable_string("foo"); ofstream ofs("strfile"); { archive::text_oarchive oa(ofs); oa << pFoo; } }

Thanks, Dan.