Publishing and subscribing C structures?

edit

So I want to publish C structure. I have my_pkg.msg

int32 a
float32 b

And C structure:

namespace my {
struct __atribute((packed)) my_pkg {
    int a;
    float b;
};
}

And then I do serialization like in this link

namespace ros
{
namespace message_traits
{
    template<> struct IsFixedSize<my::my_pkg> : public TrueType {};
    template<> struct IsSimple<my::my_pkg> : public TrueType {};

    template<>
        struct MD5Sum<my::my_pkg>
        {
            static const char* value()
            {
                return MD5Sum<my::my_pkg>::value();
            }

            static const char* value(const my::my_pkg& m)
            {
                return MD5Sum<my::my_pkg>::value(m);
            }
        };

    template<>
        struct DataType<my::my_pkg>
        {
            static const char* value()
            {
                return DataType<my::my_pkg>::value();
            }

            static const char* value(const my::my_pkg& m)
            {
                return DataType<my::header_s>::value(m);
            }
        };

    template<>
        struct Definition<my::my_pkg>
        {
            static const char* value()
            {
                return Definition<my::my_pkg>::value();
            }

            static const char* value(const my::my_pkg& m)
            {
                return Definition<my::my_pkg>::value(m);
            }
        };
} // namespace message_traits

namespace serialization
{
    template<>
        struct Serializer<my::my_pkg>
        {
            template<typename Stream, typename T>
                inline static void allInOne(Stream& stream, T item)
                {
                    stream.next(item.a);
                    stream.next(item.b);
                }

            ROS_DECLARE_ALLINONE_SERIALIZER;
        };
} // namespace serialization
} // namespace ros

And I want to publish my message so I do

ros::Publisher pub = n.advertise<my::my_pkg>("test", 1);

And I get Segmentation Fault at this level. Can someone has idea what I'm doing wrong?

EDIT: gdb

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff1a76700 (LWP 10115)]
[New Thread 0x7ffff1275700 (LWP 10116)]
[New Thread 0x7ffff0a74700 (LWP 10117)]
[New Thread 0x7fffebfff700 (LWP 10122)]

Thread 1 "example" received signal SIGSEGV, Segmentation fault.
0x000055555555b3b9 in ros::message_traits::MD5Sum<my::my_pkg>::value() ()