Boost.Log ignores overloaded stream insertion operator

Question

I have a class that I want to appear in log in a certain way, so I've overloaded its << operator:

class CWindowClassId
{
public:
    // ...
    friend std::wostream& operator<< (std::wostream& os, CWindowClassId const& classId);
}

Inserting the class above in log stream:

// ...
CWindowClassId classId(hWindow);
BOOST_LOG_TRIVIAL(debug) << "Window created, class = " << classId;

causes compilation error:

Error   1   error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const Sandbox::CWindowClassId' (or there is no acceptable conversion)    C:\local\boost_1_55_0\boost\log\utility\formatting_ostream.hpp  710

I know the error lies in the fact, that I've overloaded << for wide strings. All is fine when I use ostream instead of wostream, but I really want to use wide string version.

I've tried to set locale for a sink:

shared_ptr<log::sinks::synchronous_sink<log::sinks::text_file_backend> > sink = log::add_file_log("log.txt");
sink->imbue(boost::locale::generator()("en_US.UTF-8"));

And have BOOST_LOG_USE_WCHAR_T defined before any log-related includes.

Is there anything I can do to make logging work with wide string << operator?

I'm using Boost 1.55.0.

Answer 1

I don't think you can do this with BOOST_LOG_TRIVIAL. The trivial logger uses a underlying boost::sources::logger instead of boost::sources::wlogger, you can see that from trivial.hpp and trivial.cpp in the boost source file, and I can't see how we can change it unless we modify the source code. If you use a wlogger, it would work. Here is an example:

#include <iostream>
#include <string>
#include <boost/log/sources/logger.hpp>
#include <boost/log/common.hpp>

namespace src = boost::log::sources;

class CWindowClassId
{
public:
    // ...
    friend std::wostream& operator<< (std::wostream& os, CWindowClassId const& classId)
    {
        os << classId.ws;
        return os;
    }
public:
    std::wstring ws;
};

int main(int argc, char* argv[])
{
    src::wlogger lg;
    CWindowClassId id;
    id.ws = L"wide char";
    BOOST_LOG(lg) << "Hello, World! This is a wide character message."<<id;
    return 0;
}