C++ Logger Concept

main.cpp

#include <string>
#include <sstream>
#include <iostream>

enum LogLevel
{
    Info = 0,
    Debug,
    Warning,
    Error
};

const std::string LogLevelNames[4] = { "INFO", "DEBUG", "WARN", "ERROR" };

#define LOG_DEBUG(s, ...) Logger::Get().Log(LogLevel::Debug, __LINE__, __FILE__, s, __VA_ARGS__)

class Logger
{
public:

    static Logger& Get()
    {
        static Logger instance;
        return instance;
    }

    template<typename T, typename... U>
    void Log(LogLevel const level, int line, const char* file, T first, U... args)
    {
        m_CurrentMessage.str(std::string());
        m_CurrentMessage << "[" << LogLevelNames[level] << "] " << first;

        BuildMessage(args...);

        m_CurrentMessage << " (" << file << " @ " << line << ") ";

        if (level == LogLevel::Debug)
        {
#ifdef _DEBUG
            std::cout << m_CurrentMessage.str() << std::endl;
#endif
        }
        else
        {
            std::cout << m_CurrentMessage.str() << std::endl;
        }
    }

protected:

private:

    template<typename T, typename... U>
    void BuildMessage(T first, U... last)
    {
        m_CurrentMessage << first;
        BuildMessage(last...);
    }

    void BuildMessage()
    {

    }

    std::stringstream m_CurrentMessage;
};

int main()
{
    LOG_DEBUG("Hello World, this is a number: ", 100);
    return 0;
}

The above outputs:

[DEBUG] Hello World, this is a number: 100 (c:\path\to\main.cpp @ 70)

A concept for a basic logger with the following attributes:

• Self-building, variable number of arguments. Don't have to pre-build the string.
• Reports location of message (file and line)
• Supports multiple report levels

Obviously there is more to be added to it, and it's not thread-safe, but it serves as a basic proof.