Simple Log.h in C++

Log.h

#include <iostream>
#include <string>
#include <ctime>
#include <cstdlib>

namespace da{
struct nullstream: std::ostream{
    nullstream(): std::ostream(0){}
};

template <typename T>
nullstream &operator<<(nullstream &o, T const & x) { return o;}

nullstream  __nullstream;

class LogMessage{
    std::string level;
    std::ostream &ofs;
    static bool enable;
    public:
        LogMessage(const std::string &l)
            :level(l), ofs(enable ? std::cerr : __nullstream) {
            stream() << "[" << level << "]\t";
        }
        LogMessage(std::ostream &o)
            :level("ERROR"), ofs(o) {
            stream() << "[" << level << "]\t";
        }
        inline std::ostream &stream() {
            return ofs;
        }
        ~LogMessage() {
            stream() << std::endl;
        }

        static void Enable(bool _enable) {
            enable = _enable;
        }
};
bool LogMessage::enable = true;
}

#define LOG(type)        da::LogMessage(#type).stream()
#define DLOG(type)       da::LogMessage(#type).stream()
#define VLOG(level)      if ((level) <= FLAGS_v) LOG(INFO)

#define CHECK(x)         if (x) {} else LOG(ERROR) << #x
#define DCHECK(x)        CHECK(x)

#define CHECK_EQ(x, y)   CHECK((x) == (y))
#define CHECK_LT(x, y)   CHECK((x) < (y))
#define CHECK_GT(x, y)   CHECK((x) > (y))
#define CHECK_LE(x, y)   CHECK((x) <= (y))
#define CHECK_GE(x, y)   CHECK((x) >= (y))
#define CHECK_NE(x, y)   CHECK((x) != (y))
#define CHECK_NOTNULL(x) \
    ({ \
        CHECK_NE(x, NULL); \
        (x); \
    })

#define DCHECK_EQ(x, y)  DCHECK((x) == (y))
#define DCHECK_LT(x, y)  DCHECK((x) < (y))
#define DCHECK_GT(x, y)  DCHECK((x) > (y))
#define DCHECK_LE(x, y)  DCHECK((x) <= (y))
#define DCHECK_GE(x, y)  DCHECK((x) >= (y))
#define DCHECK_NE(x, y)  DCHECK((x) != (y))

How convenient! Thank you.