Easy benchmark boilerplate that most often works as expected

benchmark.cpp

#include <cstdio>
#include <chrono>
#include <string>

class benchmark
{
    using clock = std::chrono::steady_clock;

public:
    benchmark(std::string location, unsigned line)
        : location_{std::move(location)}, line_{line}, start_{clock::now()}
    {
    }
    ~benchmark()
    {
        const auto stop = clock::now();
        const auto diff = stop - start_;
        if (diff < std::chrono::milliseconds{2})
        {
            std::printf(
                "BENCHMARK: %s:%u | \t\t %dμs\n", location_.c_str(), line_,
                int(std::chrono::duration_cast<std::chrono::microseconds>(diff)
                        .count()));
        }
        else
        {
            std::printf(
                "BENCHMARK: %s:%u | \t\t %dms\n", location_.c_str(), line_,
                int(std::chrono::duration_cast<std::chrono::milliseconds>(diff)
                        .count()));
        }
        std::fflush(stdout);
    }

private:
    const std::string location_;
    const unsigned line_;
    const clock::time_point start_;
};

#define B_MERGE(a, b) a##b
#define B_LABEL(a) B_MERGE(bench_obj_, a)
#define B_OBJNAME B_LABEL(__LINE__)
#define BENCHMARK                                                              \
    const auto B_OBJNAME = benchmark                                           \
    {                                                                          \
        __PRETTY_FUNCTION__, __LINE__                                          \
    }