Has anyone ever had a use for the __COUNTER__ pre-processor macro?

Question

The __COUNTER__ symbol is provided by VC++ and GCC, and gives an increasing non-negative integral value each time it is used.

I\'m interested to learn w

Answer 1

It's used in ClickHouse's metrics system.

namespace CurrentMetrics
{
    #define M(NAME) extern const Metric NAME = __COUNTER__;
        APPLY_FOR_METRICS(M)
    #undef M
    constexpr Metric END = __COUNTER__;

    std::atomic values[END] {};    /// Global variable, initialized by zeros.

    const char * getDescription(Metric event)
    {
        static const char * descriptions[] =
        {
        #define M(NAME) #NAME,
            APPLY_FOR_METRICS(M)
        #undef M
        };

        return descriptions[event];
    }

    Metric end() { return END; }
}