debug_util.h

/* Excerpted from https://github.com/mongodb/mongo/blob/ea83ad3103fef1664e9385d48537c4163344ce8a/src/mongo/util/debug_util.h#L37 */

// The following declare one unique counter per enclosing function.
// NOTE The implementation double-increments on a match, but we don't really care.
#define MONGO_SOMETIMES( occasion, howOften ) for( static unsigned occasion = 0; ++occasion % howOften == 0; )
#define SOMETIMES MONGO_SOMETIMES

#define MONGO_OCCASIONALLY SOMETIMES( occasionally, 16 )
#define OCCASIONALLY MONGO_OCCASIONALLY

#define MONGO_RARELY SOMETIMES( rarely, 128 )
#define RARELY MONGO_RARELY

#define MONGO_ONCE for( static bool undone = true; undone; undone = false )
#define ONCE MONGO_ONCE

optime.cpp

/* Excerpted from https://github.com/mongodb/mongo/blob/ea83ad3103fef1664e9385d48537c4163344ce8a/src/mongo/bson/optime.cpp#L32  */
    {
        bool toLog = false;
        ONCE toLog = true;
        RARELY toLog = true;
        last.i++;
        if ( last.i & 0x80000000 )
            toLog = true;
        if ( toLog ) {
            log() << "clock skew detected  prev: " << last.secs << " now: " << (unsigned) time(0)
                  << std::endl;
        }

    }