Well, it's a C macro in Apache Thrift code base [1] #ifdef __GNUC__ #define TDB_LIKELY(val) (__builtin_expect((val), 1)) #define TDB_UNLIKELY(val) (__builtin

Well, it's a C macro in Apache Thrift code base [1] #ifdef __GNUC__ #define TDB_LIKELY(val) (__builtin_expect((val), 1)) #define TDB_UNLIKELY(val) (__builtin_expect((val), 0)) #else #define TDB_LIKELY(val) (val) #define TDB_UNLIKELY(val) (val) #endif This code is beautiful when it deal with CPU cache-line effects to speed up your program. [1] https://github.com/apache/thrift/blob/647501693bd14256df8839c13cb03659bdee4202/lib/cpp/src/thrift/transport/TBufferTransports.h#L32-L33 https://github.com/apache/thrift/blob/647501693bd14256df8839...