compile time type checking

lrk.h

#define _LRK_TYPECHECK(RET,TYPE,ARG)                            \
        ({                                                      \
                if (0) {                                        \
                        TYPE __t RD_UNUSED = (ARG);             \
                }                                               \
                RET; \
        })
#define _LRK_TYPECHECK2(RET,TYPE,ARG,TYPE2,ARG2)        \
        ({                                              \
                if (0) {                                \
                        TYPE __t RD_UNUSED = (ARG);     \
                        TYPE2 __t2 RD_UNUSED = (ARG2);  \
                }                                       \
                RET;                                    \
        })

#define RD_KAFKA_V_END RD_KAFKA_VTYPE_END
#define RD_KAFKA_V_TOPIC(topic)                                         \
        _LRK_TYPECHECK(RD_KAFKA_VTYPE_TOPIC, const char *, topic), topic
#define RD_KAFKA_V_VALUE(VALUE,LEN)                                     \
        _LRK_TYPECHECK2(RD_KAFKA_VTYPE_VALUE, void *, VALUE, size_t, LEN), \
                VALUE, LEN


// gives:
0052-msg_timestamps.c: In function ‘produce_msgs’:
0052-msg_timestamps.c:80:58: error: incompatible types when initializing type ‘const char *’ using type ‘rd_kafka_resp_err_t {aka enum <anonymous>}’
                                         RD_KAFKA_V_TOPIC(err),
                                                          ^
../src/rdkafka.h:2353:46: note: in definition of macro ‘_LRK_TYPECHECK’
                         TYPE __t RD_UNUSED = ARG;               \
                                              ^
0052-msg_timestamps.c:80:41: note: in expansion of macro ‘RD_KAFKA_V_TOPIC’
                                         RD_KAFKA_V_TOPIC(err),
                                         ^