We recently updated our version of librdkafka and noticed that producers are segfaulting when request.required.acks is set to 0. I was able to reproduce this with rdkafka_example:

$ echo testdata | ./examples/rdkafka_example -P -t test -X topic.request.required.acks=0
Segmentation fault (core dumped)

It looks like rd_kafka_produce_reply_handle is being called with an NULL reply:

rd_kafka_produce_msgset_reply (rkb=0x7ffff0001ca0, err=RD_KAFKA_RESP_ERR_NO_ERROR, reply=0x0, 
    request=0x7fffe8000aa0, opaque=0x7ffff0002320) at rdkafka_broker.c:1584
1584                    err = rd_kafka_produce_reply_handle(rkb, reply);

Git bisect makes it look like this was introduced in a52f585.

librdkafka has been a pleasure to use so far, thanks for all the work!