Assertion failed: size > 0 && (*data == 0 || *data == 1) (xpub.cpp:66)

i have a test case where a subscriber binds to a socket and a publisher connects to it. this works fine if both the publisher and subscriber are both compiled and linked against libzmq 2, or both compiled and linked against libzmq 3, but fails in the case of a v2 publisher and a v3 subscriber or in the case of a v3 publisher and a v2 subscriber.

this is the v3 publisher, v2 subscriber case.

$ ./compile
+ CFLAGS='-Wall -O0 -ggdb'
+ gcc -include /usr/include/zmq.h -Wall -O0 -ggdb -o pub2 pub.c -lzmq
+ gcc -include /usr/include/zmq.h -Wall -O0 -ggdb -o sub2 sub.c -lzmq
+ gcc -include /usr/local/include/zmq.h -Wall -O0 -ggdb -o pub3 pub.c -L/usr/local/lib -lzmq
+ gcc -include /usr/local/include/zmq.h -Wall -O0 -ggdb -o sub3 sub.c -L/usr/local/lib -lzmq
edmonds@chase{0}:~/code/test/zmq-crash$ ./pub3 ipc://testcase.ipc
publisher: zeromq version 3.1.1
./pub3: connecting to socket ipc://testcase.ipc
^Z
zsh: suspended ./pub3 ipc://testcase.ipc
$ bg
[1] + continued ./pub3 ipc://testcase.ipc
$ ./sub2 ipc://testcase.ipc
subscriber: zeromq version 2.1.10
./sub2: binding to socket ipc://testcase.ipc
Assertion failed: size > 0 && (*data == 0 || *data == 1) (xpub.cpp:66)
[1] + abort ./pub3 ipc://testcase.ipc