wcrtomb should be declared in <wchar.h> not in <stdio.h>
see
http://pubs.opengroup.org/onlinepubs/9699919799/functions/wcrtomb.html
vs
http://repo.or.cz/w/c-standard.git/blob_plain/HEAD:/n1256.html#7.24.6.3.3


pthread_kill(invalid_value, sig); required to return ESRCH which is not possible
http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_kill.html