check_c_source_runs(
    "
#include <sys/types.h>
#include <sys/socket.h>

int main (int argc, char *argv [])
{
    int s, rc, opt = 1;
    return (
        ((s = socket (PF_INET, SOCK_STREAM, 0)) == -1) ||
        ((rc = setsockopt (s, SOL_SOCKET, SO_PRIORITY, (char*) &opt, sizeof (int))) == -1)
    );
}
"
    ZMQ_HAVE_SO_PRIORITY)