nanomsg 里的 nn_pipe 是这样的

nn_pipe.c

// Let's see Mr Sustrik's masterpiece
// He must like hierarchy and cleanness to death. 
// So he defined an empty struct of nn_pipe to represent a 
// concept of connection.

// I've known this trick for a while and never thought it could 
// be used like this

// Sean at Shaanxi
// 20140901
// test for nanomsg.nn_pipe


#include <stdio.h>


struct nn_pipe;

struct nn_pipebase {
    int i;
};


int
test_pipe(struct nn_pipe *p) {
    struct nn_pipebase *pb = NULL;
    pb = (struct nn_pipebase*)p;
    printf("pb is %d\n", pb->i);
    return 0;
}


int
test(void) {
    struct nn_pipebase b;
    b.i = 3;
    test_pipe((struct nn_pipe*)&b);
    return 0;
}


int
main(int argc, char **argv) {
    test();
    return 0;
}