//
// demonstrate/test a Cygwin bug.
// dup of a serial file descriptor
// causes confusion.  One symptom
// is that select() on the dup 
// result will always return -1,
// with an errno of 0.
//
//     -Billy <billy@dadadada.net>

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/select.h>
#include <unistd.h>
#include <fcntl.h>

int
main(int argc, char **argv)
{
    char *device = "/dev/com1";
    if(argc>1){
        device = argv[1];
    }

    int comm = open(device, O_RDONLY | O_NOCTTY);
    if(comm == -1) {
        fprintf(stderr, "open '%s' failed: %s\n", device, strerror(errno));
        return 1;
    }

    int newcomm = dup(comm);
    if(newcomm==-1){
        perror("dup");
        return -1;
    }

    fd_set rfds;
    FD_ZERO(&rfds);
    FD_SET(newcomm, &rfds);
    int nsel = select(newcomm+1, &rfds, 0, 0, 0);
    fprintf(stderr, "select: nsel=%d\n", nsel);
    if(nsel==-1){
        fprintf(stderr, "errno=%d, %s\n", errno, strerror(errno));
        return 1;
    }
    return 0;
}