#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>

/* Check if a file descriptor is valid or not.
   Return 0 if the file descriptor is invalid, return non-zero otherwise. */
static int
is_valid_fd(int fd)
{
#ifdef USE_FSTAT 
    /* bpo-30225: On macOS Tiger, when stdout is redirected to a pipe
       and the other side of the pipe is closed, dup(1) succeed, whereas
       fstat(1, &st) fails with EBADF. Prefer fstat() over dup() to detect
       such error. */
    struct stat st;
    return (fstat(fd, &st) == 0);
#else
    int fd2;
    if (fd < 0)
        return 0;
    /* Prefer dup() over fstat(). fstat() can require input/output whereas
       dup() doesn't, there is a low risk of EMFILE/ENFILE at Python
       startup. */
    fd2 = dup(fd);
    if (fd2 >= 0)
        close(fd2);
    return fd2 >= 0;
#endif
}


int
main(void)
{

    printf("0: %d\n", is_valid_fd(0));
    printf("1: %d\n", is_valid_fd(1));
    printf("2: %d\n", is_valid_fd(2));

    return 0;
}