bug in pipe() and pipe2()

[Eric Blake <eblake at redhat dot com>]

I was testing the behavior when pipe() fails, in order to propose an
update to POSIX wording: http://austingroupbugs.net/view.php?id=467

However, cygwin's pipe implementation dumps core when it runs out of
fds, so I could not definitively state whether cygwin properly leaves
the fd array unchanged on error, the way Linux does.  According to a gdb
run and while using stock 1.7.9 cygwin1.dll, the crash is in
fhandler_pipe::create().

#define _POSIX_C_SOURCE 200811L
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
int
main (int argc, char **argv)
{
  int i = 0;
  while (1) {
    int fd[2] = {-2,-3};
    int err = pipe(fd);
    if (err) {
      printf ("iteration %d, pipe returned %d errno %d %s, fds %d %d\n",
          i, err, errno, strerror(errno), fd[0], fd[1]);
      break;
    }
    i++;
  }
  return 0;
}

Expected behavior is EMFILE and fd unchanged, after however many
iterations it takes to reach the ulimit on max fd.

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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