poll
====

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/poll.html

Gnulib module: poll

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: mingw, MSVC 14, HP NonStop.

  * This function doesn't work on special files like /dev/null and ttys like /dev/tty on some platforms: AIX 5.3.

Portability problems not fixed by Gnulib:

  * Under Windows, when passing a pipe, Gnulib's poll replacement might return 0 even before the timeout has passed.  Programs using it with pipes can thus busy wait.

  * On some platforms, file descriptors other than sockets do not support POLLHUP; they will return a "readable" or "writable" status instead: AIX 7.2, HP NonStop.