Re: PATCH: improve checkptycmd

[Jun T <takimoto-j@xxxxxxxxxxxxxxxxx>]

With this patch (commit 4b4ebcca) lots of tests fails on macOS
(probably all the tests that use zpty). It seems reading from zpty
returns nothing.

On macOS, HAVE_POLL is not defined because zsh_system.h:374-381 has

#if defined(__APPLE__) && defined(HAVE_SELECT)
/*
 * Prefer select() to poll() on MacOS X since poll() is known
 * to be problematic in 10.4
 */
#undef HAVE_POLL
#undef HAVE_POLL_H
#endif


In funcion checkptycmd(), at zpty.c:576
        ret = select(cmd->fd + 1, (SELECT_ARG_2_T) &fds, NULL, NULL, &tv);
returns ret=1 (and select_ret is set to 1), but at line 583
    if (ioctl(cmd->fd, FIONREAD, (char *) &val) == 0 && val > 0)
returns val = 0, and the pty is closed at line 588.

I don't know select()/ioctl() are working as expected or not.

But, if I remove the lines 374-381 in zsh_system.h, i.e., if we use poll()
also on macOS, then all the test pass, at least on the latest macOS (Sequoia).

Version 10.4 mentioned in the comment is Tiger, which is released in 2005,
and not supported since 2009, probably.

If there are someone who have older macOS, please test by removing the
lines 374-381 in zsh_system.h.