Re: [Bug-readline] [PATCH] Gnuplot on macOS does not suspend by Control-z

[Rin Okuyama]

On 2017/11/23 11:27, Chet Ramey wrote:
> Yes, it can.  If you act when select() returns -1/EINTR, check for a
> caught signal, and break out of the loop, it should do what you want.
> (I'm not sure why you put the signal check before the call to select().)
> The reason it will work is that the first thing rl_getc does is to check
> for and handle any caught signals, so you can be sure that calling it
> when you've detected a signal will cause the signal handler to be invoked.
> It's just adding a dependency on a particular implementation.
>
> I'm not sure there's a compelling reason to expose readline's internal
> signal handling to applications. If you really need it, there are a
> couple of workarounds, both covered here.

Thank you for your comment. As you pointed out, the signal check
should be within the select(2) loop. New versions would be

(1) _rl_signal_handler() is used as before:

----
int getc_wrapper(FILE *fp) {
    fd_set fds;
    int fd = fileno(fp);
    int ierr;
    if (external_fd >= 0) {
        do {
            FD_ZERO(&fds);
            FD_SET(fd, &fds);
            FD_SET(external_fd, &fds);
            ierr = select(external_fd + 1, &fds, 0, 0, NULL);
            if (ierr < 0 && errno == EINTR) {
#ifdef HAVE_LIBREADLINE
                if (_rl_caught_signal)
                    _rl_signal_handler(_rl_caught_signal);
#endif
                continue;
            }

... poll and read from external_fd ...

        } while (!FD_ISSET(fd, &fds));
    }
#ifdef HAVE_LIBREADLINE
    return rl_getc(fp);
#else
    return getc(fp);
#endif
}
----

(2) the 1st ifdef block is simply replaced by

----
#ifdef HAVE_LIBREADLINE
                return rl_getc(fp);
#endif
----

Both (1) and (2) suspend by Control-z. However, variant (2) does not
accept input from external_fd (it is actually mouse driver) after
continue from suspend, unless the first any input arrives from tty.
I guess that this is inevitable with rl_getc(). How do you think?

rin