Implement poll using kqueue on macOS

Work-around for the broken poll implementation on macOS that does not support
character devices like /dev/tty.

Author: mptre

Makefile.am

@@ -4,7 +4,11 @@ AM_CFLAGS=-Wall -Wextra
 AM_CPPFLAGS=-D_GNU_SOURCE
 
 bin_PROGRAMS=pick
-pick_SOURCES=pick.c compat-reallocarray.c compat-strtonum.c compat.h
+pick_SOURCES=compat-poll.c \
+             compat-reallocarray.c \
+             compat-strtonum.c \
+             compat.h \
+             pick.c
 pick_CPPFLAGS=$(AM_CPPFLAGS) $(NCURSES_CFLAGS)
 pick_LDADD=$(NCURSES_LIBS)
 

compat-poll.c

@@ -0,0 +1,83 @@
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+int unused;
+
+#ifdef HAVE_POLL
+
+#include <poll.h>
+
+int
+xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+	return poll(fds, nfds, timeout);
+}
+
+#else
+
+#include <sys/types.h>
+#include <sys/event.h>
+#include <sys/time.h>
+
+#include <assert.h>
+#include <err.h>
+#include <poll.h>
+#include <string.h>
+
+int
+xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+#define NKEVENT	2
+	static int	 kq = -1;
+	struct kevent	 kev[NKEVENT];
+	struct pollfd	*pfd;
+	struct timespec	 ts, *tsp;
+	unsigned int	 i;
+	int		 filter, nevents;
+
+	assert(nfds <= NKEVENT);
+
+	if (kq == -1) {
+		kq = kqueue();
+		if (kq == -1)
+			return -1;
+		for (i = 0; i < nfds; i++) {
+			if (fds[i].events & POLLIN)
+				filter = EVFILT_READ;
+			else
+				errx(1, "%x: unknown poll event",
+				    fds[i].events);
+			EV_SET(&kev[i], fds[i].fd, filter, EV_ADD, 0, 0,
+			    &fds[i]);
+		}
+		if (kevent(kq, kev, nfds, NULL, 0, NULL) == -1)
+			return -1;
+	}
+
+	if (timeout >= 0) {
+		ts.tv_sec = timeout / 1000;
+		ts.tv_nsec = (timeout % 1000) * 1000000;
+		tsp = &ts;
+	} else {
+		tsp = NULL;
+	}
+	nevents = kevent(kq, NULL, 0, kev, nfds, tsp);
+	if (nevents == -1)
+		return -1;
+	for (i = 0; i < nfds; i++)
+		fds[i].revents = 0;
+	for (i = 0; i < (unsigned int)nevents; i++) {
+		if (kev[i].flags & EV_ERROR)
+			errx(1, "kevent: %s", strerror(kev[i].data));
+
+		pfd = kev[i].udata;
+		if (kev[i].filter == EVFILT_READ)
+			pfd->revents |= POLLIN;
+		else
+			errx(1, "%d: unknown kqueue filter", kev[i].filter);
+	}
+	return nevents;
+}
+
+#endif /* !HAVE_POLL */

compat.h

@@ -32,3 +32,5 @@ long long	strtonum(const char *, long long, long long, const char **);
 #endif /* !HAVE_STRTONUM */
 
 #endif /* COMPAT_H */
+
+int xpoll(struct pollfd *, nfds_t, int);

config.h.in

@@ -6,6 +6,9 @@
 /* Define to 1 if you have the `pledge' function. */
 #undef HAVE_PLEDGE
 
+/* Define if poll(2) works with character devices */
+#undef HAVE_POLL
+
 /* Define to 1 if you have the `reallocarray' function. */
 #undef HAVE_REALLOCARRAY
 

configure.ac

@@ -2,6 +2,7 @@ AC_PREREQ([2.61])
 AC_INIT([pick], [2.0.2], [[email protected]])
 AM_INIT_AUTOMAKE([subdir-objects])
 AC_CONFIG_HEADERS([config.h])
+AC_CANONICAL_HOST
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_CHECK_FUNCS([pledge reallocarray strtonum])
@@ -16,7 +17,6 @@ AC_SEARCH_LIBS([setupterm], [curses], [], [
   )
 ])
 AC_DEFUN([AC_MALLOC_OPTIONS], [
-  AC_CANONICAL_HOST
   AC_MSG_CHECKING([for $host_os malloc hardening options])
   case "$host_os" in
   openbsd*) malloc_options="RS";;
@@ -30,5 +30,20 @@ AC_DEFUN([AC_MALLOC_OPTIONS], [
   AC_SUBST([MALLOC_OPTIONS], [$malloc_options])
 ])
 AC_MALLOC_OPTIONS
+AC_DEFUN([AC_POLL], [
+  AC_MSG_CHECKING([whether poll(2) support character devices])
+  case "$host_os" in
+  darwin*) res=0;;
+  *)       res=1;;
+  esac
+  if test "$res" -eq 1; then
+    AC_MSG_RESULT([yes])
+  else
+    AC_MSG_RESULT([no])
+  fi
+  AC_DEFINE([HAVE_POLL], [$res], [
+    Define if poll(2) works with character devices])
+])
+AC_POLL
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT

pick.c

@@ -331,7 +331,7 @@ selected_choice(void)
 	for (;;) {
 		dokey = doread = 0;
 		toggle_sigwinch(1);
-		if (poll(fds, nfds, timo) == -1 && errno != EINTR)
+		if (xpoll(fds, nfds, timo) == -1 && errno != EINTR)
 			err(1, "poll");
 		toggle_sigwinch(0);
 		if (gotsigwinch) {
@@ -357,7 +357,12 @@ selected_choice(void)
 				if (query_length > 0)
 					dofilter = 1;
 			} else {
-				nfds = 1; /* EOF */
+				/*
+				 * if xpoll uses kqueue, close the fd in order
+				 * to remove it from the event queue.
+				 */
+				close(STDIN_FILENO);
+				nfds = 1;
 			}
 		}
 		if (!dokey && query_length == 0 && length >= choices_lines)

tests/pick-test.c

@@ -6,6 +6,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>