iexec: enable not exitting together with the child

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2015 - 2021, Přemysl Eric Janouch <p@janouch.name>
+Copyright (c) 2015 - 2023, Přemysl Eric Janouch <p@janouch.name>
 
 Permission to use, copy, modify, and/or distribute this software for any
 purpose with or without fee is hereby granted.

iexec.c

@@ -1,7 +1,7 @@
 /*
  * iexec.c: run a program and restart on file change
  *
- * Copyright (c) 2017, Přemysl Eric Janouch <p@janouch.name>
+ * Copyright (c) 2017 - 2023, Přemysl Eric Janouch <p@janouch.name>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
  * purpose with or without fee is hereby granted.
@@ -24,34 +24,54 @@
 // This can also work on BSD if someone puts in the effort to support kqueue
 #include <sys/inotify.h>
 
-static pid_t g_child;
-static bool g_restarting = false;
-static int g_inotify_fd, g_inotify_wd;
+static struct
+{
+	pid_t child;                        ///< Watched child or 0
+	bool exits;                         ///< Don't restart child when it exits
+	bool respawn;                       ///< Respawn child ASAP
+	bool killing;                       ///< Waiting for child to die
+	int inotify_fd, inotify_wd;
+}
+g;
+
+// Note that this program doesn't queue up file-based restarts
+static void
+handle_inotify_event (const struct inotify_event *e, const char *base)
+{
+	if (e->wd != g.inotify_wd || strcmp (e->name, base))
+		return;
+
+	if (g.child)
+	{
+		print_debug ("file changed, killing child");
+		if (kill (g.child, SIGINT))
+			print_error ("kill: %s", strerror (errno));
+		g.killing = true;
+	}
+	else
+	{
+		print_debug ("file changed, respawning");
+		g.respawn = true;
+	}
+}
 
 static void
 handle_file_change (const char *base)
 {
-	char buf[4096]; ssize_t len; const struct inotify_event *e;
-	while ((len = read (g_inotify_fd, buf, sizeof buf)) > 0)
-	for (char *ptr = buf; ptr < buf + len; ptr += sizeof *e + e->len)
-	{
-		e = (const struct inotify_event *) buf;
-		if (e->wd != g_inotify_wd || strcmp (e->name, base))
-			continue;
-
-		print_debug ("file changed, killing child");
-		g_restarting = true;
-		if (kill (g_child, SIGINT))
-			print_error ("kill: %s", strerror (errno));
-	}
+	char buf[4096];
+	ssize_t len = 0;
+	struct inotify_event *e = NULL;
+	while ((len = read (g.inotify_fd, buf, sizeof buf)) > 0)
+		for (char *ptr = buf; ptr < buf + len; ptr += sizeof *e + e->len)
+			handle_inotify_event ((e = (struct inotify_event *) buf), base);
 }
 
 static void
 spawn (char *argv[])
 {
-	if ((g_child = fork ()) == -1)
+	if ((g.child = fork ()) == -1)
 		exit_fatal ("fork: %s", strerror (errno));
-	else if (g_child)
+	else if (g.child)
 		return;
 
 	// A linker can create spurious CLOSE_WRITEs, wait until it's executable
@@ -64,23 +84,22 @@ spawn (char *argv[])
 }
 
 static bool
-check_child_death (char *argv[])
+check_child_death (void)
 {
-	if (waitpid (g_child, NULL, WNOHANG) != g_child)
+	int status = 0;
+	if (waitpid (g.child, &status, WNOHANG) != g.child)
 		return true;
 
-	if (!g_restarting)
+	g.child = 0;
+	if (!g.killing)
 	{
 		print_debug ("child died on its own, not respawning");
-		return false;
-	}
-	else
-	{
-		print_debug ("child died on request, respawning");
-		spawn (argv);
-		g_restarting = false;
-		return true;
+		return g.exits;
 	}
+
+	g.killing = false;
+	print_debug ("child died on request, respawning");
+	return g.respawn = true;
 }
 
 static void
@@ -93,8 +112,11 @@ sigchld_handler (int signum)
 int
 main (int argc, char *argv[])
 {
+	const char *target = NULL;
 	static const struct opt opts[] =
 	{
+		{ 'f', "file", "PATH", 0, "watch this path rather than the program" },
+		{ 'e', "exits", NULL, 0, "allow the program to exit on its own" },
 		{ 'd', "debug", NULL, 0, "run in debug mode" },
 		{ 'h', "help", NULL, 0, "display this help and exit" },
 		{ 'V', "version", NULL, 0, "output version information and exit" },
@@ -111,6 +133,12 @@ main (int argc, char *argv[])
 	while ((c = opt_handler_get (&oh)) != -1)
 	switch (c)
 	{
+	case 'f':
+		target = optarg;
+		break;
+	case 'e':
+		g.exits = true;
+		break;
 	case 'd':
 		g_debug_mode = true;
 		break;
@@ -136,6 +164,9 @@ main (int argc, char *argv[])
 	argc -= optind;
 	argv += optind;
 
+	if (!target)
+		target = argv[0];
+
 	(void) signal (SIGPIPE, SIG_IGN);
 	struct sigaction sa = { .sa_handler = sigchld_handler };
 	sigemptyset (&sa.sa_mask);
@@ -148,27 +179,33 @@ main (int argc, char *argv[])
 	if (sigprocmask (SIG_BLOCK, &chld, &orig))
 		exit_fatal ("sigprocmask: %s", strerror (errno));
 
-	char *path = xstrdup (argv[0]);
+	char *path = NULL;
+	char *dir = dirname ((path = xstrdup (target)));
 
-	if ((g_inotify_fd = inotify_init1 (IN_NONBLOCK)) < 0)
+	if ((g.inotify_fd = inotify_init1 (IN_NONBLOCK)) < 0)
 		exit_fatal ("inotify_init1: %s", strerror (errno));
-	if ((g_inotify_wd = inotify_add_watch (g_inotify_fd,
-		dirname (path), IN_MOVED_TO | IN_CLOSE_WRITE)) < 0)
+	if ((g.inotify_wd = inotify_add_watch (g.inotify_fd,
+		dir, IN_MOVED_TO | IN_CLOSE_WRITE)) < 0)
 		exit_fatal ("inotify_add_watch: %s", strerror (errno));
 
 	free (path);
-	char *base = basename ((path = xstrdup (argv[0])));
-	spawn (argv);
-
+	char *base = basename ((path = xstrdup (target)));
+	g.respawn = true;
 	do
 	{
-		fd_set r; FD_SET (g_inotify_fd, &r);
-		(void) pselect (g_inotify_fd + 1, &r, NULL, NULL, NULL, &orig);
+		if (g.respawn)
+		{
+			spawn (argv);
+			g.respawn = false;
+		}
+
+		fd_set r; FD_SET (g.inotify_fd, &r);
+		(void) pselect (g.inotify_fd + 1, &r, NULL, NULL, NULL, &orig);
 		handle_file_change (base);
 	}
-	while (check_child_death (argv));
+	while (check_child_death ());
 
 	free (path);
-	close (g_inotify_fd);
+	xclose (g.inotify_fd);
 	return EXIT_SUCCESS;
 }

liberty

@@ -1 +1 @@
-Subproject commit 782a9a5977bd5f2101e8808b94d659fe52e2490a
+Subproject commit d01a1ff0348174f91bb2d3ba53145cc2c9f50a7f