Don't bother with ignoring SIGCHLD

It added complexity, especially with the differences in behavior between
handled and ignored signals across an exec().

dwl.c

@@ -297,6 +297,7 @@ static void setmon(Client *c, Monitor *m, uint32_t newtags);
 static void setpsel(struct wl_listener *listener, void *data);
 static void setsel(struct wl_listener *listener, void *data);
 static void setup(void);
+static void sigchld(int unused);
 static void spawn(const Arg *arg);
 static void startdrag(struct wl_listener *listener, void *data);
 static void tag(const Arg *arg);
@@ -397,7 +398,6 @@ static void configurex11(struct wl_listener *listener, void *data);
 static void createnotifyx11(struct wl_listener *listener, void *data);
 static Atom getatom(xcb_connection_t *xc, const char *name);
 static void sethints(struct wl_listener *listener, void *data);
-static void sigchld(int unused);
 static void xwaylandready(struct wl_listener *listener, void *data);
 static struct wl_listener new_xwayland_surface = {.notify = createnotifyx11};
 static struct wl_listener xwayland_ready = {.notify = xwaylandready};
@@ -1963,8 +1963,6 @@ run(char *startup_cmd)
 		if ((child_pid = fork()) < 0)
 			die("startup: fork:");
 		if (child_pid == 0) {
-			sa.sa_handler = SIG_DFL;
-			sigaction(SIGCHLD, &sa, NULL);
 			dup2(piperw[0], STDIN_FILENO);
 			close(piperw[0]);
 			close(piperw[1]);
@@ -2129,27 +2127,19 @@ setsel(struct wl_listener *listener, void *data)
 void
 setup(void)
 {
-	struct sigaction sa_term = {.sa_flags = SA_RESTART, .sa_handler = quitsignal};
-	struct sigaction sa_sigchld = {
-#ifdef XWAYLAND
-		.sa_flags = SA_RESTART,
-		.sa_handler = sigchld,
-#else
-		.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT | SA_RESTART,
-		.sa_handler = SIG_IGN,
-#endif
-	};
-	sigemptyset(&sa_term.sa_mask);
-	sigemptyset(&sa_sigchld.sa_mask);
+	/* Set up signal handlers */
+	struct sigaction sa = {.sa_flags = SA_RESTART, .sa_handler = sigchld};
+	sigemptyset(&sa.sa_mask);
+	sigaction(SIGCHLD, &sa, NULL);
+
+	sa.sa_handler = quitsignal;
+	sigaction(SIGINT, &sa, NULL);
+	sigaction(SIGTERM, &sa, NULL);
+
 	/* The Wayland display is managed by libwayland. It handles accepting
 	 * clients from the Unix socket, manging Wayland globals, and so on. */
 	dpy = wl_display_create();
 
-	/* Set up signal handlers */
-	sigaction(SIGCHLD, &sa_sigchld, NULL);
-	sigaction(SIGINT, &sa_term, NULL);
-	sigaction(SIGTERM, &sa_term, NULL);
-
 	/* The backend is a wlroots feature which abstracts the underlying input and
 	 * output hardware. The autocreate option will choose the most suitable
 	 * backend based on the current environment, such as opening an X11 window
@@ -2323,13 +2313,32 @@ setup(void)
 #endif
 }
 
+void
+sigchld(int unused)
+{
+#ifdef XWAYLAND
+	siginfo_t in;
+	/* We should be able to remove this function in favor of a simple
+	 *	struct sigaction sa = {.sa_handler = SIG_IGN};
+	 * 	sigaction(SIGCHLD, &sa, NULL);
+	 * but the Xwayland implementation in wlroots currently prevents us from
+	 * setting our own disposition for SIGCHLD.
+	 */
+	/* WNOWAIT leaves the child in a waitable state, in case this is the
+	 * XWayland process
+	 */
+	while (!waitid(P_ALL, 0, &in, WEXITED|WNOHANG|WNOWAIT) && in.si_pid
+			&& (!xwayland || in.si_pid != xwayland->server->pid))
+		waitpid(in.si_pid, NULL, 0);
+#else
+	while (waitpid(-1, NULL, WNOHANG) > 0);
+#endif
+}
+
 void
 spawn(const Arg *arg)
 {
 	if (fork() == 0) {
-		struct sigaction sa = {.sa_flags = SA_RESTART, .sa_handler = SIG_DFL};
-		sigemptyset(&sa.sa_mask);
-		sigaction(SIGCHLD, &sa, NULL);
 		dup2(STDERR_FILENO, STDOUT_FILENO);
 		setsid();
 		execvp(((char **)arg->v)[0], (char **)arg->v);
@@ -2772,24 +2781,6 @@ sethints(struct wl_listener *listener, void *data)
 	}
 }
 
-void
-sigchld(int unused)
-{
-	siginfo_t in;
-	/* We should be able to remove this function in favor of a simple
-	 *	struct sigaction sa = {.sa_handler = SIG_IGN};
-	 * 	sigaction(SIGCHLD, &sa, NULL);
-	 * but the Xwayland implementation in wlroots currently prevents us from
-	 * setting our own disposition for SIGCHLD.
-	 */
-	/* WNOWAIT leaves the child in a waitable state, in case this is the
-	 * XWayland process
-	 */
-	while (!waitid(P_ALL, 0, &in, WEXITED|WNOHANG|WNOWAIT) && in.si_pid
-			&& (!xwayland || in.si_pid != xwayland->server->pid))
-		waitpid(in.si_pid, NULL, 0);
-}
-
 void
 xwaylandready(struct wl_listener *listener, void *data)
 {