applied Dimitris' style patch from Dec'14, with some minor modifications

slock.c

@@ -1,4 +1,3 @@
-
 /* See LICENSE file for license details. */
 #define _XOPEN_SOURCE 500
 #if HAVE_SHADOW_H
@@ -37,20 +36,22 @@ static int nscreens;
 static Bool running = True;
 
 static void
-die(const char *errstr, ...) {
+die(const char *errstr, ...)
+{
 	va_list ap;
 
 	va_start(ap, errstr);
 	vfprintf(stderr, errstr, ap);
 	va_end(ap);
-	exit(EXIT_FAILURE);
+	exit(1);
 }
 
 #ifdef __linux__
 #include <fcntl.h>
 
 static void
-dontkillme(void) {
+dontkillme(void)
+{
 	int fd;
 
 	fd = open("/proc/self/oom_score_adj", O_WRONLY);
@@ -62,8 +63,10 @@ dontkillme(void) {
 #endif
 
 #ifndef HAVE_BSD_AUTH
+/* only run as root */
 static const char *
-getpw(void) { /* only run as root */
+getpw(void)
+{
 	const char *rval;
 	struct passwd *pw;
 
@@ -73,7 +76,7 @@ getpw(void) { /* only run as root */
 		if (errno)
 			die("slock: getpwuid: %s\n", strerror(errno));
 		else
-			die("slock: cannot retrieve password entry (make sure to suid or sgid slock)\n");
+			die("slock: cannot retrieve password entry\n");
 	}
 	rval =  pw->pw_passwd;
 
@@ -88,8 +91,8 @@ getpw(void) { /* only run as root */
 #endif
 
 	/* drop privileges */
-	if (geteuid() == 0
+	if (geteuid() == 0 &&
-	   && ((getegid() != pw->pw_gid && setgid(pw->pw_gid) < 0) || setuid(pw->pw_uid) < 0))
+	    ((getegid() != pw->pw_gid && setgid(pw->pw_gid) < 0) || setuid(pw->pw_uid) < 0))
 		die("slock: cannot drop privileges\n");
 	return rval;
 }
@@ -125,9 +128,11 @@ readpw(Display *dpy, const char *pws)
 				else if (ksym >= XK_KP_0 && ksym <= XK_KP_9)
 					ksym = (ksym - XK_KP_0) + XK_0;
 			}
-			if(IsFunctionKey(ksym) || IsKeypadKey(ksym)
+			if (IsFunctionKey(ksym) ||
-					|| IsMiscFunctionKey(ksym) || IsPFKey(ksym)
+			    IsKeypadKey(ksym) ||
-					|| IsPrivateKeypadKey(ksym))
+			    IsMiscFunctionKey(ksym) ||
+			    IsPFKey(ksym) ||
+			    IsPrivateKeypadKey(ksym))
 				continue;
 			switch (ksym) {
 			case XK_Return:
@@ -174,7 +179,8 @@ readpw(Display *dpy, const char *pws)
 }
 
 static void
-unlockscreen(Display *dpy, Lock *lock) {
+unlockscreen(Display *dpy, Lock *lock)
+{
 	if(dpy == NULL || lock == NULL)
 		return;
 
@@ -187,7 +193,8 @@ unlockscreen(Display *dpy, Lock *lock) {
 }
 
 static Lock *
-lockscreen(Display *dpy, int screen) {
+lockscreen(Display *dpy, int screen)
+{
 	char curs[] = {0, 0, 0, 0, 0, 0, 0, 0};
 	unsigned int len;
 	Lock *lock;
@@ -228,8 +235,7 @@ lockscreen(Display *dpy, int screen) {
 	}
 	if (running && (len > 0)) {
 		for (len = 1000; len; len--) {
-			if(XGrabKeyboard(dpy, lock->root, True, GrabModeAsync, GrabModeAsync, CurrentTime)
+			if (XGrabKeyboard(dpy, lock->root, True, GrabModeAsync, GrabModeAsync, CurrentTime) == GrabSuccess)
-				== GrabSuccess)
 				break;
 			usleep(1000);
 		}
@@ -240,16 +246,18 @@ lockscreen(Display *dpy, int screen) {
 		unlockscreen(dpy, lock);
 		lock = NULL;
 	}
-	else 
+	else {
 		XSelectInput(dpy, lock->root, SubstructureNotifyMask);
+	}
 
 	return lock;
 }
 
 static void
-usage(void) {
+usage(void)
+{
 	fprintf(stderr, "usage: slock [-v]\n");
-	exit(EXIT_FAILURE);
+	exit(1);
 }
 
 int
@@ -261,7 +269,7 @@ main(int argc, char **argv) {
 	int screen;
 
 	if ((argc == 2) && !strcmp("-v", argv[1]))
-		die("slock-%s, © 2006-2014 slock engineers\n", VERSION);
+		die("slock-%s, © 2006-2015 slock engineers\n", VERSION);
 	else if (argc != 1)
 		usage();
 
@@ -291,7 +299,7 @@ main(int argc, char **argv) {
 	XSync(dpy, False);
 
 	/* Did we actually manage to lock something? */
-	if (nlocks == 0) { // nothing to protect
+	if (nlocks == 0) { /* nothing to protect */
 		free(locks);
 		XCloseDisplay(dpy);
 		return 1;