From 55d985a354048e14f408dd731faaf1acbdc277f4 Mon Sep 17 00:00:00 2001
From: Leonardo Taccari <leot@NetBSD.org>
Date: Mon, 27 Jul 2026 23:27:43 +0200
Subject: [PATCH] Avoid ctype(3) abuses

Valid argument of ctype(3) functions must be either EOF or non-negative
value within the range representable as unsigned char. Invalid values
leads to undefined behavior.

Cast all such uses to avoid that.

At least in NetBSD 11 ctype(3) abuses will always crash and permit
to break slock screen locking.
---
 slock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/slock.c b/slock.c
index f16781f..3cede0f 100644
--- a/slock.c
+++ b/slock.c
@@ -181,7 +181,7 @@ readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
 					passwd[--len] = '\0';
 				break;
 			default:
-				if (num && !iscntrl((int)buf[0]) &&
+				if (num && !iscntrl((unsigned char)buf[0]) &&
 				    (len + num < sizeof(passwd))) {
 					memcpy(passwd + len, buf, num);
 					len += num;