From 0768795ce31c064e06cd4dcd65730eaa71bfef25 Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Sun, 26 Jul 2026 10:02:31 +0100
Subject: [PATCH] Test for overlong runs of combining characters, GitHub issue
 5434.

---
 regress/input-common.inc | 14 ++++++++++++++
 regress/input-unicode.sh |  4 ++++
 regress/tty-draw-line.sh | 22 ++++++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/regress/input-common.inc b/regress/input-common.inc
index 100a7be0f..ac04dbc24 100644
--- a/regress/input-common.inc
+++ b/regress/input-common.inc
@@ -174,3 +174,17 @@ check_raw_matches()
 		fi
 	done
 }
+
+check_raw_no_matches()
+{
+	name=$1
+	shift
+
+	capture_raw "$name" >"$TMP"
+	for unexpected in "$@"; do
+		if grep -Eq "$unexpected" "$TMP"; then
+			printf "%s\n" "$unexpected" >"$EXP"
+			fail "$name raw unexpected"
+		fi
+	done
+}
diff --git a/regress/input-unicode.sh b/regress/input-unicode.sh
index ca74a82e8..98c4506e2 100644
--- a/regress/input-unicode.sh
+++ b/regress/input-unicode.sh
@@ -41,5 +41,9 @@ start_pane combining-left 10 3 '\314\201A\n'
 check_capture combining-left 'A'
 check_cursor combining-left '0,1'
 
+start_pane combining-overflow 10 3 'u\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\n'
+check_raw_matches combining-overflow '^		C 0,0 data=\(1,31,u'
+check_raw_no_matches combining-overflow 'data=\(0,'
+
 $TMUX kill-server 2>/dev/null
 exit $exit_status
diff --git a/regress/tty-draw-line.sh b/regress/tty-draw-line.sh
index 59331aa0d..09a956312 100644
--- a/regress/tty-draw-line.sh
+++ b/regress/tty-draw-line.sh
@@ -34,6 +34,18 @@ captureen() {
 	$TMUX capturep -peNS0 -E- >$TMP || exit 1
 }
 
+timed() {
+	if command -v timeout >/dev/null 2>&1; then
+		timeout 5 "$@"
+	else
+		"$@"
+	fi
+}
+
+capture_timed() {
+	timed $TMUX capturep -pS0 -E- >$TMP || exit 1
+}
+
 check_line() {
 	line=$1
 	want=$2
@@ -81,6 +93,8 @@ $TMUX2 neww -d \
 	"printf '\033(0x\033(B'; exec sleep 100" || exit 1
 $TMUX2 neww -d \
 	"awk 'BEGIN { for (i = 0; i < 1100; i++) printf \"a\" }'; exec sleep 100" || exit 1
+$TMUX2 neww -d \
+	"printf 'u\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245\314\245'; exec sleep 100" || exit 1
 $TMUX2 selectw -t:0 || exit 1
 
 $TMUX -f/dev/null new -d -x20 -y6 || exit 1
@@ -245,4 +259,12 @@ capture
 len=$(sed -n 1p $TMP | wc -c)
 [ "$len" -ge 1100 ] || fail "long same-style line was truncated"
 
+# Too many combining marks on one base character must not leave a standalone
+# width-zero cell that can make tty_draw_line loop forever on redraw.
+$TMUX resizew -x20 -y6 || exit 1
+timed $TMUX2 selectw -t:13 || fail "zero-width overflow select hung"
+sleep 1
+capture_timed
+check_grep '^u'
+
 exit 0