From 96d231dfa52cdcdec91dbd71ae7402c84e1eb7f9 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 16 Feb 2025 10:02:39 +0530
Subject: [PATCH] Use buffer size in cell_as_unicode_for_fallback as well

---
 kitty/fontconfig.c | 2 +-
 kitty/line.c       | 4 ++--
 kitty/lineops.h    | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kitty/fontconfig.c b/kitty/fontconfig.c
index a9a3008dd..83c2f63c0 100644
--- a/kitty/fontconfig.c
+++ b/kitty/fontconfig.c
@@ -505,7 +505,7 @@ create_fallback_face(PyObject UNUSED *base_face, const ListOfChars *lc, bool bol
     if (!emoji_presentation && bold) { AP(FcPatternAddInteger, FC_WEIGHT, FC_WEIGHT_BOLD, "weight"); }
     if (!emoji_presentation && italic) { AP(FcPatternAddInteger, FC_SLANT, FC_SLANT_ITALIC, "slant"); }
     if (emoji_presentation) { AP(FcPatternAddBool, FC_COLOR, true, "color"); }
-    size_t num = cell_as_unicode_for_fallback(lc, char_buf);
+    size_t num = cell_as_unicode_for_fallback(lc, char_buf, arraysz(char_buf));
     add_charset(pat, num);
     d = _fc_match(pat);
 face_from_descriptor:
diff --git a/kitty/line.c b/kitty/line.c
index ccf163b73..ec127bd43 100644
--- a/kitty/line.c
+++ b/kitty/line.c
@@ -402,11 +402,11 @@ text_at(Line* self, Py_ssize_t xval) {
 }
 
 size_t
-cell_as_unicode_for_fallback(const ListOfChars *lc, Py_UCS4 *buf) {
+cell_as_unicode_for_fallback(const ListOfChars *lc, Py_UCS4 *buf, size_t sz) {
     size_t n = 1;
     buf[0] = lc->chars[0] ? lc->chars[0] : ' ';
     if (buf[0] != '\t') {
-        for (unsigned i = 1; i < lc->count; i++) {
+        for (unsigned i = 1; i < lc->count && n < sz; i++) {
             if (lc->chars[i] != VS15 && lc->chars[i] != VS16) buf[n++] = lc->chars[i];
         }
     } else buf[0] = ' ';
diff --git a/kitty/lineops.h b/kitty/lineops.h
index 86d944e4f..70b362e8e 100644
--- a/kitty/lineops.h
+++ b/kitty/lineops.h
@@ -78,7 +78,7 @@ index_type next_char_pos(const Line *self, index_type x, index_type num);
 index_type prev_char_pos(const Line *self, index_type x, index_type num);
 bool line_as_ansi(Line *self, ANSILineState *s, index_type start_at, index_type stop_before, char_type prefix_char, bool skip_multiline_non_zero_lines) __attribute__((nonnull));
 unsigned int line_length(Line *self);
-size_t cell_as_unicode_for_fallback(const ListOfChars *lc, Py_UCS4 *buf);
+size_t cell_as_unicode_for_fallback(const ListOfChars *lc, Py_UCS4 *buf, size_t sz);
 size_t cell_as_utf8_for_fallback(const ListOfChars *lc, char *buf);
 bool unicode_in_range(const Line *self, const index_type start, const index_type limit, const bool include_cc, const bool add_trailing_newline, const bool skip_zero_cells, bool skip_multiline_non_zero_lines, ANSIBuf*);
 PyObject* line_as_unicode(Line *, bool, ANSIBuf*);