master 3fe2f48: Attempt to fix segfaults caused by changes in 'lisp_string_width'

[Eli Zaretskii]

branch: master
commit 3fe2f482bd2c636934cfd8e8aa0a07631164831d
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Attempt to fix segfaults caused by changes in 'lisp_string_width'
    
    * src/character.c (lisp_string_width): Validate the value of TO
    argument before passing it to 'composition_gstring_width'.
    (Bug#48711)
---
 src/character.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/character.c b/src/character.c
index 60424fa..e44ab8d 100644
--- a/src/character.c
+++ b/src/character.c
@@ -376,9 +376,13 @@ lisp_string_width (Lisp_Object string, ptrdiff_t from, 
ptrdiff_t to,
               && find_automatic_composition (i, -1, &ignore, &end, &val, 
string)
               && end > i)
        {
-         int pixelwidth = composition_gstring_width (val, 0,
-                                                     LGSTRING_GLYPH_LEN (val),
-                                                     NULL);
+         int j;
+         for (j = 0; j < LGSTRING_GLYPH_LEN (val); j++)
+           if (NILP (LGSTRING_GLYPH (val, j)))
+             break;
+
+         int pixelwidth = composition_gstring_width (val, 0, j, NULL);
+
          /* The below is somewhat expensive, so compute it only once
             for the entire loop, and only if needed.  */
          if (font_width < 0)