Merge from origin/emacs-27

df04f3e755 Fix a rare segfault in syntax.c
fd1fe1e1ec Add doc to syntax-propertize-function saying it must do a ...
fcd599bbea Minor copyedits of doc of 'with-silent-modifications'
759399cdb1 Improve documentation of 'max-mini-window-height'
3223302aa2 Use modern constant names for the NS pasteboard
985703d380 Fix doc string of 'toggle-menu-bar-mode-from-frame'
184a4977c7 Make vc-bzr tests work with brz 3.1 (bug#43314)

# Conflicts:
#	lisp/emacs-lisp/syntax.el
#	src/syntax.c

1 files changed, 14 insertions, 11 deletions

diff --git a/src/syntax.c b/src/syntax.c
index 7f0fc341f6e..e6af8a377bb 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2542,20 +2542,23 @@ between them, return t; otherwise return nil.  */)
               bool fence_found = 0;
               ptrdiff_t ini = from, ini_byte = from_byte;
 
-              while (1)
+              if (from > stop)
                 {
-                  dec_both (&from, &from_byte);
-                  UPDATE_SYNTAX_TABLE_BACKWARD (from);
-                  c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
-                  if (SYNTAX (c) == Scomment_fence
-                      && !char_quoted (from, from_byte))
+                  while (1)
                     {
-                      fence_found = 1;
-                      break;
+                      dec_both (&from, &from_byte);
+                      UPDATE_SYNTAX_TABLE_BACKWARD (from);
+                      c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
+                      if (SYNTAX (c) == Scomment_fence
+                          && !char_quoted (from, from_byte))
+                        {
+                          fence_found = 1;
+                          break;
+                        }
+                      else if (from == stop)
+                        break;
+                      rarely_quit (++quit_count);
                     }
-                  else if (from == stop)
-                    break;
-                  rarely_quit (++quit_count);
                 }
               if (fence_found == 0)
                 {