Avoid assertion violation under visual-order-cursor-movement

* src/xdisp.c (Fmove_point_visually): Don't let point exceed the
BEGV..ZV range.  Signal Beginning of buffer error when there's a
before-string at BEGV.  (Bug#30787)

1 files changed, 5 insertions, 0 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index b003a2f9ccc..fb6729c36aa 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -22430,6 +22430,11 @@ Value is the new character position of point.  */)
                     new_pos += (row->reversed_p ? -dir : dir);
                   else
                     new_pos -= (row->reversed_p ? -dir : dir);
+                  new_pos = clip_to_bounds (BEGV, new_pos, ZV);
+                  /* If we didn't move, we've hit BEGV or ZV, so we
+                     need to signal a suitable error.  */
+                  if (new_pos == PT)
+                    break;
                 }
               else if (BUFFERP (g->object))
                 new_pos = g->charpos;