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)

diff --git a/src/xdisp.c b/src/xdisp.c
index 44eb1ebf059b6e3bad2c6f7d3bde3195ea480e7d..d5528714270838fe164f3f11f9e3daa112d6b9a6 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -22486,6 +22486,11 @@ 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;