From e20e8538610ed8b78e0b9f9cc3121c1102a8aaf0 Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Sun, 23 Mar 2025 11:30:17 +0200
Subject: [PATCH] Avoid rare segfaults in 'check_matrix_pointers'

* src/dispnew.c (check_window_matrix_pointers): No-op if the
window's frame not ready yet.  (Bug#77200)
---
 src/dispnew.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/dispnew.c b/src/dispnew.c
index 6365dcb9c4d..6cd41620b57 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -3113,18 +3113,22 @@ mirror_line_dance (struct window *w, int unchanged_at_top, int nlines, int *copy
 static void
 check_window_matrix_pointers (struct window *w)
 {
-  while (w)
-    {
-      if (WINDOWP (w->contents))
-	check_window_matrix_pointers (XWINDOW (w->contents));
-      else
-	{
-	  struct frame *f = XFRAME (w->frame);
-	  check_matrix_pointers (w->desired_matrix, f->desired_matrix);
-	  check_matrix_pointers (w->current_matrix, f->current_matrix);
-	}
+  struct frame *f = XFRAME (w->frame);
 
-      w = NILP (w->next) ? 0 : XWINDOW (w->next);
+  if (f->after_make_frame)
+    {
+      while (w)
+	{
+	  if (WINDOWP (w->contents))
+	    check_window_matrix_pointers (XWINDOW (w->contents));
+	  else
+	    {
+	      check_matrix_pointers (w->desired_matrix, f->desired_matrix);
+	      check_matrix_pointers (w->current_matrix, f->current_matrix);
+	    }
+
+	  w = NILP (w->next) ? 0 : XWINDOW (w->next);
+	}
     }
 }