Avoid infinite recursion in 'window_wants_header_line'

* src/window.c (null_header_line_format): Avoid infinite
recursion by disallowing :eval on recursive calls.
(Bug#63988)

1 files changed, 11 insertions, 1 deletions

diff --git a/src/window.c b/src/window.c
index 3802efb992a..e22fea0bb7a 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5470,6 +5470,7 @@ window_wants_mode_line (struct window *w)
           && WINDOW_PIXEL_HEIGHT (w) > WINDOW_FRAME_LINE_HEIGHT (w));
 }
 
+static int header_line_eval_called = 0;
 
 /**
  * null_header_line_format:
@@ -5497,9 +5498,18 @@ null_header_line_format (Lisp_Object fmt, struct frame *f)
         {
           if (EQ (car, QCeval))
             {
+              if (header_line_eval_called > 0)
+                return false;
+              eassert (header_line_eval_called == 0);
+              header_line_eval_called++;
               val = safe_eval_inhibit_quit (XCAR (XCDR (fmt)));
+              header_line_eval_called--;
+              eassert (header_line_eval_called == 0);
               if (!FRAME_LIVE_P (f))
-                signal_error (":eval deleted the frame being displayed", fmt);
+                {
+                  header_line_eval_called = 0;
+                  signal_error (":eval deleted the frame being displayed", fmt);
+                }
               return NILP (val);
             }
           val = find_symbol_value (car);