Avoid aborts in cm.c due to too small TTY frame

* src/frame.c (frame_windows_min_size): Limit TTY frames to a
minimum height large enough to allow for a menu bar, the mode
line, one text line and one echo-area line.  This avoids aborts in
cm.c:cmcheckmagic.  (Bug#30320)

1 files changed, 23 insertions, 8 deletions

diff --git a/src/frame.c b/src/frame.c
index d5b080d688a..a86f05191a8 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -341,7 +341,9 @@ DEFUN ("frame-windows-min-size", Fframe_windows_min_size,
  * of `window-min-height' (`window-min-width' if HORIZONTAL is non-nil).
  * With IGNORE non-nil the values of these variables are ignored.
  *
- * In either case, never return a value less than 1.
+ * In either case, never return a value less than 1.  For TTY frames,
+ * additionally limit the minimum frame height to a value large enough
+ * to support the menu bar, the mode line, and the echo area.
  */
 static int
 frame_windows_min_size (Lisp_Object frame, Lisp_Object horizontal,
@@ -349,6 +351,7 @@ frame_windows_min_size (Lisp_Object frame, Lisp_Object horizontal,
 {
   struct frame *f = XFRAME (frame);
   Lisp_Object par_size;
+  int retval;
 
   if ((!NILP (horizontal)
        && NUMBERP (par_size = get_frame_param (f, Qmin_width)))
@@ -361,15 +364,27 @@ frame_windows_min_size (Lisp_Object frame, Lisp_Object horizontal,
       if (min_size < 1)
         min_size = 1;
 
-      return (NILP (pixelwise)
-              ? min_size
-              : min_size * (NILP (horizontal)
-                            ? FRAME_LINE_HEIGHT (f)
-                            : FRAME_COLUMN_WIDTH (f)));
+      retval = (NILP (pixelwise)
+                ? min_size
+                : min_size * (NILP (horizontal)
+                              ? FRAME_LINE_HEIGHT (f)
+                              : FRAME_COLUMN_WIDTH (f)));
     }
   else
-    return XINT (call4 (Qframe_windows_min_size, frame, horizontal,
-                      ignore, pixelwise));
+    retval = XINT (call4 (Qframe_windows_min_size, frame, horizontal,
+                          ignore, pixelwise));
+  /* Don't allow too small height of text-mode frames, or else cm.c
+     might abort in cmcheckmagic.  */
+  if ((FRAME_TERMCAP_P (f) || FRAME_MSDOS_P (f)) && NILP (horizontal))
+    {
+      int min_height = (FRAME_MENU_BAR_LINES (f)
+                        + FRAME_WANTS_MODELINE_P (f)
+                        + 2);   /* one text line and one echo-area line */
+      if (retval < min_height)
+        retval = min_height;
+    }
+
+  return retval;
 }