bug#73022: 31.0.50; Crash in build_frame_matrix_from_leaf_window after C-x 2 and reducing terminal size

[martin rudalics via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Sorry, my last mail went at the wrong address.  Reposting.

 > In particular, I found a case in which an assert fails because the
 > window row glyph memory is not contained in the frame row glyph
 > memory.
 >
 > It happens in a recent build (99a03ddb2d4) built without X support.
 > I'm running it in a urxvt terminal but it happens in xterm too. It
 > crashes both with and without glyph debug. This is not related to
 > garbage collection like bug 71289.
 >
 > To reproduce:
 > 1. Open emacs -Q
 > 2. Press C-x 2 to split the frame (top/bottom)
 > 3. Make the terminal very small (I slowly resize the X window that's
 > running urxvt, to the minimum size, 1 row and 2 columns in my case).
 > This shrinking process alone can produce the crash when the window is
 > around 5 lines high
 > 4. It always crashes in my case. If it doesn't, make the terminal
 > larger again, and repeat the resizing for some seconds until it
 > crashes
 >
 > Note that the C-x 2 is required. The problem doesn't happen with a
 > left/right split (C-x 3). But it happens after a C-x 3 C-x 2.

Kindly have a look at the fix I proposed here:

https://lists.gnu.org/archive/html/emacs-devel/2024-09/msg00054.html

If necessary, I can send you a patch.

Thanks, martin