Subject: Re: bug#31312: Segmentation fault with doom-emacs, NeoTree and Zoom

From: martin rudalics <[email-masked]>
Date: Wed, 02 May 2018 08:16:26 +0200

>> Is w in reconsider_clip_changes the same as XWINDOW (selected_window)
 >> when it fails?
 >
 > Nope.  In fact, doing
 >
 >      break 13939 if (w != XWINDOW(selected_window))
 >
 > triggers only just before the bad reconsider_clip_changes call.
 >
 > #0  redisplay_internal () at ../../src/xdisp.c:13939
 > #1  0x0000000000463c16 in redisplay () at ../../src/xdisp.c:13518
 > #2  0x00000000005851ae in read_char (commandflag=1, map=XIL(0x5e99db3), prev_event=XIL(0),
 >      used_mouse_menu=0x7fffffffe41f, end_time=0x0) at ../../src/keyboard.c:2480
 > #3  0x00000000005957c5 in read_key_sequence (keybuf=0x7fffffffe570, bufsize=30, prompt=XIL(0),
 >      dont_downcase_last=false, can_return_switch_frame=true, fix_current_buffer=true,
 >      prevent_redisplay=false) at ../../src/keyboard.c:9147
 > #4  0x0000000000581d55 in command_loop_1 () at ../../src/keyboard.c:1368
 > (More stack frames follow...)
 > (gdb) p w
 > $16 = (struct window *) 0x47d22f0
 > (gdb) p sw
 > $17 = (struct window *) 0x47d22f0
 > (gdb) p XWINDOW(selected_window)
 > $18 = (struct window *) 0x61109d0
 > (gdb) p w->contents
 > $19 = XIL(0)
 > (gdb) p XWINDOW(selected_window)->contents
 > $20 = XIL(0x493e565)
 > (gdb) xpr
 > Lisp_Vectorlike
 > PVEC_BUFFER
 > $21 = (struct buffer *) 0x493e560
 > (unsigned char *) 0x4a34568 " *NeoTree*"

I'm probably too silly to understand this.  IIUC we are here

   /* do_pending_window_change could change the selected_window due to
      frame resizing which makes the selected window too small.  */
   if (WINDOWP (selected_window) && (w = XWINDOW (selected_window)) != sw)
     sw = w;

   /* Clear frames marked as garbaged.  */
   clear_garbaged_frames ();

   /* Build menubar and tool-bar items.  */
   if (NILP (Vmemory_full))
     prepare_menu_bars ();

   reconsider_clip_changes (w);

and the only ways this could cause w != XWINDOW(selected_window)
before the last call is either !WINDOWP (selected_window) or that
clear_garbaged_frames or prepare_menu_bars change selected_window.
Can you find the responsible?

martin