bug#47244: 28.0.50; SIGSEGV in long-runnning Emacs

[Eli Zaretskii <eliz@gnu.org>]

> From: Michael Welsh Duggan <mwd@cert.org>
> Cc: Michael Welsh Duggan <mwd@md5i.com>, "rudalics@gmx.at"
>  <rudalics@gmx.at>,
>         "schwab@linux-m68k.org" <schwab@linux-m68k.org>,
>         "47244@debbugs.gnu.org" <47244@debbugs.gnu.org>
> Date: Mon, 29 Mar 2021 10:06:43 -0400
> 
> #0  set_buffer_internal_2 (b=0x5555578f43d8) at ../../master/src/buffer.c:2155
>         old_buf = 0x555555593480 <_start>
>         tail = XIL(0)
> #1  0x0000555555713f28 in set_buffer_internal_1 (b=0x1)
>     at ../../master/src/buffer.c:2141
> #2  0x00005555556e4ec6 in set_buffer_internal (b=0x5555578f43d8)
>     at ../../master/src/buffer.h:1184
> #3  0x00005555556e6b21 in command_loop_1 () at ../../master/src/keyboard.c:1289
>         cmd = XIL(0x7fffffffde10)
>         keybuf = 
>           {XIL(0), XIL(0x7ffff2c27c1d), XIL(0x555555765cd4), XIL(0x11cf6b0), XIL(0x7fffffffdd70), XIL(0x55555579e20b), XIL(0x11cf6b0), XIL(0x7ffff257e4c4), XIL(0x555559de7123), XIL(0x7ffff2c27c1d), XIL(0x7ffff2c27c1d), XIL(0x555559de7123), XIL(0x7ffff257e4c4), XIL(0x11cf6b0), XIL(0), XIL(0), XIL(0x555555cc5f80), XIL(0), XIL(0), XIL(0x7fffffffdd70), XIL(0x5555556e3c73), XIL(0xffffddc0), XIL(0x555555cc5f80), XIL(0), XIL(0), XIL(0x7fffffffdda0), XIL(0x555555797d03), make_fixnum(0), XIL(0x7fffffffdde0), XIL(0x55555579b3f4)}
>         i = 1
>         prev_modiff = 0
>         prev_buffer = 0x0
>         already_adjusted = false

OK, we are switching to the selected window's buffer, and that buffer
was deleted.  We still don't understand how this happens.  Martin, any
ideas?

Please show the results of these commands:

 (gdb) p current_buffer->name_
 (gdb) xstring
 (gdb) frame 3
 (gdb) p cmd
 (gdb) xtype

Thanks.