bug#53809: 29.0.50; fatal error: assertion failed: string_immovable_p (bytestr)

[Eli Zaretskii]

> From: Gregor Zattler <telegraph@gmx.net>
> Cc: 53809@debbugs.gnu.org
> Date: Mon, 07 Feb 2022 00:44:16 +0100
> 
> Thread 1 "emacs-snapshot-" hit Breakpoint 1, terminate_due_to_signal (sig=6, 
> backtrace_limit=2147483647) at emacs.c:408
> 408     {
> (gdb) bt full
> #0  terminate_due_to_signal (sig=6, backtrace_limit=2147483647) at emacs.c:408
> #1  0x00005555557f5b38 in die (msg=0x5555559ddf05 "string_immovable_p 
> (bytestr)", file=0x5555559ddede "bytecode.c", line=361) at alloc.c:7546
> #2  0x00005555558948b2 in exec_byte_code (bytestr=XIL(0x55555baaa9f4), 
> vector=XIL(0x55555bad74f5), maxdepth=make_fixnum(3), args_template=0, 
> nargs=0, args=0x0) at bytecode.c:361

In this frame #2, what is 'bytestr'?  Try this:

  (gdb) fr 2
  (gdb) p bytestr
  (gdb) xstring