bug#71744: 29.4; SIGSEGV during completion-at-point in lsp-mode with corfu and cape

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 71744@debbugs.gnu.org
> Date: Wed, 14 Aug 2024 19:03:10 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Wed, 14 Aug 2024 15:40:34 +0000
> > From: Sigve Indregard <sigve.indregard@pm.me>
> > Cc: 71744@debbugs.gnu.org
> > 
> > (gdb) frame 3
> > #3  parse_modifiers (symbol=XIL(0x5555564e3dc0)) at /usr/src/debug/emacs/emacs-29.4-wayland/src/keyboard.c:6888
> > 6888	parse_modifiers (Lisp_Object symbol)
> > (gdb) print symbol
> > $11 = XIL(0x5555564e3dc0)
> > (gdb) xsymbol
> > $12 = (struct Lisp_Symbol *) 0xaaaaac1f1640
> > Cannot access memory at address 0xaaaaac1f1648

Btw, this 0x5555564e3dc0 value is the same as the pointer to old_kbd
inside read_char:

  #7  read_char (commandflag=0, map=0x0, prev_event=0x0, used_mouse_menu=0x0, end_time=0x7fffffffb5b0) at /usr/src/debug/emacs/emacs-29.4-wayland/src/keyboard.c:3018
	  c = <optimized out>
	  local_getcjmp = {{__jmpbuf = {93825000405056, -5147324661749537557, 1, 4611686019484352512, 5, 0, -5147324661946669845, -1313834696378178325}, __mask_was_saved = 0, __saved_mask = {__val = {0, 93825010269488, 93825104789632, 140737488335792, 18446744073709550936, 11, 93825104789616, 140737488335856, 140737279378894, 140737488335856, 140737488335920, 0, 140737488335920, 0, 93825010269488, 140737488336000}}}}
	  save_jump = {{__jmpbuf = {12048, 140737188459256, 140737488335856, 93825095637120, 16, -7692597586030666240, 48, 1}, __mask_was_saved = 1453957408, __saved_mask = {__val = {140737488335776, 2, 140737488335824, 140737488335760, 140737321006214, 1, 140737321006651, 14319535557742690304, 6, 140737488335696, 140737279373914, 93825000331312, 0, 1, 1, 93823560581122}}}}
	  tem = <optimized out>
	  save = 0x0
	  previous_echo_area_message = 0x0
	  also_record = 0x0
	  reread = false
	  recorded = false
	  polling_stopped_here = false
	  orig_kboard = 0x5555564e3dc0  <<<<<<<<<<<<<<<<<<<<<<<

So either the value of orig_kboard here is bogus (perhaps due to
optimizations), or somehow the variable C, which is supposed to hold
an input event, holds something very different instead, and then it's
a small surprise that we crash.

Which version of what compiler did you use to build Emacs, and what
were the compilation switches?