bug#34394: 27.0.50; Emacs segfaults with SLY, company and C-g

["João Távora" <joaotavora@gmail.com>]

I applied to the emacs-26 branch where it seems to have
fixed it, meaning I couldn't reproduce it anymore after
some attempts.

I would find it prudent to merge into master: since I run
a master build these days at work, where I use SLY very
much, it would equal much better testing.

So I'd push to both branches  (and maybe mark the 26 version
"don't merge").

Anyway, a big thanks!

João

PS: if you have the time, a short explanation of the
problem would be welcome/pedagogical

On Tue, Feb 12, 2019 at 7:15 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > Date: Tue, 12 Feb 2019 20:29:23 +0200
> > From: Eli Zaretskii <eliz@gnu.org>
> > Cc: 34394@debbugs.gnu.org
> >
> > > From: João Távora <joaotavora@gmail.com>
> > > Date: Tue, 12 Feb 2019 18:10:06 +0000
> > > Cc: 34394@debbugs.gnu.org
> > >
> > > If it works, can this please make it to Emacs 26.2?
> >
> > I hope so.
>
> Actually, please try this simpler patch instead:
>
> diff --git a/src/keyboard.c b/src/keyboard.c
> index 49c687f..282eac7 100644
> --- a/src/keyboard.c
> +++ b/src/keyboard.c
> @@ -364,7 +364,7 @@ static Lisp_Object make_lispy_focus_out (Lisp_Object);
>  #endif /* HAVE_WINDOW_SYSTEM */
>  static bool help_char_p (Lisp_Object);
>  static void save_getcjmp (sys_jmp_buf);
> -static void restore_getcjmp (sys_jmp_buf);
> +static void restore_getcjmp (void *);
>  static Lisp_Object apply_modifiers (int, Lisp_Object);
>  static void restore_kboard_configuration (int);
>  static void handle_interrupt (bool);
> @@ -2144,12 +2144,14 @@ read_event_from_main_queue (struct timespec *end_time,
>      return c;
>
>    /* Actually read a character, waiting if necessary.  */
> +  ptrdiff_t count = SPECPDL_INDEX ();
>    save_getcjmp (save_jump);
> +  record_unwind_protect_ptr (restore_getcjmp, save_jump);
>    restore_getcjmp (local_getcjmp);
>    if (!end_time)
>      timer_start_idle ();
>    c = kbd_buffer_get_event (&kb, used_mouse_menu, end_time);
> -  restore_getcjmp (save_jump);
> +  unbind_to (count, Qnil);
>
>    if (! NILP (c) && (kb != current_kboard))
>      {
> @@ -2638,10 +2640,12 @@ read_char (int commandflag, Lisp_Object map,
>         {
>           Lisp_Object tem0;
>
> +         ptrdiff_t count = SPECPDL_INDEX ();
>           save_getcjmp (save_jump);
> +         record_unwind_protect_ptr (restore_getcjmp, save_jump);
>           restore_getcjmp (local_getcjmp);
>           tem0 = sit_for (Vecho_keystrokes, 1, 1);
> -         restore_getcjmp (save_jump);
> +         unbind_to (count, Qnil);
>           if (EQ (tem0, Qt)
>               && ! CONSP (Vunread_command_events))
>             echo_now ();
> @@ -2712,10 +2716,12 @@ read_char (int commandflag, Lisp_Object map,
>
>           timeout = min (timeout, MOST_POSITIVE_FIXNUM / delay_level * 4);
>           timeout = delay_level * timeout / 4;
> +         ptrdiff_t count1 = SPECPDL_INDEX ();
>           save_getcjmp (save_jump);
> +         record_unwind_protect_ptr (restore_getcjmp, save_jump);
>           restore_getcjmp (local_getcjmp);
>           tem0 = sit_for (make_number (timeout), 1, 1);
> -         restore_getcjmp (save_jump);
> +         unbind_to (count1, Qnil);
>
>           if (EQ (tem0, Qt)
>               && ! CONSP (Vunread_command_events))
> @@ -3325,7 +3331,7 @@ save_getcjmp (sys_jmp_buf temp)
>  }
>
>  static void
> -restore_getcjmp (sys_jmp_buf temp)
> +restore_getcjmp (void *temp)
>  {
>    memcpy (getcjmp, temp, sizeof getcjmp);
>  }



-- 
João Távora