Subject: bug#20705: Emacs segfaults when typing "(yas-expand" after M-: in yas-minor-mode

From: Eli Zaretskii <[email-masked]>
Date: Wed, 03 Jun 2015 18:29:06 +0300

> From: Johan Bockgård <[email-masked]>
> Cc: [email-masked], Eli Zaretskii <[email-masked]>
> Date: Tue, 02 Jun 2015 19:32:50 +0200
> 
> The code looks like this:
> 
>     (defun yas--keybinding-beyond-yasnippet ()
>       "Get current keys's binding as if YASsnippet didn't exist."
>       (let* ((yas-minor-mode nil)
>              (yas--direct-keymaps nil)
>              (keys (this-single-command-keys)))
>         (or (key-binding keys t)
>             (key-binding (yas--fallback-translate-input keys) t))))
> 
> Apparently this-single-command-keys returns [] (empty vector) when run
> from a timer. This in turn makes key-binding crash.

Thanks for the analysis.

Clément, can you try the patch below?

diff --git a/src/keymap.c b/src/keymap.c
index 8f4ac0d..b69b409 100644
--- a/src/keymap.c
+++ b/src/keymap.c
@@ -1652,10 +1652,14 @@ Returns nil if COMMAND is not remapped (or not a symbol).
 
   if (NILP (position) && VECTORP (key))
     {
-      Lisp_Object event
-	/* mouse events may have a symbolic prefix indicating the
-	   scrollbar or mode line */
-	= AREF (key, SYMBOLP (AREF (key, 0)) && ASIZE (key) > 1 ? 1 : 0);
+      Lisp_Object event;
+
+      if (ASIZE (key) == 0)
+	return Qnil;
+
+      /* mouse events may have a symbolic prefix indicating the
+	 scrollbar or mode line */
+      event = AREF (key, SYMBOLP (AREF (key, 0)) && ASIZE (key) > 1 ? 1 : 0);
 
       /* We are not interested in locations without event data */