Re: [Emacs-diffs] emacs-24 r117502: Always use matched specpdl entry to record call arguments (Bug#18473).

[Stefan Monnier]

> -void
> +ptrdiff_t
>  record_in_backtrace (Lisp_Object function, Lisp_Object *args, ptrdiff_t 
> nargs)
>  {
> +  ptrdiff_t count = SPECPDL_INDEX ();
> +
>    eassert (nargs >= UNEVALLED);
>    specpdl_ptr-> bt.kind = SPECPDL_BACKTRACE;
>    specpdl_ptr-> bt.debug_on_exit = false;
> @@ -2049,6 +2045,8 @@
>    specpdl_ptr-> bt.args = args;
>    specpdl_ptr-> bt.nargs = nargs;
>    grow_specpdl ();
> +
> +  return count;
>  }

This will slow down every single function call.  Not by much, but
they're already pretty slow, so we should work hard not to make it worse.

In this respect, your previous patch (which used backtrace_top instead
of keeping a `count') was better since it only affected *some*
function calls.


        Stefan