Re: c++-mode, incorrect transition from member-init-cont to topmost-intro-cont

[Alan M. <ac...@mu...>]

Hi, Dave.

On Fri, Apr 19, 2013 at 03:53:18PM +0000, Steffen, David wrote:
> Hi,

> I'm running Gnu Emacs 24.2.1 on windows (i386-mingw-nt6.1.7601). The
> code looks like this, indented as Emacs sees fit:

> Screen_DONINFO::Screen_DONINFO()                                // line 45
>    : current_proc_data(guiglobs::proc_status.get_data()),
>      hct_set(FALSE),
>      tbv_set(FALSE),
> [...]
>      platelet_precount_value_btnface_last_keypad(0),   // line 58
> tbv(0),                                                                                                 // line 59

> Note the non-indent of the tbv initializer on line 60.  On line 59, C-c
> C-s shows((member-init-cont 1205) (that's the 'c' in the second line, '
> : current...') but on line 60, C-c C-s shows ((topmost-intro-cont
> 1166)), where 1166 is the beginning of the first line.

> This is very annoying.  The code base has huge initialization lists,
> and Emacs mis-indents most of them like this.

> (This problem existed in the CC-mode that came with the distribution,
> but persists with 5.32.3 which I just installed.)

> Any help would be appreciated.  Thanks.

I'm guessing here, but I think it's triggered by the "tbv(0)," line being
just over 500 characters (more precisely, 500 non-string, non-comment
characters) from the beginning of the function (the constructor, here).

This 500 is a limit to a backward search for "beginning-of-statement"
invoked when CC Mode is checking for the "tbv(0)," having
member-init-cont syntax.  Without the limit, searches are potentially
unbounded, and can cause a slow down in C++ mode when they fail.

I think I'm going to have to rethink this bit of the code; you're not the
first person to hit this problem.

As a workaround, I suggest you find the "500" in the CC Mode source code
and replace it by a more suitable bound - 5000, perhaps.  The pertinent
code is at (?near) line 9606 in cc-engine.el in Emacs-24.2.  This file
will be somewhere like C:\path\to\emacs\lisp\progmodes\cc-engine.el.  The
code looks like this:


	 ;; CASE 5B: After a function header but before the body (or
	 ;; the ending semicolon if there's no body).
	 ((save-excursion
	    (when (setq placeholder (c-just-after-func-arglist-p
				     (max lim (c-determine-limit 500))))     <=========
	      (setq tmp-pos (point))))
	  (cond

After editing the file, byte-compile it, e.g. with M-x byte-compile-file
and reload it with, e.g., M-x load-file.

Please let me know whether this helps.  If not, I'll need to dig further
to find the cause.

> Dave Steffen

-- 
Alan Mackenzie (Nuremberg, Germany).