I tried. It is fixed. Thanks.
在 2020年1月8日 +0800 AM4:54，Alan Mackenzie <acm@muc.de>，写道：
> Hello, HaiJun.
>
> On Tue, Jan 07, 2020 at 10:09:49 +0800, HaiJun Zhang wrote:
> > 在 2020年1月7日 +0800 AM2:08，Alan Mackenzie <acm@muc.de>，写道：
> > > I've just spent some time fixing a more serious bug in the
> > > Objective-C imenu mechanism. This only occurs when I invoke imenu
> > > through the keyboard (e.g. with M-x imenu), which might explain why
> > > it's survived so long without detection. If I invoke imenu with a
> > > mouse click, it works.
>
> > > Anyhow, with nsfns.m, do M-x imenu <tab> C <tab> and select any
> > > item. This works. Now do M-x imenu. This throws the error "Wrong
> > > type argument: stringp, nil".
>
> > > I've fixed this now, but haven't committed the fix yet.
>
> It turns out, that bug had been fixed in the Emacs core version of CC
> Mode back in 2012. ;-)
>
> > Thanks.
>
> > > Back to your bug - clearly what is happening is that the regular
> > > expression search for functions is finding things in comments (such as
> > > "Copyright (C)") which look like functions but aren't. This is easy
> > > enough to fix, by checking for comments and strings, but comes with a
> > > fairly stiff time penalty. On my 2½ year old Ryzen machine, scanning
> > > the freshly visited Objc buffer currently takes 0.0196s. With the check
> > > for comments/strings, it takes 0.0650s.
>
> > > That's a factor of ~3.25 slower. On a slower machine (factor 3) with a
> > > larger file (factor 3) this could mean the scanning would take 0.6s
> > > rather than 0.2s. This might be slow enough to annoy somebody a little.
>
> I tried the timings again this evening, and I no longer see this factor
> of ~3 slowdown. In fact just a few 10s of percent.
>
> So I've committed this fix, both to standalone CC Mode and the emacs-27
> branch at savannah (from where it will soon find its way to the master
> branch).
>
> > I'm not familiar with objc. What about searching the char '{' after
> > the current pattern? But then I see the following snippet in nsfns.m:
>
> This isn't needed any more
>
> > static Lisp_Object
> > interpret_services_menu (NSMenu *menu, Lisp_Object prefix, Lisp_Object old)
> > /* —————————————————————————————————————
> >    Turn the input menu (an NSMenu) into a lisp list for tracking on lisp side.
> >    ————————————————————————————————————— */
> > {
>
> Could I ask you to try out the new code, and if everything's OK, we can
> close the bug as fixed.
>
> Thanks!
>
> --
> Alan Mackenzie (Nuremberg, Germany).