From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753786Ab2HCR70 (ORCPT ); Fri, 3 Aug 2012 13:59:26 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:34939 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752868Ab2HCR7V (ORCPT ); Fri, 3 Aug 2012 13:59:21 -0400 X-Originating-IP: 217.70.178.144 X-Originating-IP: 173.246.103.110 Date: Fri, 3 Aug 2012 10:59:11 -0700 From: Josh Triplett To: Sasha Levin Cc: Tejun Heo , torvalds@linux-foundation.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com Subject: Re: [RFC 1/4] hashtable: introduce a small and naive hashtable Message-ID: <20120803175911.GA3737@jtriplet-mobl1> References: <501A4FC1.8040907@gmail.com> <20120802103244.GA23318@leaf> <501A633B.3010509@gmail.com> <501A7AD3.7000008@gmail.com> <20120802161556.GA25572@leaf> <501AAF47.3090708@gmail.com> <20120802174457.GA6251@jtriplet-mobl1> <501ABEE2.10007@gmail.com> <20120802204157.GB7916@jtriplet-mobl1> <501AF555.3050004@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <501AF555.3050004@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 02, 2012 at 11:47:01PM +0200, Sasha Levin wrote: > On 08/02/2012 10:41 PM, Josh Triplett wrote: > > On Thu, Aug 02, 2012 at 07:54:42PM +0200, Sasha Levin wrote: > >> /* I've "preprocessed" the DEFINE macro below */ > >> union { > >> struct hash_table table; > >> struct { > >> size_t bits; > >> struct hlist_head buckets[32]; > >> } > >> } my_hashtable; > > > > That expansion doesn't match the macros. Using the most recent > > definitions of DEFINE_HASHTABLE and DEFINE_STATIC_HASHTABLE from above, > > the definition would look something like this: > > > > static union { > > struct hash_table my_hashtable; > > struct { > > size_t bits; > > struct hlist_head buckets[1 << 5]; > > } __my_hashtable; > > } = { .my_hashtable.bits = 5 }; > > It's different because I don't think you can do what you did above with global variables. > > You won't be defining any instances of that anonymous struct, so my_hashtable won't exist anywhere. ...how strange. The above syntax ought to work, and many other compilers document it as legal syntax (and I thought that C1x's anonymous structs and unions allowed it), but indeed GCC doesn't accept it. Fair enough; looks like consolidating the macro implementations won't actually work. - Josh Triplett