From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754712AbbGXQ6V (ORCPT ); Fri, 24 Jul 2015 12:58:21 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:54852 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754292AbbGXQ6T (ORCPT ); Fri, 24 Jul 2015 12:58:19 -0400 Message-ID: <55B26EAA.70209@infradead.org> Date: Fri, 24 Jul 2015 09:58:18 -0700 From: Randy Dunlap User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Ahmed Soliman , linux-kernel@vger.kernel.org Subject: Re: how does 0x##p##q work References: In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/24/15 09:02, Ahmed Soliman wrote: > I was working on cleaning up some files in the crypto dirctory using > checkpatch.pl > and I found this strange define in crypto/gf128mul.c > #define xx(p, q) 0x##p##q > It just seems really weird macro and I cant figure out what is it > supposed to do!! ## is defined in any complete C language spec (it's a preprocessor directive). It is used for string concatenation, aka pasting or gluing strings together. google can find lots of references for it if you need more info. -- ~Randy