From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-6.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 994781FAAD for ; Mon, 30 Jan 2017 18:41:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754096AbdA3Sls (ORCPT ); Mon, 30 Jan 2017 13:41:48 -0500 Received: from bsmtp3.bon.at ([213.33.87.17]:19582 "EHLO bsmtp3.bon.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753215AbdA3Slr (ORCPT ); Mon, 30 Jan 2017 13:41:47 -0500 Received: from dx.site (unknown [93.83.142.38]) by bsmtp3.bon.at (Postfix) with ESMTPSA id 3vBysc35Hkz5tlB; Mon, 30 Jan 2017 19:41:40 +0100 (CET) Received: from [IPv6:::1] (localhost [IPv6:::1]) by dx.site (Postfix) with ESMTP id 8A15E1E7D; Mon, 30 Jan 2017 19:41:37 +0100 (CET) Subject: Re: [PATCH 1/5] add SWAP macro To: Johannes Schindelin , =?UTF-8?Q?Ren=c3=a9_Scharfe?= References: <8ef4c833-45bd-6831-0683-6d01f30aa518@web.de> <0bdb58a6-3a7f-2218-4b70-c591ae90e95e@web.de> Cc: Git List , Junio C Hamano From: Johannes Sixt Message-ID: Date: Mon, 30 Jan 2017 19:41:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Am 30.01.2017 um 17:01 schrieb Johannes Schindelin: > On Sat, 28 Jan 2017, René Scharfe wrote: >> diff --git a/git-compat-util.h b/git-compat-util.h >> index 87237b092b..66cd466eea 100644 >> --- a/git-compat-util.h >> +++ b/git-compat-util.h >> @@ -527,6 +527,16 @@ static inline int ends_with(const char *str, const char *suffix) >> return strip_suffix(str, suffix, &len); >> } >> >> +#define SWAP(a, b) do { \ >> + void *_swap_a_ptr = &(a); \ >> + void *_swap_b_ptr = &(b); \ >> + unsigned char _swap_buffer[sizeof(a)]; \ >> + memcpy(_swap_buffer, _swap_a_ptr, sizeof(a)); \ >> + memcpy(_swap_a_ptr, _swap_b_ptr, sizeof(a) + \ >> + BUILD_ASSERT_OR_ZERO(sizeof(a) == sizeof(b))); \ >> + memcpy(_swap_b_ptr, _swap_buffer, sizeof(a)); \ >> +} while (0) >> + >> #if defined(NO_MMAP) || defined(USE_WIN32_MMAP) > > It may seem as a matter of taste, or maybe not: I prefer this without the > _swap_a_ptr The purpose of these pointers is certainly to avoid that the macro arguments are evaluated more than once. -- Hannes