From patchwork Tue Sep 24 01:03:15 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Wong X-Patchwork-Id: 11157797 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EE50117EE for ; Tue, 24 Sep 2019 01:03:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D697F214DA for ; Tue, 24 Sep 2019 01:03:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503758AbfIXBDv (ORCPT ); Mon, 23 Sep 2019 21:03:51 -0400 Received: from dcvr.yhbt.net ([64.71.152.64]:59360 "EHLO dcvr.yhbt.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391859AbfIXBDv (ORCPT ); Mon, 23 Sep 2019 21:03:51 -0400 Received: from localhost (dcvr.yhbt.net [127.0.0.1]) by dcvr.yhbt.net (Postfix) with ESMTP id CA5E11F9FC; Tue, 24 Sep 2019 01:03:26 +0000 (UTC) From: Eric Wong To: Junio C Hamano Cc: Derrick Stolee , Johannes Schindelin , Phillip Wood , git@vger.kernel.org Subject: [PATCH v2 10/19] introduce container_of macro Date: Tue, 24 Sep 2019 01:03:15 +0000 Message-Id: <20190924010324.22619-11-e@80x24.org> In-Reply-To: <20190924010324.22619-1-e@80x24.org> References: <20190924010324.22619-1-e@80x24.org> MIME-Version: 1.0 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org This macro is popular within the Linux kernel for supporting intrusive data structures such as linked lists, red-black trees, and chained hash tables while allowing the compiler to do type checking. I intend to use this to remove the limitation of "hashmap_entry" being location-dependent and to allow more compile-time type checking. This macro already exists in our source as "list_entry" in list.h and making "list_entry" an alias to "container_of" as the Linux kernel has done is a possibility. Signed-off-by: Eric Wong --- git-compat-util.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/git-compat-util.h b/git-compat-util.h index 83be89de0a..4cc2c8283a 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -1312,4 +1312,14 @@ void unleak_memory(const void *ptr, size_t len); */ #include "banned.h" +/* + * container_of - Get the address of an object containing a field. + * + * @ptr: pointer to the field. + * @type: type of the object. + * @member: name of the field within the object. + */ +#define container_of(ptr, type, member) \ + ((type *) ((char *)(ptr) - offsetof(type, member))) + #endif