From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5729C4741F for ; Sat, 26 Sep 2020 21:33:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84F2B2371F for ; Sat, 26 Sep 2020 21:33:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WPdYf/wV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728121AbgIZVdE (ORCPT ); Sat, 26 Sep 2020 17:33:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727848AbgIZVdB (ORCPT ); Sat, 26 Sep 2020 17:33:01 -0400 Received: from mail-wm1-x343.google.com (mail-wm1-x343.google.com [IPv6:2a00:1450:4864:20::343]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A9E4C0613DA for ; Sat, 26 Sep 2020 14:32:59 -0700 (PDT) Received: by mail-wm1-x343.google.com with SMTP id s13so2652917wmh.4 for ; Sat, 26 Sep 2020 14:32:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:in-reply-to:references:from:date:subject:fcc :content-transfer-encoding:mime-version:to:cc; bh=fLx/oqN4eboVCzSUB4omppsZm0evzi7MY+4v/FyZl7s=; b=WPdYf/wV3oOuRjxWPwqednQBenzRdkPcx55KHJvkWAchkhUs6xQKz+oiv4BnOBFW0b oXTyAGypX2oLDv8skdZXaiQh3duEGdFwAaF9UhWjP4tBqt2WWRy9+ppjU7Uy+R93lKvj iJRYHN3VFtK9PCxSx4f9pC6nJba2yKQHakPkaRmrBjwygFvpBnp+y/DxagJAtqeNqywy Mbq+39qLmza9Yl0IPDM1Z/dn7XEN7nXms13KcdMaACoMiFqziypfqzZufXwGthj4J4jf UJjWwvzcDYs5t/SMynoTTnqgElodL1aa0MObXRlbvzmpeqAmMEZzSaD3F4uOrjMOvpIs Spiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:in-reply-to:references:from:date :subject:fcc:content-transfer-encoding:mime-version:to:cc; bh=fLx/oqN4eboVCzSUB4omppsZm0evzi7MY+4v/FyZl7s=; b=tNztxExh0h9ILXJWnTl9hYHVTz3M6Oxv/euV7nhqgMvje/2QjAS7BtmnCa3mcDt0V+ m562AyyHwmb3p0YUMVUkJugRsaMG3P7/dBoQfWFL4181Hsjt1Ow8xkgLKxXwWqEc0mEi K/4Ho3/FzCeMxvXmwE1rUv43T2sJVMe3tTnJ/x9S6560Azv6k1suIHNdy391Dwvpruqs aSCZLDox9tGRGX6MjtB++hcm1yqgxNU6AMO+op4tNWCGWyC1/cKpXGelJJEF+ULRTIuW dJdoXa91IilpvMrl3hBUTC7O95LVK1QKm+tGhJIYG+LLCdjJ1p2E6n8AnV6+ZaNM8cjC Syvw== X-Gm-Message-State: AOAM532IbuTUVUVlpvcncjQZGeqc+Miu0qF/f8IN4WRdgM6Ns4mQ0dD/ 1t5gMUDK1ZyWnxFcVExZWHA39zsoxSE= X-Google-Smtp-Source: ABdhPJxIkDYaW/9Vw5LrmotWTk9HvCOQYM9/+pKYNF4P0Pl19aX3Mzwa5PZLp4U3nHomZcv9MHSXmw== X-Received: by 2002:a1c:480a:: with SMTP id v10mr3902564wma.141.1601155978165; Sat, 26 Sep 2020 14:32:58 -0700 (PDT) Received: from [127.0.0.1] ([13.74.141.28]) by smtp.gmail.com with ESMTPSA id a81sm4067053wmf.32.2020.09.26.14.32.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2020 14:32:57 -0700 (PDT) Message-Id: <152705bbc6a105411d0be0f76b18757c8ab0f893.1601155970.git.gitgitgadget@gmail.com> In-Reply-To: References: From: "Junio C Hamano via GitGitGadget" Date: Sat, 26 Sep 2020 21:32:49 +0000 Subject: [PATCH v2 10/10] hashmap_for_each_entry(): workaround MSVC's runtime check failure #3 Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 To: git@vger.kernel.org Cc: Sibi Siddharthan , =?UTF-8?Q?=C4=90o=C3=A0n_Tr=E1=BA=A7n_C=C3=B4ng?= Danh , SZEDER =?UTF-8?Q?G=C3=A1bor?= , Eric Sunshine , Johannes Schindelin , Johannes Schindelin , Junio C Hamano Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org From: Junio C Hamano The OFFSETOF_VAR(var, member) macro is implemented in terms of offsetof(typeof(*var), member) with compilers that know typeof(), but its fallback implemenation compares &(var->member) and (var) and count the distance in bytes, i.e. ((uintptr_t)&(var)->member - (uintptr_t)(var)) MSVC's runtime check, when fed an uninitialized 'var', flags this as a use of an uninitialized variable (and that is legit---uninitialized contents of 'var' is subtracted) in a debug build. After auditing all 6 uses of OFFSETOF_VAR(), 1 of them does feed a potentially uninitialized 'var' to the macro in the beginning of the for() loop: #define hashmap_for_each_entry(map, iter, var, member) \ for (var = hashmap_iter_first_entry_offset(map, iter, \ OFFSETOF_VAR(var, member)); \ var; \ var = hashmap_iter_next_entry_offset(iter, \ OFFSETOF_VAR(var, member))) We can work around this by making sure that var has _some_ value when OFFSETOF_VAR() is called. Strictly speaking, it invites undefined behaviour to use NULL here if we end up with pointer comparison, but MSVC runtime seems to be happy with it, and most other systems have typeof() and don't even need pointer comparison fallback code. Signed-off-by: Junio C Hamano Signed-off-by: Johannes Schindelin --- hashmap.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/hashmap.h b/hashmap.h index ef220de4c6..b011b394fe 100644 --- a/hashmap.h +++ b/hashmap.h @@ -449,7 +449,8 @@ static inline struct hashmap_entry *hashmap_iter_first(struct hashmap *map, * containing a @member which is a "struct hashmap_entry" */ #define hashmap_for_each_entry(map, iter, var, member) \ - for (var = hashmap_iter_first_entry_offset(map, iter, \ + for (var = NULL, /* for systems without typeof */ \ + var = hashmap_iter_first_entry_offset(map, iter, \ OFFSETOF_VAR(var, member)); \ var; \ var = hashmap_iter_next_entry_offset(iter, \ -- gitgitgadget