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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A6FBCF9C6F for ; Mon, 23 Sep 2024 16:13:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 807F76B0083; Mon, 23 Sep 2024 12:13:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7B7F96B0085; Mon, 23 Sep 2024 12:13:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 60A426B0088; Mon, 23 Sep 2024 12:13:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 410DB6B0083 for ; Mon, 23 Sep 2024 12:13:27 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id B0B07ABC81 for ; Mon, 23 Sep 2024 16:13:26 +0000 (UTC) X-FDA: 82596498012.28.3A0000E Received: from CWXP265CU009.outbound.protection.outlook.com (mail-ukwestazon11021129.outbound.protection.outlook.com [52.101.100.129]) by imf12.hostedemail.com (Postfix) with ESMTP id D103C40010 for ; Mon, 23 Sep 2024 16:13:22 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=garyguo.net header.s=selector1 header.b=IFIsbU56; dmarc=none; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf12.hostedemail.com: domain of gary@garyguo.net designates 52.101.100.129 as permitted sender) smtp.mailfrom=gary@garyguo.net ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1727107916; a=rsa-sha256; cv=pass; b=svPWa65e1WnooWLQlAmI9YpFnHytqCusHCqhMpJLaFmwg12bQroba2W45UVVHZcstO32TU R2jaNi8h7ELjbWGQafIxOFDjM7V2pzMxkZS+J1KoZ1LjZHC9Y274hbrlC+D0lkZbGpIhC0 YrJe4bONdBcLbu0WE192EoOzwSon54c= ARC-Authentication-Results: i=2; imf12.hostedemail.com; dkim=pass header.d=garyguo.net header.s=selector1 header.b=IFIsbU56; dmarc=none; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf12.hostedemail.com: domain of gary@garyguo.net designates 52.101.100.129 as permitted sender) smtp.mailfrom=gary@garyguo.net ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1727107916; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=2TRn1Yq6L9nY52paGBhWSdK3+M4ww1kSDlc8abb174w=; b=jTEA6waqVuo/eNocMXDlnswV08+DIwYfLj1jcG+sLQFaFSACYLBHOq4EPTbcQQ9xMJMibW 4PWy59Z/UZ48iwmZVv5jJCUKEwcu9/orQj47DOTo3CHhNFFpKJ19q+0/UpQjO+fiG4FrH6 8JAMQh8etxw055cTe5T9E0a3D56/Pb8= ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=gGHfOJIDKSDs5evGu6mrZ6ZSOzMS3w9FbKzrtdTkP+wH6+XON9nxwwMK7UV2q6qpaBq3ePJaKarGsNfrQ2DSFpRZdMMOaZFZQrgR3A6QSsp+5M/6bFwllhEKvdpasb9Qb24PjeuuCcdnNCE/ZWNU/dLKykCigzdC5VqmDtKJIoCGnMe7IK5bmvyYgH9mDH4unpONbI/+IF4x9vUX6f5kdbikC0s+MLNwGkedHttpP3Y1+rxDFW9mSmq/70vafxnFccqBW+MH37rpZ0VLfZetuwhnTBLCgvxWs/zvBbFahhgCw2763dtpyH2pRKru6u06c8lHcSmaBRXeOE/9DDl+8Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=2TRn1Yq6L9nY52paGBhWSdK3+M4ww1kSDlc8abb174w=; b=F50aExVOHa6mVUsdcl2xIqEi4TMzSjrVD62V9mQYH/4IYLeyHczsKT/2iu3pEznQmucCvyU68z6KDU6ywa5Mcm1ws0+9ZzKMfDjvPj+5yb8LXKzOdv3Zwv2BadhuzzDwd6qurxllB6nye0D2DnCFQrzV8BLjQjX6UlWug/0kBFISfZajgB3ULVm9CydHc5sm5a+tNj5bFLnwd40ne9VAGnPRsmVsnuzjtOmF10VqxOIn2xat3lamgI//KRVJC7E7dS357vvZABzqxNrFrvnaEpvN/QB7N5CLiOP0lRYLT8vKV5eWowdW4TzVNfDL5nVw4eLzkFZYZDn4T+wMM79xbA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=garyguo.net; dmarc=pass action=none header.from=garyguo.net; dkim=pass header.d=garyguo.net; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=garyguo.net; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=2TRn1Yq6L9nY52paGBhWSdK3+M4ww1kSDlc8abb174w=; b=IFIsbU56j3BmsPSBpSNorjPIrSaYpg5xOGXs3lRc8HpAP/68zybHA3soJ0KRaKp3XsGpYukO8cuY0h4j4MvGZJ09QuBDyM1L4puFucVh33CmseFvHKpG5D7aAklidxeRcwrvHxiYKZnayeZ0g7efL090jAa6bAKgo8w27evFgog= Received: from LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:253::10) by LO0P265MB5525.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:274::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7982.25; Mon, 23 Sep 2024 16:13:19 +0000 Received: from LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM ([fe80::1818:a2bf:38a7:a1e7]) by LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM ([fe80::1818:a2bf:38a7:a1e7%3]) with mapi id 15.20.7982.022; Mon, 23 Sep 2024 16:13:19 +0000 Date: Mon, 23 Sep 2024 17:13:15 +0100 From: Gary Guo To: Alice Ryhl Cc: Danilo Krummrich , ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, akpm@linux-foundation.org, daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH] rust: alloc: pass `old_layout` to `Allocator` Message-ID: <20240923171315.64327fe7.gary@garyguo.net> In-Reply-To: References: <20240911225449.152928-2-dakr@kernel.org> <20240921153315.70860-1-dakr@kernel.org> X-Mailer: Claws Mail 4.2.0 (GTK 3.24.43; x86_64-pc-linux-gnu) Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: PA7P264CA0255.FRAP264.PROD.OUTLOOK.COM (2603:10a6:102:371::11) To LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:253::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LO2P265MB5183:EE_|LO0P265MB5525:EE_ X-MS-Office365-Filtering-Correlation-Id: 06c802d0-3f00-440d-1e1c-08dcdbeaa385 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|10070799003|376014|7416014|1800799024|366016; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Q1hEeGpTY3BQTnJta09iYUhjdG5TQkVOeTJhUy82RmhUVmJQTG12UUJWbDZs?= =?utf-8?B?aFRMN0Fkb1c0Sytzbk5Fa3hkRURhMXFMVFJoM2VxamwyVmdVbW0vR1pOMzYw?= =?utf-8?B?aDFIWjNHWks3bTl4N0lYU09QREI1SzNabWxlaDFPOWZLVFluOElBeHYrc1RZ?= =?utf-8?B?YTR0YW5IdGJ2ZkE4S3NvQW8vNkZNQ29rWVJ3MnByMlNZYmJ6YmZtZTdUM3Nt?= =?utf-8?B?NmZGa3lSRi9LTW53VXVGR1ZGMVB0aVIyMmJmTW1HQXhBMEFMdncwdHNRT3Za?= =?utf-8?B?ZWI5eElNQW1qR2N2Nm5CYUFieExxR0xNcEhNek9IL0xWU2hlVjV6b01NRUV2?= =?utf-8?B?aFhIS095MFBvSExWak5lTURYQ2NNeEt5dUJQaEdwbHdWa1hVNnFkTnFBbnN4?= =?utf-8?B?S0FHVkpBd0FwU0k3WE0xUUU4dno0MS9ZYnEwUTBzUDNTWFNLaktrRnlGY0Fl?= =?utf-8?B?cEVFc000RGYvRGo4MWJ2eDJwckxZSHFQOHpFVnIzd09SR2NLMkFYN1JUc0Ez?= =?utf-8?B?NE1qRjBINUcxRUlTQmlaMENUSTNmT0xGWTRjS1U0SzJhNDZlaDhiU1c3L2Qv?= =?utf-8?B?cElGQTM1SlN1bUROTEdrMitQSWpCZm9UL0RINVZCWUxBTnlmbUZUZncrRURr?= =?utf-8?B?MmViMHZjVS9jTDVZSnVDekE3S2lHbjY5a2ErZDFiV2RwUndEUmdHOGsvTUtX?= =?utf-8?B?TjRKSEhFQy9pNk41NGNTK3V4bkRtNDlmZEhLT3Q2S2k0VDljOUJJYTZydmNx?= =?utf-8?B?V3RXNk5FMEJqaDF5aG9UdElqZ3I0dmdVYXIvd0RGS3JGWDJXQjFocnN3b0xa?= =?utf-8?B?WHFQN1ZBRmJRVVY0dkp2b1g0YmZMd2RycTczNkVFc09SU1F5TEFuNzZTT2pG?= =?utf-8?B?aW9VaWVmejUyYVoyMHJvdWlpQkxVdVVFb1BjYkxvcUJDRU9oYmh5YWZZRGlF?= =?utf-8?B?bG5EcGhYYzBrbSt6SVJHeEQ2OXZxamdIZStzanhSaVNEK3pESXcyZmlhd1N6?= =?utf-8?B?S1lNZzJaWlhTRkNVMi9UcGJKbnBTTjJFdGJDbUZCOS9MTGRZMGJHNHhTaVE4?= =?utf-8?B?cVFWdCs2WklWSHJwbjl4bHhHalczTVRxUW1KNzhteW13d3JwRmVoVlJzTlV6?= =?utf-8?B?bit6MldWQ2ZudjgrMmRURHZGSlFUVGRDeE00ZGNTaHdreHdhRHVkWkk0MVhR?= =?utf-8?B?WDkyRC9jZEt3UHpHOE5PZndyS0RZY0JOd2hocHhQSjRmeCtEaTBnZmdrVCtr?= =?utf-8?B?M0F3a2dsQlIyZTloMlVHRmdnU3lWeE9EQjhnSzdlR3lJWm5wQ2JBeXZDemZN?= =?utf-8?B?cWhDWjZDZnV0NW54WUNXVnZJZk1Ibmh1Z0dsdkVPYVVuWW1wK2wybGNlWEVl?= =?utf-8?B?dVVhNmc4VGxobzFvb2xoUitQTDVNSTJsT291akwrZTAreGlzUXZaU2FGcFRu?= =?utf-8?B?UEo2SmhHU1p2enIvU0hNVDdINFZpNW1rcURUcVZudEFhbThjQUNjUStPTmpx?= =?utf-8?B?VFN1SXRSR2ljT1NxTDNzc0RqcFdabmxlL0oxTmg5dHovaEh4NFYvTEFiVDV3?= =?utf-8?B?UUhFaUdDSjZyQUI5ZTNTamtYc1U3MThuSHEvYStTTHZYYzJSelV4SHFHTURW?= =?utf-8?B?RmNaMk1QV2pLcE4wcTNvelBscjVjcVdjN2E5OVlEWndJSFFjeE9sY05JcnUx?= =?utf-8?B?dUF1eXROYWxlaFpydVV4OUZwdXJyYzlGRldLMGVYaGxHWTZMbDM1UXJRPT0=?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM;PTR:;CAT:NONE;SFS:(13230040)(10070799003)(376014)(7416014)(1800799024)(366016);DIR:OUT;SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?WHhmMlpSTE5NSlZybUl6YjViSENpWFJ4dTZOZkVxbGFZeS82ck9ZdlM0N2NI?= =?utf-8?B?V1dYOGt2S1VPcGpoM3VnOVBjblJqN1RhcjliUXJsVTlvZVgwZmJGdVpGTkw3?= =?utf-8?B?bTYrYzI5dW5BTUJwUUMyYnYvbCt0cnFYOFJZUEoydTlNdmt0TU1zWEk3VWU4?= =?utf-8?B?UTVzZHR6cmVwTEZ1WTBDRm1DZGpZb3hSUCt5QWtLU05OMUNoN0pSc085d3VR?= =?utf-8?B?TWFEMEswcHZBZGlYVzl5UEVYMjU5R0hMZkxRV3FwSCtDUnFScmtmL0w2ZWRx?= =?utf-8?B?ZjRtNVh2bVdsVkVQWnRpSm5OOG1IZUdJVkl1SWFFR1ltWmY5MVBCaVJMTTQv?= =?utf-8?B?WnViUVRZUVFUZnNSTUh6eWdmTWVObzIvMUxhcTRtWGxoYXlsTTllY0pkVUVZ?= =?utf-8?B?VzBlY2pEa3JpdUovblp2Qm9xcFB4Mm9SUHN6bU5sb1hoY2o0YkNscVlXcWVM?= =?utf-8?B?Q0lhblZEZ2x1V1lvMVFZSDhFQW5EZXFlMmdFOExkT3RMZ09XK3VxOXFBNFlV?= =?utf-8?B?clJreUVCVkE0VUpFZ2lNcm9nem1jbzZGcllsR0NKMjA3cEJLMXlnT2ZvRXkr?= =?utf-8?B?RWNtTVYvWXd3d0Z0UWZCanMrdTdTQ05WTVVZV0c0ODNBM1JqQU10aEZNaVJS?= =?utf-8?B?QkVLMUZmc3ArdmQya0NGUU1Zb095VStMWkxjYWNxeHFDSzBTRkRUQkp3QVlp?= =?utf-8?B?MzBtNGphd2VTYlRMM0dTQ2EzcjBabVB2aUJJeTlDSzFna1djZ0FaRzRBc29N?= =?utf-8?B?ZVdBem5rMDVDclpKaDJoQVhydktJcGNENVQwNUtYUG1WUkZ5WExON0lEY1Yr?= =?utf-8?B?aU8vR3hEOU1WS0pXamNSaUhZVUZ4bFQyalBsTkFLSG0xYkgybFl6MjZzM0p6?= =?utf-8?B?eldSbnpiKzJMWnByVUNsQnhxMzNkcmhoYllQUzhwbmFHMG5VQmM2T0dnM3Zl?= =?utf-8?B?clJhWHZSZEhOUWRPaTdFeGxNS3Y4V3pyTzY2U1UzS3ZyODRsSXNocWxtSW9m?= =?utf-8?B?b0locHAzNFQyTk5aMGxQaFlKTmN0cXlXeWlRMGpTZ2ltRlpFKzNlTXY5ZzZh?= =?utf-8?B?U0V3RjNuYmJLcDBaN0dJUGlhak1TSjlrSmtHd3ZOdS9ISDlUY2UyQlpNQXVD?= =?utf-8?B?MXM5MDJXeTRPejk1WGFNVmUvajdaeE5BbGlieWlKMEZCQXVRYlVvanBRdDN5?= =?utf-8?B?VFBwQlUrR0V5T2xGb0ZxNjYybERtOGVzZ211TFNzL01PRFpSNW1pNm9kVGRG?= =?utf-8?B?ZWgyaUVCcmJSanpBMlNOWXFnUGtHNVhiV3NJSGFSOXhSMk1sd09WeTYwNnBi?= =?utf-8?B?Y05vbnNPQWxuTzVSNVdjbCt2UExjKzhZaVFuNWgwdHFpYVJmR2hXZUowaGQ2?= =?utf-8?B?TlpwemNTcTFzSlp4cmJpeEEyRmI4UnZpZldTQmk0WnJWRlQ5cWswRGVEdVNV?= =?utf-8?B?OGtZeGx3SlU3NENCcE9DUnFWNjhTMlZuQjhUbVV3c3JpV016ZVdIT1haNVdN?= =?utf-8?B?MDE3Y0gyMjliQndyaWs4WjNVc09keUdDYStQZGJ3OTBHbXd1K3pUQ0JlUTlY?= =?utf-8?B?YytzUW85SEF2d0pCejV4OU5RUjlJcEFvQThkYmR3Zmt6cEJ2UGN5M2FudnY1?= =?utf-8?B?aW43VElieUU2NEFva2d1M3A3eTRxcUVQaVBTQWFkdERZVHk5VXdiaU9menpo?= =?utf-8?B?YlBZb1ZxNm1SbkppWllUbU9KYnErZmNDbnUreUhvbHBGTVFFc1htSmRqZTJu?= =?utf-8?B?aEFmOFlWcmFjMWRLM1Urb3ZuQlpxZTRuNFdDd2UwdXNlRUYrNmpsbzdDSGZi?= =?utf-8?B?cFNyb2VieE50WHQ5U09xdjlYVFc5VTlYK1FmRWdpdit1YTFVVmxBOHpPbkVP?= =?utf-8?B?bEZKQS9VZFBoMzNDeWFnQkdqOHdJMk5CN1NUSDZ2czdnRUYwdUJMZlJ2dUtX?= =?utf-8?B?NHdjWkFHL2pINk5VUEh1b05CY3RqRFBaeE5IQThkbDJpdGNYSWlUR1BWUy9Z?= =?utf-8?B?OGN2SzhLRDkwY2dVNDIzbk5WbksyWk1QeFg2UmoyT2Z1aHlJekpRS2NBRTFU?= =?utf-8?B?bWlOT1FNbFZMMDAyRklBUmx0cEdXU0JQc3M0K0dWRzdjbmI4dG50NkNWdU9m?= =?utf-8?Q?RroNU08jkCpOngGkir6FF2yB5?= X-OriginatorOrg: garyguo.net X-MS-Exchange-CrossTenant-Network-Message-Id: 06c802d0-3f00-440d-1e1c-08dcdbeaa385 X-MS-Exchange-CrossTenant-AuthSource: LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Sep 2024 16:13:19.3169 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: O1puvaz0rRRXhJPlwKQjs25fpdX3QvI8iTLs64NXMEp6qf+J3hyYCzbk5iqEtL+BoWBq8mFk/p3clI/vi5Z7ng== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LO0P265MB5525 X-Rspamd-Queue-Id: D103C40010 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 8de1jg7nme9jgwu94n5o7ikad975amgy X-HE-Tag: 1727108002-644074 X-HE-Meta: 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 8XM3lphZ k15oW+yTv7+F2+iRBpHqKepALQBvspk1LLYHEx9vkjEb9YLniEORjxEEv9sDwcmw30LNRGaT9nDybvPRUysVG7k/thn9Lv7qiDw0eqveALhP6kaZf8Z4+3d58VniflBH+88y1dNnWaJONg3x6Qkguu1DIw/TtnPN6YNSEOVYS0hC1zBlJxC6cyp1vyvF1UA2MC5uXqFrAzDxqar1ISgHG2DuG1JfYgDHesa/eDHNx5gz5hu0ChRKy+AKAK5u0YqTx+c0K26ZfFruilBk0Qu6IziFoZSAZCVB293Gm0le13h0xa3zb103nZ84FeMlQn5Im7yXcriGt55gFBjaEJbSYJAucmk+aLBm//zmjIRev8FZmUFoSVqqO69yYP/PP7Ot1NTi0iCsmrcFDZK7SL52f9zjTDEHs/plOeZ3z/gcSEo7Cqnc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.007379, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 23 Sep 2024 15:56:28 +0200 Alice Ryhl wrote: > On Sat, Sep 21, 2024 at 5:33=E2=80=AFPM Danilo Krummrich wrote: > > @@ -84,11 +92,18 @@ unsafe fn call( > > &self, > > ptr: Option>, > > layout: Layout, > > + old_layout: Layout, > > flags: Flags, > > ) -> Result, AllocError> { > > let size =3D aligned_size(layout); > > let ptr =3D match ptr { > > - Some(ptr) =3D> ptr.as_ptr(), > > + Some(ptr) =3D> { > > + if old_layout.size() =3D=3D 0 { > > + ptr::null() > > + } else { > > + ptr.as_ptr() > > + } > > + } =20 >=20 > This is making Allocator work with zero-sized types, which deviates > from std. We should not do that without a reason. What is the reason? >=20 > Alice As Benno said, this makes the API closer to Rust `allocator_api` Allocator trait as opposed to deviation. There's one benefit of doing this (discussed with Danilo off-list), which is it removes ZST special casing from caller. This RFC patch simplifies `Box` handling, and if we add this line to the safety doc `ptr` does not need to be a pointer returned by this allocator if the layout is zero-sized. then the `Vec` can also be simplified, removing all logics handling ZST specially, except for `Vec::new()` which it forges a well-aligned dangling pointer from nowhere. Best, Gary