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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 710D9C7618D for ; Thu, 6 Apr 2023 16:22:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237762AbjDFQWb (ORCPT ); Thu, 6 Apr 2023 12:22:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229736AbjDFQW2 (ORCPT ); Thu, 6 Apr 2023 12:22:28 -0400 Received: from 1wt.eu (wtarreau.pck.nerim.net [62.212.114.60]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 193191708; Thu, 6 Apr 2023 09:22:26 -0700 (PDT) Received: (from willy@localhost) by mail.home.local (8.17.1/8.17.1/Submit) id 336GMFn2004846; Thu, 6 Apr 2023 18:22:15 +0200 Date: Thu, 6 Apr 2023 18:22:15 +0200 From: Willy Tarreau To: Mark Brown Cc: Shuah Khan , Catalin Marinas , Will Deacon , "Paul E. McKenney" , linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] kselftest: Support nolibc Message-ID: References: <20230405-kselftest-nolibc-v1-0-63fbcd70b202@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 06, 2023 at 03:32:20PM +0100, Mark Brown wrote: > On Thu, Apr 06, 2023 at 04:20:29PM +0200, Willy Tarreau wrote: > > On Thu, Apr 06, 2023 at 02:56:28PM +0100, Mark Brown wrote: > > > > At present the kselftest header can't be used with nolibc since it makes > > > use of vprintf() which is not available in nolibc and seems like it would > > > be inappropriate to implement given the minimal system requirements and > > > environment intended for nolibc. > > > In fact we already have vfprintf(), and printf() is based on it, so > > wouldn't it just be a matter of adding vprintf() that calls vfprintf() > > for your case ? Maybe just something like this : > > > static int vprintf(const char *fmt, va_list args) > > { > > return vfprintf(stdout, fmt, args); > > } > > > It's possible I'm missing something, but it's also possible you didn't > > find vfprintf() which is why I prefer to raise my hand ;-) > > Oh, yes - I just didn't find that. Can't remember what I searched for > but it didn't match. No problem. I just remembered it existed because we just received a new test for it a few days ago ;-) > > > This has resulted in some open coded > > > kselftests which use nolibc to test features that are supposed to be > > > controlled via libc and therefore better exercised in an environment with > > > no libc. > > > Yeah that's ugly. In nolibc-test we now have two build targets so that > > we can more easily verify the compatibility between the default libc and > > nolibc, so my recommendation would be to stick to a common subset of both > > libcs, but not to rely on nolibc-specific stuff that could make tests > > harder to debug. > > For these features we simply never want to run with a proper libc since > if we use a libc which has support for the features then we can't > meaningfully interact with them. We're trying to test interfaces that > libc is supposed to use. Indeed, this totally makes sense then! But I think you get the idea of what I was suggesting which is to try to avoid getting trapped by a single implementation in general, by using portable stuff as much as possible. Cheers, Willy