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=-7.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 4E3BFC4743F for ; Tue, 8 Jun 2021 20:21:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BB145610F8 for ; Tue, 8 Jun 2021 20:21:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BB145610F8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45528 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lqiEO-0005H8-SL for qemu-devel@archiver.kernel.org; Tue, 08 Jun 2021 16:21:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52622) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lqiDo-0004cR-W3 for qemu-devel@nongnu.org; Tue, 08 Jun 2021 16:21:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48593) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lqiDi-0007Xh-VO for qemu-devel@nongnu.org; Tue, 08 Jun 2021 16:21:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623183665; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=uP1kam469ioHjrBfowFB0csLPpIc0a+/IpTo2tngiUk=; b=ZG5CcLs+fadYCF3mzO/Jv3uCwB1Z5r8ahA7tmKjB6b0T6iau4oO5yB5e/NkmlWJsXsBREh OZDkS5uqtsughS6asVntH7bq60uCVuScuFexKwhpzanyVQ+RDDer6rcCxOZy5vkCBA1ywG T137H9P/f4dbcOautebVJ6HjlUuD40Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-299-7DDwuWG6MuqNzUlOqWlL4g-1; Tue, 08 Jun 2021 16:21:01 -0400 X-MC-Unique: 7DDwuWG6MuqNzUlOqWlL4g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B077D8186E6; Tue, 8 Jun 2021 20:21:00 +0000 (UTC) Received: from redhat.com (ovpn-115-85.ams2.redhat.com [10.36.115.85]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3EFC95D9DC; Tue, 8 Jun 2021 20:20:58 +0000 (UTC) Date: Tue, 8 Jun 2021 21:20:53 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Richard Henderson Subject: Re: [PATCH 05/26] configure, meson: convert pam detection to meson Message-ID: References: <20210608112301.402434-1-pbonzini@redhat.com> <20210608112301.402434-6-pbonzini@redhat.com> <08135c0f-ce6b-53ad-be57-eba428fbfbf5@linaro.org> MIME-Version: 1.0 In-Reply-To: <08135c0f-ce6b-53ad-be57-eba428fbfbf5@linaro.org> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.197, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Paolo Bonzini , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Jun 08, 2021 at 12:45:51PM -0700, Richard Henderson wrote: > On 6/8/21 4:22 AM, Paolo Bonzini wrote: > > +pam = not_found > > +if not get_option('auth_pam').auto() or have_system > > + pam = cc.find_library('pam', has_headers: ['security/pam_appl.h'], > > The condition doesn't look right. > Why are we looking for pam if --disable-pam-auth? > > Surely > > if not get_option('auth_pam').disabled() and have_system This isn't entirely obvious at first glance, but the line after the one you quote with the 'required' param makes it "do the right thing (tm)". The 'auth_pam' option is a tri-state taking 'enabled', 'disabled' and 'auto', with 'auto' being the default state. When a tri-state value is passed as the value of the 'required' parameter, then required==enabled is interpreted as 'required=true' required==auto is interpreted as 'required=false' required==disabled means the entire call is a no-op So this logic: if not get_option('auth_pam').auto() or have_system pam = cc.find_library('pam', has_headers: ['security/pam_appl.h'], required: get_option('auth_pam'), ...) Means => If 'auto' is set, then only look for the library if we're building system emulators. In this case 'required:' will evaluate to 'false', and so we'll gracefully degrade if the library is missing. => If 'enabled' is set, then we'll look for the library and if it is missing then it is a fatal error as 'required' will evaluate to 'true'. => If 'disabled' is set, then the 'find_library' call will not look for anything, immediately return a 'not found' result and let the caller carry on. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|