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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 3B707C433E0 for ; Tue, 28 Jul 2020 14:42:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17647206F5 for ; Tue, 28 Jul 2020 14:42:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Meqw1z2j" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730515AbgG1OmN (ORCPT ); Tue, 28 Jul 2020 10:42:13 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:44846 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730391AbgG1OmN (ORCPT ); Tue, 28 Jul 2020 10:42:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595947331; h=from:from: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=Jrn1cXse5+cdwWbo1CALhfkNmTxz9E7sWHguisrKuqA=; b=Meqw1z2j5rS8GaoVwcTeHpsfNak2z8l/Vp7MaUYeTzmxwQoVy6im/JDYAyWx5roT2N3dtF HkrIvB7rKYRbtlTDisk9A+MVwc/B+Zwud9l5E4KORcuPhnzeiGMNHeGDYiixkOx8BXVzb+ xerRmt/Hh+RSHZFtbDEIQUa5b6AH3vA= 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-31-3j7MhVyBP7KzIBIS2mkozg-1; Tue, 28 Jul 2020 10:42:07 -0400 X-MC-Unique: 3j7MhVyBP7KzIBIS2mkozg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A55D0100AA23; Tue, 28 Jul 2020 14:42:05 +0000 (UTC) Received: from krava (unknown [10.40.192.211]) by smtp.corp.redhat.com (Postfix) with SMTP id 4B0A610013C4; Tue, 28 Jul 2020 14:42:03 +0000 (UTC) Date: Tue, 28 Jul 2020 16:42:02 +0200 From: Jiri Olsa To: Thomas Hebb Cc: linux-kernel@vger.kernel.org, Arnaldo Carvalho de Melo , David Carrillo-Cisneros , Ian Rogers , Igor Lubashev , Jiri Olsa , Namhyung Kim , Quentin Monnet , Song Liu , Stephane Eranian Subject: Re: [PATCH 1/3] tools build feature: Use CC and CXX from parent Message-ID: <20200728144202.GA1319041@krava> References: <0a6e69d1736b0fa231a648f50b0cce5d8a6734ef.1595822871.git.tommyhebb@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0a6e69d1736b0fa231a648f50b0cce5d8a6734ef.1595822871.git.tommyhebb@gmail.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 26, 2020 at 09:08:14PM -0700, Thomas Hebb wrote: > commit c8c188679ccf ("tools build: Use the same CC for feature detection > and actual build") changed these assignments from unconditional (:=) to > conditional (?=) so that they wouldn't clobber values from the > environment. However, conditional assignment does not work properly for > variables that Make implicitly sets, among which are CC and CXX. To > quote tools/scripts/Makefile.include, which handles this properly: > > # Makefiles suck: This macro sets a default value of $(2) for the > # variable named by $(1), unless the variable has been set by > # environment or command line. This is necessary for CC and AR > # because make sets default values, so the simpler ?= approach > # won't work as expected. > > In other words, the conditional assignments will not run even if the > variables are not overridden in the environment; Make will set CC to > "cc" and CXX to "g++" when it starts[1], meaning the variables are not > empty by the time the conditional assignments are evaluated. This breaks > cross-compilation when CROSS_COMPILE is set but CC isn't, since "cc" > gets used for feature detection instead of the cross compiler (and > likewise for CXX). > > To fix the issue, just pass down the values of CC and CXX computed by > the parent Makefile, which gets included by the Makefile that actually > builds whatever we're detecting features for and so is guaranteed to > have good values. This is a better solution anyway, since it means we > aren't trying to replicate the logic of the parent build system and so > don't risk it getting out of sync. > > Leave PKG_CONFIG alone, since 1) there's no common logic to compute it > in Makefile.include, and 2) it's not an implicit variable, so > conditional assignment works properly. looks good, I wonder we might need it also for CLANG in the future Acked-by: Jiri Olsa thanks, jirka > > [1] https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html > > Fixes: c8c188679ccf ("tools build: Use the same CC for feature detection and actual build") > Signed-off-by: Thomas Hebb > --- > > tools/build/Makefile.feature | 2 +- > tools/build/feature/Makefile | 2 -- > 2 files changed, 1 insertion(+), 3 deletions(-) > > diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature > index cb152370fdef..774f0b0ca28a 100644 > --- a/tools/build/Makefile.feature > +++ b/tools/build/Makefile.feature > @@ -8,7 +8,7 @@ endif > > feature_check = $(eval $(feature_check_code)) > define feature_check_code > - feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0) > + feature-$(1) := $(shell $(MAKE) OUTPUT=$(OUTPUT_FEATURES) CC=$(CC) CXX=$(CXX) CFLAGS="$(EXTRA_CFLAGS) $(FEATURE_CHECK_CFLAGS-$(1))" CXXFLAGS="$(EXTRA_CXXFLAGS) $(FEATURE_CHECK_CXXFLAGS-$(1))" LDFLAGS="$(LDFLAGS) $(FEATURE_CHECK_LDFLAGS-$(1))" -C $(feature_dir) $(OUTPUT_FEATURES)test-$1.bin >/dev/null 2>/dev/null && echo 1 || echo 0) > endef > > feature_set = $(eval $(feature_set_code)) > diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile > index b1f0321180f5..93b590d81209 100644 > --- a/tools/build/feature/Makefile > +++ b/tools/build/feature/Makefile > @@ -74,8 +74,6 @@ FILES= \ > > FILES := $(addprefix $(OUTPUT),$(FILES)) > > -CC ?= $(CROSS_COMPILE)gcc > -CXX ?= $(CROSS_COMPILE)g++ > PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config > LLVM_CONFIG ?= llvm-config > CLANG ?= clang > -- > 2.27.0 >