From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5742E3921D0; Tue, 11 Aug 2026 15:12:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786461156; cv=none; b=BI4xxWQcLvBk1x3m2hDj7FYFOOEjhx1qxwGmUUTMj4Dd+eJU18SBy/h3B0mXgP70uGshSnxBIirt9onq+QzBAop+Zw0NZ5bP2uAX+e0r4zEkTMBTRLAqB8vBwgGbBXmo4bmmie/Xc83Zg+tPU53dcFTetPEoKw7HyHkMqWrEo5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786461156; c=relaxed/simple; bh=X5bqa2yCFbfPgcX/+CLwQlcc9TS2I8QY4eRpTrTNxyI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=THYSz9CJCoK5HSZS/khHjG4kCLr5w9q4/idWRk/UyoG7613HFAhK5Xk6LNaShHARVC5fAhfuuIIzNPDSMmg1MoprXE+8sw/tzokh2LO8c6UandmtTJuDWP3NP0WfOGgVzoPn9Kuhuhm8X+mRVFcYDnIlE3osXqpl+dK8wcEuxmg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hseIw+02; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hseIw+02" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26D641F000E9; Tue, 11 Aug 2026 15:12:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786461150; bh=+BXvLb7cu7OYeArpE33yeiUjgpXx5DCGhcJwcueaKB8=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=hseIw+02BjZaT9PQiFpYpAae9SfE533m7P4+KqdUUnO+XHxSEJrm4789bZlovQpSX Y0vWj91GIvrqzORBdv1pemRXjr2IoGYWxw8J6XuQ/P05y6Tx9hMmCivZXo5fyaQG3q iMdJdhparkCLsUVCi9O6dezrmIcqFcaf/VPg0pWIGPQl0M762UupofvfIIqBe/aKP8 6ImnkL2GvT1q/4EeQYewvvQI/579aq0JTnVCqSePzlsGoIQnWpSAH9rX5lFEOV7g3k DkGR6RI1U0PMpHA+Jz5XdHsAyxObjKOjFmaJB0IiodmQQdcD8ec5DYaIT9IjhCXZLo f4pLMVSsD9UkA== Date: Tue, 11 Aug 2026 12:12:26 -0300 From: Arnaldo Carvalho de Melo To: Ian Rogers Cc: Namhyung Kim , Ingo Molnar , Thomas Gleixner , James Clark , Jiri Olsa , Adrian Hunter , Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Arnaldo Carvalho de Melo Subject: Re: [PATCH 1/7] tools build: Only probe the compiler at parse time when it is installed Message-ID: References: <20260810154437.15946-1-acme@kernel.org> <20260810154437.15946-2-acme@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Aug 10, 2026 at 11:07:40AM -0700, Ian Rogers wrote: > On Mon, Aug 10, 2026 at 8:44 AM Arnaldo Carvalho de Melo wrote: > > Two parse-time probes still invoke $(CC) unconditionally: > > - LP64 in tools/scripts/Makefile.arch, probing with > > $(CC) -E -x c, pulled in twice by tools/perf/Makefile.perf; > > - CC_NO_CLANG in tools/scripts/Makefile.include, probing with > > $(CC) -dM -E -x c /dev/null. > > In the corner case where gcc is not yet installed, the very setup the > > install-build-deps target, added in the next patch of this series, is > > meant for, these probes make even targets that never compile parse-time > > spew errors like: > > /bin/sh: 1: gcc: not found > > /bin/sh: 1: gcc: not found > > /bin/sh: 1: gcc: not found > > Guard both probes with 'command -v' using the first word of CC so a > > missing compiler is handled silently with the same result as a failing > > probe (CC_NO_CLANG and LP64 unset/0), and with no behavior change when > > the compiler is installed. > > Only the first word is consulted because CC may carry arguments such as > > 'ccache gcc', and shell implementations differ in how 'command -v' > > handles multiple words (dash only checks the first, bash any of them), > > so validating the whole CC value would silently disable both probes on > > some make SHELLs. > > Assisted-by: opencode:deepseek-v4-flash-free > > Signed-off-by: Arnaldo Carvalho de Melo > > +++ b/tools/scripts/Makefile.arch > > @@ -38,7 +38,7 @@ ifeq ($(ARCH),loongarch64) > > SRCARCH := loongarch > > endif > > -LP64 := $(shell echo __LP64__ | ${CC} ${CFLAGS} -E -x c - | tail -n 1) > > +LP64 := $(shell if command -v $(firstword ${CC}) >/dev/null 2>&1; then echo __LP64__ | ${CC} ${CFLAGS} -E -x c -; fi | tail -n 1) > > nit: It might be worth adding a comment to explain this fairly complex > one-liner. Sure, will add explanations, see below. > As there are minimum requirements to build the kernel > (https://www.kernel.org/doc/html/latest/process/changes.html) does it > make sense to be defensive about CC not being installed? Well, the point of this series is to install what is needed to build perf, gcc included, so on a freshly installed machine the user can just do: cd tools/perf make install-build-deps And the machine will have all the packages that are needed. > Perhaps install-build-deps.sh can be part of the wider kernel build > with flags to specify if you are building the kernel or a tool, where > depencies are different (e.g. perf doesn't need quota-tools but > libcapstone is useful). I think this can be a followup series, i.e. making the kernel have that target as well. Having it in perf will showcase its usability and may entice the Kbuild guys to consider accepting such a functionality. - Arnaldo acme@number:~/git/perf-tools-next$ git diff ca62b23f83ddfb8e.. diff --git a/tools/scripts/Makefile.arch b/tools/scripts/Makefile.arch index e0bca6808ec44ed8..ed5f008d400ed238 100644 --- a/tools/scripts/Makefile.arch +++ b/tools/scripts/Makefile.arch @@ -38,6 +38,12 @@ ifeq ($(ARCH),loongarch64) SRCARCH := loongarch endif +# Probe for __LP64__ only when the compiler is installed: this runs at +# parse time for every target, including ones that never compile, e.g. +# install-build-deps, and would otherwise spew "gcc: not found" when the +# compiler is not yet installed. Only the first word of CC is consulted, +# as CC may carry arguments, e.g. 'ccache gcc'. When the guard fails it +# prints nothing, leaving LP64 unset, as if the probe had failed. LP64 := $(shell if command -v $(firstword ${CC}) >/dev/null 2>&1; then echo __LP64__ | ${CC} ${CFLAGS} -E -x c -; fi | tail -n 1) ifeq ($(LP64), 1) IS_64_BIT := 1 diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include index fff453aac187536e..378387f629603e92 100644 --- a/tools/scripts/Makefile.include +++ b/tools/scripts/Makefile.include @@ -98,6 +98,12 @@ else $(call allow-override,LLVM_STRIP,llvm-strip) endif +# The CC_NO_CLANG probe also runs at parse time for targets that never +# compile, so guard it with 'command -v': when the compiler is not yet +# installed, e.g. the first install-build-deps run, it would otherwise +# spew "gcc: not found". Only the first word of CC is consulted, as CC +# may carry arguments, e.g. 'ccache gcc'. A missing compiler leaves +# CC_NO_CLANG at 1, as if the probe had failed. CC_NO_CLANG := $(shell if command -v $(firstword $(CC)) >/dev/null 2>&1; then $(CC) -dM -E -x c /dev/null; fi | grep -Fq "__clang__"; echo $$?) # Some tools require bpftool acme@number:~/git/perf-tools-next$