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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 A40DAC4320A for ; Fri, 23 Jul 2021 19:54:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84C7860F36 for ; Fri, 23 Jul 2021 19:54:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231243AbhGWTNv (ORCPT ); Fri, 23 Jul 2021 15:13:51 -0400 Received: from mail-vk1-f182.google.com ([209.85.221.182]:37458 "EHLO mail-vk1-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229808AbhGWTNu (ORCPT ); Fri, 23 Jul 2021 15:13:50 -0400 Received: by mail-vk1-f182.google.com with SMTP id d16so632227vkp.4; Fri, 23 Jul 2021 12:54:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WCrKf5Iw2o5+shGh2ncn5iHfAc+hQCz5PyiUxBmUVl8=; b=pi3uGul0dxI0whGTeI91bwsidGjZmI3OrYj5YfPI0STB/b6LedxPA9rGnkJEdDtkIz CKW6j0mJpDa1o6FLpk68qqTh4Fy4UXSVZQovSQeYNvCUWGfxujjLrIpdDAHn9DJi7Dbf GrIhPk52MNTFF4Ki/14FT4Od3yeDgU2G/IgkI3MPP7byJpa/otMufbibrFdhaLgyRbdb /2dLfP/L23Rw1MeVX9yNX1p8OhqSeuTk4pyb3/BMR+vGlsF+TZ40i45LAQNuGFx6xnro MPMIcMXMrj6V4RHxno5RHUy8vBRacfSirK9C2oZd9Mq6Sv+fB574kTrldPEsjJXf6OVv Aelg== X-Gm-Message-State: AOAM530MtPOLAsDEDO9sZdYj2KInS/IaIbD3c010+NPEkwjOJ9N2d8HF lGxkOsn1CHx6CjGy2sp+i7xxilbmMZV5ht8/h4E= X-Google-Smtp-Source: ABdhPJy7yL/c/PrB/qgOazP2a0kVPM0D75VBNd4uc3fh/YhPMfft5NwOTFf/CwNczJQK8qIofi9Vcu4MS/fwvRdW1Ho= X-Received: by 2002:a05:6122:a12:: with SMTP id 18mr5316680vkn.1.1627070062009; Fri, 23 Jul 2021 12:54:22 -0700 (PDT) MIME-Version: 1.0 References: <20210708232522.3118208-1-ndesaulniers@google.com> <20210708232522.3118208-3-ndesaulniers@google.com> In-Reply-To: From: Geert Uytterhoeven Date: Fri, 23 Jul 2021 21:54:10 +0200 Message-ID: Subject: Re: [PATCH v2 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for LLVM=1 LLVM_IAS=1 To: Masahiro Yamada Cc: Arnd Bergmann , Linus Torvalds , Nick Desaulniers , Miguel Ojeda , Fangrui Song , Michal Marek , Linux Kernel Mailing List , Linux Kbuild mailing list , clang-built-linux , Christoph Hellwig , Nathan Chancellor Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Yamada-san, On Wed, Jul 21, 2021 at 6:05 AM Masahiro Yamada wrote: > On Wed, Jul 21, 2021 at 4:58 AM Arnd Bergmann wrote: > > On Tue, Jul 20, 2021 at 7:43 PM Linus Torvalds > > wrote: > > > On Tue, Jul 20, 2021 at 1:05 AM Masahiro Yamada wrote: > > > > > > We do most of the other heavy lifting in this area in Kconfig anyway, > > > why not add that compiler choice? > > > > > > Obviously it would be gated by the tests to see which compilers are > > > _installed_ (and that they are valid versions), so that it doesn't ask > > > stupid things ("do you want gcc or clang" when only one of them is > > > installed and/or viable). > > > > I don't see a good way of making Kconfig options both select the > > compiler and defining variables based on the compiler, since that > > would mean teaching Kconfig about re-evaluating all compiler > > dependent settings whenever the first option changes. > > > > I do have another idea that I think would work though. > > > > > Hmm? So then any "LLVM=1" thing would be about the "make config" > > > stage, not the actual build stage. > > > > > > (It has annoyed me for years that if you want to cross-compile, you > > > first have to do "make ARCH=xyz config" and then remember to do "make > > > ARCH=xyz" for the build too, but I cross-compile so seldom that I've > > > never really cared). > > > > The best thing that I have come up with is a pre-configure step, where > > an object tree gets seeded with a makefile fragment that gets included > > for any 'make' invocation. This would set 'ARCH=', 'CROSS_COMPILE', > > 'CC=' and possibly any other option that gets passed to 'make' as > > a variable and has to exist before calling 'make *config'. > > > There is no need to add a hook to include such makefile fragment(s). > > Quite opposite, you can put your Makefile (in a different filename) > that includes the top Makefile. > > > I think this is what people are already doing: > > > GNU Make looks for 'GNUmakefile', 'makefile', and 'Makefile' > in this order. Exactly. I only have a few source repositories, but lots of build directories (I never build in a repo directory). Each build directory has a GNUmakefile: build/linux-riscv-starlight$ cat GNUmakefile MAKEARGS = ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- include ~/linux/default.mk build/linux-riscv-starlight$ cat ~/linux/default.mk MAKEFLAGS += --no-print-directory .PHONY: all $(MAKECMDGOALS) all := $(filter-out all Makefile,$(MAKECMDGOALS)) all: @$(MAKE) $(MAKEARGS) $(all) -f Makefile Makefile:; $(all): all @: %/: all @: build/linux-riscv-starlight$ Perhaps we could have a "make setup ARCH=foo CROSS_COMPILE=bar" target, which creates such a GNUmakefile? P.S. I put the extra logic in ~/linux/default.mk, so I don't have to update all GNUmakefiles when I want to make a change to the main logic. For build dirs where I want to track a specific config, I have a slightly different version: build/linux-m68k-allmodconfig-sun3$ cat GNUmakefile MAKEARGS = ARCH=m68k KCONFIG_ALLCONFIG=1 DEFCONFIG = allmodconfig include ~/linux/override-oldconfig.mk build/linux-m68k-allmodconfig-sun3$ cat ~/linux/override-oldconfig.mk MAKEFLAGS += --no-print-directory .PHONY: all oldconfig realoldconfig $(MAKECMDGOALS) all := $(filter-out all oldconfig realoldconfig Makefile,$(MAKECMDGOALS)) all: @$(MAKE) $(MAKEARGS) $(all) -f Makefile # Replace oldconfig by $(DEFCONFIG) oldconfig: @$(MAKE) $(MAKEARGS) $(DEFCONFIG) -f Makefile realoldconfig: @$(MAKE) $(MAKEARGS) oldconfig -f Makefile Makefile:; $(all): all @: %/: all @: build/linux-m68k-allmodconfig-sun3$ That way I can always just type "make oldconfig", and it will do what I want. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds