From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755994AbdLVByM (ORCPT ); Thu, 21 Dec 2017 20:54:12 -0500 Received: from mail-io0-f194.google.com ([209.85.223.194]:45989 "EHLO mail-io0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755533AbdLVBxr (ORCPT ); Thu, 21 Dec 2017 20:53:47 -0500 X-Google-Smtp-Source: ACJfBovHPR9EBzJwo1QUym+h+7BoSkcfV3ng+20veDvLNhGa7fARZourObpF7oHciE6Xfu3bVDtxaw== From: Douglas Anderson To: Masahiro Yamada Cc: malat@debian.org, dave.hansen@intel.com, yang.s@alibaba-inc.com, linux@roeck-us.net, Douglas Anderson , Matthias Kaehlcke , Cao jin , Arnd Bergmann , Mark Charlebois , linux-kernel@vger.kernel.org, Josh Poimboeuf , Ingo Molnar Subject: [PATCH 1/2] kbuild: Require a 'make clean' if we detect gcc changed underneath us Date: Thu, 21 Dec 2017 17:53:02 -0800 Message-Id: <20171222015303.112071-2-dianders@chromium.org> X-Mailer: git-send-email 2.15.1.620.gb9897f4670-goog In-Reply-To: <20171222015303.112071-1-dianders@chromium.org> References: <20171222015303.112071-1-dianders@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Several people reported that the commit 3298b690b21c ("kbuild: Add a cache for generated variables") caused them problems when they updated gcc versions. Specifically the reports all looked something similar to this: > In file included from ./include/uapi/linux/uuid.h:21:0, > from ./include/linux/uuid.h:19, > from ./include/linux/mod_devicetable.h:12, > from scripts/mod/devicetable-offsets.c:2: > ./include/linux/string.h:8:20: fatal error: stdarg.h: No such file or > directory > #include Masahiro Yamada determined that the problem was with: NOSTDINC_FLAGS += -nostdinc -isystem $(call shell-cached,$(CC) -print-file-name=include) Specifically that the stale result of -print-file-name is stored in the cache file. It was determined that a "make clean" fixed the problems in all cases. In this particular case we could certainly try to clean just the cache when we detect a gcc update, but it seems like overall it's a bad idea to do an incremental build when gcc changes. We should warn the user and tell them that they need a 'make clean'. Fixes: 3298b690b21c ("kbuild: Add a cache for generated variables") Reported-by: Yang Shi Reported-by: Dave Hansen Reported-by: Mathieu Malaterre Signed-off-by: Douglas Anderson --- scripts/Kbuild.include | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 065324a8046f..56dee20fb2b8 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -222,6 +222,10 @@ cc-version = $(call shell-cached,$(CONFIG_SHELL) $(srctree)/scripts/gcc-version. cc-fullversion = $(call shell-cached,$(CONFIG_SHELL) \ $(srctree)/scripts/gcc-version.sh -p $(CC)) +# cc-fullversion-uncached +cc-fullversion-uncached := $(shell $(CONFIG_SHELL) \ + $(srctree)/scripts/gcc-version.sh -p $(CC)) + # cc-ifversion # Usage: EXTRA_CFLAGS += $(call cc-ifversion, -lt, 0402, -O1) cc-ifversion = $(shell [ $(cc-version) $(1) $(2) ] && echo $(3) || echo $(4)) @@ -475,3 +479,14 @@ endif endef # ############################################################################### + +# Require a 'make clean' if the compiler changed; not only does the .cache.mk +# need to be thrown out but we should also start with fresh object files. +# +# NOTE: it's important that we don't error out when the goal is actually to +# try to make clean, distclean or mrproper. +ifeq ($(filter %clean,$(MAKECMDGOALS))$(filter mrproper,$(MAKECMDGOALS)),) + ifneq ($(cc-fullversion-uncached),$(cc-fullversion)) + $(error Detected new CC version ($(cc-fullversion-uncached) vs $(cc-fullversion)). Please 'make clean') + endif +endif -- 2.15.1.620.gb9897f4670-goog