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From:   Masahiro Yamada <masahiroy@kernel.org>
To:     linux-kbuild@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nicolas Schier <nicolas@fjasle.eu>
Subject: [PATCH 1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS
Date:   Tue,  6 Dec 2022 13:07:30 +0900
Message-Id: <20221206040731.442499-1-masahiroy@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

CONFIG_WERROR turns warnings into errors, which happens only for *.c
files because -Werror is added to KBUILD_CFLAGS.

Adding it to KBUILD_CPPFLAGS makes more sense because preprocessors
understand the -Werror option.

For example, you can put a #warning directive in any preprocessed code.

    warning: #warning "this is a warning message" [-Wcpp]

If -Werror is added, it is promoted to an error.

    error: #warning "this is a warning message" [-Werror=cpp]

This commit moves -Werror to KBUILD_CPPFLAGS so it works in the same way
for *.c, *.S, *.lds.S or whatever needs preprocessing.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---

 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 53fa1a9fba8a..f84b57910667 100644
--- a/Makefile
+++ b/Makefile
@@ -869,7 +869,8 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
 
 KBUILD_CFLAGS += $(stackp-flags-y)
 
-KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
+KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
+KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
 
 KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
-- 
2.34.1