linux-kernel - [PATCH 2/2] kbuild: add -Wall to KBUILD

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Date:   Wed, 25 Mar 2020 12:14:32 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        kernel-hardening@...ts.openwall.com,
        Masahiro Yamada <masahiroy@...nel.org>,
        Emese Revfy <re.emese@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] kbuild: add -Wall to KBUILD_HOSTCXXFLAGS

Add -Wall to catch more warnings for C++ host programs.

When I submitted the previous version, the 0-day bot reported
-Wc++11-compat warnings for old GCC:

  HOSTCXX -fPIC scripts/gcc-plugins/latent_entropy_plugin.o
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/tm.h:28:0,
                 from scripts/gcc-plugins/gcc-common.h:15,
                 from scripts/gcc-plugins/latent_entropy_plugin.c:78:
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/config/elfos.h:102:21: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
    fprintf ((FILE), "%s"HOST_WIDE_INT_PRINT_UNSIGNED"\n",\
                     ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/config/elfos.h:170:24: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
       fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n",  \
                        ^
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/tm.h:42:0,
                 from scripts/gcc-plugins/gcc-common.h:15,
                 from scripts/gcc-plugins/latent_entropy_plugin.c:78:
/usr/lib/gcc/x86_64-linux-gnu/4.8/plugin/include/defaults.h:126:24: warning: C++11 requires a space between string literal and macro [-Wc++11-compat]
       fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n",  \
                        ^

The source of the warnings is in the plugin headers, so we have no
control of it. I just suppressed them by adding -Wno-c++11-compat to
scripts/gcc-plugins/Makefile.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 Makefile                     | 2 +-
 scripts/gcc-plugins/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 3b57ccab367b..593d8f1bbe90 100644
--- a/Makefile
+++ b/Makefile
@@ -400,7 +400,7 @@ HOSTCXX      = g++
 KBUILD_HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
 		-fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \
 		$(HOSTCFLAGS)
-KBUILD_HOSTCXXFLAGS := -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
 
diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
index f2ee8bd7abc6..efff00959a9c 100644
--- a/scripts/gcc-plugins/Makefile
+++ b/scripts/gcc-plugins/Makefile
@@ -10,7 +10,7 @@ else
   HOSTLIBS := hostcxxlibs
   HOST_EXTRACXXFLAGS += -I$(GCC_PLUGINS_DIR)/include -I$(src) -std=gnu++98 -fno-rtti
   HOST_EXTRACXXFLAGS += -fno-exceptions -fasynchronous-unwind-tables -ggdb
-  HOST_EXTRACXXFLAGS += -Wno-narrowing -Wno-unused-variable
+  HOST_EXTRACXXFLAGS += -Wno-narrowing -Wno-unused-variable -Wno-c++11-compat
   export HOST_EXTRACXXFLAGS
 endif
 
-- 
2.17.1