From: Leo Yan <leo.yan@arm.com>
To: Quentin Monnet <qmo@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>,
Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
Shuah Khan <shuah@kernel.org>, Lorenz Bauer <lmb@isovalent.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
James Clark <james.clark@linaro.org>,
Kees Cook <kees@kernel.org>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, llvm@lists.linux.dev,
Leo Yan <leo.yan@arm.com>
Subject: [PATCH 3/6] libbpf: Initialize CFLAGS before including Makefile.include
Date: Mon, 23 Mar 2026 15:40:04 +0000 [thread overview]
Message-ID: <20260323-tools_build_fix_zero_init_bpf_only-v1-3-d1cfad2f4cd1@arm.com> (raw)
In-Reply-To: <20260323-tools_build_fix_zero_init_bpf_only-v1-0-d1cfad2f4cd1@arm.com>
tools/scripts/Makefile.include may expand EXTRA_CFLAGS in a future
change. This could alter the initialization of CFLAGS, as the default
options "-g -O2" would never be set once EXTRA_CFLAGS is expanded.
Prepare for this by moving the CFLAGS initialization before including
tools/scripts/Makefile.include, so it is not affected by the extended
EXTRA_CFLAGS.
Append EXTRA_CFLAGS to CFLAGS only after including Makefile.include and
place it last so that the extra flags propagate properly and can
override the default options.
tools/scripts/Makefile.include already appends $(CLANG_CROSS_FLAGS) to
CFLAGS, the Makefile appends $(CLANG_CROSS_FLAGS) again, remove the
redundant append.
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
tools/lib/bpf/Makefile | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 168140f8e6461bd06db40e23d21a3fb8847ccbf4..eca584fb061e16013e76827e4203f6be0477a73e 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -49,6 +49,14 @@ man_dir_SQ = '$(subst ','\'',$(man_dir))'
export man_dir man_dir_SQ INSTALL
export DESTDIR DESTDIR_SQ
+# Defer assigning EXTRA_CFLAGS to CFLAGS until after including
+# tools/scripts/Makefile.include, as it may add flags to EXTRA_CFLAGS.
+ifdef EXTRA_CFLAGS
+ CFLAGS :=
+else
+ CFLAGS := -g -O2
+endif
+
include $(srctree)/tools/scripts/Makefile.include
# copy a bit from Linux kbuild
@@ -70,13 +78,6 @@ LIB_TARGET = libbpf.a libbpf.so.$(LIBBPF_VERSION)
LIB_FILE = libbpf.a libbpf.so*
PC_FILE = libbpf.pc
-# Set compile option CFLAGS
-ifdef EXTRA_CFLAGS
- CFLAGS := $(EXTRA_CFLAGS)
-else
- CFLAGS := -g -O2
-endif
-
# Append required CFLAGS
override CFLAGS += -std=gnu89
override CFLAGS += $(EXTRA_WARNINGS) -Wno-switch-enum
@@ -84,7 +85,7 @@ override CFLAGS += -Werror -Wall
override CFLAGS += $(INCLUDES)
override CFLAGS += -fvisibility=hidden
override CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
-override CFLAGS += $(CLANG_CROSS_FLAGS)
+override CFLAGS += $(EXTRA_CFLAGS)
# flags specific for shared library
SHLIB_FLAGS := -DSHARED -fPIC
--
2.34.1
next prev parent reply other threads:[~2026-03-23 15:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-23 15:40 [PATCH 0/6] tools build: bpf: Append EXTRA_CFLAGS and HOST_EXTRACFLAGS Leo Yan
2026-03-23 15:40 ` [PATCH 1/6] bpftool: Avoid adding EXTRA_CFLAGS to HOST_CFLAGS Leo Yan
2026-03-31 8:46 ` kernel test robot
2026-03-23 15:40 ` [PATCH 2/6] bpftool: Append extra host flags Leo Yan
2026-03-23 15:40 ` Leo Yan [this message]
2026-03-23 22:50 ` [PATCH 3/6] libbpf: Initialize CFLAGS before including Makefile.include Ihor Solodrai
2026-03-23 15:40 ` [PATCH 4/6] tools/bpf: build: Append extra cflags Leo Yan
2026-03-23 15:40 ` [PATCH 5/6] selftests/bpf: Initialize operation name before use Leo Yan
2026-03-23 22:52 ` Ihor Solodrai
2026-03-24 6:58 ` Leo Yan
2026-03-24 15:55 ` Alexei Starovoitov
2026-03-23 15:40 ` [PATCH 6/6] selftests/bpf: Append extra cflags Leo Yan
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