From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Leo Yan <leo.yan@arm.com>, 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
Subject: Re: [PATCH 3/6] libbpf: Initialize CFLAGS before including Makefile.include
Date: Mon, 23 Mar 2026 15:50:30 -0700 [thread overview]
Message-ID: <11402a16-d675-4957-83fb-703082b070e6@linux.dev> (raw)
In-Reply-To: <20260323-tools_build_fix_zero_init_bpf_only-v1-3-d1cfad2f4cd1@arm.com>
On 3/23/26 8:40 AM, Leo Yan wrote:
> 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)
Acked-by: Ihor Solodrai <ihor.solodrai@linux.dev>
>
> # flags specific for shared library
> SHLIB_FLAGS := -DSHARED -fPIC
>
next prev parent reply other threads:[~2026-03-23 22:50 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 ` [PATCH 3/6] libbpf: Initialize CFLAGS before including Makefile.include Leo Yan
2026-03-23 22:50 ` Ihor Solodrai [this message]
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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