linux-kernel - [PATCH bpf-next v2 1/2] bpftool: Add -Wformat-signedness flag to detect format errors

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Message-ID: <20250311112809.81901-2-jiayuan.chen@linux.dev>
Date: Tue, 11 Mar 2025 19:28:08 +0800
From: Jiayuan Chen <jiayuan.chen@...ux.dev>
To: bpf@...r.kernel.org,
	qmo@...nel.org
Cc: daniel@...earbox.net,
	linux-kernel@...r.kernel.org,
	ast@...nel.org,
	davem@...emloft.net,
	kuba@...nel.org,
	hawk@...nel.org,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	mrpre@....com,
	Jiayuan Chen <jiayuan.chen@...ux.dev>
Subject: [PATCH bpf-next v2 1/2] bpftool: Add -Wformat-signedness flag to detect format errors

This commit adds the -Wformat-signedness compiler flag to detect and
prevent printf format errors, where signed or unsigned types are
mismatched with format specifiers. This helps to catch potential issues at
compile-time, ensuring that our code is more robust and reliable. With
this flag, the compiler will now warn about incorrect format strings, such
as using %d with unsigned types or %u with signed types.

Signed-off-by: Jiayuan Chen <jiayuan.chen@...ux.dev>
---
 tools/bpf/bpftool/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index dd9f3ec84201..efe867dd2821 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -71,7 +71,12 @@ prefix ?= /usr/local
 bash_compdir ?= /usr/share/bash-completion/completions
 
 CFLAGS += -O2
-CFLAGS += -W -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers
+CFLAGS += -W
+CFLAGS += -Wall
+CFLAGS += -Wextra
+CFLAGS += -Wformat-signedness
+CFLAGS += -Wno-unused-parameter
+CFLAGS += -Wno-missing-field-initializers
 CFLAGS += $(filter-out -Wswitch-enum -Wnested-externs,$(EXTRA_WARNINGS))
 CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
 	-I$(or $(OUTPUT),.) \
-- 
2.47.1