linux-kernel - [PATCH v2] selftests/user_events: silence a clang warning: address of packed member

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Message-ID: <20240527214704.300444-1-jhubbard@nvidia.com>
Date: Mon, 27 May 2024 14:47:04 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Shuah Khan <shuah@...nel.org>
Cc: Beau Belgrave <beaub@...ux.microsoft.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mark Brown <broonie@...nel.org>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	sunliming <sunliming@...inos.cn>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Valentin Obst <kernel@...entinobst.de>,
	linux-kselftest@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	llvm@...ts.linux.dev,
	John Hubbard <jhubbard@...dia.com>
Subject: [PATCH v2] selftests/user_events: silence a clang warning: address of packed member

When building with clang, via:

    make LLVM=1 -C tools/testing/selftest

..clang warns about "taking address of packed member 'write_index' ".
This is not particularly helpful, because the test code really wants to
write to exactly this location, and if it ends up being unaligned, then
the test won't work (and may segfault, depending on the CPU type).

If that ever comes up, it will be obvious and can be fixed. But all it's
doing now is prevent a clean clang build, so disable the warning.

Signed-off-by: John Hubbard <jhubbard@...dia.com>
---

Changes since the first version:

1) Rebased onto Linux 6.10-rc1


thanks,
John Hubbard


 tools/testing/selftests/user_events/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/user_events/Makefile b/tools/testing/selftests/user_events/Makefile
index 10fcd0066203..617e94344711 100644
--- a/tools/testing/selftests/user_events/Makefile
+++ b/tools/testing/selftests/user_events/Makefile
@@ -1,5 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 CFLAGS += -Wl,-no-as-needed -Wall $(KHDR_INCLUDES)
+
+ifneq ($(LLVM),)
+    CFLAGS += -Wno-address-of-packed-member
+endif
+
 LDLIBS += -lrt -lpthread -lm
 
 TEST_GEN_PROGS = ftrace_test dyn_test perf_test abi_test

base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b
-- 
2.45.1