linux-kernel - [PATCH 1/2] selftests/openat2: fix clang build failures: -static-libasan, LOCAL

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Date: Fri,  3 May 2024 21:43:35 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Shuah Khan <shuah@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Christian Brauner <brauner@...nel.org>,
	Muhammad Usama Anjum <usama.anjum@...labora.com>,
	Alexey Gladkov <legion@...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 1/2] selftests/openat2: fix clang build failures: -static-libasan, LOCAL_HDRS

When building with clang via:

    make LLVM=1 -C tools/testing/selftests

two distinct failures occur:

1) gcc requires -static-libasan in order to ensure that Address
Sanitizer's library is the first one loaded. However, this leads to
build failures on clang, when building via:

       make LLVM=1 -C tools/testing/selftests

However, clang already does the right thing by default: it statically
links the Address Sanitizer if -fsanitize is specified. Therefore, fix
this by simply omitting -static-libasan for clang builds. And leave
behind a comment, because the whole reason for static linking might not
be obvious.

2) clang won't accept invocations of this form, but gcc will:

    $(CC) file1.c header2.h

Fix this by using selftests/lib.mk facilities for tracking local header
file dependencies: add them to LOCAL_HDRS, leaving only the .c files to
be passed to the compiler.

Cc: Ryan Roberts <ryan.roberts@....com>
Signed-off-by: John Hubbard <jhubbard@...dia.com>
---
 tools/testing/selftests/openat2/Makefile | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
index 254d676a2689..185dc76ebb5f 100644
--- a/tools/testing/selftests/openat2/Makefile
+++ b/tools/testing/selftests/openat2/Makefile
@@ -1,8 +1,18 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan
+CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
 TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
 
+# gcc requires -static-libasan in order to ensure that Address Sanitizer's
+# library is the first one loaded. However, clang already statically links the
+# Address Sanitizer if -fsanitize is specified. Therefore, simply omit
+# -static-libasan for clang builds.
+ifeq ($(LLVM),)
+    CFLAGS += -static-libasan
+endif
+
+LOCAL_HDRS += helpers.h
+
 include ../lib.mk
 
-$(TEST_GEN_PROGS): helpers.c helpers.h
+$(TEST_GEN_PROGS): helpers.c

base-commit: ddb4c3f25b7b95df3d6932db0b379d768a6ebdf7
prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
-- 
2.45.0