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From:   Andre Przywara <andre.przywara@arm.com>
To:     Shuah Khan <shuah@kernel.org>, Nhat Pham <nphamcs@gmail.com>,
        Johannes Weiner <hannes@cmpxchg.org>
Cc:     linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/3] selftests: cachestat: properly link in librt
Date:   Tue, 15 Aug 2023 16:56:10 +0100
Message-Id: <20230815155612.2535947-2-andre.przywara@arm.com>
In-Reply-To: <20230815155612.2535947-1-andre.przywara@arm.com>
References: <20230815155612.2535947-1-andre.przywara@arm.com>
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Libraries should be listed last on the compiler's command line, so that
the linker can look for and find still unresolved symbols. The librt
library, required for the shm_* functions, was announced using CFLAGS,
which puts the library *before* the source files, and fails compilation
on my system:
======================
gcc -isystem /src/linux-selftests/usr/include -Wall -lrt test_cachestat.c
  -o /src/linux-selftests/kselftest/cachestat/test_cachestat
/usr/bin/ld: /tmp/cceQWO3u.o: in function `test_cachestat_shmem':
test_cachestat.c:(.text+0x890): undefined reference to `shm_open'
/usr/bin/ld: test_cachestat.c:(.text+0x99c): undefined reference to `shm_unlink'
collect2: error: ld returned 1 exit status
make[4]: *** [../lib.mk:181: /src/linux-selftests/kselftest/cachestat/test_cachestat] Error 1
======================

Announce the library using the LDLIBS variable, which ensures the proper
ordering on the command line.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 tools/testing/selftests/cachestat/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/cachestat/Makefile b/tools/testing/selftests/cachestat/Makefile
index fca73aaa7d141..778b54ebb0364 100644
--- a/tools/testing/selftests/cachestat/Makefile
+++ b/tools/testing/selftests/cachestat/Makefile
@@ -3,6 +3,6 @@ TEST_GEN_PROGS := test_cachestat
 
 CFLAGS += $(KHDR_INCLUDES)
 CFLAGS += -Wall
-CFLAGS += -lrt
+LDLIBS += -lrt
 
 include ../lib.mk
-- 
2.25.1