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From:   Thomas Richter <tmricht@linux.ibm.com>
To:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        acme@kernel.org, wangnan0@huawei.com, jolsa@kernel.org
Cc:     svens@linux.ibm.com, gor@linux.ibm.com, sumanthk@linux.ibm.com,
        hca@linux.ibm.com, Thomas Richter <tmricht@linux.ibm.com>
Subject: [PATCH] perf build: Fix broken feature check for clang due to C++ standard and changed library packaging
Date:   Wed, 12 Jul 2023 10:30:37 +0200
Message-Id: <20230712083037.4081444-2-tmricht@linux.ibm.com>
In-Reply-To: <20230712083037.4081444-1-tmricht@linux.ibm.com>
References: <20230712083037.4081444-1-tmricht@linux.ibm.com>
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Perf build auto-detects features and packages already installed
for its build. This is done in directory tools/build/feature. This
directory contains small sample programs. When they successfully
compile the necessary prereqs in form of libraries and header
files are present.

Such a check is also done for clang. And this check fails.

Fix this and update to the latest C++ standard and use the
new library provided by clang (which contains new packaging)
see this link for reference:
 https://fedoraproject.org/wiki/Changes/Stop-Shipping-Individual-Component-Libraries-In-clang-lib-Package

Output before:
 # rm -f ./test-clang.bin; make test-clang.bin; ./test-clang.bin; \
	ll test-clang.make.output
 g++  -MD -Wall -Werror -o test-clang.bin test-clang.cpp \
	 	> test-clang.make.output 2>&1 -std=gnu++14 \
	-I/usr/include 		\
	-L/usr/lib64		\
	-Wl,--start-group -lclangBasic -lclangDriver	\
	  -lclangFrontend -lclangEdit -lclangLex	\
	  -lclangAST -Wl,--end-group 			\
	-lLLVM-16	\
			\
	> test-clang.make.output 2>&1
 make: *** [Makefile:356: test-clang.bin] Error 1
 -bash: ./test-clang.bin: No such file or directory
 -rw-r--r--. 1 root root 252041 Jul 12 09:56 test-clang.make.output
 #

File test-clang.make.output contains many lines of unreferenced
symbols.

Output after:
 # rm -f ./test-clang.bin; make test-clang.bin; ./test-clang.bin; \
	cat test-clang.make.output
 g++  -MD -Wall -Werror -o test-clang.bin test-clang.cpp \
	 > test-clang.make.output 2>&1 -std=gnu++17	\
	-I/usr/include 		\
	-L/usr/lib64		\
	-Wl,--start-group -lclang-cpp -Wl,--end-group	\
	-lLLVM-16	\
			\
	> test-clang.make.output 2>&1
 #

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/build/feature/Makefile | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index f8db69654791..0b4a6e43c5cc 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -353,12 +353,10 @@ $(OUTPUT)test-llvm-version.bin:
 		> $(@:.bin=.make.output) 2>&1
 
 $(OUTPUT)test-clang.bin:
-	$(BUILDXX) -std=gnu++14					\
+	$(BUILDXX) -std=gnu++17					\
 		-I$(shell $(LLVM_CONFIG) --includedir) 		\
 		-L$(shell $(LLVM_CONFIG) --libdir)		\
-		-Wl,--start-group -lclangBasic -lclangDriver	\
-		  -lclangFrontend -lclangEdit -lclangLex	\
-		  -lclangAST -Wl,--end-group 			\
+		-Wl,--start-group -lclang-cpp -Wl,--end-group	\
 		$(shell $(LLVM_CONFIG) --libs Core option)	\
 		$(shell $(LLVM_CONFIG) --system-libs)		\
 		> $(@:.bin=.make.output) 2>&1
-- 
2.41.0