Libc++.so.1 (llvmtools) requires libatomic.so.1

[dslm4515]

llvmtools' libc++.so.1 from libcxx should NOT rely on libatomic.so.1, which is provided by GCC.

$ ldd /llvmtools/lib/libc++.so.1
        ldd (0x7fb67cb49000)
        libc.so => ldd (0x7fb67cb49000)
Error loading shared library libatomic.so.1: No such file or directory (needed by /llvmtools/lib/libc++.so.1)
        libunwind.so.1 => /llvmtools/lib/../lib/libunwind.so.1 (0x7fb67ca6b000)
        libc++abi.so.1 => /llvmtools/lib/../lib/libc++abi.so.1 (0x7fb67ca0f000)

This will require to build LLVM for llvmtools with a LD_LIBARARY_PATH hack

[owl4ce]

hmmmmmm
http://llvmweekly.org/issue/336

[dslm4515]

Re-built llvmtools and made sure libcxx did not require libatomic.

now llvm/clang for llvmtools fails to build:

FAILED: include/llvm/IR/Attributes.inc 
cd /mnt/cmlfs/sources/llvm/build && /mnt/cmlfs/sources/llvm/build/bin/llvm-tblgen -gen-attrs -I /mnt/cmlfs/sources/llvm/include/llvm/IR -I /mnt/cmlfs/sources/llvm/build/include -I /mnt/cmlfs/sources/llvm/include /mnt/cmlfs/sources/llvm/include/llvm/IR/Attributes.td --write-if-changed -o include/llvm/IR/Attributes.inc -d include/llvm/IR/Attributes.inc.d
/bin/sh: /mnt/cmlfs/sources/llvm/build/bin/llvm-tblgen: No such file or directory
[220/3316] Building CXX object lib/BinaryFormat/CMakeFiles/LLVMBinaryFormat.dir/MsgPackDocument.cpp.o
ninja: build stopped: subcommand failed.

[dslm4515]

hmmmmmm
http://llvmweekly.org/issue/336

Looks like for libcxx, I’ll have to set a flag to disable libatomic

[owl4ce]

hmmmmmm
http://llvmweekly.org/issue/336

Looks like for libcxx, I’ll have to set a flag to disable libatomic

How?

[dslm4515]

Looks like I’ll have to patch libcxx/cmake/Modules/CheckLibcxxAtomic.cmake

[dslm4515]

Although it’s strange that after rebuilding llvmtools... llvmtools’ Libc++.so.1 no longer requires libatomic.

not sure if it matters that PATH=/cgnutools/bin:/llvmtools/bin:/bin:/usr/bin

[owl4ce]

Commenting this will disable libatomic detection for Linux when configure libcxx (cmake).

check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)

projects/libcxx/cmake/config-ix.cmake

102 else()
103   check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
104   check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
105   check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
106   set(LIBCXX_HAS_SYSTEM_LIB NO)
107 #  check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
108 endif()

[owl4ce]

I wonder how atomic detected when building libcxx

[dslm4515]

I probably will include a check for libunwind, libcxx, and libcxxabi to make sure there are no GCC dependencies. It’s annoying to finally build LLVM for llvmtools only to realize llvmtools has GCC dependencies.

[owl4ce]

LLVM 12.0.0

Successful by using above trick!
While building libcxx in llvmtools (deletes matched PATTERN):

sed -i '/check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)/d' \
${LLVMSRC}/projects/libcxx/cmake/config-ix.cmake

Progress of building Clang/LLVM in llvmtools (I'm prefer GNU's Make btw):

[ 99%] Built target clangStaticAnalyzerFrontend
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
[ 99%] Building C object tools/clang/tools/c-index-test/CMakeFiles/c-index-test.dir/c-index-test.c.o
[ 99%] Building CXX object tools/clang/tools/c-index-test/CMakeFiles/c-index-test.dir/core_main.cpp.o
[100%] Linking CXX executable ../../../../bin/c-arcmt-test
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
[100%] Built target c-arcmt-test
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
[100%] Linking CXX static library ../../../../lib/libclangFrontendTool.a
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
[100%] Built target clangFrontendTool
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
make[2]: Entering directory '/mnt/cmlfs/sources/llvm/build'
[100%] Linking CXX static library ../../../../../lib/libclangDependencyScanning.a
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
[100%] Built target clangDependencyScanning
[100%] Linking CXX executable ../../../../bin/c-index-test
make[2]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
[100%] Built target c-index-test
make[1]: Leaving directory '/mnt/cmlfs/sources/llvm/build'
make: Leaving directory '/mnt/cmlfs/sources/llvm/build

@dslm4515

[dslm4515]

Commenting this will disable libatomic detection for Linux when configure libcxx (cmake).

check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)

projects/libcxx/cmake/config-ix.cmake

102 else()
103   check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
104   check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
105   check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
106   set(LIBCXX_HAS_SYSTEM_LIB NO)
107 #  check_library_exists(atomic __atomic_fetch_add_8 "" LIBCXX_HAS_ATOMIC_LIB)
108 endif()

Closing issue as @owl4ce fixed issue