add openmp and libc++ to clang

[VinInn]

In my clang installation I used this

cmake -S llvm -B build -G Ninja -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;compiler-rt;openmp" -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" -DCMAKE_INSTALL_PREFIX=/afs/cern.ch/user/i/innocent/w5/
ninja -j 8 -k 1024 -C build
ninja install -C build

and managed to use openmp and libc++

clang++ test.cc -o sample -fopenmp -stdlib=libstd++ -v
clang++ test.cc -o sample -fopenmp -stdlib=libc++ -v

even compiling for gpu target...

clang++ --offload-arch=native -xhip testGPU.cc -o sample -fopenmp -v -stdlib=libc++ -std=c++20 > & /dev/null ; ./sample
clang++ --offload-arch=native -xhip testGPU.cc -o sample -fopenmp -v -stdlib=libstdc++ -std=c++20 > & /dev/null ; ./sample

the latter uses the "system" gcc (well the one I used to build clang) not a random local one as hip does...

it could be useful to have it in cmsdist if anybody else is interested

[cmsbuild]

cms-bot internal usage

[cmsbuild]

A new Issue was created by @VinInn.

@Dr15Jones, @antoniovilela, @makortel, @mandrenguyen, @rappoccio, @sextonkennedy, @smuzaffar can you please review it and eventually sign/assign? Thanks.

cms-bot commands are listed here

[smuzaffar]

@VinInn , I have add -DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" to our llvm build https://github.com/cms-sw/cmsdist/pull/9585/files#diff-c2d3d97c0a4df72090325e985e0d86c7711a23e659157bff2b17bf23f48d624fR45 . Can you please check latest CMSSW_15_0_CLANG_X IBs to see if you can use openmp and libc++ ?

[smuzaffar]

I was not able to build clang++ test.cc -o sample -fopenmp -stdlib=libstd++ -v successfully as it complains about '-stdlib=libstd++'

Singularity> clang++ test.cc -o sample -fopenmp -stdlib=libstd++ -v
clang version 19.1.6
Target: x86_64-redhat-linux-gnu
Thread model: posix
InstalledDir: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin
Configuration file: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/clang++.cfg
Found candidate GCC installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1
Selected GCC installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1
Candidate multilib: .;@m64
Selected multilib: .;@m64
Found CUDA installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/cuda/12.6.3-5a3ec66b8ad2d34f244786daf432fc85, version 
clang++: error: invalid library name in argument '-stdlib=libstd++'

[smuzaffar]

I guess it should be -stdlib=libstdc++ (which works) .... right?

[VinInn]

with CMSSW_15_0_CLANG_X_2025-01-28-2300

I get this
innocent@lxplus809 ctest]$ clang++ -O3 memoryTest.cpp -stdlib=libc++
/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/bin/ld: cannot find -lc++: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

[innocent@lxplus809 ctest]$ clang++ -O3 memoryTest.cpp -stdlib=libc++ -v
clang version 19.1.6
Target: x86_64-redhat-linux-gnu
Thread model: posix
InstalledDir: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin
Configuration file: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/clang++.cfg
Found candidate GCC installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1
Selected GCC installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1
Candidate multilib: .;@m64
Selected multilib: .;@m64
Found CUDA installation: /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/cuda/12.6.3-5a3ec66b8ad2d34f244786daf432fc85, version
"/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/clang-19" -cc1 -triple x86_64-redhat-linux-gnu -emit-obj -dumpdir a- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name memoryTest.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fdebug-compilation-dir=/afs/cern.ch/user/i/innocent/public/ctest -v -fcoverage-compilation-dir=/afs/cern.ch/user/i/innocent/public/ctest -resource-dir /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/lib64/clang/19 -internal-isystem /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/../include/x86_64-redhat-linux-gnu/c++/v1 -internal-isystem /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/../include/c++/v1 -internal-isystem /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/lib64/clang/19/include -internal-isystem /usr/local/include -internal-isystem /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -O3 -fdeprecated-macro -ferror-limit 19 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fcxx-exceptions -fexceptions -fcolor-diagnostics -vectorize-loops -vectorize-slp -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/innocent/memoryTest-235243.o -x c++ memoryTest.cpp
clang -cc1 version 19.1.6 based upon LLVM 19.1.6 default target x86_64-redhat-linux-gnu
ignoring nonexistent directory "/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/include"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/../include/x86_64-redhat-linux-gnu/c++/v1
/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/bin/../include/c++/v1
/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/lib64/clang/19/include
/usr/local/include
/usr/include
End of search list.
"/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/bin/ld" --hash-style=gnu --eh-frame-hdr -m elf_x86_64 -pie -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o a.out /lib/../lib64/Scrt1.o /lib/../lib64/crti.o /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/crtbeginS.o -L/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/llvm/19.1.6-b3e79a82e07a6c1c8c45519298a26f36/lib64/clang/19/lib/x86_64-redhat-linux-gnu -L/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1 -L/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/lib -L/lib -L/usr/lib /tmp/innocent/memoryTest-235243.o -lc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/crtendS.o /lib/../lib64/crtn.o
/cvmfs/cms-ib.cern.ch/sw/x86_64/nweek-02874/el8_amd64_gcc12/external/gcc/12.3.1-40d504be6370b5a30e3947a6e575ca28/lib/gcc/x86_64-redhat-linux-gnu/12.3.1/../../../../x86_64-redhat-linux-gnu/bin/ld: cannot find -lc++: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

maybe one need more in the library path