I have been trying to find CMake option to build libc++ only. In the past (LLVM 13.0.0) I was able to launch a Cmake command directly from the libcxx directory but from the more recent version, I seem to need to build it from the root of the llvm-project with the option -DLLVM_ENABLE_RUNTIMES="libcxx".
This takes way longer (>3K build targets instead of the 300 I'm used to).
cmake -GNinja -DLLVM_PATH="${LLVM_FOLDER}/llvm" \
-DCMAKE_BUILD_TYPE=Release \
-DCMAKE_CXX_COMPILER="clang++" \
-DCMAKE_C_COMPILER="clang" \
-DLIBCXX_CXX_ABI_INCLUDE_PATHS="${LLVM_FOLDER}/libcxxabi/include" \
-DLIBCXX_CXX_ABI=libcxxabi \
-DLIBCXX_CXX_ABI_LIBRARY_PATH="${BUILD_DIR}/lib" \
-DLIBCXX_HAS_GCC_S_LIB=ON \
-DLIBCXX_ENABLE_SHARED=ON \
-DLIBCXX_ENABLE_FILESYSTEM=OFF \
-DLLVM_ENABLE_RUNTIMES="libunwind;libcxxabi;libcxx" \
-DLIBCXX_BUILD_BENCHMARKS_NATIVE_STDLIB=OFF \
-DLLVM_THIRD_PARTY_DIR=. \
-DLIBCXX_INCLUDE_BENCHMARKS=OFF \
"${LLVM_FOLDER}/libcxx"
This return an error about a missing build target:
CMake Error at src/CMakeLists.txt:309 (add_dependencies):
The dependency target "cxx" of target "cxxabi-test-depends" does not exist.
I face the same issue with libcxxabi.
Google only returns outdated documentation. Any help would be welcome!
For me the key was to set -S runtimes and it went down to around 1'000 targets which are quickly compiled.