How to build libcxx/libcxxabi for riscv target

Runtimes
,
1

Hello,

I am tring to build libcxx and libcxxabi for riscv target, by following steps here Building libc++ — libc++ documentation , using the script below:

    BUILDDIR=${HOME}/rvllvm
    TARGET=riscv64-unknown-elf
    arch=rv32imac
    abi=ilp32
    llvm_bin=${BUILDDIR}/bin
    target=${TARGET}
    runtimes_flags="-march=${arch} -mabi=${abi} -mcmodel=medany -ffunction-sections -fdata-sections"
    instlibprefix=${INSTDIR}/${target}/lib/${arch}/${abi}
    instincprefix=${INSTDIR}/${target}/include
    mkdir -p buildruntime
    pushd buildruntime
    cmake -G Ninja \
        -DCMAKE_AR=${llvm_bin}/llvm-ar \
        -DCMAKE_ASM_COMPILER_TARGET=${target} \
        -DCMAKE_ASM_FLAGS="${runtimes_flags}" \
        -DCMAKE_BUILD_TYPE=MinSizeRel \
        -DCMAKE_CXX_COMPILER=${llvm_bin}/clang++ \
        -DCMAKE_CXX_COMPILER_TARGET=${target} \
        -DCMAKE_CXX_FLAGS="${runtimes_flags} -std=gnu++20" \
        -DCMAKE_C_COMPILER=${llvm_bin}/clang \
        -DCMAKE_C_COMPILER_TARGET=${target} \
        -DCMAKE_C_FLAGS="${runtimes_flags}" \
        -DCMAKE_INSTALL_PREFIX=${instlibprefix} \
        -DCMAKE_NM=${llvm_bin}/llvm-nm \
        -DCMAKE_RANLIB=${llvm_bin}/llvm-ranlib \
        -DCMAKE_C_COMPILER_TARGET=${TARGET}   \
        -DCMAKE_CXX_COMPILER_TARGET=${TARGET} \
        -DCMAKE_ASM_COMPILER_TARGET=${TARGTE} \
        -DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY \
        -DLLVM_ENABLE_RUNTIMES="libcxxabi;libcxx;libunwind" \
        -DLIBCXXABI_BAREMETAL=ON \
        -DLIBCXXABI_ENABLE_ASSERTIONS=OFF \
        -DLIBCXXABI_ENABLE_SHARED=OFF \
        -DLIBCXXABI_ENABLE_STATIC=ON \
        -DLIBCXXABI_LIBCXX_INCLUDES=${instincprefix}/c++/v1 \
        -DLIBCXXABI_USE_COMPILER_RT=ON \
        -DLIBCXXABI_USE_LLVM_UNWINDER=ON \
        -DLIBCXX_CXX_ABI=libcxxabi \
        -DLIBCXX_ENABLE_DEBUG_MODE_SUPPORT=OFF \
        -DLIBCXX_ENABLE_FILESYSTEM=OFF \
        -DLIBCXX_ENABLE_SHARED=OFF \
        -DLIBCXX_ENABLE_STATIC=ON \
        -DLIBCXX_INCLUDE_BENCHMARKS=OFF \
        -DLIBUNWIND_ENABLE_SHARED=OFF \
        -DLIBUNWIND_ENABLE_STATIC=ON \
        -DLIBUNWIND_IS_BAREMETAL=ON \
        -DLIBUNWIND_REMEMBER_HEAP_ALLOC=ON \
        -DLIBUNWIND_USE_COMPILER_RT=ON \
        -DLIBCXXABI_ENABLE_EXCEPTIONS=OFF \
        -DLIBCXXABI_ENABLE_THREADS=OFF \
        -DLIBCXX_ENABLE_EXCEPTIONS=OFF \
        -DLIBCXX_ENABLE_MONOTONIC_CLOCK=OFF \
        -DLIBCXX_ENABLE_RANDOM_DEVICE=OFF \
        -DLIBCXX_ENABLE_RTTI=OFF \
        -DLIBCXX_ENABLE_THREADS=OFF \
        -DLIBCXX_ENABLE_WIDE_CHARACTERS=ON \
        -DLIBUNWIND_ENABLE_THREADS=OFF \
        -DLLVM_CONFIG_PATH=${llvm_bin}/llvm-config \
        ../runtimes
    ninja

It build failed with following error:

llvm-project/llvmbuild/202302/buildruntime/include/c++/v1/math.h:972:92: error: no member named 'logl' in the global namespace
inline _LIBCPP_INLINE_VISIBILITY long double log(long double __lcpp_x) _NOEXCEPT {return ::logl(__lcpp_x);}
                                                                                         ~~^
llvm-project/llvmbuild/202302/buildruntime/include/c++/v1/math.h:984:94: error: no member named 'log10l' in the global namespace
inline _LIBCPP_INLINE_VISIBILITY long double log10(long double __lcpp_x) _NOEXCEPT {return ::log10l(__lcpp_x);}
                                                                                           ~~^
llvm-project/llvmbuild/202302/buildruntime/include/c++/v1/math.h:996:116: error: no member named 'modfl' in the global namespace
inline _LIBCPP_INLINE_VISIBILITY long double modf(long double __lcpp_x, long double* __lcpp_y) _NOEXCEPT {return ::modfl(__lcpp_x, __lcpp_y);}
                                                                                                                 ~~^
llvm-project/llvmbuild/202302/buildruntime/include/c++/v1/math.h:1003:114: error: no member named 'powl' in the global namespace
inline _LIBCPP_INLINE_VISIBILITY long double pow(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::powl(__lcpp_x, __lcpp_y);}
                                                                                                               ~~^
llvm-project/llvmbuild/202302/buildruntime/include/c++/v1/math.h:1026:92: error: no member named 'sinl' in the global namespace
inline _LIBCPP_INLINE_VISIBILITY long double sin(long double __lcpp_x) _NOEXCEPT {return ::sinl(__lcpp_x);}
                                                                                         ~~^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
[855/860] Building CXX object libcxx/src/CMakeFiles/cxx_static.dir/locale.cpp.o

Did anyone met the same issue? could you give some guidance.

Thanks

2

I’ve no experience with riscv. Looking at the errors it seems you libc doesn’t have an implementation of powl. libc++ depends on libc to provide these functions.

Does powl work in C applications?

3

Ok, I got it. So it rely on libc, or I can use newlibc to build it. Thanks