[llvm-dev] Which libc/libc++ to use with LLVM RISCV?

[Tobias Hieta via llvm-dev]

LLVM libc is not ready for use yet. You need to either have a sysroot from
the target system or build something like musl libc yourself. Check this
guide, it should apply to risc as well:

https://llvm.org/docs/HowToCrossCompileLLVM.html


On Sat, 22 May 2021 at 18:41, Chen Zou via llvm-dev <llvm-dev at lists.llvm.org>
wrote:

>
> I hope I am posting this question in the right place.
>
> Knowing that rvv intrinsics support is pushed to LVV upstream. I am eager
> to try it out.
> But it seems I could not get libc set up correctly.
>
> If I configured LLVM compilation with:
> cmake -G "Unix Makefiles" -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi"
>  -DCMAKE_BUILD_TYPE="Release" -DLLVM_BUILD_TESTS=False
>  -DLLVM_TARGETS_TO_BUILD="RISCV" -DCMAKE_INSTALL_PREFIX=$RISCV   ../llvm &&
> make -j16
> I got compilation errors as attached at the end of this email.
>
> The compilation would succeed if I omit libcxx libcxxabi from
> LLVM_ENABLE_PROJECTS. But it seems clang would not find assert.h:
> clang -static --target=riscv32 -menable-experimental-extensions
> -march=rv32imv0p10 -mabi=ilp32 -g -O2 -Wall -fPIC -I../../include -std=c11
>   -c -o ../../sep/test.o ../../sep/test.c
> ../../sep/test.c:4:10: fatal error: 'stdio.h' file not found
> #include <stdio.h>
>          ^~~~~~~~~
>
>
> Attached compilation error for libcxx:
>
> In file included from
> $HOME/riscv/llvm-project/build/include/c++/v1/exception:84:0,
>          from
> $HOME/riscv/llvm-project/libcxxabi/src/cxa_default_handlers.cpp:11:
> $HOME/riscv/llvm-project/build/include/c++/v1/type_traits: In substitution
> of ‘template<class ... _Args> using _SecondType = typename
> std::__1::_MetaBase<(sizeof... (_Args) >= 2)>::_SecondImpl<_Args ...> [with
> _Args = {_Tp ..., _Dep}]’:
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1000:51: required from
> here
> $HOME/riscv/llvm-project/build/include/c++/v1/type_traits:501:117: error:
> pack expansion argument for non-pack parameter ‘<template-parameter-1-1>’
> of alias template ‘template<class, class _Second, class ...> using
> _SecondImpl = _Second’
>  using _SecondType _LIBCPP_NODEBUG_TYPE = typename
> _MetaBase<(sizeof...(_Args) >= 2)>::template _SecondImpl<_Args...>;
>                                                            ^
> In file included from
> $HOME/riscv/llvm-project/build/include/c++/v1/exception:84:0,
>          from
> $HOME/riscv/llvm-project/libcxxabi/src/cxa_default_handlers.cpp:11:
> $HOME/riscv/llvm-project/build/include/c++/v1/type_traits:473:13: note:
> declared here
>   template <class, class _Second, class...>
>        ^
> In file included from
> $HOME/riscv/llvm-project/build/include/c++/v1/memory:678:0,
>          from
> $HOME/riscv/llvm-project/libcxxabi/src/include/atomic_support.h:17,
>          from
> $HOME/riscv/llvm-project/libcxxabi/src/cxa_default_handlers.cpp:18:
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1000:66: error:
> template argument 1 is invalid
>        is_assignable<_SecondType<_Tp..., _Dep>&, _Up2 const&>
>                                  ^
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1001:9: error:
> template argument 4 is invalid
>      >::value
>      ^
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1002:9: error:
> template argument 1 is invalid
>    ,int> = 0>
>      ^
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1019:59: error:
> template argument 1 is invalid
>        is_assignable<_SecondType<_Tp..., _Dep>&, _Up2>
>                               ^
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1020:9: error:
> template argument 4 is invalid
>      >::value
>      ^
> $HOME/riscv/llvm-project/build/include/c++/v1/tuple:1021:9: error:
> template argument 1 is invalid
>    ,int> = 0>
>      ^
> projects/libcxxabi/src/CMakeFiles/cxxabi_shared.dir/build.make:95: recipe
> for target
> 'projects/libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_default_handlers.cpp.o'
> failed
> make[2]: ***
> [projects/libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_default_handlers.cpp.o]
> Error 1
> CMakeFiles/Makefile2:19706: recipe for target
> 'projects/libcxxabi/src/CMakeFiles/cxxabi_shared.dir/all' failed
> make[1]: *** [projects/libcxxabi/src/CMakeFiles/cxxabi_shared.dir/all]
> Error 2
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