Clang without GCC or MSVC - c++

Question

I'd like to use clang without GCC on Linux and without MSVC on Windows. My understanding is that this wasn't possible in the past due to:
A LLVM linker wasn't available.
A compatible STL wasn't available.
However, my impression what that this should be possible with v8.0.0 as there is now a viable linker and a compatible STL library.
Unfortunately, I get different errors on Linux and Windows when exercising this scenario (see more info below).
Can you help me out with this? Unfortunately, I've found it a bit challenging to find a definitive answer through various searches.
Thanks for the help!
Test Code: test.cpp
#include <vector>
#include <iostream>
int main(void) {
std::vector<int> const v{ 1, 2, 3 };
std::cout << "Hello world\n";
std::cout << v[0] << "\n";
return 0;
}
Linux output
The following output is from Windows Subsystem for Linux, but the behavior is the same on a proper Linux install.
clang -v /mnt/c/Temp/test.cpp -I/mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/include/c++/v1
clang version 8.0.0 (tags/RELEASE_800/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8.0.1
"/mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/bin/clang-8" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name test.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -v -resource-dir /mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/lib/clang/8.0.0 -I /mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/include/c++/v1 -internal-isystem /usr/local/include -internal-isystem /mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/lib/clang/8.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdeprecated-macro -fdebug-compilation-dir /mnt/c/Code/v3/Common/cpp/Clang/8 -ferror-limit 19 -fmessage-length 200 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/test-284194.o -x c++ /mnt/c/Temp/test.cpp -faddrsig
clang -cc1 version 8.0.0 based upon LLVM 8.0.0 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/include/c++/v1
/usr/local/include
/mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/lib/clang/8.0.0/include
/usr/include
End of search list.
In file included from /mnt/c/Temp/test.cpp:1:
In file included from /mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/include/c++/v1/vector:273:
/mnt/c/Code/v3/Common/cpp/Clang/8/Tools/Clang/v8.0.0/Ubuntu/wsl/include/c++/v1/__config:206:12: fatal error: 'features.h' file not found
# include <features.h>
^~~~~~~~~~~~
1 error generated.
Windows Output
clang -v c:\temp\test.cpp
clang version 8.0.0 (tags/RELEASE_800/final)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\bin
clang: warning: unable to find a Visual Studio installation; try running Clang from a developer command prompt [-Wmsvc-not-found]
"C:\\Code\\v3\\Common\\cpp\\Clang\\8\\Tools\\Clang\\v8.0.0\\Windows\\DefaultEnv\\bin\\clang.exe" -cc1 -triple x86_64-pc-windows-msvc19.11.0 -emit-obj -mrelax-all -mincremental-linker-compatible -disable-free -disable-llvm-verifier -discard-value-names -main-file-name test.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -momit-leaf-frame-pointer -v -resource-dir "C:\\Code\\v3\\Common\\cpp\\Clang\\8\\Tools\\Clang\\v8.0.0\\Windows\\DefaultEnv\\lib\\clang\\8.0.0" -internal-isystem "C:\\Code\\v3\\Common\\cpp\\Clang\\8\\Tools\\Clang\\v8.0.0\\Windows\\DefaultEnv\\lib\\clang\\8.0.0\\include" -internal-isystem "C:\\Code\\v3\\Common\\cpp\\Clang\\8\\Tools\\Clang\\v8.0.0\\Windows\\DefaultEnv\\include\\c++\\v1" -internal-isystem "C:\\Code\\v3\\Common\\cpp\\Common\\Libraries\\C++\\Catch2\\v2.7.0" -internal-isystem "C:\\Code\\v3\\Common\\cpp\\Common\\Libraries\\C++\\GSL\\v2.0.0\\include" -fdeprecated-macro -fdebug-compilation-dir "C:\\Code\\v3\\Common\\cpp\\Clang\\8" -ferror-limit 19 -fmessage-length 200 -fno-use-cxa-atexit -fms-extensions -fms-compatibility -fms-compatibility-version=19.11 -std=c++14 -fdelayed-template-parsing -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o "C:\\Users\\brownell\\AppData\\Local\\Temp\\test-9329b0.o" -x c++ "c:\\temp\\test.cpp" -faddrsig
clang -cc1 version 8.0.0 based upon LLVM 8.0.0 default target x86_64-pc-windows-msvc
#include "..." search starts here:
#include <...> search starts here:
C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\lib\clang\8.0.0\include
C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\include\c++\v1
C:\Code\v3\Common\cpp\Common\Libraries\C++\Catch2\v2.7.0
C:\Code\v3\Common\cpp\Common\Libraries\C++\GSL\v2.0.0\include
End of search list.
In file included from c:\temp\test.cpp:1:
In file included from C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\include\c++\v1\vector:274:
In file included from C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\include\c++\v1\iosfwd:96:
C:\Code\v3\Common\cpp\Clang\8\Tools\Clang\v8.0.0\Windows\DefaultEnv\include\c++\v1\wchar.h:119:15: fatal error: 'wchar.h' file not found
#include_next <wchar.h>
^~~~~~~~~
1 error generated.

Answer 1

For linux
On linux clag will default to using gnu's implementation of the standard library which is libstdc++. To use llvm's implementation - libc++ - you first need to install it. On ubuntu, for instance: sudo apt install libc++-9-dev libc++abi-9-dev. You might need to add the apple repos. Follow these instructions for more systems and latest versions. Then you need to explicit specify it when compiling: -stdlib=libc++. Please see https://libcxx.llvm.org/docs/UsingLibcxx.html
For linking install lld (sudo apt install lld-9) then specify it when compiling with -fuse-ld=lld