`wide-exec-charset` dose not change the charset of `wchar_t` - c++

Question

Here is the simple C++ code.
#include <iostream>
#include <locale>
int main() {
std::wcout.sync_with_stdio(false);
std::wcout.imbue(std::locale(""));
std::cout << std::locale("").name() << std::endl; // C.UTF-8
wchar_t s {L'\xd0b8'};
std::wcout << s << std::endl;
// expected: и
// actual: 킸
}
'\xd0b8' is и in UTF-8 and is 킸 in UTF-16
The reference mentioned:
The encoding of narrow multibyte string literals (1) and wide string literals (2) is implementation-defined. For example, gcc selects them with the commandline options -fexec-charset and -fwide-exec-charset.
I complied and executed the code with g++ -O3 -fwide-exec-charset=UTF-8 source.cc -o out.a && out.a in Ubuntu 20.04.1 LTS (WSL) and expected the output is и, however, the actual output is 킸. g++ doesn't treat the hex in the literal string which was used to directly initialize the wide char s. How to make g++ consider the wide char in UTF-8?
System Infomation:
> lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.1 LTS
Release: 20.04
Codename: focal
> g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/9/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 9.3.0-10ubuntu2' --with-bugurl=file:///usr/share/doc/gcc-9/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,gm2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-9 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none,hsa --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 9.3.0 (Ubuntu 9.3.0-10ubuntu2)

Answer 1

man gcc says
-fwide-exec-charset=charset
Set the wide execution character set, used for wide string and character
constants. The default is UTF-32 or UTF-16, whichever corresponds to the width
of "wchar_t". As with -fexec-charset, charset can be any encoding supported by
the system's "iconv" library routine; however, you will have problems with
encodings that do not fit exactly in "wchar_t".
UTF-8 is a multi-byte encoding which does not fit exactly in wchar_t. So you've got exactly what is specified in the documentation: problems. Since sizeof(wchar_t) on Linux is 4, you need to specify a 4-bytes-wide encoding such as UTF-32.
There is no real reason to use wchar_t for anything except interfacing with legacy code anyway.