I was reading "A Tour of C++, Third Edition" and I found this "Hello World" example:

import std;

int main() {
    std::cout << "Hello, World!\n"; 
}

I am completely new to C++ and I wanted to try this example.

I made a file "hello.cpp" with that content and I tried to compile it with clang like this: clang hello.cpp

This gives me the error "unknown type name 'import'" because I have to specify a newer C++ version. I can do that like this:

clang --std=c++23 hello.cpp

Unfortunately the default clang version is a bit too old and gives this error:

invalid value 'c++23' in '--std=c++23'

Luckily it is easy to install a new version of clang with brew:

brew install llvm@17

(The default llvm version is 18 at the moment, but that gives me this error: import of module 'std' imported non C++20 importable modules)

After installing there is some usage information about LDFLAGS and CPPFLAGS:

export LDFLAGS="-L/opt/homebrew/opt/llvm@17/lib/c++ -Wl,-rpath,/opt/homebrew/opt/llvm@17/lib/c++"
export CPPFLAGS="-I/opt/homebrew/opt/llvm@17/include"

Now I can compile my source like this:

/opt/homebrew/Cellar/llvm@17/17.0.6/bin/clang++ --std=c++23 -fmodules ./hello.cpp

(Don't forget -fmodules)

This results in "a.out" that I can finally run!

The next steps are probably using cmake and getting it working with vscode, but this is it for now.

Happy coding.

Update:
I tried getting it to work with clangd in vscode, but it seems modules is not yet supported: https://github.com/clangd/clangd/issues/1293

I had a .clangd file like this:

CompileFlags:
  Add: [-std=c++23, -fmodules, -L/opt/homebrew/opt/llvm@17/lib/c++, '-Wl,-rpath,/opt/homebrew/opt/llvm@17/lib/c++', -I/opt/homebrew/opt/llvm@17/include"]
  Compiler: /opt/homebrew/Cellar/llvm@17/17.0.6/bin/clang++

And this in settings.json for the clangd extension:
"clangd.path": "/opt/homebrew/Cellar/llvm@17/17.0.6/bin/clangd"