C++23 Standard Library Modules Example

This project demonstrates how to use C++23's import std; feature with CMake.

Prerequisites

To build this project, you need a compiler that supports C++23 Standard Library Modules:

• Clang 17+ (Upstream LLVM, not Apple Clang)
• GCC 14+
• CMake 3.30+

The "Magic" in CMakeLists.txt

The line:

set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")

is required because support for import std; is still experimental in CMake. This UUID is a "gatekeeper" hash that acknowledges you are using an unstable feature. It may change in future CMake versions.

Building on macOS

Apple Clang (the default clang++ on macOS) does not fully support import std; yet. You need to install upstream LLVM:

brew install llvm

Then build with the specific compiler:

# Point to the Homebrew LLVM clang++
export CXX=$(brew --prefix llvm)/bin/clang++
cmake -S . -B build
cmake --build build
./build/main