CppStandardLibraryModule

Enable C++23 standard library module feature, a.k.a. import std (P2465R3) in your CMake (≥ 3.26) project. It also supported in C++20 as compiler extension.

How to do?

There are prerequisites for using this repository.

• Your compiler must support the standard library module feature.
  • Clang ≥ 17 with custom module build: support for both C++20 and C++23. Ninja ≥ 1.11 is required.
  • MSVC: support for C++23 (≥ 19.36), C++20 (≥ 19.38).
• You need CMake ≥ 3.26 for module support in CMake.

All prerequisites satisfied, your simplest program will be:

CMakeLists.txt

cmake_minimum_required(VERSION3.28)
project(CppStandardLibraryModule)
# --------------------# Enable C++20 module support in CMake.# Below code must be uncommented when use CMake < 3.28.# --------------------#if (CMAKE_VERSION VERSION_LESS "3.28.0")# if(CMAKE_VERSION VERSION_LESS "3.27.0")# set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "2182bf5c-ef0d-489a-91da-49dbc3090d2a")# else()# set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "aa1f7df0-828a-4fcd-9afc-2dc80491aca7")# endif()# set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)#else()# cmake_policy(VERSION 3.28)#endif()# --------------------# Include CMake scripts.# --------------------file(DOWNLOADhttps://raw.githubusercontent.com/stripe2933/CppStandardLibraryModule/main/cmake/EnableStandardLibraryModule.cmake${CMAKE_BINARY_DIR}/EnableStandardLibraryModule.cmake
)
include(${CMAKE_BINARY_DIR}/EnableStandardLibraryModule.cmake)
# --------------------# Main executable.# --------------------add_executable(CppStandardLibraryModulemain.cpp)

main.cpp

import std;
// import std.compat also available.intmain(){
std::cout << "Hello, world!\n";
}

Or simply, you can just clone this template repository.

Clang

Build Standard Library Module from LLVM repository.

git clone https://github.com/llvm/llvm-project.git
cd llvm-project
mkdir build
cmake -G Ninja -S runtimes -B build \
-DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind"
ninja -C build

After that, specify the CMake variable LIBCXX_BUILD to your custom module build directory, explained at Libc++ website in detail.

cd<your-project-dir>
mkdir build
cmake -S . -B build -G Ninja \
-DCMAKE_CXX_STANDARD=20 \
-DLIBCXX_BUILD=<build-dir>
ninja -C build
# Your executable will be at /build

Here's the Clang CI for your insight.

MSVC

Specify the CMake variable VCTOOLS_INSTALL_DIR, which can be directly fetched via $env:VCToolsInstallDir in x86 Native Tools Command Prompt for VS, explained at Microsoft documentation in detail.

cd<your-project-dir>
mkdir build
cmake -S . -B build -G "Visual Studio 17 2022" -T v143 ` -DCMAKE_CXX_STANDARD=20 `
-DVCTOOLS_INSTALL_DIR="$env:VCToolsInstallDir"
cmake --build build -j4
# Your executable will be at build\Release

Here's the MSVC CI for your insight.