# Installation And Usage This chapter provides all the necessary information to obtain and build the code using **mp-units**. It also describes how to build or distribute the library and generate its documentation. ## C++ compiler support { #cpp-compiler-support } !!! info **mp-units** library tries to provide the best user experience possible with the C++ language. To achieve that, it extensively uses C++20 features and the [explicit object parameter](https://en.cppreference.com/w/cpp/language/member_functions#Explicit_object_parameter) from C++23. Even though the library benefits from C++23 (if available), C++20 is enough to compile and use all of the library's functionality. C++23 features are hidden behind a [preprocessor macro](../users_guide/framework_basics/systems_of_quantities.md#defining-quantities) providing a backward-compatible way to use it. The below table provides the minimum compiler version required to compile the code using the specific feature: | Feature | gcc | clang | apple-clang | MSVC | |----------------------|:---:|:-----:|:-----------:|:----:| | **Minimum support** | 12 | 16 | 15 | None | | **`std::format`** | 13 | 17 | None | None | | **C++ modules** | 14 | 17 | None | None | | **C++23 extensions** | 14 | 18 | None | None | More requirements for C++ modules support can be found in the [CMake's documentation](https://cmake.org/cmake/help/latest/manual/cmake-cxxmodules.7.html). ## Modules The **mp-units** library provides the following C++ modules. ```mermaid flowchart TD mp_units --- mp_units.systems --- mp_units.core ``` | C++ Module | CMake Target | Contents | |--------------------|----------------------|----------------------------------------------------------| | `mp_units.core` | `mp-units::core` | Core library framework and systems-independent utilities | | `mp_units.systems` | `mp-units::systems` | All the systems of quantities and units | | `mp_units` | `mp-units::mp-units` | Core + Systems | !!! note C++ modules are provided within the package only when [`cxx_modules`](#cxx_modules) Conan option is set to `True`. ## Repository structure and dependencies This repository contains three independent CMake-based projects: - _./src_ - header-only project containing whole **mp-units** library - _./src/CMakeList.txt_ file is intended as an **entry point for library users** - in case this library becomes part of the C++ standard, it will have no external dependencies but until then, it depends on the following: - [gsl-lite](https://github.com/gsl-lite/gsl-lite) to verify runtime contracts with the `gsl_Expects` macro, - [{fmt}](https://github.com/fmtlib/fmt) to provide text formatting of quantities (if `std::format` is not supported yet on a specific compiler). - _._ - project used as an **entry point for library development and CI/CD** - it wraps _./src_ project together with usage examples and tests - additionally to the dependencies of _./src_ project, it uses: - [Catch2](https://github.com/catchorg/Catch2) library as a unit tests framework, - [linear algebra](https://github.com/BobSteagall/wg21/tree/master/include) library based on proposal [P1385](https://wg21.link/P1385) used in some examples and tests. - *./test_package* - CMake library installation and Conan package verification. !!! important "Important: Library users should not use the top-level CMake file" Top level _CMakeLists.txt_ file should only be used by **mp-units** developers and contributors as an entry point for the project's development. We want to ensure that everyone will build **ALL** the code correctly before pushing a commit. Having such options would allow unintended issues to leak to PRs and CI. This is why our projects have two entry points: - _./CMakeLists.txt_ is **to be used by projects developers** to build **ALL** the project code with really restrictive compilation flags, - _./src/CMakeLists.txt_ contains only a pure library definition and **should be used by the customers** that prefer to use CMake's [`add_subdirectory()`](https://cmake.org/cmake/help/latest/command/add_subdirectory.html) to handle the dependencies. To learn more about the rationale, please check our [FAQ](faq.md#why-dont-we-have-cmake-options-to-disable-building-of-tests-and-examples). ## Obtaining dependencies This library assumes that most of the dependencies will be provided by the [Conan Package Manager](https://conan.io/). If you want to obtain required dependencies by other means, some modifications to the library's CMake files might be needed. The rest of the dependencies responsible for documentation generation are provided by `python3-pip`. ### Conan quick intro In case you are not familiar with Conan, to install it (or upgrade) just do: ```shell pip3 install -U conan ``` After that, you might need to add a custom profile file for your development environment in _~/.conan2/profiles_ directory. An example profile can look as follows: ```ini hl_lines="5" title="~/.conan2/profiles/gcc12" [settings] arch=x86_64 build_type=Release compiler=gcc compiler.cppstd=20 compiler.libcxx=libstdc++11 compiler.version=12 os=Linux [conf] tools.build:compiler_executables={"c": "gcc-12", "cpp": "g++-12"} ``` !!! tip "Setting the language version" Please note that the **mp-units** library requires at least C++20 to be set in a Conan profile or forced via the Conan command line. If we do the former, we will not need to provide `-s compiler.cppstd=20` every time we run a Conan command line (as provided in the command line instructions below). !!! tip "Using Ninja as a CMake generator for Conan" It is highly recommended to set Ninja as a CMake generator for Conan. To do so, we should create a _~/.conan2/global.conf_ file that will set `tools.cmake.cmaketoolchain:generator` to one of the Ninja generators. For example: ```text title="~/.conan2/global.conf" tools.cmake.cmaketoolchain:generator="Ninja Multi-Config" ``` !!! tip "Separate build folders for different configurations" _~/.conan2/global.conf_ file may also set `tools.cmake.cmake_layout:build_folder_vars` which [makes working with several compilers or build configurations easier](https://docs.conan.io/2/reference/tools/cmake/cmake_layout.html#multi-setting-option-cmake-layout). For example, the below line will force Conan to generate separate CMake presets and folders for each compiler and C++ standard version: ```text title="~/.conan2/global.conf" tools.cmake.cmake_layout:build_folder_vars=["settings.compiler", "settings.compiler.version", "settings.compiler.cppstd"] ``` In such a case, we will need to use a configuration-specific preset name in the Conan instructions provided below rather than just `conan-default` and `conan-release` (e.g. `conan-gcc-13-23` and `conan-gcc-13-23-release`) ## Build options ### Conan options [cxx_modules](#cxx_modules){ #cxx_modules } : [:octicons-tag-24: 2.2.0][cxx modules support] · :octicons-milestone-24: `True`/`False` (Default: `False`) Configures CMake to add C++ modules to the list of default targets. [cxx modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 [use_fmtlib](#use_fmtlib){ #use_fmtlib } : [:octicons-tag-24: 2.2.0][use fmtlib support] · :octicons-milestone-24: `True`/`False` (Default: `False`) Forces usage of [{fmt}](https://github.com/fmtlib/fmt) library instead of the C++20 Standard Library features. [use fmtlib support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 ### Conan configuration properties [`user.mp-units.build:all`](#user.mp-units.build-all){ #user.mp-units.build-all } : [:octicons-tag-24: 2.2.0][build all support] · :octicons-milestone-24: `True`/`False` (Default: `False`) Enables compilation of all the source code, including tests and examples. To support this, it requires some additional Conan build dependencies described in [Repository Structure and Dependencies](#repository-structure-and-dependencies). It also runs unit tests during Conan build (unless [`tools.build:skip_test`](https://docs.conan.io/2/reference/commands/config.html?highlight=tools.build:skip_test#conan-config-list) configuration property is set to `True`). [build all support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 [`user.mp-units.build:skip_la`](#user-skip-la){ #user-skip-la } : [:octicons-tag-24: 2.2.0][skip la support] · :octicons-milestone-24: `True`/`False` (Default: `False`) If `user.mp-units.build:all` is enabled, among others, Conan installs the external [wg21-linear_algebra](https://conan.io/center/recipes/wg21-linear_algebra) dependency and enables the compilation of linear algebra-based tests and usage examples. Such behavior can be disabled with this option. [skip la support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 ### CMake options [`MP_UNITS_BUILD_CXX_MODULES`](#MP_UNITS_BUILD_CXX_MODULES){ #MP_UNITS_BUILD_CXX_MODULES } : [:octicons-tag-24: 2.2.0][build_cxx_modules support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`) Adds C++ modules to the list of default targets. [build_cxx_modules support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 [`MP_UNITS_USE_FMTLIB`](#MP_UNITS_USE_FMTLIB){ #MP_UNITS_USE_FMTLIB } : [:octicons-tag-24: 2.2.0][use fmtlib support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`) Forces usage of [{fmt}](https://github.com/fmtlib/fmt) library instead of the C++20 Standard Library features. [use fmtlib support]: https://github.com/mpusz/mp-units/releases/tag/v2.2.0 [`MP_UNITS_BUILD_LA`](#MP_UNITS_BUILD_LA){ #MP_UNITS_BUILD_LA } : [:octicons-tag-24: 2.0.0][build la support] · :octicons-milestone-24: `ON`/`OFF` (Default: `ON`) Enables building code depending on the linear algebra library. [build la support]: https://github.com/mpusz/mp-units/releases/tag/v2.0.0 [`MP_UNITS_IWYU`](#MP_UNITS_IWYU){ #MP_UNITS_IWYU } : [:octicons-tag-24: 2.0.0][iwyu support] · :octicons-milestone-24: `ON`/`OFF` (Default: `OFF`) Enables `include-what-you-use` when compiling with a clang compiler. Additionally turns on [`MP_UNITS_AS_SYSTEM_HEADERS`](#MP_UNITS_AS_SYSTEM_HEADERS). [iwyu support]: https://github.com/mpusz/mp-units/releases/tag/v2.0.0 ## CMake with presets support It is recommended to use at least CMake 3.23 to build this project as this version introduced support for CMake Presets schema version 4, used now by Conan to generate presets files. All build instructions below assume that you have such support. If not, your CMake invocations have to be replaced with something like: ```shell mkdir build && cd build cmake .. -G "Ninja Multi-Config" -DCMAKE_TOOLCHAIN_FILE=/conan_toolchain.cmake cmake --build . --config Release ``` !!! tip In case you can't use CMake 3.23 but you have access to CMake 3.20 or later, you can append `-c tools.cmake.cmaketoolchain.presets:max_schema_version=2` to the `conan install` command which will force Conan to use an older version of the CMake Presets schema. ## Installation and reuse There are many different ways of installing/reusing **mp-units** in your project. Below we mention only a few of many options possible. !!! important "Important: Prefer using Conan if possible" The easiest and most recommended way to obtain **mp-units** is with the Conan package manager. See [Conan + CMake (release)](#conan-cmake-release) for a detailed instruction. ### Copy As **mp-units** is a C++ header-only library you can simply copy all needed _src/*/include_ subdirectories to your source tree. !!! note In such a case, you are on your own to ensure all the dependencies are installed and their header files can be located during the build. Please also note that some compiler-specific flags are needed to make the code compile without issues. ### Copy + CMake If you copy the whole **mp-units** repository to your project's file tree, you can reuse CMake targets defined by the library. To do so, **you should use _CMakeLists.txt_ file from the _./src_ directory**: ```cmake add_subdirectory(/src) # ... target_link_libraries( mp-units::mp-units) ``` !!! note You are still on your own to make sure all the dependencies are installed and their header and CMake configuration files can be located during the build. ### Conan + CMake (release) !!! tip If you are new to the Conan package manager, it is highly recommended to read [Obtaining Dependencies](#obtaining-dependencies) and refer to [Consuming packages](https://docs.conan.io/2/tutorial/consuming_packages.html) chapter of the official Conan documentation for more information. **mp-units** releases are hosted on [Conan-Center](https://conan.io/center/recipes/mp-units). The following steps may be performed to obtain an official library release: 1. Create Conan configuration file (either _conanfile.txt_ or _conanfile.py_) in your project's top-level directory and add **mp-units** as a dependency of your project. For example, the simplest file may look as follows: ```ini title="conanfile.txt" [requires] mp-units/2.1.0 [options] mp-units:cxx_modules=True [layout] cmake_layout [generators] CMakeToolchain CMakeDeps ``` 2. Import **mp-units** and its dependencies definitions to your project's build procedure with `find_package`: ```cmake find_package(mp-units REQUIRED) ``` 3. Link your CMake targets with **mp-units**: ```cmake target_link_libraries( mp-units::mp-units) ``` 4. Download, build, and install Conan dependencies before running the CMake configuration step: ```shell conan install . -pr -s compiler.cppstd=20 -b=missing cmake --preset conan-default cmake --build --preset conan-release ``` ### Conan + CMake (Live At Head) This chapter describes the procedure to Live At Head, which means using the latest stable version of **mp-units** all the time. !!! note Please note that even though the Conan packages that you will be using are generated **ONLY** for builds that are considered stable (passed our CI tests), some minor regressions may happen (our CI and C++20 build environment is not perfect yet). Also, please expect that the library interface might, and probably will, change occasionally. Even though we do our best, such changes might not be reflected in the project's documentation right away. The procedure is similar to the one described in [Conan + CMake (release)](#conan-cmake-release) with the following differences: 1. Before starting the previous procedure, add **mp-units** remote to your Conan configuration: ```shell conan remote add conan-mpusz https://mpusz.jfrog.io/artifactory/api/conan/conan-oss ``` 2. In your Conan configuration file, provide the package identifier of the `mpusz/testing` stream: ```ini title="conanfile.txt" hl_lines="2" [requires] mp-units/2.2.0@mpusz/testing [options] mp-units:cxx_modules=True [layout] cmake_layout [generators] CMakeToolchain CMakeDeps ``` !!! tip The identifiers of the latest packages can always be found in [the project's README file](https://github.com/mpusz/mp-units/blob/master/README.md) or on [the project's Artifactory](https://mpusz.jfrog.io/ui/packages/conan:%2F%2Fmp-units). 3. Force Conan to check for updated recipes with `-u`: ```shell conan install . -pr -s compiler.cppstd=20 -b=missing -u ``` ### Install In case you don't want to use Conan in your project and just want to install the **mp-units** library on your file system and use `find_package(mp-units)` from another repository to find it; it is enough to perform the following steps: ```shell conan install . -pr -s compiler.cppstd=20 -b=missing mv CMakeUserPresets.json src cd src cmake --preset conan-default -DCMAKE_INSTALL_PREFIX= cmake --build --preset conan-release --target install ``` ## Contributing (or just building all the tests and examples) In case you would like to build all the **mp-units** source code (with unit tests and examples), you should: 1. Use the _CMakeLists.txt_ from the top-level directory. 2. Run Conan with [`user.mp-units.build:all`](#user.mp-units.build-all) = `True`. ```shell git clone https://github.com/mpusz/mp-units.git && cd units conan build . -pr -s compiler.cppstd=23 -o cxx_modules=True -c user.mp-units.build:all=True -b missing ``` The above will download and install all of the dependencies needed for the development of the library, build all of the source code, and run unit tests. If you prefer to build the project via CMake rather than Conan, then you should replace the `conan build` with `conan install` command and then follow with a regular CMake build: ```shell cmake --preset conan-default cmake --build --preset conan-release cmake --build --preset conan-release --target all_verify_interface_header_sets cmake --build --preset conan-release --target test ``` ## Building documentation Starting from **mp-units 2.0** we are using [Material for MkDocs](https://squidfunk.github.io/mkdocs-material/) to build our documentation. The easiest way to install all the required dependencies is with `pip`: ```shell pip install -U mkdocs-material mkdocs-rss-plugin ``` Additionally, a [Cairo Graphics library](https://www.cairographics.org/) is required by Material for MkDocs. Please follow the [official MkDocs documentation to install it](https://squidfunk.github.io/mkdocs-material/plugins/requirements/image-processing/#cairo-graphics). After that, you can either: - easily [start a live server to preview the documentation as you write](https://squidfunk.github.io/mkdocs-material/creating-your-site/#previewing-as-you-write) ```shell mkdocs serve ``` - [build the documentation](https://squidfunk.github.io/mkdocs-material/creating-your-site/#building-your-site) ```shell mkdocs build ``` ## Packaging To test CMake installation and Conan packaging or create a Conan package run: ```shell conan create . --user --channel -pr -s compiler.cppstd=20 -o cxx_modules=True -c user.mp-units.build:all=True -b missing ``` The above will create a Conan package and run tests provided in _./test_package_ directory. ## Uploading **mp-units** package to the Conan server ```shell conan upload -r --all mp-units/2.1.0@/ ```