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ModernCppComponentLibraryExample

Setting up a new C++ project usually requires a significant amount of preparation and boilerplate code, even more so for modern C++ projects with tests, executables and continuous integration. This template is the result of learnings from many previous projects and should help reduce the work required to setup up a modern C++ project.

This repository is intended as a template to show the "proper" way to setup a "Modern CMake" project with components. The required usage (for a downstream library) should be nothing more than:

  find_package(
    MathFunctions 1
    COMPONENTS Addition SquareRoot
    REQUIRED
  )

  /#..

  target_link_libraries(
    MathFunctionsTests Boost::ut MathFunctions::Addition MathFunctions::SquareRoot
  )

Features

Tips

Usage

Adjust the template to your needs

  • Use this repo as a template and replace all occurrences of "MathFunctions" in the relevant CMakeLists.txt with the name of your project
  • Replace the source files with your own
  • Happy coding!

Eventually, you can remove any unused files, such as the standalone directory or irrelevant github workflows for your project. Feel free to replace the License with one suited for your project.

To cleanly separate the library and subproject code, the outer CMakeLists.txt only defines the library itself while the tests and other subprojects are self-contained in their own directories. During development it is usually convenient to build all subprojects at once.

Use the makefile wrapper on unix bash or with GVIM

There is a makefile to wrap the CMake command-line interface for esay use at bash shell.

Build and run the standalone target

Use the following command to build and run the executable target.

make standalone

# or
cmake --build build/standalone
build/standalone/MathFunctionsStandalone 2.0

Build and run test suite

Use the following commands from the project's root directory to run the test suite.

make test

# or
cmake -S test -B build/test
cmake --build build/test
CTEST_OUTPUT_ON_FAILURE=1 cmake --build build/test --target test

# or simply call the executable:
build/test/MathFunctionsTest

To collect code coverage information, run CMake with the -DENABLE_TEST_COVERAGE=1 option.

Generate a GCC Code Coverage Report

To generate or update with gcovr the html files reports/gcov/index.html:

make gcov

Run clang-tidy

The .clang-tidy checks supports you to write clean code!

To check your project with clang-tidy simply do

make tidy

Run clang-format

Use the following commands from the project's root directory to check and fix C++ and CMake source style. This requires clang-format, cmake-format and pyyaml to be installed on the current system.

make format

# or
cmake -S test -B build/test

# view changes
cmake --build build/test --target format

# apply changes
cmake --build build/test --target fix-format

See Format.cmake for details.

Build the documentation

To manually build documentation, call the following command.

make doc

# or
cmake -S documentation -B build/doc
cmake --build build/doc --target GenerateDocs
# view the docs
open build/doc/doxygen/html/index.html

To build the documentation locally, you will need Doxygen, jinja2 and Pygments on installed your system.

Build everything at once

The project also includes an all directory that allows building all targets at the same time. This is useful during development, as it exposes all subprojects to your IDE and avoids redundant builds of the library.

IDE

Use Qt Creator as IDE

It creates the best usable results when open the project via all/CMakeLists.txt. And it supports to direct import a existing CMake build directory create with:

make all

# or
cmake -S all -B build
cmake --build build

# run tests
build/test/MathFunctionsTest
# format code
cmake --build build --target fix-format
# run standalone
build/standalone/MathFunctionsStandalone 42.0
# build docs
cmake --build build --target GenerateDocs

Additional tools

The test and standalone subprojects include the tools.cmake file which is used to import additional tools on-demand through CMake configuration arguments. The following are currently supported.

Sanitizers

Sanitizers can be enabled by configuring CMake with -DUSE_SANITIZER=<Address | Memory | MemoryWithOrigins | Undefined | Thread | Leak | 'Address;Undefined'>.

Static Analyzers

Static Analyzers can be enabled by setting -DUSE_STATIC_ANALYZER=<clang-tidy | iwyu | cppcheck>, or a combination of those in quotation marks, separated by semicolons. By default, analyzers will automatically find configuration files such as .clang-format. Additional arguments can be passed to the analyzers by setting the CLANG_TIDY_ARGS, IWYU_ARGS or CPPCHECK_ARGS variables.

Ccache

Ccache can be enabled by configuring with -DUSE_CCACHE=<ON | OFF>.

FAQ

Can I use this for header-only libraries?

Yes, however you will need to change the library type to an INTERFACE library as documented in the CMakeLists.txt. See here for an example header-only library based on the template.

I don't need a standalone target / documentation. How can I get rid of it?

Simply remove the standalone / documentation directory and according github workflow file.

Can I build the standalone and tests at the same time? / How can I tell my IDE about all subprojects?

To keep the template modular, all subprojects derived from the library have been separated into their own CMake modules. This approach makes it trivial for third-party projects to re-use the projects library code. To allow IDEs to see the full scope of the project, the template includes the all directory that will create a single build for all subprojects. Use this as the main directory for best IDE support.

I see you are using GLOB to add source files in CMakeLists.txt. Isn't that evil?

Glob is considered bad because any changes to the source file structure might not be automatically caught by CMake's builders and you will need to manually invoke CMake on changes. I personally prefer the GLOB solution for its simplicity, but feel free to change it to explicitly listing sources.

I want create additional targets that depend on my library. Should I modify the main CMakeLists.txt to include them?

Avoid including derived projects from the libraries CMakeLists.txt (even though it is a common sight in the C++ world), as this effectively inverts the dependency tree and makes the build system hard to reason about. Instead, create a new directory or project with a CMakeLists.txt that adds the library as a dependency (e.g. like the standalone directory). Depending type it might make sense move these components into a separate repositories and reference a specific commit or version of the library. This has the advantage that individual libraries and components can be improved and updated independently.

You recommend to add external dependencies using CPM.cmake. Will this force users of my library to use CPM as well?

CPM.cmake should be invisible to library users as it's a self-contained CMake Script. If problems do arise, users can always opt-out by defining CPM_USE_LOCAL_PACKAGES, which will override all calls to CPMAddPackage with find_package. Alternatively, you could use CPMFindPackage instead of CPMAddPackage, which will try to use find_package before calling CPMAddPackage as a fallback. Both approaches should be compatible with common C++ package managers without modifications, however come with the cost of reproducible builds.

Can I configure and build my project offline?

Using CPM, all missing dependencies are downloaded at configure time. To avoid redundant downloads, it's recommended to set a CPM cache directory, e.g.: export CPM_SOURCE_CACHE=$HOME/.cache/CPM. This will also allow offline configurations if all dependencies are present. No internet connection is required for building.

Can I use CPack to create a package installer for my project?

As there are a lot of possible options and configurations, this is not (yet) in the scope of this template. See the CPack documentation for more information on setting up CPack installers.

This is too much, I just want to create a singe C++ library.

Perhaps the ModernCppStarter

This is too much, I just want to play with C++ code and test some libraries.

Perhaps the MiniCppStarter is something for you!