Makefile

Makefile

A cross-platform C++ Makefile for any project!

Features

• Cross-platform: works on Linux, macOS, and Windows
• Automatic: all source files are automatically found and compiled
• Efficient: only the modified files are recompiled and their dependencies are automatically generated
• Debug and release configurations
• Configurable: easily add libraries or change compilation settings
• Package manager-compatible (Conan and vcpkg)
• Testing with the library of your choice
• Formatting with clang-format
• Linting with clang-tidy
• Generate documentation from Doxygen comments
• Built-in generation of compile_commands.json
• Compatible with VS Code’s Makefile Tools extension

See the table of contents at the end.

Prerequisites

Make & GCC

Alternatively, Clang can be used instead of GCC (see here). The instructions below will focus on GCC.

• Linux:
  • Debian/Ubuntu: sudo apt install build-essential
  • Fedora: sudo dnf install make gcc-c++
  • openSUSE: sudo zypper install make gcc-c++
  • Arch Linux: sudo pacman -S make gcc
• macOS:
  1. Run the following command: xcode-select --install
  2. In the window which pops up, click “Install” and follow the instructions.
• Windows:
  1. Install MinGW-w64 from WinLibs.com.
  2. Add the path to MinGW-64’s bin directory to Windows’s system PATH environment variable.

     You will need to use mingw32-make instead of make each time the make command is used in this README.

  3. Install Git Bash by installing Git for Windows.

     You will need to use Git Bash instead of PowerShell or cmd.exe each time the make command is used in this README.

Optional dependencies

• For formatting: clang-format
• For linting: clang-tidy
• For generating documentation: Doxygen and Graphviz

Usage

Overview of commands

$ make help
Usage: make target... [options]...

Targets:
  all             Build executable and tests (debug configuration by default) (default target)
  run             Build and run executable (debug configuration by default)
  test            Build and run tests (debug configuration by default)
  copyassets      Copy assets to executable directory for selected platform and configuration
  cleanassets     Clean assets from executable directories (all platforms)
  clean           Clean build directory (all platforms)
  compdb          Generate JSON compilation database (compile_commands.json)
  format          Format source code using clang-format
  format-check    Check that source code is formatted using clang-format
  lint            Lint source code using clang-tidy
  lint-fix        Lint and fix source code using clang-tidy
  docs            Generate documentation with Doxygen
  help            Print this information
  printvars       Print Makefile variables for debugging

Options:
  release=1       Run target using release configuration rather than debug

Note: the above options affect the following targets: all, run, test, copyassets, compdb, printvars

Building

make

This will compile the executable (and optionally, tests) and output it inside the current bin directory (build/<platform>/<configuration>/bin). This is equivalent to make all.

Using a different compiler

By default, all builds use GCC. To use another compiler, override the CXX variable when invoking make. For example, to use Clang:

make CXX=clang++

Running

make run

This will run the executable, rebuilding it first if it was out of date. The working directory will be the executable’s directory, i.e. the current bin directory.

Testing

If your project contains tests, you can run them with the following command:

make test

This will run the test executable, rebuilding it first if it was out of date. The working directory will be the current bin directory.

See here for information on setting up tests for your project.

Assets

Copying assets

To add files to be copied next to the executable’s output location, simply add them to the assets directory. Then, use the following command:

make copyassets

This will copy the contents of assets to the current bin directory, preserving their folder structure.

Platform-specific assets

If you have certain assets which you wish to only copy for certain platforms, you can do the following:

1. Create an assets_os/<platform> directory at the root of the project. The <platform> directory should be named either linux, macos, or windows based on the desired platform for the assets.
2. Inside this new directory, add all the assets to be copied only for this platform.

You can then use the make copyassets command as usual.

The files copied to the current bin directory will be the combination of the files in assets and assets_os, with files in assets_os overwriting those in assets in case of naming clashes.

The assets_os directory is useful for holding Windows DLLs which need to be copied next to the executable (using assets_os/windows).

Cleaning assets

make cleanassets

This will remove all the files in all bin directories, except for executables and tests.

Cleaning

make clean

This will remove the entire build directory.

Options

Options can be specified when building, running, testing, and copying assets. These will modify the settings used to build the executable (and optionally, tests) and affect what is considered the current bin directory when running a command.

Release configuration

By default, builds use the debug configuration. To build for release (including optimizations), add the release=1 option when invoking make:

make release=1

To use the release version of the executable, release=1 must also be specified when running or when copying assets. For example:

make copyassets run release=1

Generating a JSON compilation database

Some language servers and tools, like clangd or clang-tidy, rely on a JSON compilation database (compile_commands.json). To generate this file, use the following command:

make compdb

This will create the compilation database in build/compile_commands.json. You should rerun this command any time you add files to your project.

Formatting

make format

This will format all files (both sources and headers) using clang-format according to the options set in .clang-format.

To only verify if the files are correctly formatted, use the following command:

make format-check

This will return exit code 1 if any files are not formatted.

Linting

make lint

This will lint all files (both sources and headers) using clang-tidy according to the options set in .clang-tidy. This will return exit code 1 if any files have lint errors.

To apply the suggested fixes to errors found by clang-tidy, use the following command:

make lint-fix

Generating documentation

Documentation can be generated from documentation comments using Doxygen.

First-time use

1. Create a new docs directory at the root of the project.

2. Generate a new Doxyfile in docs/Doxyfile:

   cd docs
   doxygen -g
   

   Or, to use the graphical wizard instead:

   cd docs
   doxywizard
   

Updating the documentation

make docs

This will generate the documentation according to the rules found in docs/Doxyfile and output it in the docs directory.

Adding libraries

There are several ways to add a library to your project.

Using a package manager

For more complex projects, using a package manager is the recommended way to add libraries. This method ensures that your libraries are managed consistently across platforms.

Conan

You can integrate Conan with the Makefile by using the MakeDeps generator.

1. Install Conan using pip:

   pip install conan
   

2. Create a Conan profile:

   conan profile detect --force
   

   The path of the generated profile can be found using conan profile path default. You can edit this file and set compiler.cppstd to your desired C++ standard (e.g. compiler.cppstd=20).

   Note: on Windows, you should modify the default profile to use MinGW (GCC) instead of MSVC. Make the following changes to the default profile:

   compiler=gcc
   compiler.cppstd=<desired C++ standard, e.g. 20>
   compiler.libcxx=libstdc++11
   compiler.version=<installed GCC version, e.g. 13>
   

   The compiler.runtime setting should be removed, as it is specific to MSVC.

3. Create a conanfile.txt at the root of the project:

   [requires]
   # Add dependencies...
   
   [generators]
   MakeDeps
   

4. Edit the Makefile:

   # Includes
   INCLUDE_DIR =
   INCLUDES = $(addprefix -I,$(SRC_DIR) $(INCLUDE_DIR)) $(CONAN_INCLUDE_DIRS)
   TEST_INCLUDES = -I$(TEST_DIR)
   
   # C preprocessor settings
   CPPFLAGS = $(INCLUDES) -MMD -MP $(CONAN_DEFINES)
   
   [...]
   
   # Linker flags
   LDFLAGS = $(CONAN_LIB_DIRS)
   TEST_LDFLAGS =
   
   # Libraries to link
   LDLIBS = $(CONAN_LIBS_<LIBRARY_NAME>) $(CONAN_SYSTEM_LIBS)
   TEST_LDLIBS =
   
   [...]
   
   # Object, bin, and Conan directories
   OBJ_DIR := $(BUILD_DIR)/obj
   BIN_DIR := $(BUILD_DIR)/bin
   CONAN_DIR := $(BUILD_DIR)/conan
   
   # Conan
   ifneq ($(MAKECMDGOALS),clean)
       CONAN_DEFINE_FLAG = -D
       CONAN_INCLUDE_DIR_FLAG = -isystem
       CONAN_LIB_DIR_FLAG = -L
       CONAN_BIN_DIR_FLAG = -L
       CONAN_LIB_FLAG = -l
       CONAN_SYSTEM_LIB_FLAG = -l
       include $(CONAN_DIR)/conandeps.mk
   endif
   
   [...]
   
   # Generate Conan dependencies
   $(CONAN_DIR)/conandeps.mk: conanfile.txt
       @echo "Generating: $@"
       @mkdir -p $(@D)
       @conan install . --output-folder=$(CONAN_DIR) --build=missing
   
   # Build executable
   [...]
   

$(CONAN_LIBS_<LIBRARY_NAME>) should be repeated for each dependency, replacing <LIBRARY_NAME> with the library’s name. Libraries which depend on other libraries should be listed before the libraries they depend on.

See this gist for an example of the modifications to make.

vcpkg

You can integrate vcpkg with the Makefile by using the manual integration.

1. Add vcpkg as a submodule:

   git submodule add https://github.com/Microsoft/vcpkg.git
   

2. Run the bootstrap script to build vcpkg:

   ./vcpkg/bootstrap-vcpkg.sh
   

3. Create a vcpkg.json at the root of the project:

   {
       "dependencies": [
           // Add dependencies...
       ]
   }
   

4. Install the dependencies listed in vcpkg.json:

   ./vcpkg/vcpkg install
   

   Note: on Windows, you should set the target and host triplet to the MinGW triplet. This can be done by setting the following environment variables before running the previous command:

   export VCPKG_DEFAULT_TRIPLET=x64-mingw-static
   export VCPKG_DEFAULT_HOST_TRIPLET=x64-mingw-static
   

5. Edit the Makefile:

   # Platform-specific settings
   ifeq ($(OS),windows)
       [...]
   
       # Windows-specific settings
       INCLUDES += -isystem vcpkg_installed/x64-mingw-static/include
       LDFLAGS += -Lvcpkg_installed/x64-mingw-static/lib
       LDLIBS += # Add libraries with -l...
   else ifeq ($(OS),macos)
       # macOS-specific settings
       INCLUDES += -isystem vcpkg_installed/x64-osx/include
       LDFLAGS += -Lvcpkg_installed/x64-osx/lib
       LDLIBS += # Add libraries with -l...
   else ifeq ($(OS),linux)
       # Linux-specific settings
       INCLUDES += -isystem vcpkg_installed/x64-linux/include
       LDFLAGS += -Lvcpkg_installed/x64-linux/lib
       LDLIBS += # Add libraries with -l...
   endif
   

See this gist for an example of the modifications to make.

Header-only library

Header-only libraries are composed solely of header files. This way, no separate compilation or linking is necessary.

1. If this is the first library you are adding, create a new external directory at the root of the project.
2. Inside the external directory, create a <library-name> sudirectory to contain the library’s header files.
3. Download the library’s header files and add them to external/<library-name>.
4. Add the library’s header files to the preprocessor’s search path: add -isystem external/<library-name> to the INCLUDES variable (line 28 of the Makefile).

Library installed system-wide

Some libraries can be installed system-wide, using your system’s package manager. For example:

• On macOS, using Homebrew or MacPorts
• On Debian/Ubuntu, using apt
• On Fedora, using dnf
• On openSUSE, using zypper
• On Arch Linux, using pacman

These system package managers install dependencies in a default system-wide directory, such as /usr/lib and /usr/include on Linux. Some important system-wide libraries may also come preinstalled on your system.

Relying on a system package manager for your libraries can make it less straightforward for other developers using a different platform to start working on your project. Nevertheless, this can be a quick way for you to start using a library, especially if this library is already required by the system.

1. Use your system package manager to install the library’s development package. Often, development packages will have the -dev or -devel suffix.

2. Link with the library: add -l<library-name> to the LDLIBS variable (line 44 of the Makefile).

   Depending on the library, more than one library name may need to be added with the -l option. Refer to your library’s documentation for the names to use with the -l option in this step.

   Note: on macOS, you may need to link your library using -framework rather than -l.

Library built from source

Alternatively, if a library is not available in any package manager, you can build it from source or download its compiled artifacts and add them to your project.

1. If this is the first library you are adding, create a new external directory at the root of the project.

2. Inside the external directory, create a <library-name> sudirectory to contain the library’s files.

3. Build or download the library’s compiled files and add them to external/<library-name>.

   You may instead prefer to add the library as a Git submodule inside the external directory to make updates easier.

4. Add the library’s header files to the preprocessor’s search path: add -isystem /<library-name>/include to the INCLUDES variable (line 28 of the Makefile).

5. Add the library’s compiled files to the linker’s search path: add -Lexternal/<library-name>/lib to the LDFLAGS variable (line 40 of the Makefile).

6. Link with the library: add -l<library-name> to the LDLIBS variable (line 44 of the Makefile).

   Depending on the library, more than one library name may need to be added with the -l option. Refer to your library’s documentation for the names to use with the -l option in this step.

   Note: on macOS, you may need to link your library using -framework rather than -l.

Note that the folder structure inside external/<library-name> will vary from one library to the next. In the above instructions:

• The include subdirectory refers to a directory containing all of the library’s header files.
• The lib subdirectory refers to a directory containing all of the library’s compiled files (e.g. .so, .a, .lib, .framework, etc.). If you have chosen to build the library from source, you should copy the output of the compiled library to the lib directory.

These directories may be named differently: refer to your library’s documentation for more information.

Setting up tests

1. Create a new tests directory at the root of the project to hold your test source files.

2. Pick your preferred C++ testing framework. For example:

   • Catch2 (recommended)
   • doctest
   • GoogleTest

3. Make the testing framework available to your project using one of the methods described in adding libraries.

   Using a package manager such as Conan or vcpkg is the recommended way to add this library.

   However, do not add the flags for the library to the INCLUDES, LDFLAGS, or LDLIBS variables. This is because only tests should link against the test framework library, not the main executable. See the next step for how to do this.

   For the simplest possible setup, you may instead prefer to use doctest, which is available as a single header file.

4. Add the necessary flags to link with the library, as described in your chosen method for adding libraries, but with the following replacements:

   • Use TEST_INCLUDES (line 29) instead of INCLUDES (line 28) to add the library’s header files to the preprocessor’s search path.
   • Use TEST_LDFLAGS (line 41) instead of LDFLAGS (line 40) to add the library’s compiled files to the linker’s search path (if applicable).
   • Use TEST_LDLIBS (line 45) instead of LDLIBS (line 44) to link with the library (if applicable).

   The TEST_INCLUDES, TEST_LDFLAGS, and TEST_LDLIBS variables apply only to tests. These are appended to the regular INCLUDES, LDFLAGS, and LDLIBS variables when building the tests.

5. Add at least one test source file to the tests directory.

See this gist for an example using Catch2 with Conan.

Once this is done, running make (or make all) will now build both the executable and tests. To build and run the tests, use make test.

The test executable is built from all the source files under both tests and src, except for src/main.cpp. This means you can test any functions defined in src, as long as these are not defined in src/main.cpp.

Configuration

Frequently changed settings

The following table presents an overview of the most commonly changed settings of the Makefile:

Configuration	Variable	Line
Change the output executable name	EXEC	6
Select the C++ compiler (e.g. g++ or clang++)	CXX	35
Add preprocessor settings (e.g. -D<macro-name>)	CPPFLAGS	32
Change C++ compiler settings (useful for setting the C++ standard version)	CXXFLAGS	36
Add/remove compiler warnings	WARNINGS	37
Add includes for libraries common to all platforms (e.g. -isystem external/<library-name>/include)	INCLUDES	28
Add linker flags for libraries common to all platforms (e.g. -Lexternal/<library-name>/lib)	LDFLAGS	40
Add libraries common to all platforms (e.g. -l<library-name>)	LDLIBS	44
Add includes/linker flags/libraries for specific platforms	INCLUDES, LDFLAGS, LDLIBS	61-80
Add additional includes/linker flags/libraries for tests	TEST_INCLUDES, TEST_LDFLAGS, TEST_LDLIBS	29, 41, 45

All the configurable options are defined between lines 1-80. For most uses, the Makefile should not need to be modified beyond line 80.

Platform-specific library configuration

The section on adding libraries explains how to add a library using the common INCLUDES, LDFLAGS, and LDLIBS variables which are shared between all platforms. However, in some cases, a library may need to be linked differently by platform. Examples of such platform-specific library configurations include:

• Adding a library needed only for code enabled on a certain platform.
• Using -framework over -l to link a library on macOS.
• Specifying a different path for a library’s compiled files with -L.

The Makefile is designed to support these kinds of platform-specific configurations alongside one another.

Lines 61-80 of the Makefile contain platform-specific INCLUDES, LDFLAGS, and LDLIBS variables which should be used for this purpose. To add a library for a certain platform, simply add the options to the variables under the comment indicating the platform.

The common INCLUDES (line 28), LDFLAGS (line 40), and LDLIBS (line 44) variables should only contain options which are identical for all platforms. Any platform-specific options should instead be specified using lines 61-80.

Separate directories for headers and sources

By default, your project’s header files should be placed under src, next to their associated source files. Headers which are only used by tests should be placed under tests.

However, if you wish to place your header files in a separate directory from your source files, you can do so by setting the INCLUDE_DIR variable (line 27 of the Makefile):

INCLUDE_DIR = include

This will add the include directory to the preprocessor’s search path.

This can be useful when developing a library: in this configuration, your library’s public headers should be placed under include, and its private headers under src.

Project layout

.
├── assets
│   └── <assets>
├── assets_os
│   └── linux | macos | windows
│       └── <assets>
├── build
│   └── linux | macos | windows
│       └── debug | release
│           ├── bin
│           │   ├── executable
│           │   └── <assets>
│           └── obj
│               ├── **/*.o
│               └── **/*.d
├── docs
│   ├── Doxyfile
│   └── **/*.html
├── include (optional)
│   └── **/*.h
├── src
│   ├── main.cpp
│   ├── **/*.cpp
│   └── **/*.h
├── tests
│   ├── **/*.cpp
│   └── **/*.h
├── .clang-format
├── .clang-tidy
├── .gitattributes
├── .gitignore
├── Makefile
└── README.md

License

MIT

To comply with the terms of the MIT license in your project, simply copy-pasting the entire contents of the provided LICENSE file as a comment at the top of the Makefile is sufficient. By doing so, you do not need to include the LICENSE file directly since it is is now contained in the Makefile. You can then reuse the LICENSE filename for your own license if you wish.

Table of contents

• Features
• Prerequisites
  • Make & GCC
  • Optional dependencies
• Usage
  • Overview of commands
  • Building
    • Using a different compiler
  • Running
  • Testing
  • Assets
    • Copying assets
    • Platform-specific assets
    • Cleaning assets
  • Cleaning
  • Options
    • Release configuration
  • Generating a JSON compilation database
  • Formatting
  • Linting
  • Generating documentation
    • First-time use
    • Updating the documentation
• Adding libraries
  • Using a package manager
    • Conan
    • vcpkg
  • Header-only library
  • Library installed system-wide
  • Library built from source
• Setting up tests
• Configuration
  • Frequently changed settings
  • Platform-specific library configuration
  • Separate directories for headers and sources
• Project layout
• License
• Table of contents