CPM.cmake is a CMake script that adds dependency management capabilities to CMake. It's built as a thin wrapper around CMake's FetchContent module that adds version control, caching and a simple API.
Any downloadable project or resource can be added as a version-controlled dependency though CPM, it is not necessary to modify or package anything. Projects using modern CMake are automatically configured and their targets can be used immediately. For everything else, the targets can be created manually after the dependency has been downloaded (see the snippets below for examples).
After CPM.cmake
has been added to your project, the function CPMAddPackage
or CPMFindPackage
can be used to fetch and configure a dependency.
Afterwards, any targets defined in the dependency can be used directly.
CPMFindPackage
and CPMAddPackage
take the following named parameters.
CPMAddPackage(
NAME # The unique name of the dependency (should be the exported target's name)
VERSION # The minimum version of the dependency (optional, defaults to 0)
OPTIONS # Configuration options passed to the dependency (optional)
DOWNLOAD_ONLY # If set, the project is downloaded, but not configured (optional)
[...] # Origin parameters forwarded to FetchContent_Declare, see below
)
The origin may be specified by a GIT_REPOSITORY
, but other sources, such as direct URLs, are also supported.
If GIT_TAG
hasn't been explicitly specified it defaults to v(VERSION)
, a common convention for git projects.
On the other hand, if VERSION
hasn't been explicitly specified, CPM can automatically identify the version from the git tag in some common cases.
GIT_TAG
can also be set to a specific commit or a branch name such as master
to always download the most recent version.
The optional argument FIND_PACKAGE_ARGUMENTS
can be specified to a string of parameters that will be passed to find_package
if enabled (see below).
After calling CPMAddPackage
or CPMFindPackage
, the following variables are defined in the local scope, where <dependency>
is the name of the dependency.
<dependency>_SOURCE_DIR
is the path to the source of the dependency.<dependency>_BINARY_DIR
is the path to the build directory of the dependency.<dependency>_ADDED
is set toYES
if the dependency has not been added before, otherwise it is set toNO
.
The difference between CPMFindPackage
and CPMAddPackage
is that CPMFindPackage
will try to find a local dependency via CMake's find_package
and fallback to CPMAddPackage
if the dependency is not found.
This behaviour can be also modified globally via CPM options.
cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
# create project
project(MyProject)
# add executable
add_executable(tests tests.cpp)
# add dependencies
include(cmake/CPM.cmake)
CPMAddPackage(
NAME Catch2
GITHUB_REPOSITORY catchorg/Catch2
VERSION 2.5.0
)
# link dependencies
target_link_libraries(tests Catch2)
See the examples directory for complete examples with source code or the wiki for example snippets.
To add CPM to your current project, simply add cmake/CPM.cmake
to your project's cmake
directory. The command below will perform this automatically.
mkdir -p cmake
wget -O cmake/CPM.cmake https://github.com/TheLartians/CPM.cmake/releases/latest/download/CPM.cmake
You can also use CMake to download CPM for you. See the wiki for more details.
To update CPM to the newest version, update the script in the project's root directory, for example by running the command above. Dependencies using CPM will automatically use the updated script of the outermost project.
- Small and reusable projects CPM takes care of all project dependencies, allowing developers to focus on creating small, well-tested libraries.
- Cross-Platform CPM adds projects directly at the configure stage and is compatible with all CMake toolchains and generators.
- Reproducible builds By versioning dependencies via git commits or tags it is ensured that a project will always be buildable.
- Recursive dependencies Ensures that no dependency is added twice and all are added in the minimum required version.
- Plug-and-play No need to install anything. Just add the script to your project and you're good to go.
- No packaging required Simply add all external sources as a dependency.
- Simple source distribution CPM makes including projects with source files and dependencies easy, reducing the need for monolithic header files or git submodules.
- No pre-built binaries For every new build directory, all dependencies are initially downloaded and built from scratch. To avoid extra downloads it is recommend to set the
CPM_SOURCE_CACHE
environmental variable. Using a caching compiler such as ccache can drastically reduce build time. - Dependent on good CMakeLists Many libraries do not have CMakeLists that work well for subprojects. Luckily this is slowly changing, however, until then, some manual configuration may be required (see the snippets below for examples). For best practices on preparing projects for CPM, see the wiki.
- First version used In diamond-shaped dependency graphs (e.g.
A
depends onC
@1.1 andB
, which itself depends onC
@1.2 the first added dependency will be used (in this caseC
@1.1). In this case, B requires a newer version ofC
thanA
, so CPM will emit a warning. This can be easily resolved by adding a new version of the dependency in the outermost project, or by introducing a package lock file.
For projects with more complex needs and where an extra setup step doesn't matter, it may be worth to check out an external C++ package manager such as vcpkg, conan or hunter.
Dependencies added with CPMFindPackage
should work with external package managers.
Additionally, the option CPM_USE_LOCAL_PACKAGES
will enable find_package
for all CPM dependencies.
To avoid re-downloading dependencies, CPM has an option CPM_SOURCE_CACHE
that can be passed to CMake as -DCPM_SOURCE_CACHE=<path to an external download directory>
.
This will also allow projects to be configured offline, as long as the dependencies have been added to the cache before.
It may also be defined system-wide as an environmental variable, e.g. by exporting CPM_SOURCE_CACHE
in your .bashrc
or .bash_profile
.
export CPM_SOURCE_CACHE=$HOME/.cache/CPM
Note that passing the variable as a configure option to CMake will always override the value set by the environmental variable.
If set, CPM will forward all calls to CPMFindPackage
as CPMAddPackage
.
This is useful to create reproducible builds or to determine if the source parameters have all been set correctly.
This can also be set as an environmental variable.
CPM can be configured to use find_package
to search for locally installed dependencies first by setting the CMake option CPM_USE_LOCAL_PACKAGES
.
If the option CPM_LOCAL_PACKAGES_ONLY
is set, CPM will emit an error if the dependency is not found locally.
These options can also be set as environmental variables.
Library developers are often in the situation where they work on a locally checked out dependency at the same time as on a consumer project.
It is possible to override the consumer's dependency with the version by supplying the CMake option CPM_<dependency name>_SOURCE
set to the absolute path of the local library.
For example, to use the local version of the dependency Dep
at the path /path/to/dep
, the consumer can be built with the following command.
cmake -Bbuild -DCPM_Dep_SOURCE=/path/to/dep
In large projects with many transitive dependencies, it can be useful to introduce a package lock file.
This will list all CPM.cmake dependencies and can be used to update dependencies without modifying the original CMakeLists.txt
.
To use a package lock, add the following line directly after including CPM.cmake.
CPMUsePackageLock(package-lock.cmake)
To create or update the package lock file, build the cpm-update-package-lock
target.
cmake -Bbuild
cmake --build build --target cpm-update-package-lock
See the wiki for more info.
These examples demonstrate how to include some well-known projects with CPM. See the wiki for more snippets.
CPMAddPackage(
NAME Catch2
GITHUB_REPOSITORY catchorg/Catch2
VERSION 2.5.0
)
CPMAddPackage(
NAME boost-cmake
GITHUB_REPOSITORY Orphis/boost-cmake
VERSION 1.67.0
)
CPMAddPackage(
NAME cxxopts
GITHUB_REPOSITORY jarro2783/cxxopts
VERSION 2.2.0
OPTIONS
"CXXOPTS_BUILD_EXAMPLES Off"
"CXXOPTS_BUILD_TESTS Off"
)
CPMAddPackage(
NAME yaml-cpp
GITHUB_REPOSITORY jbeder/yaml-cpp
# 0.6.2 uses deprecated CMake syntax
VERSION 0.6.3
# 0.6.3 is not released yet, so use a recent commit
GIT_TAG 012269756149ae99745b6dafefd415843d7420bb
OPTIONS
"YAML_CPP_BUILD_TESTS Off"
"YAML_CPP_BUILD_CONTRIB Off"
"YAML_CPP_BUILD_TOOLS Off"
)
CPMAddPackage(
NAME benchmark
GITHUB_REPOSITORY google/benchmark
VERSION 1.4.1
OPTIONS
"BENCHMARK_ENABLE_TESTING Off"
)
if (benchmark_ADDED)
# compile with C++17
set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
endif()
CPMAddPackage(
NAME nlohmann_json
VERSION 3.6.1
# the git repo is incredibly large, so we download the archived include directory
URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
)
if (nlohmann_json_ADDED)
add_library(nlohmann_json INTERFACE IMPORTED)
target_include_directories(nlohmann_json INTERFACE ${nlohmann_json_SOURCE_DIR})
endif()
CPMAddPackage(
NAME range-v3
URL https://github.com/ericniebler/range-v3/archive/0.5.0.zip
VERSION 0.5.0
# the range-v3 CMakeLists screws with configuration options
DOWNLOAD_ONLY True
)
if(range-v3_ADDED)
add_library(range-v3 INTERFACE IMPORTED)
target_include_directories(range-v3 INTERFACE "${range-v3_SOURCE_DIR}/include")
endif()
CPMAddPackage(
NAME lua
GIT_REPOSITORY https://github.com/lua/lua.git
VERSION 5.3.5
DOWNLOAD_ONLY YES
)
if (lua_ADDED)
# lua has no CMake support, so we create our own target
FILE(GLOB lua_sources ${lua_SOURCE_DIR}/*.c)
add_library(lua STATIC ${lua_sources})
target_include_directories(lua
PUBLIC
$<BUILD_INTERFACE:${lua_SOURCE_DIR}>
)
endif()
For a full example on using CPM to download and configure lua with sol2 see here.
See the examples directory for full examples with source code and check out the wiki for many more example snippets.