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A CMake script for setup-free, reproducible cross-platform dependency management
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README.md

Build Status

Setup-free CMake dependency management

CPM is a CMake script that adds dependency management capabilities to CMake. It's built as a wrapper around CMake's FetchContent module that adds version control and a simple API.

Manage everything

Anything can be added as a version-controlled dependency though CPM, no packaging required. Projects using CMake are automatically configured and their targets can be used immediately. For everything else, a target can be created manually (see below).

Usage

After CPM.cmake has been added to your project, the function CPMAddPackage can be used to fetch and configure a dependency. Afterwards, any targets defined in the dependency can be used directly. CPMAddPackage takes the following named paramters.

CPMAddPackage(
  NAME          # The unique name of the dependency (should be the main 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 paramters 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. GIT_TAG can also be set to a specific commit or a branch name such as master to download the most recent version.

Besides downloading and to configuring the dependency, 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 to YES if the dependency has not been added before, otherwise it is set to NO.

Full CMakeLists Example

cmake_minimum_required(VERSION 3.14 FATAL_ERROR)

# create project
project(MyProject)

# add executable
add_executable(myProject myProject.cpp)
set_target_properties(myProject PROPERTIES CXX_STANDARD 17)

# add dependencies
include(cmake/CPM.cmake)

CPMAddPackage(
  NAME LarsParser
  VERSION 1.8
  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
  OPTIONS
    "LARS_PARSER_BUILD_GLUE_EXTENSION ON"
)

target_link_libraries(myProject LarsParser)

See the examples directory for more examples with source code.

Adding CPM

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://raw.githubusercontent.com/TheLartians/CPM/master/cmake/CPM.cmake

Updating CPM

To update CPM to the newest version, simply update the script in the project's cmake directory, for example by running the command above. Dependencies using CPM will automatically use the updated script of the outermost project.

Advantages

  • Small and reusable projects CPM takes care of all project dependencies, allowing developers to focus on creating small, well-tested frameworks.
  • Cross-Plattform CPM adds projects via add_subdirectory, which is compatible with all cmake toolchains and generators.
  • Reproducable builds By using versioning via git tags it is ensured that a project will always be in the same state everywhere.
  • Recursive dependencies Ensures that no dependency is added twice and is 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 There is a good chance your existing projects already work as CPM dependencies.
  • Simple source distribution CPM makes including projects with source files and dependencies easy, reducing the need for monolithic header files.

Limitations

  • No pre-built binaries For every new project, all dependencies must be downloaded and built from scratch. A possible workaround is to use CPM to fetch a pre-built binary or to enable local packages (see below).
  • 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 below).
  • First version used In diamond-shaped dependency graphs (e.g. A depends on C@1.1 and B, which itself depends on C@1.2 the first added dependency will be used (in this case C@1.1). In this case, B requires a newer version of C than A, so CPM will emit an error. This can be resolved by updating the outermost dependency version.

For projects with more complex needs and where an extra setup step doesn't matter, it is worth to check out fully featured C++ package managers such as conan, vcpkg or hunter. Support for package managers is also planned for a future version of CPM.

Local packages

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.

Snipplets

These examples demonstrate how to include some well-known projects with CPM.

Catch2

CPMAddPackage(
  NAME Catch2
  GITHUB_REPOSITORY catchorg/Catch2
  VERSION 2.5.0
)

Doctest

CPMAddPackage(
  NAME doctest
  GITHUB_REPOSITORY onqtam/doctest
  VERSION 2.3.2
  GIT_TAG 2.3.2
)

google/benchmark

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()

nlohmann/json

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()

Range-v3

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()

Yaml-cpp

CPMAddPackage(
  NAME yaml-cpp
  GITHUB_REPOSITORY jbeder/yaml-cpp
  # 0.6.2 uses depricated 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"
)

Lua

CPMAddPackage(
  NAME lua
  GIT_REPOSITORY https://github.com/lua/lua.git
  VERSION 5-3-4
  DOWNLOAD_ONLY YES
)

if (lua_ADDED)
  # lua has no CMakeLists, 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.

Examples

See the examples directory for more examples with source code.

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