CMakePackageConfigHelpers

Helper functions for creating config files that can be included by other projects to find and use a package.

Generating a Package Configuration File

configure_package_config_file

Create a config file for a project:

configure_package_config_file(<input> <output>
  INSTALL_DESTINATION <path>
  [PATH_VARS <var1> <var2> ... <varN>]
  [NO_SET_AND_CHECK_MACRO]
  [NO_CHECK_REQUIRED_COMPONENTS_MACRO]
  [INSTALL_PREFIX <path>]
  )

configure_package_config_file() should be used instead of the plain configure_file() command when creating the <PackageName>Config.cmake or <PackageName>-config.cmake file for installing a project or library. It helps make the resulting package relocatable by avoiding hardcoded paths in the installed <PackageName>Config.cmake file.

In a FooConfig.cmake file there may be code like this to make the install destinations known to the using project:

set(FOO_INCLUDE_DIR   "@CMAKE_INSTALL_FULL_INCLUDEDIR@" )
set(FOO_DATA_DIR   "@CMAKE_INSTALL_PREFIX@/@RELATIVE_DATA_INSTALL_DIR@" )
set(FOO_ICONS_DIR   "@CMAKE_INSTALL_PREFIX@/share/icons" )
#...logic to determine installedPrefix from the own location...
set(FOO_CONFIG_DIR  "${installedPrefix}/@CONFIG_INSTALL_DIR@" )

All four options shown above are not sufficient The first three hardcode the absolute directory locations. The fourth case works only if the logic to determine the installedPrefix is correct, and if CONFIG_INSTALL_DIR contains a relative path, which in general cannot be guaranteed. This has the effect that the resulting FooConfig.cmake file would work poorly under Windows and macOS, where users are used to choosing the install location of a binary package at install time, independent from how CMAKE_INSTALL_PREFIX was set at build/cmake time.

Using configure_package_config_file() helps. If used correctly, it makes the resulting FooConfig.cmake file relocatable. Usage:

1. Write a FooConfig.cmake.in file as you are used to.

2. Insert a line at the top containing only the string @PACKAGE_INIT@.

3. Instead of set(FOO_DIR "@SOME_INSTALL_DIR@"), use set(FOO_DIR "@PACKAGE_SOME_INSTALL_DIR@") (this must be after the @PACKAGE_INIT@ line).

4. Instead of using the normal configure_file() command, use configure_package_config_file().

The <input> and <output> arguments are the input and output file, the same way as in configure_file().

The <path> given to INSTALL_DESTINATION must be the destination where the FooConfig.cmake file will be installed to. This path can either be absolute, or relative to the INSTALL_PREFIX path.

The variables <var1> to <varN> given as PATH_VARS are the variables which contain install destinations. For each of them, the macro will create a helper variable PACKAGE_<var...>. These helper variables must be used in the FooConfig.cmake.in file for setting the installed location. They are calculated by configure_package_config_file() so that they are always relative to the installed location of the package. This works both for relative and also for absolute locations. For absolute locations, it works only if the absolute location is a subdirectory of INSTALL_PREFIX.

New in version 3.30: The variable PACKAGE_PREFIX_DIR will always be defined after the @PACKAGE_INIT@ line. It will hold the value of the base install location. In general, variables defined via the PATH_VARS mechanism should be used instead, but PACKAGE_PREFIX_DIR can be used for those cases not easily handled by PATH_VARS, such as for files installed directly to the base install location rather than a subdirectory of it.

Note

When consumers of the generated file use CMake 3.29 or older, the value of PACKAGE_PREFIX_DIR can be changed by a call to find_dependency() or find_package(). If a project relies on PACKAGE_PREFIX_DIR, it is the project's responsibility to ensure that the value of PACKAGE_PREFIX_DIR is preserved across any such calls, or any other calls which might include another file generated by configure_package_config_file().

New in version 3.1: If the INSTALL_PREFIX argument is passed, this is used as the base path to calculate all the relative paths. The <path> argument must be an absolute path. If this argument is not passed, the CMAKE_INSTALL_PREFIX variable will be used instead. The default value is good when generating a FooConfig.cmake file to use your package from the install tree. When generating a FooConfig.cmake file to use your package from the build tree, this option should be used.

By default, configure_package_config_file() also generates two helper macros, set_and_check() and check_required_components(), into the FooConfig.cmake file.

set_and_check() should be used instead of the normal set() command for setting directories and file locations. In addition to setting the variable, it also checks that the referenced file or directory actually exists and fails with a fatal error if it doesn't. This ensures that the generated FooConfig.cmake file does not contain wrong references. Add the NO_SET_AND_CHECK_MACRO option to prevent the generation of the set_and_check() macro in the FooConfig.cmake file.

check_required_components(<PackageName>) should be called at the end of the FooConfig.cmake file. This macro checks whether all requested, non-optional components have been found, and if this is not the case, it sets the Foo_FOUND variable to FALSE so that the package is considered to be not found. It does that by testing the Foo_<Component>_FOUND variables for all requested required components. This macro should be called even if the package doesn't provide any components to make sure users are not specifying components erroneously. Add the NO_CHECK_REQUIRED_COMPONENTS_MACRO option to prevent the generation of the check_required_components() macro in the FooConfig.cmake file.

See also Example Generating Package Files.

Generating a Package Version File

write_basic_package_version_file

Create a version file for a project:

write_basic_package_version_file(<filename>
  [VERSION <major.minor.patch>]
  COMPATIBILITY <AnyNewerVersion|SameMajorVersion|SameMinorVersion|ExactVersion>
  [ARCH_INDEPENDENT] )

Writes a file for use as a <PackageName>ConfigVersion.cmake file to <filename>. See the documentation of find_package() for details on such files.

<filename> is the output filename, which should be in the build tree. <major.minor.patch> is the version number of the project to be installed.

If no VERSION is given, the PROJECT_VERSION variable is used. If this hasn't been set, it errors out.

The COMPATIBILITY mode AnyNewerVersion means that the installed package version will be considered compatible if it is newer or exactly the same as the requested version. This mode should be used for packages which are fully backward compatible, also across major versions. If SameMajorVersion is used instead, then the behavior differs from AnyNewerVersion in that the major version number must be the same as requested, e.g. version 2.0 will not be considered compatible if 1.0 is requested. This mode should be used for packages which guarantee backward compatibility within the same major version. If SameMinorVersion is used, the behavior is the same as SameMajorVersion, but both major and minor version must be the same as requested, e.g version 0.2 will not be compatible if 0.1 is requested. If ExactVersion is used, then the package is only considered compatible if the requested version matches exactly its own version number (not considering the tweak version). For example, version 1.2.3 of a package is only considered compatible to requested version 1.2.3. This mode is for packages without compatibility guarantees. If your project has more elaborate version matching rules, you will need to write your own custom <PackageName>ConfigVersion.cmake file instead of using this macro.

New in version 3.11: The SameMinorVersion compatibility mode.

New in version 3.14: If ARCH_INDEPENDENT is given, the installed package version will be considered compatible even if it was built for a different architecture than the requested architecture. Otherwise, an architecture check will be performed, and the package will be considered compatible only if the architecture matches exactly. For example, if the package is built for a 32-bit architecture, the package is only considered compatible if it is used on a 32-bit architecture, unless ARCH_INDEPENDENT is given, in which case the package is considered compatible on any architecture.

Note

ARCH_INDEPENDENT is intended for header-only libraries or similar packages with no binaries.

New in version 3.19: The version file generated by AnyNewerVersion, SameMajorVersion and SameMinorVersion arguments of COMPATIBILITY handle the version range, if one is specified (see find_package() command for the details). ExactVersion mode is incompatible with version ranges and will display an author warning if one is specified.

Internally, this macro executes configure_file() to create the resulting version file. Depending on the COMPATIBILITY, the corresponding BasicConfigVersion-<COMPATIBILITY>.cmake.in file is used. Please note that these files are internal to CMake and you should not call configure_file() on them yourself, but they can be used as a starting point to create more sophisticated custom <PackageName>ConfigVersion.cmake files.

Generating an Apple Platform Selection File

generate_apple_platform_selection_file

New in version 3.29.

Create an Apple platform selection file:

generate_apple_platform_selection_file(<filename>
  INSTALL_DESTINATION <path>
  [INSTALL_PREFIX <path>]
  [MACOS_INCLUDE_FILE <file>]
  [IOS_INCLUDE_FILE <file>]
  [IOS_SIMULATOR_INCLUDE_FILE <file>]
  [IOS_CATALYST_INCLUDE_FILE <file>]
  [TVOS_INCLUDE_FILE <file>]
  [TVOS_SIMULATOR_INCLUDE_FILE <file>]
  [WATCHOS_INCLUDE_FILE <file>]
  [WATCHOS_SIMULATOR_INCLUDE_FILE <file>]
  [VISIONOS_INCLUDE_FILE <file>]
  [VISIONOS_SIMULATOR_INCLUDE_FILE <file>]
  [ERROR_VARIABLE <variable>]
  )

Write a file that includes an Apple-platform-specific .cmake file, e.g., for use as <PackageName>Config.cmake. This can be used in conjunction with the XCFRAMEWORK_LOCATION argument of export(SETUP) to export packages in a way that a project built for any Apple platform can use them.

INSTALL_DESTINATION <path>

Path to which the generated file will be installed by the caller, e.g., via install(FILES). The path may be either relative to the INSTALL_PREFIX or absolute.

INSTALL_PREFIX <path>

Path prefix to which the package will be installed by the caller. The <path> argument must be an absolute path. If this argument is not passed, the CMAKE_INSTALL_PREFIX variable will be used instead.

MACOS_INCLUDE_FILE <file>

File to include if the platform is macOS.

IOS_INCLUDE_FILE <file>

File to include if the platform is iOS.

IOS_SIMULATOR_INCLUDE_FILE <file>

File to include if the platform is iOS Simulator.

IOS_CATALYST_INCLUDE_FILE <file>

New in version 3.31.

File to include if the platform is iOS Catalyst.

TVOS_INCLUDE_FILE <file>

File to include if the platform is tvOS.

TVOS_SIMULATOR_INCLUDE_FILE <file>

File to include if the platform is tvOS Simulator.

WATCHOS_INCLUDE_FILE <file>

File to include if the platform is watchOS.

WATCHOS_SIMULATOR_INCLUDE_FILE <file>

File to include if the platform is watchOS Simulator.

VISIONOS_INCLUDE_FILE <file>

File to include if the platform is visionOS.

VISIONOS_SIMULATOR_INCLUDE_FILE <file>

File to include if the platform is visionOS Simulator.

ERROR_VARIABLE <variable>

If the consuming project is built for an unsupported platform, set <variable> to an error message. The includer may use this information to pretend the package was not found. If this option is not given, the default behavior is to issue a fatal error.

If any of the optional include files is not specified, and the consuming project is built for its corresponding platform, the generated file will consider the platform to be unsupported. The behavior is determined by the ERROR_VARIABLE option.

Generating an Apple Architecture Selection File

generate_apple_architecture_selection_file

New in version 3.29.

Create an Apple architecture selection file:

generate_apple_architecture_selection_file(<filename>
  INSTALL_DESTINATION <path>
  [INSTALL_PREFIX <path>]
  [SINGLE_ARCHITECTURES <arch>...
   SINGLE_ARCHITECTURE_INCLUDE_FILES <file>...]
  [UNIVERSAL_ARCHITECTURES <arch>...
   UNIVERSAL_INCLUDE_FILE <file>]
  [ERROR_VARIABLE <variable>]
  )

Write a file that includes an Apple-architecture-specific .cmake file based on CMAKE_OSX_ARCHITECTURES, e.g., for inclusion from an Apple-specific <PackageName>Config.cmake file.

INSTALL_DESTINATION <path>

Path to which the generated file will be installed by the caller, e.g., via install(FILES). The path may be either relative to the INSTALL_PREFIX or absolute.

INSTALL_PREFIX <path>

Path prefix to which the package will be installed by the caller. The <path> argument must be an absolute path. If this argument is not passed, the CMAKE_INSTALL_PREFIX variable will be used instead.

SINGLE_ARCHITECTURES <arch>...

Architectures provided by entries of SINGLE_ARCHITECTURE_INCLUDE_FILES.

SINGLE_ARCHITECTURE_INCLUDE_FILES <file>...

Architecture-specific files. One of them will be loaded when CMAKE_OSX_ARCHITECTURES contains a single architecture matching the corresponding entry of SINGLE_ARCHITECTURES.

UNIVERSAL_ARCHITECTURES <arch>...

Architectures provided by the UNIVERSAL_INCLUDE_FILE.

The list may include $(ARCHS_STANDARD) to support consumption using the Xcode generator, but the architectures should always be listed individually too.

UNIVERSAL_INCLUDE_FILE <file>

A file to load when CMAKE_OSX_ARCHITECTURES contains a (non-strict) subset of the UNIVERSAL_ARCHITECTURES and does not match any one of the SINGLE_ARCHITECTURES.

ERROR_VARIABLE <variable>

If the consuming project is built for an unsupported architecture, set <variable> to an error message. The includer may use this information to pretend the package was not found. If this option is not given, the default behavior is to issue a fatal error.

Example Generating Package Files

Example using both the configure_package_config_file() and write_basic_package_version_file() commands:

CMakeLists.txt

include(GNUInstallDirs)
set(INCLUDE_INSTALL_DIR ${CMAKE_INSTALL_INCLUDEDIR}/Foo
    CACHE PATH "Location of header files" )
set(SYSCONFIG_INSTALL_DIR ${CMAKE_INSTALL_SYSCONFDIR}/foo
    CACHE PATH "Location of configuration files" )
#...
include(CMakePackageConfigHelpers)
configure_package_config_file(FooConfig.cmake.in
  ${CMAKE_CURRENT_BINARY_DIR}/FooConfig.cmake
  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Foo
  PATH_VARS INCLUDE_INSTALL_DIR SYSCONFIG_INSTALL_DIR)
write_basic_package_version_file(
  ${CMAKE_CURRENT_BINARY_DIR}/FooConfigVersion.cmake
  VERSION 1.2.3
  COMPATIBILITY SameMajorVersion )
install(FILES ${CMAKE_CURRENT_BINARY_DIR}/FooConfig.cmake
              ${CMAKE_CURRENT_BINARY_DIR}/FooConfigVersion.cmake
        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Foo )

FooConfig.cmake.in

set(FOO_VERSION x.y.z)
...
@PACKAGE_INIT@
...
set_and_check(FOO_INCLUDE_DIR "@PACKAGE_INCLUDE_INSTALL_DIR@")
set_and_check(FOO_SYSCONFIG_DIR "@PACKAGE_SYSCONFIG_INSTALL_DIR@")

check_required_components(Foo)