1506f9ca56
The find_package command, on Windows, has always searched build trees recently visited by cmake-gui (or CMakeSetup at one time). This was done when the command was created with the intention of simplifying workflows involving building multiple dependent projects. However, this behavior depends on recent developer interaction and therefore can create different find results based on transient system states. It can lead to surprising results and user confusion. Since this behavior was first added CMake has gained many more search options, better error messages when a package is not found, and a package registry. The latter in particular allows projects to make their build trees available for dependent projects to find without user intervention. Therefore the originally intended workflow can be achieved in other, more stable ways. After the above evoluion of find_package we have now decided that the magic search-where-cmake-gui-was behavior does more harm than good. Drop it. We do not need a policy for this behavior change because it only affects interactive use.
346 lines
15 KiB
ReStructuredText
346 lines
15 KiB
ReStructuredText
find_package
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------------
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Load settings for an external project.
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::
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find_package(<package> [version] [EXACT] [QUIET] [MODULE]
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[REQUIRED] [[COMPONENTS] [components...]]
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[OPTIONAL_COMPONENTS components...]
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[NO_POLICY_SCOPE])
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Finds and loads settings from an external project. ``<package>_FOUND``
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will be set to indicate whether the package was found. When the
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package is found package-specific information is provided through
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variables and :ref:`Imported Targets` documented by the package itself. The
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``QUIET`` option disables messages if the package cannot be found. The
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``MODULE`` option disables the second signature documented below. The
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``REQUIRED`` option stops processing with an error message if the package
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cannot be found.
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A package-specific list of required components may be listed after the
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``COMPONENTS`` option (or after the ``REQUIRED`` option if present).
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Additional optional components may be listed after
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``OPTIONAL_COMPONENTS``. Available components and their influence on
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whether a package is considered to be found are defined by the target
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package.
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The ``[version]`` argument requests a version with which the package found
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should be compatible (format is ``major[.minor[.patch[.tweak]]]``). The
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``EXACT`` option requests that the version be matched exactly. If no
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``[version]`` and/or component list is given to a recursive invocation
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inside a find-module, the corresponding arguments are forwarded
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automatically from the outer call (including the ``EXACT`` flag for
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``[version]``). Version support is currently provided only on a
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package-by-package basis (details below).
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User code should generally look for packages using the above simple
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signature. The remainder of this command documentation specifies the
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full command signature and details of the search process. Project
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maintainers wishing to provide a package to be found by this command
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are encouraged to read on.
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The command has two modes by which it searches for packages: "Module"
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mode and "Config" mode. Module mode is available when the command is
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invoked with the above reduced signature. CMake searches for a file
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called ``Find<package>.cmake`` in the :variable:`CMAKE_MODULE_PATH`
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followed by the CMake installation. If the file is found, it is read
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and processed by CMake. It is responsible for finding the package,
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checking the version, and producing any needed messages. Many
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find-modules provide limited or no support for versioning; check
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the module documentation. If no module is found and the ``MODULE``
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option is not given the command proceeds to Config mode.
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The complete Config mode command signature is::
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find_package(<package> [version] [EXACT] [QUIET]
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[REQUIRED] [[COMPONENTS] [components...]]
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[CONFIG|NO_MODULE]
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[NO_POLICY_SCOPE]
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[NAMES name1 [name2 ...]]
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[CONFIGS config1 [config2 ...]]
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[HINTS path1 [path2 ... ]]
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[PATHS path1 [path2 ... ]]
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[PATH_SUFFIXES suffix1 [suffix2 ...]]
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[NO_DEFAULT_PATH]
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[NO_CMAKE_ENVIRONMENT_PATH]
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[NO_CMAKE_PATH]
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[NO_SYSTEM_ENVIRONMENT_PATH]
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[NO_CMAKE_PACKAGE_REGISTRY]
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[NO_CMAKE_BUILDS_PATH] # Deprecated; does nothing.
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[NO_CMAKE_SYSTEM_PATH]
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[NO_CMAKE_SYSTEM_PACKAGE_REGISTRY]
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[CMAKE_FIND_ROOT_PATH_BOTH |
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ONLY_CMAKE_FIND_ROOT_PATH |
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NO_CMAKE_FIND_ROOT_PATH])
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The ``CONFIG`` option may be used to skip Module mode explicitly and
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switch to Config mode. It is synonymous to using ``NO_MODULE``. Config
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mode is also implied by use of options not specified in the reduced
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signature.
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Config mode attempts to locate a configuration file provided by the
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package to be found. A cache entry called ``<package>_DIR`` is created to
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hold the directory containing the file. By default the command
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searches for a package with the name ``<package>``. If the ``NAMES`` option
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is given the names following it are used instead of ``<package>``. The
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command searches for a file called ``<name>Config.cmake`` or
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``<lower-case-name>-config.cmake`` for each name specified. A
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replacement set of possible configuration file names may be given
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using the ``CONFIGS`` option. The search procedure is specified below.
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Once found, the configuration file is read and processed by CMake.
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Since the file is provided by the package it already knows the
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location of package contents. The full path to the configuration file
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is stored in the cmake variable ``<package>_CONFIG``.
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All configuration files which have been considered by CMake while
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searching for an installation of the package with an appropriate
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version are stored in the cmake variable ``<package>_CONSIDERED_CONFIGS``,
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the associated versions in ``<package>_CONSIDERED_VERSIONS``.
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If the package configuration file cannot be found CMake will generate
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an error describing the problem unless the ``QUIET`` argument is
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specified. If ``REQUIRED`` is specified and the package is not found a
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fatal error is generated and the configure step stops executing. If
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``<package>_DIR`` has been set to a directory not containing a
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configuration file CMake will ignore it and search from scratch.
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When the ``[version]`` argument is given Config mode will only find a
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version of the package that claims compatibility with the requested
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version (format is ``major[.minor[.patch[.tweak]]]``). If the ``EXACT``
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option is given only a version of the package claiming an exact match
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of the requested version may be found. CMake does not establish any
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convention for the meaning of version numbers. Package version
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numbers are checked by "version" files provided by the packages
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themselves. For a candidate package configuration file
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``<config-file>.cmake`` the corresponding version file is located next
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to it and named either ``<config-file>-version.cmake`` or
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``<config-file>Version.cmake``. If no such version file is available
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then the configuration file is assumed to not be compatible with any
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requested version. A basic version file containing generic version
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matching code can be created using the
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:module:`CMakePackageConfigHelpers` module. When a version file
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is found it is loaded to check the requested version number. The
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version file is loaded in a nested scope in which the following
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variables have been defined:
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``PACKAGE_FIND_NAME``
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the ``<package>`` name
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``PACKAGE_FIND_VERSION``
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full requested version string
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``PACKAGE_FIND_VERSION_MAJOR``
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major version if requested, else 0
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``PACKAGE_FIND_VERSION_MINOR``
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minor version if requested, else 0
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``PACKAGE_FIND_VERSION_PATCH``
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patch version if requested, else 0
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``PACKAGE_FIND_VERSION_TWEAK``
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tweak version if requested, else 0
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``PACKAGE_FIND_VERSION_COUNT``
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number of version components, 0 to 4
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The version file checks whether it satisfies the requested version and
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sets these variables:
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``PACKAGE_VERSION``
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full provided version string
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``PACKAGE_VERSION_EXACT``
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true if version is exact match
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``PACKAGE_VERSION_COMPATIBLE``
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true if version is compatible
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``PACKAGE_VERSION_UNSUITABLE``
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true if unsuitable as any version
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These variables are checked by the ``find_package`` command to determine
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whether the configuration file provides an acceptable version. They
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are not available after the find_package call returns. If the version
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is acceptable the following variables are set:
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``<package>_VERSION``
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full provided version string
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``<package>_VERSION_MAJOR``
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major version if provided, else 0
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``<package>_VERSION_MINOR``
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minor version if provided, else 0
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``<package>_VERSION_PATCH``
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patch version if provided, else 0
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``<package>_VERSION_TWEAK``
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tweak version if provided, else 0
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``<package>_VERSION_COUNT``
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number of version components, 0 to 4
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and the corresponding package configuration file is loaded. When
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multiple package configuration files are available whose version files
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claim compatibility with the version requested it is unspecified which
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one is chosen. No attempt is made to choose a highest or closest
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version number.
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Config mode provides an elaborate interface and search procedure.
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Much of the interface is provided for completeness and for use
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internally by find-modules loaded by Module mode. Most user code
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should simply call::
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find_package(<package> [major[.minor]] [EXACT] [REQUIRED|QUIET])
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in order to find a package. Package maintainers providing CMake
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package configuration files are encouraged to name and install them
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such that the procedure outlined below will find them without
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requiring use of additional options.
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CMake constructs a set of possible installation prefixes for the
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package. Under each prefix several directories are searched for a
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configuration file. The tables below show the directories searched.
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Each entry is meant for installation trees following Windows (W), UNIX
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(U), or Apple (A) conventions::
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<prefix>/ (W)
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<prefix>/(cmake|CMake)/ (W)
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<prefix>/<name>*/ (W)
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<prefix>/<name>*/(cmake|CMake)/ (W)
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<prefix>/(lib/<arch>|lib|share)/cmake/<name>*/ (U)
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<prefix>/(lib/<arch>|lib|share)/<name>*/ (U)
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<prefix>/(lib/<arch>|lib|share)/<name>*/(cmake|CMake)/ (U)
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On systems supporting OS X Frameworks and Application Bundles the
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following directories are searched for frameworks or bundles
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containing a configuration file::
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<prefix>/<name>.framework/Resources/ (A)
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<prefix>/<name>.framework/Resources/CMake/ (A)
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<prefix>/<name>.framework/Versions/*/Resources/ (A)
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<prefix>/<name>.framework/Versions/*/Resources/CMake/ (A)
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<prefix>/<name>.app/Contents/Resources/ (A)
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<prefix>/<name>.app/Contents/Resources/CMake/ (A)
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In all cases the ``<name>`` is treated as case-insensitive and corresponds
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to any of the names specified (``<package>`` or names given by ``NAMES``).
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Paths with ``lib/<arch>`` are enabled if the
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:variable:`CMAKE_LIBRARY_ARCHITECTURE` variable is set. If ``PATH_SUFFIXES``
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is specified the suffixes are appended to each (W) or (U) directory entry
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one-by-one.
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This set of directories is intended to work in cooperation with
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projects that provide configuration files in their installation trees.
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Directories above marked with (W) are intended for installations on
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Windows where the prefix may point at the top of an application's
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installation directory. Those marked with (U) are intended for
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installations on UNIX platforms where the prefix is shared by multiple
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packages. This is merely a convention, so all (W) and (U) directories
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are still searched on all platforms. Directories marked with (A) are
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intended for installations on Apple platforms. The cmake variables
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``CMAKE_FIND_FRAMEWORK`` and ``CMAKE_FIND_APPBUNDLE``
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determine the order of preference as specified below.
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The set of installation prefixes is constructed using the following
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steps. If ``NO_DEFAULT_PATH`` is specified all ``NO_*`` options are
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enabled.
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1. Search paths specified in cmake-specific cache variables. These
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are intended to be used on the command line with a ``-DVAR=value``.
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This can be skipped if ``NO_CMAKE_PATH`` is passed::
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CMAKE_PREFIX_PATH
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CMAKE_FRAMEWORK_PATH
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CMAKE_APPBUNDLE_PATH
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2. Search paths specified in cmake-specific environment variables.
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These are intended to be set in the user's shell configuration.
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This can be skipped if ``NO_CMAKE_ENVIRONMENT_PATH`` is passed::
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<package>_DIR
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CMAKE_PREFIX_PATH
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CMAKE_FRAMEWORK_PATH
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CMAKE_APPBUNDLE_PATH
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3. Search paths specified by the ``HINTS`` option. These should be paths
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computed by system introspection, such as a hint provided by the
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location of another item already found. Hard-coded guesses should
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be specified with the ``PATHS`` option.
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4. Search the standard system environment variables. This can be
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skipped if ``NO_SYSTEM_ENVIRONMENT_PATH`` is passed. Path entries
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ending in ``/bin`` or ``/sbin`` are automatically converted to their
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parent directories::
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PATH
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5. Search paths stored in the CMake :ref:`User Package Registry`.
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This can be skipped if ``NO_CMAKE_PACKAGE_REGISTRY`` is passed or by
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setting the :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`
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to ``TRUE``.
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See the :manual:`cmake-packages(7)` manual for details on the user
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package registry.
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6. Search cmake variables defined in the Platform files for the
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current system. This can be skipped if ``NO_CMAKE_SYSTEM_PATH`` is
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passed::
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CMAKE_SYSTEM_PREFIX_PATH
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CMAKE_SYSTEM_FRAMEWORK_PATH
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CMAKE_SYSTEM_APPBUNDLE_PATH
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7. Search paths stored in the CMake :ref:`System Package Registry`.
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This can be skipped if ``NO_CMAKE_SYSTEM_PACKAGE_REGISTRY`` is passed
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or by setting the
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:variable:`CMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY` to ``TRUE``.
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See the :manual:`cmake-packages(7)` manual for details on the system
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package registry.
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8. Search paths specified by the ``PATHS`` option. These are typically
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hard-coded guesses.
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.. |FIND_XXX| replace:: find_package
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.. |FIND_ARGS_XXX| replace:: <package>
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.. |CMAKE_FIND_ROOT_PATH_MODE_XXX| replace::
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:variable:`CMAKE_FIND_ROOT_PATH_MODE_PACKAGE`
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.. include:: FIND_XXX_MAC.txt
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.. include:: FIND_XXX_ROOT.txt
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.. include:: FIND_XXX_ORDER.txt
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Every non-REQUIRED ``find_package`` call can be disabled by setting the
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:variable:`CMAKE_DISABLE_FIND_PACKAGE_<PackageName>` variable to ``TRUE``.
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When loading a find module or package configuration file ``find_package``
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defines variables to provide information about the call arguments (and
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restores their original state before returning):
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``CMAKE_FIND_PACKAGE_NAME``
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the ``<package>`` name which is searched for
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``<package>_FIND_REQUIRED``
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true if ``REQUIRED`` option was given
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``<package>_FIND_QUIETLY``
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true if ``QUIET`` option was given
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``<package>_FIND_VERSION``
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full requested version string
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``<package>_FIND_VERSION_MAJOR``
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major version if requested, else 0
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``<package>_FIND_VERSION_MINOR``
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minor version if requested, else 0
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``<package>_FIND_VERSION_PATCH``
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patch version if requested, else 0
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``<package>_FIND_VERSION_TWEAK``
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tweak version if requested, else 0
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``<package>_FIND_VERSION_COUNT``
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number of version components, 0 to 4
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``<package>_FIND_VERSION_EXACT``
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true if ``EXACT`` option was given
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``<package>_FIND_COMPONENTS``
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list of requested components
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``<package>_FIND_REQUIRED_<c>``
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true if component ``<c>`` is required,
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false if component ``<c>`` is optional
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In Module mode the loaded find module is responsible to honor the
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request detailed by these variables; see the find module for details.
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In Config mode ``find_package`` handles ``REQUIRED``, ``QUIET``, and
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``[version]`` options automatically but leaves it to the package
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configuration file to handle components in a way that makes sense
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for the package. The package configuration file may set
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``<package>_FOUND`` to false to tell ``find_package`` that component
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requirements are not satisfied.
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See the :command:`cmake_policy` command documentation for discussion
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of the ``NO_POLICY_SCOPE`` option.
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