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| -rw-r--r-- | Help/manual/cmake-packages.7.rst | 129 |
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diff --git a/Help/manual/cmake-packages.7.rst b/Help/manual/cmake-packages.7.rst index e87eb83..1723826 100644 --- a/Help/manual/cmake-packages.7.rst +++ b/Help/manual/cmake-packages.7.rst @@ -488,3 +488,132 @@ Here, the ``ClimbingStats_NOTFOUND_MESSAGE`` is set to a diagnosis that the pack could not be found because an invalid component was specified. This message variable can be set for any case where the ``_FOUND`` variable is set to ``False``, and will be displayed to the user. + +.. _`Package Registry`: + +Package Registry +================ + +CMake provides two central locations to register packages that have +been built or installed anywhere on a system: + +* `User Package Registry`_ +* `System Package Registry`_ + +The registries are especially useful to help projects find packages in +non-standard install locations or directly in their own build trees. +A project may populate either the user or system registry (using its own +means, see below) to refer to its location. +In either case the package should store at the registered location a +`Package Configuration File`_ (``<package>Config.cmake``) and optionally a +`Package Version File`_ (``<package>ConfigVersion.cmake``). + +The :command:`find_package` command searches the two package registries +as two of the search steps specified in its documentation. If it has +sufficient permissions it also removes stale package registry entries +that refer to directories that do not exist or do not contain a matching +package configuration file. + +.. _`User Package Registry`: + +User Package Registry +--------------------- + +The User Package Registry is stored in a per-user location. +The :command:`export(PACKAGE)` command may be used to register a project +build tree in the user package registry. CMake currently provides no +interface to add install trees to the user package registry. Installers +must be manually taught to register their packages if desired. + +On Windows the user package registry is stored in the Windows registry +under a key in ``HKEY_CURRENT_USER``. + +A ``<package>`` may appear under registry key:: + + HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\<package> + +as a ``REG_SZ`` value, with arbitrary name, that specifies the directory +containing the package configuration file. + +On UNIX platforms the user package registry is stored in the user home +directory under ``~/.cmake/packages``. A ``<package>`` may appear under +the directory:: + + ~/.cmake/packages/<package> + +as a file, with arbitrary name, whose content specifies the directory +containing the package configuration file. + +.. _`System Package Registry`: + +System Package Registry +----------------------- + +The System Package Registry is stored in a system-wide location. +CMake currently provides no interface to add to the system package registry. +Installers must be manually taught to register their packages if desired. + +On Windows the system package registry is stored in the Windows registry +under a key in ``HKEY_LOCAL_MACHINE``. A ``<package>`` may appear under +registry key:: + + HKEY_LOCAL_MACHINE\Software\Kitware\CMake\Packages\<package> + +as a ``REG_SZ`` value, with arbitrary name, that specifies the directory +containing the package configuration file. + +There is no system package registry on non-Windows platforms. + +Package Registry Example +------------------------ + +A simple convention for naming package registry entries is to use content +hashes. They are deterministic and unlikely to collide +(:command:`export(PACKAGE)` uses this approach). +The name of an entry referencing a specific directory is simply the content +hash of the directory path itself. + +If a project arranges for package registry entries to exist, such as:: + + > reg query HKCU\Software\Kitware\CMake\Packages\MyPackage + HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\MyPackage + 45e7d55f13b87179bb12f907c8de6fc4 REG_SZ c:/Users/Me/Work/lib/cmake/MyPackage + 7b4a9844f681c80ce93190d4e3185db9 REG_SZ c:/Users/Me/Work/MyPackage-build + +or:: + + $ cat ~/.cmake/packages/MyPackage/7d1fb77e07ce59a81bed093bbee945bd + /home/me/work/lib/cmake/MyPackage + $ cat ~/.cmake/packages/MyPackage/f92c1db873a1937f3100706657c63e07 + /home/me/work/MyPackage-build + +then the ``CMakeLists.txt`` code: + +.. code-block:: cmake + + find_package(MyPackage) + +will search the registered locations for package configuration files +(``MyPackageConfig.cmake``). The search order among package registry +entries for a single package is unspecified and the entry names +(hashes in this example) have no meaning. Registered locations may +contain package version files (``MyPackageConfigVersion.cmake``) to +tell :command:`find_package` whether a specific location is suitable +for the version requested. + +Package Registry Ownership +-------------------------- + +Package registry entries are individually owned by the project installations +that they reference. A package installer is responsible for adding its own +entry and the corresponding uninstaller is responsible for removing it. + +The :command:`export(PACKAGE)` command populates the user package registry +with the location of a project build tree. Build trees tend to be deleted by +developers and have no "uninstall" event that could trigger removal of their +entries. In order to keep the registries clean the :command:`find_package` +command automatically removes stale entries it encounters if it has sufficient +permissions. CMake provides no interface to remove an entry referencing an +existing build tree once :command:`export(PACKAGE)` has been invoked. +However, if the project removes its package configuration file from the build +tree then the entry referencing the location will be considered stale. |