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98 lines
3.8 KiB
CMake
98 lines
3.8 KiB
CMake
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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# file Copyright.txt or https://cmake.org/licensing for details.
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#[=======================================================================[.rst:
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CMakeFindDependencyMacro
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------------------------
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.. command:: find_dependency
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The ``find_dependency()`` macro wraps a :command:`find_package` call for
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a package dependency::
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find_dependency(<dep> [...])
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It is designed to be used in a
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:ref:`Package Configuration File <Config File Packages>`
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(``<PackageName>Config.cmake``). ``find_dependency`` forwards the correct
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parameters for ``QUIET`` and ``REQUIRED`` which were passed to
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the original :command:`find_package` call. Any additional arguments
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specified are forwarded to :command:`find_package`.
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If the dependency could not be found it sets an informative diagnostic
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message and calls :command:`return` to end processing of the calling
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package configuration file and return to the :command:`find_package`
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command that loaded it.
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.. note::
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The call to :command:`return` makes this macro unsuitable to call
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from :ref:`Find Modules`.
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Package Dependency Search Optimizations
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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If ``find_dependency`` is called with arguments identical to a previous
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call in the same directory, perhaps due to diamond-shaped package
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dependencies, the underlying call to :command:`find_package` is optimized
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out. This optimization is important to support large package dependency
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graphs while avoiding a combinatorial explosion of repeated searches.
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However, the heuristic cannot account for ambient variables that
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affect package behavior, such as ``<PackageName>_USE_STATIC_LIBS``,
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offered by some packages. Therefore package configuration files should
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avoid setting such variables before their calls to ``find_dependency``.
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.. versionchanged:: 3.15
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Previously, the underlying call to :command:`find_package` was always
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optimized out if the package had already been found. CMake 3.15
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removed the optimization to support cases in which ``find_dependency``
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call arguments request different components.
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.. versionchanged:: 3.26
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The pre-3.15 optimization was restored, but with the above-described
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heuristic to account for varying ``find_dependency`` call arguments.
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#]=======================================================================]
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macro(find_dependency dep)
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string(SHA256 cmake_fd_call_hash "${dep};${ARGN};${${CMAKE_FIND_PACKAGE_NAME}_FIND_REQUIRED}")
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if(_CMAKE_${dep}_${cmake_fd_call_hash}_FOUND)
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unset(cmake_fd_call_hash)
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else()
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list(APPEND _CMAKE_${dep}_HASH_STACK ${cmake_fd_call_hash})
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set(cmake_fd_quiet_arg)
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if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
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set(cmake_fd_quiet_arg QUIET)
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endif()
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set(cmake_fd_required_arg)
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if(${CMAKE_FIND_PACKAGE_NAME}_FIND_REQUIRED)
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set(cmake_fd_required_arg REQUIRED)
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endif()
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get_property(cmake_fd_alreadyTransitive GLOBAL PROPERTY
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_CMAKE_${dep}_TRANSITIVE_DEPENDENCY
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)
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find_package(${dep} ${ARGN}
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${cmake_fd_quiet_arg}
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${cmake_fd_required_arg}
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)
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list(POP_BACK _CMAKE_${dep}_HASH_STACK cmake_fd_call_hash)
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set("_CMAKE_${dep}_${cmake_fd_call_hash}_FOUND" "${${dep}_FOUND}")
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if(NOT DEFINED cmake_fd_alreadyTransitive OR cmake_fd_alreadyTransitive)
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set_property(GLOBAL PROPERTY _CMAKE_${dep}_TRANSITIVE_DEPENDENCY TRUE)
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endif()
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unset(cmake_fd_alreadyTransitive)
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unset(cmake_fd_call_hash)
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unset(cmake_fd_quiet_arg)
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unset(cmake_fd_required_arg)
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if (NOT ${dep}_FOUND)
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set(${CMAKE_FIND_PACKAGE_NAME}_NOT_FOUND_MESSAGE "${CMAKE_FIND_PACKAGE_NAME} could not be found because dependency ${dep} could not be found.")
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set(${CMAKE_FIND_PACKAGE_NAME}_FOUND False)
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return()
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endif()
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endif()
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endmacro()
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