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101 lines
4.3 KiB
101 lines
4.3 KiB
Step 11: Adding Export Configuration
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====================================
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During :guide:`tutorial/Installing and Testing` of the tutorial we added the
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ability for CMake to install the library and headers of the project. During
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:guide:`tutorial/Packaging an Installer` we added the ability to package up
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this information so it could be distributed to other people.
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The next step is to add the necessary information so that other CMake projects
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can use our project, be it from a build directory, a local install or when
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packaged.
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The first step is to update our :command:`install(TARGETS)` commands to not
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only specify a ``DESTINATION`` but also an ``EXPORT``. The ``EXPORT`` keyword
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generates and installs a CMake file containing code to import all targets
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listed in the install command from the installation tree. So let's go ahead and
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explicitly ``EXPORT`` the ``MathFunctions`` library by updating the ``install``
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command in ``MathFunctions/CMakeLists.txt`` to look like:
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.. literalinclude:: Complete/MathFunctions/CMakeLists.txt
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:caption: MathFunctions/CMakeLists.txt
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:name: MathFunctions/CMakeLists.txt-install-TARGETS-EXPORT
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:language: cmake
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:start-after: # install rules
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Now that we have ``MathFunctions`` being exported, we also need to explicitly
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install the generated ``MathFunctionsTargets.cmake`` file. This is done by
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adding the following to the bottom of the top-level ``CMakeLists.txt``:
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.. literalinclude:: Complete/CMakeLists.txt
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:caption: CMakeLists.txt
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:name: CMakeLists.txt-install-EXPORT
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:language: cmake
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:start-after: # install the configuration targets
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:end-before: include(CMakePackageConfigHelpers)
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At this point you should try and run CMake. If everything is setup properly
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you will see that CMake will generate an error that looks like:
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.. code-block:: console
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Target "MathFunctions" INTERFACE_INCLUDE_DIRECTORIES property contains
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path:
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"/Users/robert/Documents/CMakeClass/Tutorial/Step11/MathFunctions"
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which is prefixed in the source directory.
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What CMake is trying to say is that during generating the export information
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it will export a path that is intrinsically tied to the current machine and
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will not be valid on other machines. The solution to this is to update the
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``MathFunctions`` :command:`target_include_directories` to understand that it
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needs different ``INTERFACE`` locations when being used from within the build
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directory and from an install / package. This means converting the
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:command:`target_include_directories` call for ``MathFunctions`` to look like:
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.. literalinclude:: Step12/MathFunctions/CMakeLists.txt
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:caption: MathFunctions/CMakeLists.txt
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:name: MathFunctions/CMakeLists.txt-target_include_directories
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:language: cmake
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:start-after: # to find MathFunctions.h, while we don't.
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:end-before: # should we use our own math functions
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Once this has been updated, we can re-run CMake and verify that it doesn't
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warn anymore.
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At this point, we have CMake properly packaging the target information that is
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required but we will still need to generate a ``MathFunctionsConfig.cmake`` so
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that the CMake :command:`find_package` command can find our project. So let's go
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ahead and add a new file to the top-level of the project called
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``Config.cmake.in`` with the following contents:
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.. literalinclude:: Step12/Config.cmake.in
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:caption: Config.cmake.in
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:name: Config.cmake.in
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Then, to properly configure and install that file, add the following to the
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bottom of the top-level ``CMakeLists.txt``:
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.. literalinclude:: Step12/CMakeLists.txt
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:caption: CMakeLists.txt
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:name: CMakeLists.txt-install-Config.cmake
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:language: cmake
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:start-after: # install the configuration targets
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:end-before: # generate the export
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At this point, we have generated a relocatable CMake Configuration for our
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project that can be used after the project has been installed or packaged. If
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we want our project to also be used from a build directory we only have to add
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the following to the bottom of the top level ``CMakeLists.txt``:
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.. literalinclude:: Step12/CMakeLists.txt
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:caption: CMakeLists.txt
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:name: CMakeLists.txt-export
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:language: cmake
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:start-after: # needs to be after the install(TARGETS ) command
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With this export call we now generate a ``Targets.cmake``, allowing the
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configured ``MathFunctionsConfig.cmake`` in the build directory to be used by
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other projects, without needing it to be installed.
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