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Diffstat (limited to 'Help/guide/tutorial/Adding Export Configuration.rst')
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diff --git a/Help/guide/tutorial/Adding Export Configuration.rst b/Help/guide/tutorial/Adding Export Configuration.rst new file mode 100644 index 0000000..55cb3e2 --- /dev/null +++ b/Help/guide/tutorial/Adding Export Configuration.rst @@ -0,0 +1,88 @@ +Step 11: Adding Export Configuration +==================================== + +During `Installing and Testing (Step 4)`_ of the tutorial we added the ability +for CMake to install the library and headers of the project. During +`Building an Installer (Step 7)`_ we added the ability to package up this +information so it could be distributed to other people. + +The next step is to add the necessary information so that other CMake projects +can use our project, be it from a build directory, a local install or when +packaged. + +The first step is to update our :command:`install(TARGETS)` commands to not +only specify a ``DESTINATION`` but also an ``EXPORT``. The ``EXPORT`` keyword +generates and installs a CMake file containing code to import all targets +listed in the install command from the installation tree. So let's go ahead and +explicitly ``EXPORT`` the MathFunctions library by updating the ``install`` +command in ``MathFunctions/CMakeLists.txt`` to look like: + +.. literalinclude:: Complete/MathFunctions/CMakeLists.txt + :language: cmake + :start-after: # install rules + +Now that we have MathFunctions being exported, we also need to explicitly +install the generated ``MathFunctionsTargets.cmake`` file. This is done by +adding the following to the bottom of the top-level ``CMakeLists.txt``: + +.. literalinclude:: Complete/CMakeLists.txt + :language: cmake + :start-after: # install the configuration targets + :end-before: include(CMakePackageConfigHelpers) + +At this point you should try and run CMake. If everything is setup properly +you will see that CMake will generate an error that looks like: + +.. code-block:: console + + Target "MathFunctions" INTERFACE_INCLUDE_DIRECTORIES property contains + path: + + "/Users/robert/Documents/CMakeClass/Tutorial/Step11/MathFunctions" + + which is prefixed in the source directory. + +What CMake is trying to say is that during generating the export information +it will export a path that is intrinsically tied to the current machine and +will not be valid on other machines. The solution to this is to update the +MathFunctions :command:`target_include_directories` to understand that it needs +different ``INTERFACE`` locations when being used from within the build +directory and from an install / package. This means converting the +:command:`target_include_directories` call for MathFunctions to look like: + +.. literalinclude:: Step12/MathFunctions/CMakeLists.txt + :language: cmake + :start-after: # to find MathFunctions.h, while we don't. + :end-before: # should we use our own math functions + +Once this has been updated, we can re-run CMake and verify that it doesn't +warn anymore. + +At this point, we have CMake properly packaging the target information that is +required but we will still need to generate a ``MathFunctionsConfig.cmake`` so +that the CMake :command:`find_package` command can find our project. So let's go +ahead and add a new file to the top-level of the project called +``Config.cmake.in`` with the following contents: + +.. literalinclude:: Step12/Config.cmake.in + +Then, to properly configure and install that file, add the following to the +bottom of the top-level ``CMakeLists.txt``: + +.. literalinclude:: Step12/CMakeLists.txt + :language: cmake + :start-after: # install the configuration targets + :end-before: # generate the export + +At this point, we have generated a relocatable CMake Configuration for our +project that can be used after the project has been installed or packaged. If +we want our project to also be used from a build directory we only have to add +the following to the bottom of the top level ``CMakeLists.txt``: + +.. literalinclude:: Step12/CMakeLists.txt + :language: cmake + :start-after: # needs to be after the install(TARGETS ) command + +With this export call we now generate a ``Targets.cmake``, allowing the +configured ``MathFunctionsConfig.cmake`` in the build directory to be used by +other projects, without needing it to be installed. |