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Diffstat (limited to 'Help/guide/tutorial/Adding Generator Expressions.rst')
| -rw-r--r-- | Help/guide/tutorial/Adding Generator Expressions.rst | 191 |
1 files changed, 17 insertions, 174 deletions
diff --git a/Help/guide/tutorial/Adding Generator Expressions.rst b/Help/guide/tutorial/Adding Generator Expressions.rst index aba9f7ad4d..3dab97ff04 100644 --- a/Help/guide/tutorial/Adding Generator Expressions.rst +++ b/Help/guide/tutorial/Adding Generator Expressions.rst @@ -27,168 +27,7 @@ expressions are the ``0`` and ``1`` expressions. A ``$<0:...>`` results in the empty string, and ``<1:...>`` results in the content of ``...``. They can also be nested. -Exercise 1 - Setting the C++ Standard with Interface Libraries -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Before we use :manual:`generator expressions <cmake-generator-expressions(7)>` -let's refactor our existing code to use an ``INTERFACE`` library. We will -use that library in the next step to demonstrate a common use for -:manual:`generator expressions <cmake-generator-expressions(7)>`. - -Goal ----- - -Add an ``INTERFACE`` library target to specify the required C++ standard. - -Helpful Resources ------------------ - -* :command:`add_library` -* :command:`target_compile_features` -* :command:`target_link_libraries` - -Files to Edit -------------- - -* ``CMakeLists.txt`` -* ``MathFunctions/CMakeLists.txt`` - -Getting Started ---------------- - -In this exercise, we will refactor our code to use an ``INTERFACE`` library to -specify the C++ standard. - -The starting source code is provided in the ``Step4`` directory. In this -exercise, complete ``TODO 1`` through ``TODO 3``. - -Start by editing the top level ``CMakeLists.txt`` file. Construct an -``INTERFACE`` library target called ``tutorial_compiler_flags`` and -specify ``cxx_std_11`` as a target compiler feature. - -Modify ``CMakeLists.txt`` and ``MathFunctions/CMakeLists.txt`` so that all -targets have a :command:`target_link_libraries` call to -``tutorial_compiler_flags``. - -Build and Run -------------- - -Make a new directory called ``Step4_build``, run the :manual:`cmake <cmake(1)>` -executable or the :manual:`cmake-gui <cmake-gui(1)>` to configure the project -and then build it with your chosen build tool or by using ``cmake --build .`` -from the build directory. - -Here's a refresher of what that looks like from the command line: - -.. code-block:: console - - mkdir Step4_build - cd Step4_build - cmake ../Step4 - cmake --build . - -Next, use the newly built ``Tutorial`` and verify that it is working as -expected. - -Solution --------- - -Let's update our code from the previous step to use interface libraries -to set our C++ requirements. - -To start, we need to remove the two :command:`set` calls on the variables -:variable:`CMAKE_CXX_STANDARD` and :variable:`CMAKE_CXX_STANDARD_REQUIRED`. -The specific lines to remove are as follows: - -.. literalinclude:: Step4/CMakeLists.txt - :caption: CMakeLists.txt - :name: CMakeLists.txt-CXX_STANDARD-variable-remove - :language: cmake - :start-after: # specify the C++ standard - :end-before: # TODO 6: Create helper variables - -Next, we need to create an interface library, ``tutorial_compiler_flags``. And -then use :command:`target_compile_features` to add the compiler feature -``cxx_std_11``. - - -.. raw:: html - - <details><summary>TODO 1: Click to show/hide answer</summary> - -.. literalinclude:: Step5/CMakeLists.txt - :caption: TODO 1: CMakeLists.txt - :name: CMakeLists.txt-cxx_std-feature - :language: cmake - :start-after: # specify the C++ standard - :end-before: # add compiler warning flags just - -.. raw:: html - - </details> - -Finally, with our interface library set up, we need to link our -executable ``Target``, our ``MathFunctions`` library, and our ``SqrtLibrary`` -library to our new -``tutorial_compiler_flags`` library. Respectively, the code will look like -this: - -.. raw:: html - - <details><summary>TODO 2: Click to show/hide answer</summary> - -.. literalinclude:: Step5/CMakeLists.txt - :caption: TODO 2: CMakeLists.txt - :name: CMakeLists.txt-target_link_libraries-step4 - :language: cmake - :start-after: add_executable(Tutorial tutorial.cxx) - :end-before: # add the binary tree to the search path for include file - -.. raw:: html - - </details> - -this: - -.. raw:: html - - <details><summary>TODO 3: Click to show/hide answer</summary> - -.. literalinclude:: Step5/MathFunctions/CMakeLists.txt - :caption: TODO 3: MathFunctions/CMakeLists.txt - :name: MathFunctions-CMakeLists.txt-target_link_libraries-step4 - :language: cmake - :start-after: # link our compiler flags interface library - :end-before: target_link_libraries(MathFunctions - -.. raw:: html - - </details> - -and this: - -.. raw:: html - - <details><summary>TODO 4: Click to show/hide answer</summary> - -.. literalinclude:: Step5/MathFunctions/CMakeLists.txt - :caption: TODO 4: MathFunctions/CMakeLists.txt - :name: MathFunctions-SqrtLibrary-target_link_libraries-step4 - :language: cmake - :start-after: target_link_libraries(SqrtLibrary - :end-before: endif() - -.. raw:: html - - </details> - - -With this, all of our code still requires C++ 11 to build. Notice -though that with this method, it gives us the ability to be specific about -which targets get specific requirements. In addition, we create a single -source of truth in our interface library. - -Exercise 2 - Adding Compiler Warning Flags with Generator Expressions +Exercise 1 - Adding Compiler Warning Flags with Generator Expressions ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A common usage of @@ -218,8 +57,8 @@ Files to Edit Getting Started --------------- -Start with the resulting files from Exercise 1. Complete ``TODO 5`` through -``TODO 8``. +Open the file ``Step4/CMakeLists.txt`` and complete ``TODO 1`` through +``TODO 4``. First, in the top level ``CMakeLists.txt`` file, we need to set the :command:`cmake_minimum_required` to ``3.15``. In this exercise we are going @@ -233,12 +72,16 @@ given a language and a set of compiler ids. Build and Run ------------- -Since we have our build directory already configured from Exercise 1, simply -rebuild our code by calling the following: +Make a new directory called ``Step4_build``, run the :manual:`cmake <cmake(1)>` +executable or the :manual:`cmake-gui <cmake-gui(1)>` to configure the project +and then build it with your chosen build tool or by using ``cmake --build .`` +from the build directory. .. code-block:: console + mkdir Step4_build cd Step4_build + cmake ../Step4 cmake --build . Solution @@ -249,10 +92,10 @@ version ``3.15``: .. raw:: html - <details><summary>TODO 5: Click to show/hide answer</summary> + <details><summary>TODO 1: Click to show/hide answer</summary> .. literalinclude:: Step5/CMakeLists.txt - :caption: TODO 5: CMakeLists.txt + :caption: TODO 1: CMakeLists.txt :name: MathFunctions-CMakeLists.txt-minimum-required-step4 :language: cmake :end-before: # set the project name and version @@ -268,10 +111,10 @@ variables ``gcc_like_cxx`` and ``msvc_cxx`` as follows: .. raw:: html - <details><summary>TODO 6: Click to show/hide answer</summary> + <details><summary>TODO 2: Click to show/hide answer</summary> .. literalinclude:: Step5/CMakeLists.txt - :caption: TODO 6: CMakeLists.txt + :caption: TODO 2: CMakeLists.txt :name: CMakeLists.txt-compile_lang_and_id :language: cmake :start-after: # the BUILD_INTERFACE genex @@ -289,10 +132,10 @@ interface library. .. raw:: html - <details><summary>TODO 7: Click to show/hide answer</summary> + <details><summary>TODO 3: Click to show/hide answer</summary> .. code-block:: cmake - :caption: TODO 7: CMakeLists.txt + :caption: TODO 3: CMakeLists.txt :name: CMakeLists.txt-compile_flags target_compile_options(tutorial_compiler_flags INTERFACE @@ -311,10 +154,10 @@ condition. The resulting full code looks like the following: .. raw:: html - <details><summary>TODO 8: Click to show/hide answer</summary> + <details><summary>TODO 4: Click to show/hide answer</summary> .. literalinclude:: Step5/CMakeLists.txt - :caption: TODO 8: CMakeLists.txt + :caption: TODO 4: CMakeLists.txt :name: CMakeLists.txt-target_compile_options-genex :language: cmake :start-after: set(msvc_cxx "$<COMPILE_LANG_AND_ID:CXX,MSVC>") |