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diff --git a/Help/command/try_compile.rst b/Help/command/try_compile.rst new file mode 100644 index 0000000..edbf92c --- /dev/null +++ b/Help/command/try_compile.rst @@ -0,0 +1,191 @@ +try_compile +----------- + +.. only:: html + + .. contents:: + +Try building some code. + +Try Compiling Whole Projects +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: cmake + + try_compile(<resultVar> <bindir> <srcdir> + <projectName> [<targetName>] [CMAKE_FLAGS <flags>...] + [OUTPUT_VARIABLE <var>]) + +Try building a project. The success or failure of the ``try_compile``, +i.e. ``TRUE`` or ``FALSE`` respectively, is returned in ``<resultVar>``. + +In this form, ``<srcdir>`` should contain a complete CMake project with a +``CMakeLists.txt`` file and all sources. The ``<bindir>`` and ``<srcdir>`` +will not be deleted after this command is run. Specify ``<targetName>`` to +build a specific target instead of the ``all`` or ``ALL_BUILD`` target. See +below for the meaning of other options. + +Try Compiling Source Files +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: cmake + + try_compile(<resultVar> <bindir> <srcfile|SOURCES srcfile...> + [CMAKE_FLAGS <flags>...] + [COMPILE_DEFINITIONS <defs>...] + [LINK_OPTIONS <options>...] + [LINK_LIBRARIES <libs>...] + [OUTPUT_VARIABLE <var>] + [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]] + [<LANG>_STANDARD <std>] + [<LANG>_STANDARD_REQUIRED <bool>] + [<LANG>_EXTENSIONS <bool>] + ) + +Try building an executable or static library from one or more source files +(which one is determined by the :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` +variable). The success or failure of the ``try_compile``, i.e. ``TRUE`` or +``FALSE`` respectively, is returned in ``<resultVar>``. + +In this form, one or more source files must be provided. If +:variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` is unset or is set to ``EXECUTABLE``, +the sources must include a definition for ``main`` and CMake will create a +``CMakeLists.txt`` file to build the source(s) as an executable. +If :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` is set to ``STATIC_LIBRARY``, +a static library will be built instead and no definition for ``main`` is +required. For an executable, the generated ``CMakeLists.txt`` file would +contain something like the following: + +.. code-block:: cmake + + add_definitions(<expanded COMPILE_DEFINITIONS from caller>) + include_directories(${INCLUDE_DIRECTORIES}) + link_directories(${LINK_DIRECTORIES}) + add_executable(cmTryCompileExec <srcfile>...) + target_link_options(cmTryCompileExec PRIVATE <LINK_OPTIONS from caller>) + target_link_libraries(cmTryCompileExec ${LINK_LIBRARIES}) + +The options are: + +``CMAKE_FLAGS <flags>...`` + Specify flags of the form ``-DVAR:TYPE=VALUE`` to be passed to + the ``cmake`` command-line used to drive the test build. + The above example shows how values for variables + ``INCLUDE_DIRECTORIES``, ``LINK_DIRECTORIES``, and ``LINK_LIBRARIES`` + are used. + +``COMPILE_DEFINITIONS <defs>...`` + Specify ``-Ddefinition`` arguments to pass to :command:`add_definitions` + in the generated test project. + +``COPY_FILE <fileName>`` + Copy the built executable or static library to the given ``<fileName>``. + +``COPY_FILE_ERROR <var>`` + Use after ``COPY_FILE`` to capture into variable ``<var>`` any error + message encountered while trying to copy the file. + +``LINK_LIBRARIES <libs>...`` + Specify libraries to be linked in the generated project. + The list of libraries may refer to system libraries and to + :ref:`Imported Targets <Imported Targets>` from the calling project. + + If this option is specified, any ``-DLINK_LIBRARIES=...`` value + given to the ``CMAKE_FLAGS`` option will be ignored. + +``LINK_OPTIONS <options>...`` + Specify link step options to pass to :command:`target_link_options` or to + set the :prop_tgt:`STATIC_LIBRARY_OPTIONS` target property in the generated + project, depending on the :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` variable. + +``OUTPUT_VARIABLE <var>`` + Store the output from the build process in the given variable. + +``<LANG>_STANDARD <std>`` + Specify the :prop_tgt:`C_STANDARD`, :prop_tgt:`CXX_STANDARD`, + :prop_tgt:`OBJC_STANDARD`, :prop_tgt:`OBJCXX_STANDARD`, + or :prop_tgt:`CUDA_STANDARD` target property of the generated project. + +``<LANG>_STANDARD_REQUIRED <bool>`` + Specify the :prop_tgt:`C_STANDARD_REQUIRED`, + :prop_tgt:`CXX_STANDARD_REQUIRED`, :prop_tgt:`OBJC_STANDARD_REQUIRED`, + :prop_tgt:`OBJCXX_STANDARD_REQUIRED`,or :prop_tgt:`CUDA_STANDARD_REQUIRED` + target property of the generated project. + +``<LANG>_EXTENSIONS <bool>`` + Specify the :prop_tgt:`C_EXTENSIONS`, :prop_tgt:`CXX_EXTENSIONS`, + :prop_tgt:`OBJC_EXTENSIONS`, :prop_tgt:`OBJCXX_EXTENSIONS`, + or :prop_tgt:`CUDA_EXTENSIONS` target property of the generated project. + +In this version all files in ``<bindir>/CMakeFiles/CMakeTmp`` will be +cleaned automatically. For debugging, ``--debug-trycompile`` can be +passed to ``cmake`` to avoid this clean. However, multiple sequential +``try_compile`` operations reuse this single output directory. If you use +``--debug-trycompile``, you can only debug one ``try_compile`` call at a time. +The recommended procedure is to protect all ``try_compile`` calls in your +project by ``if(NOT DEFINED <resultVar>)`` logic, configure with cmake +all the way through once, then delete the cache entry associated with +the try_compile call of interest, and then re-run cmake again with +``--debug-trycompile``. + +Other Behavior Settings +^^^^^^^^^^^^^^^^^^^^^^^ + +If set, the following variables are passed in to the generated +try_compile CMakeLists.txt to initialize compile target properties with +default values: + +* :variable:`CMAKE_ENABLE_EXPORTS` +* :variable:`CMAKE_LINK_SEARCH_START_STATIC` +* :variable:`CMAKE_LINK_SEARCH_END_STATIC` +* :variable:`CMAKE_MSVC_RUNTIME_LIBRARY` +* :variable:`CMAKE_POSITION_INDEPENDENT_CODE` + +If :policy:`CMP0056` is set to ``NEW``, then +:variable:`CMAKE_EXE_LINKER_FLAGS` is passed in as well. + +If :policy:`CMP0083` is set to ``NEW``, then in order to obtain correct +behavior at link time, the ``check_pie_supported()`` command from the +:module:`CheckPIESupported` module must be called before using the +:command:`try_compile` command. + +The current settings of :policy:`CMP0065` and :policy:`CMP0083` are propagated +through to the generated test project. + +Set the :variable:`CMAKE_TRY_COMPILE_CONFIGURATION` variable to choose +a build configuration. + +Set the :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` variable to specify +the type of target used for the source file signature. + +Set the :variable:`CMAKE_TRY_COMPILE_PLATFORM_VARIABLES` variable to specify +variables that must be propagated into the test project. This variable is +meant for use only in toolchain files and is only honored by the +``try_compile()`` command for the source files form, not when given a whole +project. + +If :policy:`CMP0067` is set to ``NEW``, or any of the ``<LANG>_STANDARD``, +``<LANG>_STANDARD_REQUIRED``, or ``<LANG>_EXTENSIONS`` options are used, +then the language standard variables are honored: + +* :variable:`CMAKE_C_STANDARD` +* :variable:`CMAKE_C_STANDARD_REQUIRED` +* :variable:`CMAKE_C_EXTENSIONS` +* :variable:`CMAKE_CXX_STANDARD` +* :variable:`CMAKE_CXX_STANDARD_REQUIRED` +* :variable:`CMAKE_CXX_EXTENSIONS` +* :variable:`CMAKE_OBJC_STANDARD` +* :variable:`CMAKE_OBJC_STANDARD_REQUIRED` +* :variable:`CMAKE_OBJC_EXTENSIONS` +* :variable:`CMAKE_OBJCXX_STANDARD` +* :variable:`CMAKE_OBJCXX_STANDARD_REQUIRED` +* :variable:`CMAKE_OBJCXX_EXTENSIONS` +* :variable:`CMAKE_CUDA_STANDARD` +* :variable:`CMAKE_CUDA_STANDARD_REQUIRED` +* :variable:`CMAKE_CUDA_EXTENSIONS` + +Their values are used to set the corresponding target properties in +the generated project (unless overridden by an explicit option). + +For the :generator:`Green Hills MULTI` generator the GHS toolset and target +system customization cache variables are also propagated into the test project. |