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