mirror of
https://github.com/Kitware/CMake.git
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aa9220d3a0
Introduce a new signature for try_compile (and try_run) which removes the `bindir` argument and requires the SOURCES tag. This will eventually allow us to add other ways of providing sources, but also allows us to change the behavior without breaking compatibility. The old signature uses a special, but non-unique temporary location inside the specified `bindir`, which conventionally is just the project's build directory. The new signature unconditionally uses the a unique temporary directory which is unconditionally within the project's build directory (which is no longer separately specified). This ensures that successive runs do not overwrite previous runs, will simplify debugging, and should also, eventually, allow us to execute multiple trials in parallel.
247 lines
9.5 KiB
ReStructuredText
247 lines
9.5 KiB
ReStructuredText
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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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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.. versionchanged:: 3.24
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CMake variables describing platform settings, and those listed by the
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:variable:`CMAKE_TRY_COMPILE_PLATFORM_VARIABLES` variable, are propagated
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into the project's build configuration. See policy :policy:`CMP0137`.
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Previously this was only done by the
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:ref:`source file <Try Compiling Source Files>` signature.
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.. _`Try Compiling Source Files`:
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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> 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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.. versionadded:: 3.25
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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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CMake will automatically generate a unique directory for each ``try_compile``
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operation in an unspecified location within the project's binary directory.
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These directories will be cleaned automatically unless
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:option:`--debug-trycompile <cmake --debug-trycompile>` is passed to ``cmake``.
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Such directories from previous runs are also unconditionally cleaned at the
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beginning of any ``cmake`` execution.
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This command also supports an alternate signature
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which was present in older versions of CMake:
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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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In this version, ``try_compile`` will use ``<bindir>/CMakeFiles/CMakeTmp`` for
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its operation, and all such files will be cleaned automatically.
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For debugging, :option:`--debug-trycompile <cmake --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, if given the same ``<bindir>``, will reuse this
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single output directory, such that you can only debug one such ``try_compile``
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call at a time. Use of the newer signature is recommended to simplify
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debugging of multiple ``try_compile`` operations.
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The options are:
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``CMAKE_FLAGS <flags>...``
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Specify flags of the form :option:`-DVAR:TYPE=VALUE <cmake -D>` to be passed
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to the :manual:`cmake(1)` 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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.. versionadded:: 3.14
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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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.. versionadded:: 3.8
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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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.. versionadded:: 3.8
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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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.. versionadded:: 3.8
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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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Other Behavior Settings
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^^^^^^^^^^^^^^^^^^^^^^^
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.. versionadded:: 3.4
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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_CUDA_RUNTIME_LIBRARY`
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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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* :variable:`CMAKE_WATCOM_RUNTIME_LIBRARY`
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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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.. versionchanged:: 3.14
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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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.. versionadded:: 3.6
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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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.. versionadded:: 3.6
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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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.. versionchanged:: 3.8
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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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.. versionchanged:: 3.14
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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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.. versionadded:: 3.24
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The :variable:`CMAKE_TRY_COMPILE_NO_PLATFORM_VARIABLES` variable may be
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set to disable passing platform variables into the test project.
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