mirror of
https://github.com/Kitware/CMake.git
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0e96a20478
Replace our hard-coded default for `/Zi` with a first-class abstraction to select the debug information format an enumeration of logical names. We've long hesitated to do this because the idea of "debug information format" touches on related concepts on several platforms. Avoid that scope creep by simply defining an abstraction that applies only when targeting the MSVC ABI on Windows. Removing the old default flag requires a policy because existing projects may rely on string processing to edit them and choose a runtime library under the old behavior. Add policy CMP0141 to provide compatibility. Fixes: #10189
252 lines
9.7 KiB
ReStructuredText
252 lines
9.7 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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.. versionadded:: 3.25
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If :policy:`CMP0141` is set to ``NEW``, one can use
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:variable:`CMAKE_MSVC_DEBUG_INFORMATION_FORMAT` to specify MSVC debug
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information format.
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