try_compile
-----------
.. only:: html
.. contents::
Try building some code.
.. _`Try Compiling Whole Projects`:
Try Compiling Whole Projects
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.. code-block:: cmake
try_compile(<resultVar> PROJECT <projectName>
SOURCE_DIR <srcdir>
[BINARY_DIR <bindir>]
[TARGET <targetName>]
[NO_CACHE]
[CMAKE_FLAGS <flags>...]
[OUTPUT_VARIABLE <var>])
.. versionadded:: 3.25
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.
.. versionchanged:: 3.24
CMake variables describing platform settings, and those listed by the
:variable:`CMAKE_TRY_COMPILE_PLATFORM_VARIABLES` variable, are propagated
into the project's build configuration. See policy :policy:`CMP0137`.
Previously this was only done by the
:ref:`source file <Try Compiling Source Files>` signature.
This command also supports an alternate signature
which was present in older versions of CMake:
.. code-block:: cmake
try_compile(<resultVar> <bindir> <srcdir>
<projectName> [<targetName>]
[NO_CACHE]
[CMAKE_FLAGS <flags>...]
[OUTPUT_VARIABLE <var>])
.. _`Try Compiling Source Files`:
Try Compiling Source Files
^^^^^^^^^^^^^^^^^^^^^^^^^^
.. code-block:: cmake
try_compile(<resultVar>
<SOURCES <srcfile...>] |
SOURCE_FROM_CONTENT <name> <content>] |
SOURCE_FROM_VAR <name> <var>] |
SOURCE_FROM_FILE <name> <path> >...
[NO_CACHE]
[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>]
)
.. versionadded:: 3.25
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. Additionally, one of
``SOURCES`` and/or ``SOURCE_FROM_*`` must precede other keywords.
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 ${LINK_LIBRARIES})
CMake automatically generates, for each ``try_compile`` operation, a
unique directory under ``${CMAKE_BINARY_DIR}/CMakeFiles/CMakeScratch``
with an unspecified name. These directories are cleaned automatically unless
:option:`--debug-trycompile <cmake --debug-trycompile>` is passed to ``cmake``.
Such directories from previous runs are also unconditionally cleaned at the
beginning of any ``cmake`` execution.
This command also supports an alternate signature
which was present in older versions of CMake:
.. code-block:: cmake
try_compile(<resultVar> <bindir> <srcfile|SOURCES srcfile...>
[NO_CACHE]
[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>]
)
In this version, ``try_compile`` will use ``<bindir>/CMakeFiles/CMakeTmp`` for
its operation, and all such files will be cleaned automatically.
For debugging, :option:`--debug-trycompile <cmake --debug-trycompile>` can be
passed to ``cmake`` to avoid this clean. However, multiple sequential
``try_compile`` operations, if given the same ``<bindir>``, will reuse this
single output directory, such that you can only debug one such ``try_compile``
call at a time. Use of the newer signature is recommended to simplify
debugging of multiple ``try_compile`` operations.
The options are:
``CMAKE_FLAGS <flags>...``
Specify flags of the form :option:`-DVAR:TYPE=VALUE <cmake -D>` to be passed
to the :manual:`cmake(1)` 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>...``
.. versionadded:: 3.14
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.
``NO_CACHE``
.. versionadded:: 3.25
The result will be stored in a normal variable rather than a cache entry.
The result variable is normally cached so that a simple pattern can be used
to avoid repeating the test on subsequent executions of CMake:
.. code-block:: cmake
if(NOT DEFINED RESULTVAR)
# ...(check-specific setup code)...
try_compile(RESULTVAR ...)
# ...(check-specific logging and cleanup code)...
endif()
If the guard variable and result variable are not the same (for example, if
the test is part of a larger inspection), ``NO_CACHE`` may be useful to avoid
leaking the intermediate result variable into the cache.
``OUTPUT_VARIABLE <var>``
Store the output from the build process in the given variable.
``SOURCE_FROM_CONTENT <name> <content>``
.. versionadded:: 3.25
Write ``<content>`` to a file named ``<name>`` in the operation directory.
This can be used to bypass the need to separately write a source file when
the contents of the file are dynamically specified. The specified ``<name>``
is not allowed to contain path components.
``SOURCE_FROM_CONTENT`` may be specified multiple times.
``SOURCE_FROM_FILE <name> <path>``
.. versionadded:: 3.25
Copy ``<path>`` to a file named ``<name>`` in the operation directory. This
can be used to consolidate files into the operation directory, which may be
useful if a source which already exists (i.e. as a stand-alone file in a
project's source repository) needs to refer to other file(s) created by
``SOURCE_FROM_*``. (Otherwise, ``SOURCES`` is usually more convenient.) The
specified ``<name>`` is not allowed to contain path components.
``SOURCE_FROM_VAR <name> <var>``
.. versionadded:: 3.25
Write the contents of ``<var>`` to a file named ``<name>`` in the operation
directory. This is the same as ``SOURCE_FROM_CONTENT``, but takes the
contents from the specified CMake variable, rather than directly, which may
be useful when passing arguments through a function which wraps
``try_compile``. The specified ``<name>`` is not allowed to contain path
components.
``SOURCE_FROM_VAR`` may be specified multiple times.
``<LANG>_STANDARD <std>``
.. versionadded:: 3.8
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>``
.. versionadded:: 3.8
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>``
.. versionadded:: 3.8
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.
Other Behavior Settings
^^^^^^^^^^^^^^^^^^^^^^^
.. versionadded:: 3.4
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_CUDA_RUNTIME_LIBRARY`
* :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`
* :variable:`CMAKE_WATCOM_RUNTIME_LIBRARY`
If :policy:`CMP0056` is set to ``NEW``, then
:variable:`CMAKE_EXE_LINKER_FLAGS` is passed in as well.
.. versionchanged:: 3.14
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.
.. versionadded:: 3.6
Set the :variable:`CMAKE_TRY_COMPILE_TARGET_TYPE` variable to specify
the type of target used for the source file signature.
.. versionadded:: 3.6
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.
.. versionchanged:: 3.8
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).
.. versionchanged:: 3.14
For the :generator:`Green Hills MULTI` generator the GHS toolset and target
system customization cache variables are also propagated into the test project.
.. versionadded:: 3.24
The :variable:`CMAKE_TRY_COMPILE_NO_PLATFORM_VARIABLES` variable may be
set to disable passing platform variables into the test project.
.. versionadded:: 3.25
If :policy:`CMP0141` is set to ``NEW``, one can use
:variable:`CMAKE_MSVC_DEBUG_INFORMATION_FORMAT` to specify MSVC debug
information format.