CMake 3.18 Release Notes
************************

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Changes made since CMake 3.17 include the following.

New Features
============

Languages
---------

* The ``CUDA`` language can now be compiled using Clang on non-Windows
  platforms. Separable compilation is not yet supported on any platform.

Command-Line
------------

* :manual:`cmake(1)` gained support for profiling of CMake scripts through
  the parameters ``--profiling-output`` and ``--profiling-format``.

* :manual:`cmake(1)` gained a ``cat`` command line
  option that can be used to concatenate files and print them
  on standard output.

Commands
--------

* The :command:`add_library` and :command:`add_executable` commands
  learned to create :ref:`Alias Targets` referencing non-``GLOBAL``
  :ref:`Imported Targets`.

* The :command:`cmake_language()` command was added for meta-operations on
  scripted or built-in commands, starting with a mode to ``CALL`` other
  commands, and ``EVAL CODE`` to inplace evaluate a CMake script.

* The :command:`execute_process` command gained the ``ECHO_OUTPUT_VARIABLE``
  and ``ECHO_ERROR_VARIABLE`` options.

* The :command:`export` command now raise an error if used multiple times with
  same ``FILE`` without ``APPEND``. See policy :policy:`CMP0103`.

* The :command:`file` command gained the ``ARCHIVE_CREATE`` and
  ``ARCHIVE_EXTRACT`` subcommands to expose the :manual:`cmake(1)` ``-E tar``
  functionality to CMake scripting code.

* The :command:`file(CONFIGURE)` subcommand was created in order to replicate
  the :command:`configure_file` functionality without resorting to a
  pre-existing file on disk as input. The content is instead passed as a
  string.

* The :command:`file(UPLOAD)` command gained ``TLS_VERIFY`` and ``TLS_CAINFO``
  options to control server certificate verification.

* The :command:`find_program`, :command:`find_library`, :command:`find_path`
  and :command:`find_file` commands gained a new ``REQUIRED`` option that will
  stop processing with an error message if nothing is found.

* The :command:`get_property` command with ``SOURCE`` scope gained the
  ``DIRECTORY`` and ``TARGET_DIRECTORY`` options to get a property
  from the provided directory scope.

* The :command:`get_source_file_property` command gained the ``DIRECTORY``
  and ``TARGET_DIRECTORY`` options to get a property from the
  provided directory scope.

* The :command:`list` operation ``SORT`` gained the ``NATURAL`` sort
  option to sort using natural order (see ``strverscmp(3)`` manual).

* The :command:`set_property` command with the ``SOURCE`` scope gained the
  ``DIRECTORY`` and ``TARGET_DIRECTORY`` options to set properties
  in the provided directory scopes.

* The :command:`set_source_files_properties` command gained the ``DIRECTORY``
  and ``TARGET_DIRECTORY`` options to set properties in the provided
  directory scopes.

* The :command:`string` command learned a new ``HEX`` sub-command, which
  converts strings into their hexadecimal representation.

Variables
---------

* A :variable:`CMAKE_CUDA_ARCHITECTURES` variable was added to specify
  CUDA output architectures.  Users are encouraged to use this instead of
  specifying options manually, as this approach is compiler-agnostic.
  The variable is initialized automatically when
  :variable:`CMAKE_CUDA_COMPILER_ID <CMAKE_<LANG>_COMPILER_ID>` is ``NVIDIA``.
  The variable is used to initialize the new :prop_tgt:`CUDA_ARCHITECTURES`
  target property.  See policy :policy:`CMP0104`.

* The :variable:`CMAKE_PCH_WARN_INVALID` variable was added to initialize the
  :prop_tgt:`PCH_WARN_INVALID` target property to allow the removal of the
  precompiled header invalid warning.

Properties
----------

* The :prop_tgt:`CUDA_ARCHITECTURES` target property was added to specify
  CUDA output architectures. Users are encouraged to use this instead of
  specifying options manually, as this approach is compiler-agnostic.
  The property is initialized by the new :variable:`CMAKE_CUDA_ARCHITECTURES`
  variable.  See policy :policy:`CMP0104`.

* The :prop_tgt:`Fortran_PREPROCESS` target property and
  :prop_sf:`Fortran_PREPROCESS` source-file property were added to
  control preprocessing of Fortran source files.

* The :prop_tgt:`FRAMEWORK_MULTI_CONFIG_POSTFIX_<CONFIG>` target property
  and associated :variable:`CMAKE_FRAMEWORK_MULTI_CONFIG_POSTFIX_<CONFIG>`
  variable were created to allow adding a postfix to the name of a
  framework file name when using a multi-config generator.

* The :prop_sf:`OBJECT_OUTPUTS` source file property now supports
  :manual:`generator expressions <cmake-generator-expressions(7)>`.

* The :prop_tgt:`PCH_WARN_INVALID` target property was added to allow the
  removal of the precompiled header invalid warning.

* The :prop_tgt:`UNITY_BUILD_MODE` target property was added to tell
  generators which algorithm to use for grouping included source
  files.

* The :prop_tgt:`VS_SOURCE_SETTINGS_<tool>` target property was added
  to tell :ref:`Visual Studio Generators` for VS 2010 and above to add
  metadata to non-built source files using ``<tool>``.

* The :prop_sf:`VS_SETTINGS` source file property was added to tell
  :ref:`Visual Studio Generators` for VS 2010 and above to add
  metadata to a non-built source file.

* The :prop_tgt:`VS_PLATFORM_TOOLSET` target property was added to tell
  :ref:`Visual Studio Generators` for VS 2010 and above to override
  the platform toolset.

* The :prop_tgt:`VS_SOLUTION_DEPLOY` target property was added to tell
  :ref:`Visual Studio Generators` for VS 2010 and above to mark a
  target for deployment even when not building for Windows Phone/Store/CE.

Modules
-------

* The :module:`CheckLinkerFlag` module has been added to provide a
  facility to check validity of link flags.

* The :module:`ExternalProject` module :command:`ExternalProject_Add` command
  gained a new ``GIT_REMOTE_UPDATE_STRATEGY`` keyword.  This can be used to
  specify how failed rebase operations during a git update should be handled.
  The ``CMAKE_EP_GIT_REMOTE_UPDATE_STRATEGY`` variable was also added as a
  global default and is honored by both the :module:`ExternalProject` and
  :module:`FetchContent` modules.

* The :module:`FetchContent` module :command:`FetchContent_Declare` command
  now supports a ``SOURCE_SUBDIR`` option.  It can be used to direct
  :command:`FetchContent_MakeAvailable` to look in a different location
  for the ``CMakeLists.txt`` file.

* The :module:`FindBLAS` module now provides an imported target.

* The :module:`FindCUDAToolkit` module:

  * gained the variable
    ``CUDAToolkit_LIBRARY_ROOT``, which is the directory containing the
    ``nvvm`` directory and ``version.txt``.

  * uses toolkit and library root found during ``CUDA`` compiler detection.

* The :module:`FindLAPACK` module now provides an imported target.

* The :module:`FindPython3`, :module:`FindPython2` and :module:`FindPython`
  modules:

  * gained the possibility to create per-artifact cache variables for
    interactive editing in :manual:`cmake-gui(1)` and :manual:`ccmake(1)`.

  * gained sub-components ``Development.Module`` and
    ``Development.Embed`` under the ``Development`` component.

  * gained the capability to specify which Python implementations to find,
    including ``IronPython`` and ``PyPy``.

* The :module:`FindRuby` module input and output variables were all renamed
  from ``RUBY_`` to ``Ruby_`` for consistency with other find modules.
  Input variables of the old case will be honored if provided, and output
  variables of the old case are always provided.

* The :module:`FindSWIG` module now accepts target languages as  ``COMPONENTS``
  and ``OPTIONAL_COMPONENTS`` arguments to ``find_package``.

* The :module:`GoogleTest` module :command:`gtest_discover_tests` command:

  * gained a new ``DISCOVERY_MODE`` option to control when the test
    discovery step is run.  It offers a new ``PRE_TEST`` setting to
    run the discovery at test time instead of build time.  A new
    ``CMAKE_GTEST_DISCOVER_TESTS_DISCOVERY_MODE`` variable can be used
    to change the default globally.

  * gained a new optional parameter ``XML_OUTPUT_DIR``. When set the
    JUnit XML test results are stored in that directory.

* The :module:`FindLibXslt` module now provides imported targets.

* The :module:`UseSWIG` module now supports Fortran as a target language if
  the ``SWIG_EXECUTABLE`` is SWIG-Fortran_.

.. _`SWIG-Fortran`: https://github.com/swig-fortran/swig

Generator Expressions
---------------------

* The ``$<DEVICE_LINK:...>`` and ``$<HOST_LINK:...>``
  :manual:`generator expressions <cmake-generator-expressions(7)>` were added
  to manage device and host link steps.

* The ``$<LINK_LANGUAGE:...>`` and ``$<LINK_LANG_AND_ID:...>``
  :manual:`generator expressions <cmake-generator-expressions(7)>` were added.

CTest
-----

* :manual:`ctest(1)` gained a new :variable:`CTEST_RESOURCE_SPEC_FILE`
  variable, which can be used to specify a
  :ref:`resource specification file <ctest-resource-specification-file>`.

* :manual:`ctest(1)` gained a ``--stop-on-failure`` option,
  which can be used to stop running the tests once one has failed.

* The :command:`ctest_test` command gained a ``STOP_ON_FAILURE`` option
  which can be used to stop running the tests once one has failed.

* The :module:`CTestCoverageCollectGCOV` module
  :command:`ctest_coverage_collect_gcov` command gained a
  ``TARBALL_COMPRESSION`` option to control compression of the
  tarball of collected results.

CPack
-----

* The :cpack_gen:`CPack Archive Generator`'s ``TXZ`` format learned the
  :variable:`CPACK_ARCHIVE_THREADS` variable to enable parallel compression.
  Requires support in the ``liblzma`` used by CMake.

* The :cpack_gen:`CPack NSIS Generator` gained a new variable
  :variable:`CPACK_NSIS_MANIFEST_DPI_AWARE` to declare that the
  installer is DPI-aware.

* The :cpack_gen:`CPack RPM Generator` gained
  :variable:`CPACK_RPM_PRE_TRANS_SCRIPT_FILE` and
  :variable:`CPACK_RPM_POST_TRANS_SCRIPT_FILE`
  variables to specify pre- and post-transaction scripts.

Other
-----

* :manual:`cmake-gui(1)` now populates its generator selection
  widget default value from the :envvar:`CMAKE_GENERATOR` environment
  variable.  Additionally, environment variables
  :envvar:`CMAKE_GENERATOR_PLATFORM` and :envvar:`CMAKE_GENERATOR_TOOLSET`
  are used to populate their respective widget defaults.

* :manual:`ccmake(1)` learned to read a :envvar:`CCMAKE_COLORS`
  environment variable to customize colors.

Deprecated and Removed Features
===============================

* The :module:`Documentation` module has been deprecated via
  :policy:`CMP0106`. This module was essentially VTK code that CMake should
  not be shipping anymore.

* An explicit deprecation diagnostic was added for policy ``CMP0070``
  and policy ``CMP0071`` (``CMP0069`` and below were already deprecated).
  The :manual:`cmake-policies(7)` manual explains that the OLD behaviors
  of all policies are deprecated and that projects should port to the
  NEW behaviors.

Other Changes
=============

* On Windows, the :generator:`Ninja` and :generator:`Ninja Multi-Config`
  generators, when a compiler is not explicitly specified, now select
  the first compiler (of any name) found in directories listed by the
  ``PATH`` environment variable.

* The :prop_tgt:`LINK_OPTIONS` and :prop_tgt:`INTERFACE_LINK_OPTIONS` target
  properties are now used for the device link step.
  See policy :policy:`CMP0105`.

* Creation of an ``ALIAS`` target overwriting an existing target now raises an
  error. See policy :policy:`CMP0107`.

* Linking a target to itself through an alias now raises an error.
  See policy :policy:`CMP0108`.

* The :module:`FindPackageHandleStandardArgs` module option ``REQUIRED_VARS``
  is now optional if ``HANDLE_COMPONENTS`` is specified.

* The :command:`source_group` command now also recognizes forward slashes
  as subgroup delimiters, not just backslashes.

* :manual:`ctest(1)` now logs environment variables that it sets for each test,
  either due to the :prop_test:`ENVIRONMENT` property or the
  :ref:`resource allocation <ctest-resource-allocation>` feature, and submits
  this log to CDash. It does not log environment variables that were set
  outside of CTest.

* When building CMake itself from source and not using a system-provided
  libcurl, HTTP/2 support is now enabled for commands supporting
  network communication via ``http(s)``, such as :command:`file(DOWNLOAD)`,
  :command:`file(UPLOAD)`, and :command:`ctest_submit`.
  The precompiled binaries provided on ``cmake.org`` now support HTTP/2.

* The :manual:`cmake-file-api(7)` "codemodel" version 2 ``version`` field has
  been updated to 2.1.

* The :manual:`cmake-file-api(7)` "codemodel" version 2 "target" object gained
  a new ``precompileHeaders`` field in the ``compileGroups`` objects.

Updates
=======

Changes made since CMake 3.18.0 include the following.

3.18.1
------

* The :generator:`Xcode` generator, when :variable:`CMAKE_OSX_ARCHITECTURES`
  is not defined, now selects ``$(NATIVE_ARCH_ACTUAL)`` as the default
  architecture (the Xcode ``ARCHS`` setting).  This is needed for Xcode 12
  to select the host's architecture, which older versions of Xcode did
  by default.

* In CMake 3.18.0 the :command:`add_test` command learned to support
  special characters in test names.  This was accidentally left out of
  its release notes.  Unfortunately the fix breaks existing projects
  that were using manual quoting or escaping to work around the prior
  limitation.  This fix has been reverted in 3.18.1, but may be
  re-introduced in future versions of CMake with a policy for compatibility.
