CMake 3.20 Release Notes
************************

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Changes made since CMake 3.19 include the following.

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

Presets
-------

* :manual:`cmake-presets(7)` gained support for build and test presets.

Generators
----------

* :ref:`Makefile Generators`, for some toolchains, now use the compiler
  to extract implicit dependencies while compiling source files.

Languages
---------

* C++23 compiler modes may now be specified via the :prop_tgt:`CXX_STANDARD`,
  :prop_tgt:`CUDA_STANDARD`, or :prop_tgt:`OBJCXX_STANDARD` target properties,
  or via the :manual:`Compile Features <cmake-compile-features(7)>`
  functionality's ``cxx_std_23`` meta-feature.

* ``CUDA`` language support now works when ``nvcc`` is a symbolic link,
  for example due to a ``ccache`` or ``colornvcc`` wrapper script.

* The :envvar:`CUDAARCHS` environment variable was added for initializing
  :variable:`CMAKE_CUDA_ARCHITECTURES`. Useful in cases where the compiler
  default is unsuitable for the machine's GPU.

Compilers
---------

* The NVIDIA HPC SDK compilers are now supported with compiler id ``NVHPC``.

* The Intel oneAPI NextGen LLVM compilers are now supported with
  compiler id ``IntelLLVM``:

  * The ``icx``/``icpx`` C/C++ compilers on Linux, and the ``icx``
    C/C++ compiler on Windows, are fully supported as of oneAPI 2021.1.

  * The ``ifx`` Fortran compiler on Linux is partially supported.
    As of oneAPI 2021.1, ``ifx`` does not define several identification
    macros, so CMake identifies it as the classic ``Intel`` compiler.
    This works in many cases because ``ifx`` accepts the same command line
    parameters as ``ifort``.  A future version of oneAPI may fix this.

  * The ``ifx`` Fortran compiler on Windows is not yet supported.

  The Intel oneAPI Classic compilers (``icc``, ``icpc``, and ``ifort``)
  continue to be supported with compiler id ``Intel``.

Platforms
---------

* CMake's support for :ref:`Cross Compiling for Android`
  is now merged with the Android NDK's toolchain file.
  They now have similar behavior, though some variable names differ.
  User-facing changes include:

  - ``find_*`` functions will search NDK ABI / API specific paths by default.

  - The default :variable:`CMAKE_BUILD_TYPE` for Android is
    now ``RelWithDebInfo``.

File-Based API
--------------

* The :manual:`cmake-file-api(7)` gained a new "toolchains" object
  kind that describes the compiler used for each enabled language.

Commands
--------

* :command:`add_custom_command` and :command:`add_custom_target` now
  support :manual:`generator expressions <cmake-generator-expressions(7)>`
  in their ``OUTPUT`` and ``BYPRODUCTS`` options.

  Their ``COMMAND``, ``WORKING_DIRECTORY``, and ``DEPENDS`` options gained
  support for new generator expressions ``$<COMMAND_CONFIG:...>`` and
  ``$<OUTPUT_CONFIG:...>`` that control cross-config handling when using
  the :generator:`Ninja Multi-Config` generator.

* The :command:`add_custom_command` command gained ``DEPFILE`` support on
  :ref:`Makefile Generators`.

* The :command:`add_library` command previously prohibited imported object
  libraries when using potentially multi-architecture configurations.
  This mostly affected the :generator:`Xcode` generator, e.g. when targeting
  iOS or one of the other device platforms.  This restriction has now been
  removed.

* The :command:`cmake_path` command was added for operations on
  filesystem paths.

* The :command:`configure_file` command gained ``USE_SOURCE_PERMISSIONS``
  and ``FILE_PERMISSIONS`` options to support copying of permissions of the
  source file and using specified permissions respectively.

* The :command:`file(GENERATE)` command gained a ``NEWLINE_STYLE`` option to
  specify how newlines are handled for the generated file.

* The :command:`file(GENERATE)` command gained ``NO_SOURCE_PERMISSIONS``,
  ``USE_SOURCE_PERMISSIONS``, and ``FILE_PERMISSIONS`` options for controlling
  the permissions of the generated file.

* The :command:`install(FILES)` command ``RENAME`` option learned to
  support :manual:`generator expressions <cmake-generator-expressions(7)>`.

* The :command:`target_include_directories` command gained a new option
  ``AFTER``.

* The :command:`target_sources` command now supports targets created
  by the :command:`add_custom_target` command.

* The :command:`try_run` command gained a ``WORKING_DIRECTORY`` option to
  set the working directory in which to run the compiled check executable.

Variables
---------

* The :variable:`CMAKE_<LANG>_BYTE_ORDER` variable was added to provide the
  target architecture byte order detected from the toolchain.

* The :variable:`CMAKE_RUNTIME_OUTPUT_DIRECTORY`,
  :variable:`CMAKE_LIBRARY_OUTPUT_DIRECTORY`, and
  :variable:`CMAKE_ARCHIVE_OUTPUT_DIRECTORY` variables now support
  target-dependent generator expressions.

Properties
----------

* The :prop_tgt:`<LANG>_CLANG_TIDY` target property and the associated
  :variable:`CMAKE_<LANG>_CLANG_TIDY` variable learned to support
  the ``OBJC`` and ``OBJCXX`` languages.

* The :prop_tgt:`EXPORT_COMPILE_COMMANDS` target property was added
  for the associated :variable:`CMAKE_EXPORT_COMPILE_COMMANDS` variable
  to allow for configuration of exporting compile commands per target.

* The :prop_sf:`GENERATED` source-file property is now visible
  from any directory scope, regardless of the scope in which it is set.
  See policy :policy:`CMP0118`.

* The :prop_tgt:`UNITY_BUILD_UNIQUE_ID` target property
  was added to support generation of an identifier that is
  unique per source file in unity builds.  It can help to
  resolve duplicate symbol problems with anonymous namespaces.

* The :prop_tgt:`WIN32_EXECUTABLE` target property now works with Clang
  on Windows.

* The :prop_tgt:`XCODE_EMBED_FRAMEWORKS <XCODE_EMBED_<type>>` target property
  was added to tell the :generator:`Xcode` generator to embed frameworks.
  Aspects of the embedding can be customized with the
  :prop_tgt:`XCODE_EMBED_FRAMEWORKS_PATH <XCODE_EMBED_<type>>`,
  :prop_tgt:`XCODE_EMBED_FRAMEWORKS_CODE_SIGN_ON_COPY`, and
  :prop_tgt:`XCODE_EMBED_FRAMEWORKS_REMOVE_HEADERS_ON_COPY` target properties.

Modules
-------

* The :module:`ExternalData` module :command:`ExternalData_Add_Target`
  function gained a ``SHOW_PROGRESS <bool>`` option for controlling whether
  or not to show progress output during the build.

* The :module:`ExternalProject` module :command:`ExternalProject_Add` function
  gained a ``CONFIGURE_HANDLED_BY_BUILD`` option.  This can be used to make
  subsequent runs of the configure step be triggered by the build step when
  an external project dependency rebuilds instead of always re-running the
  configure step in such cases.

* The :module:`FindBoost` module gained a ``Boost_NO_WARN_NEW_VERSIONS``
  option to silence the warning about unknown dependencies for new
  Boost versions.

* The :module:`FindCUDAToolkit` module gained support for finding CUDA
  toolkits when ``nvcc`` is a symbolic link,
  for example due to a ``ccache`` or ``colornvcc`` wrapper script.

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

* The :module:`FindOpenSSL` module learned to support a version range.

* The :module:`FindPython3`, :module:`FindPython2` and :module:`FindPython`
  modules gained options controlling how unversioned interpreter names are
  searched.

* The :module:`UseJava` module ``add_jar()`` command's
  ``GENERATE_NATIVE_HEADERS`` feature gained options to export the
  generated target.

* The :module:`UseSWIG` module gained the capability, for
  :ref:`Makefile <Makefile Generators>` and :ref:`Ninja <Ninja Generators>`
  generators, to use the ``swig`` tool to generate implicit dependencies.

Autogen
-------

* The :ref:`Qt AUTOMOC` feature now works with per-config sources.

CTest
-----

* :manual:`ctest(1)` gained a ``--test-dir`` option to specify the directory
  in which to look for tests.

CPack
-----

* :module:`CPack` gained the :variable:`CPACK_THREADS` variable to
  control the number of threads used for parallelized operations,
  such as compressing the installer package.

* The :cpack_gen:`CPack DEB Generator` learned a new
  :variable:`CPACK_DEBIAN_PACKAGE_SHLIBDEPS_PRIVATE_DIRS`
  variable to specify additional search directories for
  resolving private library dependencies when using
  ``dpkg-shlibdeps``.

* The :cpack_gen:`CPack IFW Generator` gained a new
  :variable:`CPACK_IFW_PACKAGE_WIZARD_SHOW_PAGE_LIST` variable to
  control visibility of the widget listing installer pages on the left side
  of the wizard. This feature available only since QtIFW 4.0.

* The :cpack_gen:`CPack NSIS Generator` gained new
  :variable:`CPACK_NSIS_BRANDING_TEXT` and
  :variable:`CPACK_NSIS_BRANDING_TEXT_TRIM_POSITION` variables to change
  the text at the bottom of the install window and change its trim position

* The :cpack_gen:`CPack NSIS Generator` now correctly handles Unicode
  characters.  If you want to have a :variable:`CPACK_RESOURCE_FILE_LICENSE`
  with UTF-8 characters, it needs to be encoded in UTF-8 BOM.

* The :cpack_gen:`CPack NuGet Generator` gained options:

  - :variable:`CPACK_NUGET_PACKAGE_ICON` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_ICON`
    allow package icons to be specified by local files.
  - :variable:`CPACK_NUGET_PACKAGE_LICENSE_EXPRESSION` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_LICENSE_EXPRESSION` add
    support for specifying licenses recognized by the
    `Software Package Data Exchange`_ (SPDX).
  - :variable:`CPACK_NUGET_PACKAGE_LICENSE_FILE_NAME` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_LICENSE_FILE_NAME` allow
    licenses to be specified by local files.
  - :variable:`CPACK_NUGET_PACKAGE_LANGUAGE` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_LANGUAGE` allow the locale
    for a package to be specified, for example ``en_CA``.

.. _Software Package Data Exchange: https://spdx.org/

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

* The :manual:`cmake-server(7)` mode has been removed.
  Clients should use the :manual:`cmake-file-api(7)` instead.

* The :module:`WriteCompilerDetectionHeader` module has been deprecated
  via policy :policy:`CMP0120`.  Projects should be ported away from it.

* The :module:`TestBigEndian` module has been deprecated in favor
  of the :variable:`CMAKE_<LANG>_BYTE_ORDER` variable.

* The :module:`AddFileDependencies` module is deprecated.
  Port projects to use :command:`set_property` directly.

* The :cpack_gen:`CPack NuGet Generator` deprecated some variables to reflect
  changes in the NuGet specification:

  - :variable:`CPACK_NUGET_PACKAGE_ICONURL` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_ICONURL` have been deprecated;
    replace with a reference to a local icon file.
  - :variable:`CPACK_NUGET_PACKAGE_LICENSEURL` and
    :variable:`CPACK_NUGET_<compName>_PACKAGE_LICENSEURL` have been deprecated;
    replace with a reference to the project's license file or SPDX
    license expression.

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

* Source file extensions must now be explicit.
  See policy :policy:`CMP0115` for details.

* The :prop_sf:`LANGUAGE` source file property now forces compilation
  as the specified language.  See policy :policy:`CMP0119`.

* On AIX, installation of XCOFF executables and shared libraries
  no longer requires relinking to change the runtime search path
  from the build-tree RPATH to the install-tree RPATH.  CMake now
  edits the XCOFF binaries directly during installation, as has
  long been done on ELF platforms.

* With MSVC-like compilers the value of
  :variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_FLAGS>` no longer contains
  the ``/GR`` flag for runtime type information by default.
  See policy :policy:`CMP0117`.

* Ninja generators now transform the ``DEPFILE`` generated by an
  :command:`add_custom_command`. See policy :policy:`CMP0116` for details.

* The implementation of the :module:`ExternalProject` module was
  significantly refactored.  The patch step gained support for
  using the terminal with a new ``USES_TERMINAL_PATCH`` keyword
  as a by-product of that work.

* The :module:`FetchContent` module no longer creates a separate
  sub-build to implement the content population.  It now invokes
  the step scripts directly from within the main project's
  configure stage.  This significantly speeds up the configure
  phase when the required content is already populated and
  up-to-date.

* The precompiled Linux binaries provided on
  `cmake.org <https://cmake.org/download/>`_ have changed their naming pattern
  to ``cmake-$ver-linux-$arch``, where ``$arch`` is either ``x86_64`` or
  ``aarch64``.

* The precompiled Windows binaries provided on
  `cmake.org <https://cmake.org/download/>`_ have changed their naming pattern
  to ``cmake-$ver-windows-$arch``, where ``$arch`` is either ``x86_64`` or
  ``i386``.
