CMake 3.18 Release Notes — CMake 4.2.6 Documentation

# CMake 3.18 Release Notes

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

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

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

### Commands

- The `add_library()` and `add_executable()` commands learned to create Alias Targets referencing non-`GLOBAL` Imported Targets.

- The `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 `execute_process()` command gained the `ECHO_OUTPUT_VARIABLE` and `ECHO_ERROR_VARIABLE` options.

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

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

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

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

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

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

- The `get_source_file_property()` command gained the `DIRECTORY` and `TARGET_DIRECTORY` options to get a property from the provided directory scope.

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

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

- The `set_source_files_properties()` command gained the `DIRECTORY` and `TARGET_DIRECTORY` options to set properties in the provided directory scopes.

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

### Variables

- A `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 `CMAKE_CUDA_COMPILER_ID` is `NVIDIA`. The variable is used to initialize the new `CUDA_ARCHITECTURES` target property. See policy `CMP0104`.

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

### Properties

- The `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 `CMAKE_CUDA_ARCHITECTURES` variable. See policy `CMP0104`.

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

- The `FRAMEWORK_MULTI_CONFIG_POSTFIX_<CONFIG>` target property and associated `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 `OBJECT_OUTPUTS` source file property now supports `generator expressions`.

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

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

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

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

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

- The `VS_SOLUTION_DEPLOY` target property was added to tell 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 `CheckLinkerFlag` module has been added to provide a facility to check validity of link flags.

- The `ExternalProject` module `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 `ExternalProject` and `FetchContent` modules.

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

- The `FindBLAS` module now provides an imported target.

- The `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 `FindLAPACK` module now provides an imported target.

- The `FindPython3`, `FindPython2` and `FindPython` modules:

  - gained the possibility to create per-artifact cache variables for interactive editing in `cmake-gui(1)` and `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 `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 `FindSWIG` module now accepts target languages as `COMPONENTS` and `OPTIONAL_COMPONENTS` arguments to `find_package`.

- The `GoogleTest` module `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 `FindLibXslt` module now provides imported targets.

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

### Generator Expressions

- The `$<DEVICE_LINK:...>` and `$<HOST_LINK:...>` generator expressions were added to manage device and host link steps.

- The `$<LINK_LANGUAGE:...>` and `$<LINK_LANG_AND_ID:...>` generator expressions were added.

### CTest

- `ctest(1)` gained a new `CTEST_RESOURCE_SPEC_FILE` variable, which can be used to specify a resource specification file.

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

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

- The `CTestCoverageCollectGCOV` module `ctest_coverage_collect_gcov()` command gained a `TARBALL_COMPRESSION` option to control compression of the tarball of collected results.

### CPack

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

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

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

### Other

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

- `ccmake(1)` learned to read a `CCMAKE_COLORS` environment variable to customize colors.

- The `Compile Features` functionality is now aware of the availability of C11 features in MSVC 19.27 and 19.28, including support for the `c_restrict`, `c_static_assert` features and the `-std:c11` flag.

## Deprecated and Removed Features

- The `Documentation` module has been deprecated via `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 `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 `Ninja` and `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 `LINK_OPTIONS` and `INTERFACE_LINK_OPTIONS` target properties are now used for the device link step. See policy `CMP0105`.

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

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

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

- The `source_group()` command now also recognizes forward slashes as subgroup delimiters, not just backslashes.

- `ctest(1)` now logs environment variables that it sets for each test, either due to the `ENVIRONMENT` property or the 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 `file(DOWNLOAD)`, `file(UPLOAD)`, and `ctest_submit()`. The precompiled binaries provided on `cmake.org` now support HTTP/2.

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

- The `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 `Xcode` generator, when `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 `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.

### 3.18.2

- The default value of `CMAKE_AUTOMOC_PATH_PREFIX` was changed to `OFF` because this feature can break existing projects that have identically named header files in different include directories. This restores compatibility with behavior of CMake 3.15 and below. The default was also changed to `OFF` in 3.16.9 and 3.17.5.

- The `Compile Features` functionality was updated for MSVC 19.27 as mentioned above (`c_restrict`).

### 3.18.3

- The `Compile Features` functionality was updated for MSVC 19.28 as mentioned above (`c_static_assert`).