# CMake 4.0 Release Notes

Changes made since CMake 3.31 include the following.

## New Features

### File-Based API

- The `cmake-file-api(7)` "codemodel" version 2 `version` field has been updated to 2.8.

- The `cmake-file-api(7)` "codemodel" version 2 "target" object gained a new `debugger` field.

### Command-Line

- The `cmake --link-no-warning-as-error` option was added to suppress the effects of the `LINK_WARNING_AS_ERROR` target property and `CMAKE_LINK_WARNING_AS_ERROR` variable.

- The `cmake --project-file` option was added to specify an alternate filename for `CMakeLists.txt` files. This is intended for temporary use by developers during an incremental transition and not for publication of a final product. CMake will always emit a warning when the project file is anything other than `CMakeLists.txt`.

### Commands

- The `target_link_libraries()` command now supports the `LINKER:` prefix.

### Variables

- The `AIX` and `CMAKE_HOST_AIX` variables are now set to true when the target or host system is AIX, respectively.

- Linker flag variables learned to support the `LINKER:` prefix:

  - `CMAKE_EXE_LINKER_FLAGS`

  - `CMAKE_EXE_LINKER_FLAGS_<CONFIG>`

  - `CMAKE_SHARED_LINKER_FLAGS`

  - `CMAKE_SHARED_LINKER_FLAGS_<CONFIG>`

  - `CMAKE_MODULE_LINKER_FLAGS`

  - `CMAKE_MODULE_LINKER_FLAGS_<CONFIG>`

  See policy `CMP0181`.

- The `CMAKE_EXECUTE_PROCESS_COMMAND_ERROR_IS_FATAL` variable was added to specify the `execute_process()` command's default `COMMAND_ERROR_IS_FATAL` behavior.

- The `CMAKE_<LANG>_LINK_MODE` and `CMAKE_<LANG>_DEVICE_LINK_MODE` variables were added to provide information on how the link step is done.

- The `CMAKE_LINK_WARNING_AS_ERROR` variable and corresponding `LINK_WARNING_AS_ERROR` target property were added to link using a linker-specific flag to treat warnings as errors.

- The `CMAKE_MSVC_RUNTIME_CHECKS` variable and `MSVC_RUNTIME_CHECKS` target property were introduced to select runtime checks for compilers targeting the MSVC ABI. See policy `CMP0184`.

- The `CMAKE_POLICY_VERSION_MINIMUM` variable was added to help packagers and end users try to configure existing projects that have not been updated to work with supported CMake versions. The `CMAKE_POLICY_VERSION_MINIMUM` environment variable was added to initialize it.

- The `CMAKE_UNITY_BUILD_RELOCATABLE` variable and corresponding `UNITY_BUILD_RELOCATABLE` target property were added to make sources generated for `CMAKE_UNITY_BUILD` to `#include` the original source files using relative paths where possible.

- The `CMAKE_XCODE_SCHEME_LLDB_INIT_FILE` variable and corresponding `XCODE_SCHEME_LLDB_INIT_FILE` target property were added to tell the `Xcode` generator what to put in the scheme's "LLDB Init File" setting.

- The `CMAKE_XCODE_SCHEME_TEST_CONFIGURATION` variable and corresponding `XCODE_SCHEME_TEST_CONFIGURATION` target property were added to tell the `Xcode` generator what to put in the scheme's "Build Configuration" setting for the test action.

### Properties

- The `DEBUGGER_WORKING_DIRECTORY` target property and corresponding `CMAKE_DEBUGGER_WORKING_DIRECTORY` variable were added to tell generators what debugger working directory should be set for targets.

- The `STATIC_LIBRARY_OPTIONS` target property now supports an `ARCHIVER:` prefix to pass options to the archiver through the compiler driver in a portable way.

- The `Swift_MODULE_DIRECTORY` target property now supports `generator expressions`.

- The `VS_CUSTOM_COMMAND_DISABLE_PARALLEL_BUILD` source file property was added to tell Visual Studio Generators not to run a custom command in parallel.

- The `VS_SOLUTION_ITEMS` directory property was added to tell Visual Studio Generators to attach files directly to the Solution (`.sln`).

### Modules

- The `ExternalData` module gained a `ExternalData_HTTPHEADERS` variable to specify HTTP headers.

- The `ExternalProject` module's `ExternalProject_Add()` command gained an `INSTALL_JOB_SERVER_AWARE` option to enable integration of the GNU Make job server when using an explicit `INSTALL_COMMAND` with Makefile Generators.

- The `FeatureSummary` module `add_feature_info()` command now supports full Condition Syntax. See policy `CMP0183`.

- The `FindBISON` module `bison_target()` command gained an `OPTIONS` option to specify Bison command-line options.

- The `FindCURL` module now provides a `CURL_VERSION` result variable to match upstream cURL's CMake package.

- The `FindFLEX` module `flex_target()` command gained an `OPTIONS` option to specify Flex command-line options.

- The `FindPatch` module now supports running in cmake -P script mode by skipping the creation of the imported target.

- The `FindProtobuf` module `protobuf_generate()` command gained a `PROTOC_EXE` option to specify a custom `protoc` executable.

- The `FindPython`, `FindPython2`, and `FindPython3` modules gained the possibility to do multiple calls in the same directory by using, respectively, the variables `Python_ARTIFACTS_PREFIX`, `Python2_ARTIFACTS_PREFIX`, and `Python3_ARTIFACTS_PREFIX`.

- The `FindRuby` module learned to find rbenv-provided installations.

### Generator Expressions

- The `$<PATH>` generator expression gained the `NATIVE_PATH` operation to convert a CMake path into a native one.

### CTest

- The `ctest --interactive-debug-mode` option on Windows now enables Windows Error Reporting by default in test processes, allowing them to creating debug popup windows and core dumps. This restores behavior previously removed by CMake 3.11 after updates to `libuv` made it possible.

### CPack

- The `CPack Archive Generator` learned to generate `.tar` packages without compression.

- The `CPack Archive Generator` now honors the `CPACK_ARCHIVE_FILE_NAME` variable for all packages. Previously, this variable worked only for component-based packages.

## Deprecated and Removed Features

- Compatibility with versions of CMake older than 3.5 has been removed. Calls to `cmake_minimum_required()` or `cmake_policy()` that set the policy version to an older value now issue an error. Note that calls to those commands can still support older versions of CMake by using their `VERSION` arguments' `<min>...<max>` syntax. This requires only the `<min>` version of CMake, but when running a newer version, sets policies up to the `<max>` version.

- The `Visual Studio 14 2015` and `Visual Studio 15 2017` generators no longer support specifying a platform as part of the generator name. See Visual Studio Platform Selection.

- The `CMAKE_<LANG>_USING_LINKER_MODE` variable is no longer used to determine the type of the contents of the `CMAKE_<LANG>_USING_LINKER_<TYPE>` variable. The `CMAKE_<LANG>_LINK_MODE` variable, set by CMake, is used instead.

- The `FindGDAL` module is now deprecated in favor of upstream GDAL's official CMake package configuration file. Port projects to the latter by calling `find_package(GDAL CONFIG)`. For further details, see GDAL's documentation on CMake integration.

- The `FindRuby` module no longer provides variables with the upper-case `RUBY_` prefix. See policy `CMP0185`.

- CTest's undocumented declarative scripting mode has been removed. This mode used to be triggered by a `ctest -S` script which did not call any CTest Commands unless `CTEST_RUN_CURRENT_SCRIPT` was explicitly set to `OFF`.

- The `ctest_run_script()` command may no longer be called without any arguments.

## Other Changes

- On macOS with Ninja Generators and Makefile Generators, when a compiler is found in `/usr/bin`, it is now used as-is and is no longer mapped to the corresponding compiler inside Xcode. The mapping was introduced by CMake 3.2 to allow build trees to continue to work with their original compiler even when `xcode-select` switches to a different Xcode installation. However, the compilers inside Xcode cannot be used without explicit `-isysroot` flags and are therefore not suitable for passing to arbitrary third-party build systems. Furthermore, the mapping behavior can override user-specified compiler paths. Therefore, this behavior has been reverted.

- In builds targeting macOS, `CMAKE_OSX_SYSROOT` now defaults to empty, deferring to the compiler's default macOS SDK selection. In order to pass an explicit macOS SDK via the compiler's `-isysroot` flag, users may configure their build tree with `-DCMAKE_OSX_SYSROOT=macosx`, or `export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"` in their environment.

  Notes:

  - macOS compilers in `/usr/bin`, when not invoked with `-isysroot`, search for headers in `/usr/local/include` before system SDK paths, matching the convention on many platforms. Users on macOS-x86_64 hosts with Homebrew installed in `/usr/local` should pass an explicit SDK, as described above, when not building with Homebrew tools.

  - Some Clang compilers have no default macOS SDK selection. For these, if `CMAKE_OSX_SYSROOT` is empty, CMake will automatically pass `-isysroot` with the macOS SDK printed by `xcrun --show-sdk-path`.

- On Windows, file paths named in project code, e.g., in `CMakeLists.txt`, are no longer automatically converted to their on-disk upper/lower case. Projects are expected to spell source file paths consistently using their canonical case, e.g., in calls to `add_library()`, `set_property(SOURCE)`, or `set_source_files_properties()`. This matches the behavior on platforms with case-sensitive filesystems.

- On AIX, `SHARED` library targets now produce a shared library archive by default. See policy `CMP0182`.

- The `cmake --preset` command no longer outputs a summary of the preset's CMake cache and environment variables by default. That summary is now only shown when the message log level is set to `VERBOSE`, `DEBUG`, or `TRACE` via the `cmake --log-level` option or the `CMAKE_MESSAGE_LOG_LEVEL` cache variable.

- Precompiled SunOS `sparc64` and `x86_64` binaries are now provided on cmake.org.

## Updates

Changes made since CMake 4.0.0 include the following.

### 4.0.1

- This version made no changes to documented features or interfaces. Some implementation updates were made to support ecosystem changes and/or fix regressions.

### 4.0.2

- When building for macOS with a Clang that has no default macOS SDK, if `CMAKE_OSX_SYSROOT` is empty, CMake now automatically passes `-isysroot` with the macOS SDK printed by `xcrun --show-sdk-path`. This restores support for using LLVM/Clang on macOS without manually setting `CMAKE_OSX_SYSROOT`, which was broken by CMake 4.0.0's removal of a default value.

- The `DEBUGGER_WORKING_DIRECTORY` target property is now used by the `Xcode` generator as a fallback for the `XCODE_SCHEME_WORKING_DIRECTORY` target property.

### 4.0.3, 4.0.4

- These versions made no changes to documented features or interfaces. Some implementation updates were made to support ecosystem changes and/or fix regressions.

### 4.0.5

- When building for macOS with the `Xcode` generator, `CMAKE_OSX_DEPLOYMENT_TARGET` once again defaults to the host's macOS version if it is older than the macOS SDK version, as it did in CMake versions prior to 4.0.

- The `execute_process()` command once again terminates child processes when its `TIMEOUT` is reached. This was accidentally regressed by CMake 3.29.