cmake-policies - Man Page

Added in version 3.31.

project() always sets <PROJECT-NAME>_* as normal variables.

In CMake 3.29 and below, the project() command set <PROJECT-NAME>_SOURCE_DIR, <PROJECT-NAME>_BINARY_DIR, and <PROJECT-NAME>_IS_TOP_LEVEL as cache entries, but not as normal variables.  CMake 3.30 started setting them as normal variables, but only if they are already set as normal variables.  This was needed to preserve support for some FetchContent use cases under policy CMP0169's NEW behavior, while also preserving behavior of nested directories that call project() with the same project name. See release notes for 3.30.3, 3.30.4, and 3.30.5 for details.

CMake 3.31 and later prefer to always set <PROJECT-NAME>_SOURCE_DIR, <PROJECT-NAME>_BINARY_DIR, and <PROJECT-NAME>_IS_TOP_LEVEL, as both cache entries and normal variables, regardless of what cache or normal variables already exist.  This policy provides compatibility for projects that have not been updated to expect this behavior.

The OLD behavior for this policy will only set normal variables for <PROJECT-NAME>_SOURCE_DIR, <PROJECT-NAME>_BINARY_DIR, and <PROJECT-NAME>_IS_TOP_LEVEL if there is already a normal variable by that name when project() is called. The NEW behavior for this policy will always set normal variables for <PROJECT-NAME>_SOURCE_DIR, <PROJECT-NAME>_BINARY_DIR, and <PROJECT-NAME>_IS_TOP_LEVEL when project() is called.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.31.

De-duplication of static libraries on link lines keeps first occurrence. This policy is only relevant when policy CMP0156 is set to NEW.

Based on the linker capabilities, the static libraries can be de-duplicated. See policy CMP0156 for more information.

CMake 3.30 and below may choose to keep, on some platforms, the last occurrence of the static libraries rather than the fist occurrence when they are de-duplicated.

CMake 3.31 and above prefer to keep, on all platforms, the first occurrence of the static libraries when they are de-duplicated.

The OLD behavior for this policy is to keep, on some platforms, the last occurrence of the static libraries when they are de-duplicated.  The NEW behavior for this policy is to keep the first occurrence of the static libraries when they are de-duplicated, regardless of the platform.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.31.

Test command lines preserve empty arguments.

Empty values in the TEST_LAUNCHER and CROSSCOMPILING_EMULATOR target properties are now preserved for tests added by the following:

• The add_test() command.
• The ExternalData_Add_Test() command from the ExternalData module.
• The gtest_add_tests() or gtest_discover_tests() commands from the GoogleTest module.

For the gtest_add_tests() and gtest_discover_tests() commands, empty elements in the values passed after the EXTRA_ARGS keyword are also now preserved.

The OLD behavior of this policy silently discards empty list items from the TEST_LAUNCHER and CROSSCOMPILING_EMULATOR target properties in the above-mentioned cases.  It also silently discards empty items from the values given after EXTRA_ARGS for the gtest_add_tests() and gtest_discover_tests() commands.

The NEW behavior of this policy preserves empty list items in the TEST_LAUNCHER and CROSSCOMPILING_EMULATOR target properties, and in values given after EXTRA_ARGS for gtest_add_tests() and gtest_discover_tests().

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.31.

install() DESTINATION paths are normalized.

The install() command has a number of different forms, and most of them take a DESTINATION keyword, some in more than one place. CMake 3.30 and earlier used the value given after the DESTINATION keyword as provided with no transformations.  The install(EXPORT) form assumes the path contains no .. or . path components when computing a path relative to the DESTINATION, and if the project provided a path that violated that assumption, the computed path would be incorrect.

CMake 3.31 normalizes all DESTINATION values given in any form of the install() command, except for the INCLUDES DESTINATION of the install(TARGETS) form.  The normalization performed is the same as for the cmake_path() command (see Normalization).

The OLD behavior of this policy performs no translation on the DESTINATION values of any install() command.  They are used exactly as provided.  If a destination path contains .. or . path components, install(EXPORT) will use the same wrong paths as CMake 3.30 and earlier.

The NEW behavior will normalize all DESTINATION values except for INCLUDES DESTINATION.  If a destination path contains a generator expression, it will be wrapped in a $<PATH:CMAKE_PATH,NORMALIZE,...> generator expression.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake will warn if it detects a path that would be different if normalized, and uses OLD behavior.  If a destination path contains a generator expression, no such warning will be issued regardless of the value.

NOTE:

Added in version 3.31.

execute_process() ENCODING is UTF-8 by default.

The ENCODING option is meaningful only on Windows.  It specifies the character encoding expected in the process's output on stdout and stderr. In CMake 3.14 and below the default encoding was NONE, which corresponds to CMake's internal UTF-8 encoding.  In CMake 3.15 through CMake 3.30 the default encoding was accidentally changed to AUTO, but the change went unnoticed and was not documented.

CMake 3.31 and above prefer the ENCODING default to be UTF-8. This policy provides compatibility with projects that may have been relying on the default being AUTO.

The OLD behavior of this policy is for execute_process() to use AUTO by default if no ENCODING is specified.  The NEW behavior for this policy is to use UTF-8 as the default ENCODING.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.31.

add_custom_command() rejects invalid arguments.

CMake 3.30 and earlier silently ignored unsupported keywords and missing or invalid arguments for the different forms of the add_custom_command() command. CMake 3.31 implements more rigorous argument checking and will flag invalid or missing arguments as errors.

The OLD behavior of this policy will accept the same invalid keywords or arguments as CMake 3.30 and earlier. The NEW behavior will flag the following as errors that previously went unreported:

• The OUTPUT form does not accept PRE_BUILD, PRE_LINK, or POST_BUILD keywords.
• When the APPEND keyword is given, the OUTPUT form also does not accept BYPRODUCTS, COMMAND_EXPAND_LISTS, DEPENDS_EXPLICIT_ONLY, DEPFILE, JOB_POOL, JOB_SERVER_AWARE, USES_TERMINAL, or VERBATIM keywords.
• The TARGET form requires exactly one of PRE_BUILD, PRE_LINK, or POST_BUILD to be given.  Previously, if none were given, POST_BUILD was assumed, or if multiple keywords were given, the last one was used.
• The TARGET form does not accept DEPENDS, DEPENDS_EXPLICIT_ONLY, DEPFILE, IMPLICIT_DEPENDS, MAIN_DEPENDENCY, JOB_POOL, or JOB_SERVER_AWARE keywords.
• The TARGET form now requires at least one COMMAND to be given.
• If a keyword expects a value to be given after it, but no value is provided, that was previously treated as though the keyword was not given at all.
• The COMMENT keyword expects exactly one value after it.  If multiple values are given, or if the COMMENT keyword is given more than once, this is an error.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.31.

cmake_parse_arguments(PARSE_ARGV) defines a variable for an empty string after a single-value keyword.

One of the main reasons for using the PARSE_ARGV form of the cmake_parse_arguments() command is to more robustly handle corner cases related to empty values.  The non-PARSE_ARGV form doesn't preserve empty arguments, but the PARSE_ARGV form does.  For each single-value keyword given, a variable should be defined if the keyword is present, even if it is followed by an empty string.

Prior to CMake 3.31, no variable would be defined if the value given after a single-value keyword was an empty string.  This meant the code could not detect the difference between the keyword not being given, and it being given but with an empty value, except by iterating over all the arguments and checking if the keyword is present.

For the OLD behavior of this policy, cmake_parse_arguments(PARSE_ARGV) does not define a variable for a single-value keyword followed by an empty string, or followed by no value at all.

For the NEW behavior, cmake_parse_arguments(PARSE_ARGV) always defines a variable for each keyword given in the arguments, even a single-value keyword with an empty string as its value or no value at all.  With the NEW behavior, the code can robustly check if a single-value keyword was given using just if(DEFINED <prefix>_<keyword>).

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.31.

The CMakeFindFrameworks module is removed.

CMake's framework handling has evolved well beyond what the CMakeFindFrameworks module supports. The module lacks any handling of XCFrameworks, it never documented the one command it provides, and find_library() provides superior capabilities in all respects.

The OLD behavior of this policy is for CMakeFindFrameworks to continue to provide the undocumented cmake_find_frameworks() command. The NEW behavior halts with a fatal error if anything tries to include the module.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.31.

The CPack module enables per-machine installation by default in the CPack WIX Generator.

The CPack WIX Generator's CPACK_WIX_INSTALL_SCOPE option controls the scope of the generated Windows Installer package. When CPACK_WIX_VERSION is set to 4 or higher, the default scope is perMachine.  However, when using WIX 3 the default scope is NONE, and CPack does not set any InstallScope in the package specification. The resulting installer requires administrative privileges and installs into the system-wide ProgramFiles directory, but the start menu entry and uninstaller registration are created only for the current user.

The CPack module in CMake 3.30 and older does not specify any CPACK_WIX_INSTALL_SCOPE value by default, so CPack uses no installation scope by default with WIX 3.  CMake 3.31 and newer instead prefer to set CPACK_WIX_INSTALL_SCOPE to perMachine by default to make the behavior consistent across all WIX versions.  This policy provides compatibility for projects that have not been updated to expect perMachine behavior.

The OLD behavior for this policy is to not set CPACK_WIX_INSTALL_SCOPE by default.  The NEW behavior for this policy is to set CPACK_WIX_INSTALL_SCOPE to perMachine by default.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0172 variable to control the warning.

NOTE:

Added in version 3.31.

codegen is a reserved target name.

CMake 3.30 and earlier did not reserve codegen as a builtin target name, leaving projects free to create their own target with that name. CMake 3.31 and later prefer to reserve codegen as a builtin target name to drive custom commands created with the CODEGEN option to add_custom_command().  In order to support building the codegen target in scripted environments, e.g., cmake --build . --target codegen, the codegen target needs to be generated even if no custom commands use the CODEGEN option.  This policy provides compatibility for projects that have not been updated to avoid creating a target named codegen.

The OLD behavior of this policy allows projects to create a target with the name codegen.  The NEW behavior halts with a fatal error if a target with the name codegen is created.

This policy was introduced in CMake version 3.31. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.30.

When FETCHCONTENT_FULLY_DISCONNECTED is set to true, FetchContent_MakeAvailable() and FetchContent_Populate() enforce the constraint that their source directory must already be populated. The requirement has always been documented, but it was not checked or enforced with CMake 3.29 or older.  This sometimes led to hard-to-trace errors when a project expected a dependency to have been populated, but its population was silently skipped.

CMake 3.30 and above prefers to check and enforce the constraint. This policy provides compatibility for situations where the user cannot easily prevent FETCHCONTENT_FULLY_DISCONNECTED from being inappropriately set to true.

The OLD behavior of this policy allows FETCHCONTENT_FULLY_DISCONNECTED to be set to true even if a dependency's source directory has not been populated. The NEW behavior halts with a fatal error if FETCHCONTENT_FULLY_DISCONNECTED is set to true and a dependency population would be skipped, but that dependency's source directory doesn't exist.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.30.

Calling FetchContent_Populate() with a single argument (the name of a declared dependency) is deprecated.

Prior to the introduction of FetchContent_MakeAvailable(), projects populated previously declared content (with FetchContent_Declare()) using the following pattern:

FetchContent_GetProperties(depname)
if(NOT depname_POPULATED)
  FetchContent_Populate(depname)
  add_subdirectory(${depname_SOURCE_DIR} ${depname_BINARY_DIR})
endif()

The above pattern does not support a number of features that have been added to FetchContent over time. It ignores options like SYSTEM and EXCLUDE_FROM_ALL which may be given to FetchContent_Declare(), but can't be made known to the above project code. It also does not support dependency providers. Projects should call FetchContent_MakeAvailable() instead of using the above pattern.

CMake 3.30 and above prefers to reject calls to FetchContent_Populate() with the name of a declared dependency. This policy provides compatibility for projects that have not been updated to call FetchContent_MakeAvailable() instead.

The OLD behavior of this policy allows FetchContent_Populate() to be called with the name of a declared dependency. The NEW behavior halts with a fatal error in such cases.

NOTE:

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.30.

The FetchContent module implements steps directly instead of through a sub-build.

CMake 3.29 and below implement FetchContent as a separate sub-build. This required configuring that separate project and using a build tool. This approach can be very slow with some generators and operating systems. CMake 3.30 and above prefer to implement the download, update, and patch steps directly as part of the main project.

The NEW behavior has the following characteristics:

• No sub-build is used. All operations are implemented directly from the main project's CMake configure step. When running in CMake script mode, no build tool needs to be available.
• Generator expressions and GNU Make variables of the form $(SOMEVAR) are not supported. They should not be used in any argument to FetchContent_Declare() or FetchContent_Populate().
• All LOG_... and USES_TERMINAL_... options, the QUIET option, and the FETCHCONTENT_QUIET variable are ignored. FetchContent output is always part of the main project's configure output. This also means it now respects the message logging level (see CMAKE_MESSAGE_LOG_LEVEL and --log-level). The default message log level should be comparable to using QUIET with the OLD policy setting, except that warnings will now be shown.
• The PREFIX, TMP_DIR, STAMP_DIR, LOG_DIR, and DOWNLOAD_DIR options and their associated directory properties are ignored. The FetchContent module controls those locations internally.
• cmake --fresh will remove the stamp and script files used for tracking and populating the dependency. This will force the dependency's download, update, and patch steps to be re-executed. The directory used for downloads is not affected by cmake --fresh, so any previously downloaded files for the URL download method can still be re-used.

The OLD behavior has the following characteristics:

• A sub-build is always used to implement the download, update, and patch steps. A build tool must be available, even when using FetchContent_Populate() in CMake script mode.
• Generator expressions and GNU Make variables of the form $(SOMEVAR) can be used, although such use is almost always inappropriate. They are evaluated in the sub-build, so they do not see any information from the main build.
• All logging, terminal control, and directory options related to the download, update, or patch steps are supported.
• If the QUIET option is used, or the FETCHCONTENT_QUIET variable is set to true, warnings will not be shown in the output.
• cmake --fresh has no effect on the dependency's stamp or script files. Previously executed steps will only re-run if details about the dependency have changed.

There's a reasonably good chance that users can set the CMAKE_POLICY_DEFAULT_CMP0168 variable to NEW to globally switch to the NEW behavior while waiting for the project and its dependencies to be updated use the NEW policy setting by default. Projects don't typically make use of the features that the NEW behavior no longer supports, and even those projects that do will often still work fine when those options are ignored. Before setting this behavior globally, check whether any FetchContent_Declare() or FetchContent_Populate() calls use the ignored options in a way that would change observable behavior, other than putting temporary or internally-generated files in different locations.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.30.

The FindBoost module is removed.

CMake 3.29 and below provide a FindBoost module, but it needs constant updates to keep up with upstream Boost releases.  Upstream Boost 1.70 and above provide a BoostConfig.cmake package configuration file. find_package(Boost CONFIG) finds the upstream package directly, without the find module.

CMake 3.30 and above prefer to not provide the FindBoost module so that find_package(Boost) calls, without the CONFIG or NO_MODULE options, find the upstream BoostConfig.cmake directly. This policy provides compatibility for projects that have not been ported to use the upstream Boost package.

The OLD behavior of this policy is for find_package(Boost) to load CMake's FindBoost module.  The NEW behavior is for find_package(Boost) to search for the upstream BoostConfig.cmake.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.30.

TARGET_PROPERTY evaluates link properties transitively over private dependencies of static libraries.

In CMake 3.29 and below, the TARGET_PROPERTY generator expression evaluates properties INTERFACE_LINK_OPTIONS, INTERFACE_LINK_DIRECTORIES, and INTERFACE_LINK_DEPENDS as if they were Transitive Compile Properties rather than Transitive Link Properties, even when policy CMP0099 is set to NEW.  Private dependencies of static libraries, which appear in their INTERFACE_LINK_LIBRARIES guarded by LINK_ONLY generator expressions, are not followed.  This is inconsistent with evaluation of the same target properties during buildsystem generation.

CMake 3.30 and above prefer that TARGET_PROPERTY evaluates properties INTERFACE_LINK_OPTIONS, INTERFACE_LINK_DIRECTORIES, and INTERFACE_LINK_DEPENDS as Transitive Link Properties such that private dependencies of static libraries, which appear in their INTERFACE_LINK_LIBRARIES guarded by LINK_ONLY generator expressions, are followed. This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is for TARGET_PROPERTY to evaluate properties INTERFACE_LINK_OPTIONS, INTERFACE_LINK_DIRECTORIES, and INTERFACE_LINK_DEPENDS as if they were Transitive Compile Properties by not following private dependencies of static libraries.  The NEW behavior for this policy is to evaluate them as Transitive Link Properties by following private dependencies of static libraries.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.30.

enable_language() must not be called before project().

In CMake 3.29 and below, if a project called enable_language() before the first call to project(), the language would be enabled but possibly using unset details that were expected to be set. In CMake 3.30 and above, enable_language() prefers to reject this case and stop with a fatal error instead if it detects that project() has not yet been called.  This policy provides compatibility for projects that happened to work when enable_language() was called before project() and have not been updated to call these commands in the required order.

The OLD behavior for this policy is to allow enable_language() to be called before project().  The NEW behavior for this policy is to fail with a fatal error in such cases.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.30.

add_library() rejects SHARED libraries when not supported by the platform.

In CMake 3.29 and below, on platforms that do not support shared libraries (TARGET_SUPPORTS_SHARED_LIBS is false), the add_library() command automatically converts SHARED libraries to STATIC libraries to help users build projects on such platforms.  However, the semantics of shared and static libraries are different enough that such automatic conversion cannot work in general.  Projects using shared libraries need to be ported to such platforms on a case-by-case basis.

In CMake 3.30 and above, add_library() prefers to reject creation of shared libraries on platforms that do not support them, and fail with a fatal error message.  This policy provides compatibility for projects that happened to work with the automatic conversion to static libraries and have not been updated with an explicit port.

The OLD behavior for this policy is to implicitly create a static library with a developer warning.  The NEW behavior for this policy is to fail.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn about the behavior change, and uses OLD behavior.

NOTE:

Added in version 3.30.

The GENERATED source file property is now visible in all directories.

In CMake 3.29 and below, the GENERATED source file property, like other source file properties, was scoped in every directory separately. Although policy CMP0118 allowed sources marked GENERATED in one directory to be used in other directories without manually marking them as GENERATED again, the GENERATED property was still not visible to get_property() and get_source_file_property() calls.

Whether or not a source file is generated is an all-or-nothing global property of the source: a source is either generated or it is not. CMake 3.30 and above prefer to treat the GENERATED source file property as globally scoped.  Once it is set in one directory, it is immediately visible to get_property() and get_source_file_property() calls in other directories. This policy provides compatibility for projects that have not been updated for this behavior.

The OLD behavior of this policy is for the GENERATED source file property to be visible only in the directories in which it is set.  The NEW behavior of this policy is to allow the GENERATED source file property to be visible in all directories once set in any directory. Furthermore, the NEW behavior of this policy implies the NEW behavior of policy CMP0118: the GENERATED property may be set only to boolean values, and may not be turned off once turned on.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.30.

Visual Studio Generators add UseDebugLibraries indicators by default.

The "Use Debug Libraries" setting in Visual Studio projects indicates what configurations are considered debug configurations.  In standalone projects, this may affect MSBuild's default selection of MSVC runtime library, optimization flags, runtime checks, and similar settings.  CMake typically generates all those settings explicitly based on the project's specification, so CMake 3.29 and below do not write any UseDebugLibraries indicators to .vcxproj files.

CMake 3.30 and above prefer to write UseDebugLibraries indicators because they are useful for reference by both humans and tools, and may also affect the behavior of platform-specific SDKs.  The indicator for each configuration of a target is determined as follows:

• If the target compiles sources for a known MSVC runtime library (such as that specified by MSVC_RUNTIME_LIBRARY), then UseDebugLibraries is true for configurations that compile for a "Debug" runtime library, and false for others.
• Otherwise, such as in targets created by add_custom_target(), UseDebugLibraries is true for the Debug configuration, and false for others.

This policy provides compatibility for projects that have not been updated to expect the indicators.  The policy setting is recorded by each target as it is created and used to determine the default behavior for that target's .vcxproj file.

The OLD behavior for this policy is to not generate UseDebugLibraries indicators by default.  The NEW behavior for this policy is to generate UseDebugLibraries indicators by default.

If the CMAKE_VS_USE_DEBUG_LIBRARIES variable and/or VS_USE_DEBUG_LIBRARIES target property is set, it explicitly controls UseDebugLibraries generation regardless of this policy.

This policy was introduced in CMake version 3.30. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.29.

The CPACK_PRODUCTBUILD_DOMAINS variable defaults to true.

Before CMake 3.29, the CPACK_PRODUCTBUILD_DOMAINS variable is unset by default.  When using the CPack productbuild Generator, this disables the use of the domains attribute in the productbuild Distribution XML, and falls back to the auth attribute instead. These attributes control where a productbuild package is allowed to be installed.  But the auth attribute has been deprecated by Apple, so projects should migrate to using domains instead.

CMake 3.29 and above prefer to use a default value of true for CPACK_PRODUCTBUILD_DOMAINS, which means domains will be used by default unless the project explicitly sets CPACK_PRODUCTBUILD_DOMAINS to false. This policy provides compatibility with projects that enabled the CPack productbuild Generator, but did not explicitly set CPACK_PRODUCTBUILD_DOMAINS.

The OLD behavior for this policy is to leave CPACK_PRODUCTBUILD_DOMAINS unset if it hasn't been set. The NEW behavior for this policy is to use a default value of true for CPACK_PRODUCTBUILD_DOMAINS.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

Note that a warning will only be emitted if the CPACK_BINARY_PRODUCTBUILD variable is set to true and the project is being built for an Apple platform.

NOTE:

Added in version 3.29.

More read-only target properties now error when trying to set them.

The set_target_properties() and set_property() commands are intended to error out on all read-only properties. However, CMake 3.28 and below only did this for the following properties:

• HEADER_SETS
• INTERFACE_HEADER_SETS
• IMPORTED_GLOBAL
• MANUALLY_ADDED_DEPENDENCIES
• NAME
• TYPE

This policy enforces the read-only nature of the following target properties:

• ALIAS_GLOBAL
• BINARY_DIR
• CXX_MODULE_SETS
• IMPORTED
• INTERFACE_CXX_MODULE_SETS
• LOCATION
• LOCATION_<CONFIG>
• SOURCE_DIR

The OLD behavior for this policy is to only error out for the properties MANUALLY_ADDED_DEPENDENCIES, NAME, and TYPE. The NEW behavior for this policy is to error out on all target properties that are documented as read-only.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.29.

file(STRINGS) with REGEX updates CMAKE_MATCH_<n>.

In CMake 3.28 and below the file(STRINGS) command's REGEX option does not affect CMAKE_MATCH_<n> variables.  CMake 3.29 and above prefer to update the CMAKE_MATCH_<n> variables using captures from the last match in the file, similar to the string(REGEX MATCHALL) command.  This policy provides compatibility for projects that have not been updated to expect the behavior.

The OLD behavior for this policy is for file(STRINGS) with REGEX to not store capture groups in CMAKE_MATCH_<n> variables.  The NEW behavior is to store the capture groups.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.29.

add_test() honors CMAKE_CROSSCOMPILING_EMULATOR only when cross-compiling.

In CMake 3.28 and below, add_test() unconditionally used the CROSSCOMPILING_EMULATOR target property (initialized by the CMAKE_CROSSCOMPILING_EMULATOR variable) to run test commands naming executable targets.  CMake 3.29 and above prefer to use the emulator only when the CMAKE_CROSSCOMPILING variable is enabled.  The CMAKE_TEST_LAUNCHER variable may be used instead when not cross-compiling.  This policy provides compatibility for projects that have not been updated.

The OLD behavior for this policy is for add_test() to use the CROSSCOMPILING_EMULATOR target property unconditionally. The NEW behavior for this policy is for add_test() to use the CROSSCOMPILING_EMULATOR target property only when cross-compiling.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.29.

Swift compilation mode is selected by an abstraction.

The Swift compiler can compile modules in different modes. The desired build mode depends whether the developer is iterating and wants to incrementally make changes, or if they are building a release for distribution and want more optimizations applied to the resulting binary.

CMake versions 3.26 through 3.28 build Swift binaries with whole-module optimizations enabled when configured in a non-debug build type. For CMake versions earlier than 3.26, the developer needs to specify the necessary flag manually for the Ninja Generators, and cannot not specify whole-module optimizations to the Xcode generator.

CMake versions 3.29 and above prefer to set the compilation mode using the Swift_COMPILATION_MODE target property, which can be initialized by the CMAKE_Swift_COMPILATION_MODE variable.

This policy provides compatibility for projects that have not been updated. The policy setting takes effect as of the first project() or enable_language() command that enables the Swift language.

NOTE:

The OLD behavior for this policy builds all Swift targets in wholemodule mode for non-debug configurations.  Ninja Generators prepend the -wmo flag to the default set of Swift flags. The Xcode generator sets the SWIFT_COMPILATION_MODE attribute to wholemodule in the generated Xcode project file.

The NEW behavior for this policy is to apply the compilation mode specified in the Swift_COMPILATION_MODE target property, initialized as each target is created by the CMAKE_Swift_COMPILATION_MODE variable.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.29.

De-duplicate libraries on link lines based on linker capabilities.

Traditional linkers maintain a set of undefined symbols during linking. The linker processes each file in the order in which it appears on the command line, until the set of undefined symbols becomes empty. An object file is linked into the output object when it is encountered, with its undefined symbols added to the set. Upon encountering an archive file a traditional linker searches the objects contained therein, and processes those that satisfy symbols in the unresolved set.

Handling mutually dependent archives may be awkward when using a traditional linker. Archive files may have to be specified multiple times.

Some linkers (for instance Apple or Windows linkers, as well as LLVM LLD) record all symbols found in objects and archives as they iterate over command line arguments. When one of these linkers encounters an undefined symbol that can be resolved by an object file contained in a previously processed archive file, it immediately extracts and links it into the output object.

CMake 3.28 and below may generate link lines that repeat static libraries as a traditional linker would need, even when using a linker that does not need it. They may also de-duplicate shared libraries by keeping their last occurrence, which on Windows platforms can change DLL load order.

CMake 3.29 and above prefer to apply different strategies based on linker capabilities.  So, when targeting Apple and Windows platforms, all libraries are de-duplicated.  Moreover, on Windows platforms, libraries are de-duplicated by keeping their first occurrence, thus respecting the project-specified order.  This policy provides compatibility with projects that have not been updated to expect the latter behavior.

NOTE:

The OLD behavior for this policy is to always repeat static libraries as if using a traditional linker, and always de-duplicate shared libraries by keeping the last occurrence of each.  The NEW behavior for this policy is to apply different strategies based on linker capabilities.

This policy was introduced in CMake version 3.29. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.28.

C++ sources in targets with at least C++20 are scanned for imports when supported.

CMake 3.27 and below assume that C++ sources do not import modules. CMake 3.28 and above prefer to assume that C++ sources in targets using C++20 or higher might import modules, and must be scanned before compiling, unless explicitly disabled.  This policy provides compatibility for projects that use C++20 or higher, without modules, that have not been updated to turn off scanning, e.g., via the CMAKE_CXX_SCAN_FOR_MODULES variable. See the cmake-cxxmodules(7) manual for more details on C++ module support.

The OLD behavior for this policy is to assume that C++ 20 and newer sources do not import modules.  The NEW behavior for this policy is to assume that C++ 20 and newer files may import modules if the compiler understands how to scan for their dependencies, and need to be scanned.

This policy was introduced in CMake version 3.28. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.28.

Generated files are private by default in targets using File Sets.

CMake 3.27 and below assume that any file generated as an output or byproduct of add_custom_command() or add_custom_target() may be a public header file meant for inclusion by dependents' source files.  This requires Ninja Generators to add conservative order-only dependencies that prevent a target's source files from compiling before custom commands from the target's dependencies are finished, even if those custom commands only produce sources private to their own target.

File Sets, introduced by CMake 3.23, provide a way to express the visibility of generated header files.  CMake 3.28 and above prefer to assume that, in targets using file sets, generated files are private to their own target by default.  Generated public headers must be specified as members of a PUBLIC (or INTERFACE) FILE_SET, typically of type HEADERS.  With this information, Ninja Generators may omit the above-mentioned conservative dependencies and produce more efficient build graphs.

Additionally, if the custom command's output is a member of a file set of type CXX_MODULES, it will additionally not be required to exist before compiling other sources in the same target.  Since these files should not be included at compile time directly, they may not be implicitly required to exist for other compilation rules.

This policy provides compatibility for projects using file sets in targets with generated header files that have not been updated.  Such projects should be updated to express generated public headers in a file set. For example:

add_custom_command(
  OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/foo.h
  ...
)
target_sources(foo
  PUBLIC FILE_SET HEADERS
    BASE_DIRS ${CMAKE_CURRENT_BINARY_DIR}
    FILES     ${CMAKE_CURRENT_BINARY_DIR}/foo.h
)

The OLD behavior for this policy is to assume generated files are public, even in targets using file sets, and for Ninja Generators to produce conservative build graphs.  The NEW behavior for this policy is to assume generated files are private in targets using file sets, and for Ninja Generators to produce more efficient build graphs.

This policy was introduced in CMake version 3.28. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.28.

The exec_program() command should not be called.

This command has long been superseded by the execute_process() command and has been deprecated since CMake 3.0.

CMake >= 3.28 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.28. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.28.

file(REAL_PATH) resolves symlinks before collapsing ../ components.

In CMake 3.27 and below, file(REAL_PATH) collapsed any ../ components in a path before resolving symlinks.  This produced incorrect results when the ../ collapsed away a symlink.

The OLD behavior for this policy is to collapse ../ components before resolving symlinks. The NEW behavior for this policy is to resolve all symlinks before collapsing ../ components.

This policy was introduced in CMake version 3.28. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.27.

AUTOMOC include directory is a system include directory by default.

Headers generated for AUTOMOC are placed in target-specific include directories.  CMake 3.26 and older added these as normal include directories. CMake 3.27 and newer prefer to add them as system include directories. This policy provides compatibility for projects that have not been updated to expect this.

If the AUTOGEN_USE_SYSTEM_INCLUDE target property is set, perhaps via the CMAKE_AUTOGEN_USE_SYSTEM_INCLUDE variable, then its value is used regardless of the setting of this policy.

The OLD behavior for this policy is to add autogen include directory to the target's include directories. The NEW behavior for this policy is to add autogen include directory to the target's system include directories.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.27.

ExternalProject_Add() and FetchContent_Declare() commands treat relative GIT_REPOSITORY paths as being relative to the parent project's remote.

Earlier versions of these commands always treated relative paths in GIT_REPOSITORY as local paths, but the base directory it was treated as relative to was both undocumented and unintuitive.  The OLD behavior for this policy is to interpret relative paths used for GIT_REPOSITORY as local paths relative to the following:

• The parent directory of SOURCE_DIR for ExternalProject_Add().
• FETCHCONTENT_BASE_DIR for FetchContent_Declare().

The NEW behavior is to determine the remote from the parent project and interpret the path relative to that remote.  The value of CMAKE_CURRENT_SOURCE_DIR when ExternalProject_Add() or FetchContent_Declare() is called determines the parent project. The remote is selected according to the following (the first match is used):

• If the parent project is checked out on a branch with an upstream remote defined, use that remote.
• If only one remote is defined, use that remote.
• If multiple remotes are defined and one of them is named origin, use origin's remote but also issue a warning.

If an appropriate remote cannot be determined from the above, a fatal error will be raised.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns when a relative path is encountered, and uses OLD behavior.

NOTE:

Added in version 3.27.

Visual Studio Generators select latest Windows SDK by default.

Visual Studio Generators select a Windows SDK version to put in the WindowsTargetPlatformVersion setting in .vcxproj files. CMake sets the CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION variable to the selected SDK version.

Prior to CMake 3.27, the SDK version was always selected by the value of the CMAKE_SYSTEM_VERSION variable.  Users or toolchain files could set that variable to one of the exact Windows SDK versions available on the host system.  Since CMAKE_SYSTEM_VERSION defaults to CMAKE_HOST_SYSTEM_VERSION, and it is not guaranteed that a matching Windows SDK version is available, CMake had to fall back to using the latest Windows SDK version if no exact match was available. This approach was problematic:

• The latest Windows SDK might or might not be selected based on whether the host version of Windows happens to match an available SDK version.
• An old Windows SDK version might be selected that has not been updated for newer language standards such as C11.

CMake 3.27 and higher prefer to ignore the exact value of CMAKE_SYSTEM_VERSION and by default select the latest SDK version available.  An exact SDK version may be specified explicitly using a version= field in the CMAKE_GENERATOR_PLATFORM variable.  See Visual Studio Platform Selection.

This policy provides compatibility for projects, toolchain files, and build scripts that have not been ported away from using CMAKE_SYSTEM_VERSION to specify an exact SDK version.

NOTE:

The OLD behavior for this policy is to use the exact value of CMAKE_SYSTEM_VERSION if possible.  The NEW behavior for this policy is to ignore it.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.27.

The FindPythonInterp and FindPythonLibs modules are removed.

These modules have been deprecated since CMake 3.12. CMake 3.27 and above prefer to not provide the modules. This policy provides compatibility for projects that have not been ported away from them.

Projects using the FindPythonInterp and/or FindPythonLibs modules should be updated to use one of their replacements:

• FindPython3
• FindPython2
• FindPython

The OLD behavior of this policy is for find_package(PythonInterp) and find_package(PythonLibs) to load the deprecated modules.  The NEW behavior is for uses of the modules to fail as if they do not exist.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.27.

Visual Studio Generators build custom commands in parallel.

Visual Studio 15.8 (2017) and newer support building custom commands in parallel.  CMake 3.27 and above prefer to enable this behavior by adding a BuildInParallel setting to custom commands in .vcxproj files. This policy provides compatibility for projects that have not been updated to expect this, e.g., because their custom commands were accidentally relying on serial execution by MSBuild.

The OLD behavior for this policy is to not add BuildInParallel. The NEW behavior for this policy is to add BuildInParallel for VS 15.8 and newer.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.27.

The FindCUDA module is removed.

The FindCUDA module has been deprecated since CMake 3.10. CMake 3.27 and above prefer to not provide the module. This policy provides compatibility for projects that have not been ported away from it.

Projects using the FindCUDA module should be updated to use CMake's first-class CUDA language support.  List CUDA among the languages named in the top-level call to the project() command, or call the enable_language() command with CUDA. Then one can add CUDA (.cu) sources directly to targets, similar to other languages.

The OLD behavior of this policy is for find_package(CUDA) to load the deprecated module.  The NEW behavior is for uses of the module to fail as if it does not exist.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.27.

The Dart and FindDart modules are removed.

These modules were added very early in CMake's development to support driving tests with a "DART" tool, but DART has not been distributed or maintained for many years.  Projects would include(Dart) to use it, and the Dart module would run find_package(Dart) internally. Since ctest(1) was created, the Dart module has just been a compatibility shim that finds Dart to support some legacy functionality and then forwards to the CTest module.

CMake 3.27 and above prefer to not provide the Dart or FindDart modules.  This policy provides compatibility for projects that have not been ported away from them.  Projects using the Dart module should be updated to use the CTest module directly.

The OLD behavior of this policy is for include(Dart) and find_package(Dart) to load the deprecated modules.  The NEW behavior is for uses of the modules to fail as if they do not exist.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.27.

find_package() uses upper-case <PACKAGENAME>_ROOT variables.

In CMake 3.27 and above the find_package(<PackageName>) command now searches prefixes specified by the upper-case <PACKAGENAME>_ROOT CMake variable and the <PACKAGENAME>_ROOT environment variable in addition to the case-preserved <PackageName>_ROOT and <PackageName>_ROOT variables used since policy CMP0074. This policy provides compatibility with projects that have not been updated to avoid using <PACKAGENAME>_ROOT variables for other purposes.

The OLD behavior for this policy is to ignore <PACKAGENAME>_ROOT variables if the original <PackageName> has lower-case characters. The NEW behavior for this policy is to use <PACKAGENAME>_ROOT variables.

This policy was introduced in CMake version 3.27. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.26.

USE_FOLDERS global property is treated as ON by default.

When using CMake 3.25 or earlier, USE_FOLDERS is treated as OFF by default unless projects enable the feature.  For example:

cmake_minimum_required(VERSION 3.25)
project(foobar LANGUAGES CXX)
set_property(GLOBAL PROPERTY USE_FOLDERS ON)

CMake 3.26 and later prefer to enable the feature by default.

Note that it is the policy setting at the end of the top level CMakeLists.txt file that matters.  The policy setting applies globally to the whole project.

This policy provides compatibility with projects that have not been updated to expect enabling of folders.  Enabling folders causes projects to appear differently in IDEs.

This policy was introduced in CMake version 3.26. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.25.

The Xcode generator does not append per-config suffixes to library search paths.

In CMake 3.24 and below, the Xcode generator preceded each entry of a library search path with a copy of itself appended with $(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME).  This was left from very early versions of CMake in which per-config directories were not well modeled.  Such paths often do not exist, resulting in warnings from the toolchain.  CMake 3.25 and above prefer to not add such library search paths.  This policy provides compatibility for projects that may have been accidentally relying on the old behavior.

The OLD behavior for this policy is to append $(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME) to all library search paths. The NEW behavior is to not modify library search paths.

This policy was introduced in CMake version 3.25. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.25.

MSVC debug information format flags are selected by an abstraction.

Compilers targeting the MSVC ABI have flags to select the debug information format. Debug information format selection typically varies with build configuration.

In CMake 3.24 and below, debug information format flags are added to the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries by CMake automatically.  This allows users to edit their cache entries to adjust the flags.  However, the presence of such default flags is problematic for projects that want to choose a different runtime library programmatically. In particular, it requires string editing of the CMAKE_<LANG>_FLAGS_<CONFIG> variables with knowledge of the CMake builtin defaults so they can be replaced.

CMake 3.25 and above prefer to leave the debug information format flags out of the default CMAKE_<LANG>_FLAGS_<CONFIG> values and instead offer a first-class abstraction.  The CMAKE_MSVC_DEBUG_INFORMATION_FORMAT variable and MSVC_DEBUG_INFORMATION_FORMAT target property may be set to select the MSVC debug information format.  If they are not set, CMake enables debug information in debug configurations using the default value $<$<CONFIG:Debug,RelWithDebInfo>:ProgramDatabase>, if supported by the compiler, and otherwise $<$<CONFIG:Debug,RelWithDebInfo>:Embedded>.

This policy provides compatibility with projects that have not been updated to be aware of the abstraction.  The policy setting takes effect as of the first project() or enable_language() command that enables a language whose compiler targets the MSVC ABI.

NOTE:

The OLD behavior for this policy is to place MSVC debug information format flags in the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries and ignore the CMAKE_MSVC_DEBUG_INFORMATION_FORMAT abstraction.  The NEW behavior for this policy is to not place MSVC debug information format flags in the default cache entries and use the abstraction instead.

This policy was introduced in CMake version 3.25. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.25.

The return() command checks its parameters.

The OLD behavior for this policy is to ignore any parameters given to the command. The NEW behavior is to check the validity of the parameters.

This policy was introduced in CMake version 3.25. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.24.

The if() command supports path comparisons using PATH_EQUAL operator.

The OLD behavior for this policy is to ignore the PATH_EQUAL operator. The NEW behavior is to interpret the PATH_EQUAL operator.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.24.

CheckIPOSupported uses flags from calling project.

The CheckIPOSupported module check_ipo_supported() command compiles a test project to determine whether the toolchain supports INTERPROCEDURAL_OPTIMIZATION.  CMake 3.23 and below run the check with the default values of the CMAKE_<LANG>_FLAGS and CMAKE_<LANG>_FLAGS_<CONFIG> variables for the current environment and toolchain settings. However, some projects may modify these flag variables to add flags that affect availability of the toolchain's IPO features. CMake 3.24 and above prefer to honor the calling project's values for these variables.  This policy provides compatibility for projects that have not been updated to expect this behavior.

The OLD behavior for this policy is to ignore the calling project's values of CMAKE_<LANG>_FLAGS and CMAKE_<LANG>_FLAGS_<CONFIG>.  The NEW behavior for this policy is to use the values of those variables as compiler flags in the test project.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

try_compile() passes platform variables in project mode.

The try_compile() command source file signature propagates CMake variables containing platform settings, and those specified by the CMAKE_TRY_COMPILE_PLATFORM_VARIABLES variable, into the generated test project.  This helps the test project drive the toolchain the same way the calling project will.  In CMake 3.23 and below, the whole-project signature does not propagate platform variables automatically.  CMake 3.24 and above prefer to propagate platform variables in the whole-project signature.  This policy provides compatibility with projects that have not been updated to expect the behavior.

The OLD behavior for this policy is to not pass any additional variables to the whole-project signature. The NEW behavior for this policy is to pass the same variables that the source file signature does.

Regardless of the policy setting, the CMAKE_TRY_COMPILE_NO_PLATFORM_VARIABLES variable may be set to suppress passing the platform variables through either signature.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

Watcom runtime library flags are selected by an abstraction.

Compilers targeting the Watcom ABI have flags to select the Watcom runtime library.

In CMake 3.23 and below, Watcom runtime library selection flags are added to the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries by CMake automatically.  This allows users to edit their cache entries to adjust the flags.  However, the presence of such default flags is problematic for projects that want to choose a different runtime library programmatically. In particular, it requires string editing of the CMAKE_<LANG>_FLAGS_<CONFIG> variables with knowledge of the CMake builtin defaults so they can be replaced.

CMake 3.24 and above prefer to leave the Watcom runtime library selection flags out of the default CMAKE_<LANG>_FLAGS_<CONFIG> values and instead offer a first-class abstraction.  The CMAKE_WATCOM_RUNTIME_LIBRARY variable and WATCOM_RUNTIME_LIBRARY target property may be set to select the Watcom runtime library.  If they are not set then CMake uses the default value MultiThreadedDLL on Windows and SingleThreaded on other platforms, which is equivalent to the original flags.

This policy provides compatibility with projects that have not been updated to be aware of the abstraction.  The policy setting takes effect as of the first project() or enable_language() command that enables a language whose compiler targets the Watcom ABI.

NOTE:

The OLD behavior for this policy is to place Watcom runtime library flags in the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries and ignore the CMAKE_WATCOM_RUNTIME_LIBRARY abstraction. The NEW behavior for this policy is to not place Watcom runtime library flags in the default cache entries and use the abstraction instead.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

When using the URL download method with the ExternalProject_Add() or FetchContent_Declare() commands, CMake 3.23 and below sets the timestamps of the extracted contents to the same as the timestamps in the archive. When the URL changes, the new archive is downloaded and extracted, but the timestamps of the extracted contents might not be newer than the previous contents. Anything that depends on the extracted contents might not be rebuilt, even though the contents may change.

CMake 3.24 and above prefers to set the timestamps of all extracted contents to the time of the extraction. This ensures that anything that depends on the extracted contents will be rebuilt whenever the URL changes.

The DOWNLOAD_EXTRACT_TIMESTAMP option to the ExternalProject_Add() and FetchContent_Declare() commands can be used to explicitly specify how timestamps should be handled. When DOWNLOAD_EXTRACT_TIMESTAMP is not given, this policy controls the default behavior. The OLD behavior for this policy is to restore the timestamps from the archive. The NEW behavior sets the timestamps of extracted contents to the time of extraction.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.24.

The default registry view is TARGET for the find_file(), find_path(), find_library(), and find_package() commands and BOTH for the find_program() command.

The default registry views in CMake 3.23 and below are selected using the following rules:

• if CMAKE_SIZEOF_VOID_P has value 8:

  • Use view 64 for all find_* commands except find_program() command.
  • Use view 64_32 for find_program() command.

• if CMAKE_SIZEOF_VOID_P has value 4 or is undefined:

  • Use view 32 for all find_* commands except find_program() command.
  • Use view 32_64 for find_program() command.

The OLD behavior for this policy is to use registry views 64 and 64_32 or 32_64 and 32 as default, depending of CMAKE_SIZEOF_VOID_P variable value. The NEW behavior for this policy is to use registry views TARGET and BOTH as default.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

The CPack module disables SLA by default in the CPack DragNDrop Generator.

The CPack DragNDrop Generator in CMake 3.22 and below attach a Software License Agreement (SLA) to .dmg files using the file specified by CPACK_RESOURCE_FILE_LICENSE, if set to a non-default value. macOS 12.0 deprecated the tools used to do this, so CMake 3.23 added the CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE option to control the behavior.  CMake 3.23 enables that option by default for compatibility with older versions. CMake 3.24 and above prefer to not enable the CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE option by default. This policy provides compatibility with projects that have not been updated to account for the lack of a SLA in their .dmg packages.

The OLD behavior for this policy is to enable CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE by default. The NEW behavior for this policy is to not enable it by default.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0133 variable to control the warning.

NOTE:

Added in version 3.24.

Do not set compiler environment variables on first run.

Apart from when using the Xcode generator and some Visual Studio generators, CMake 3.23 and below will set environment variables like CC, CXX, etc. when the corresponding language is enabled. This only occurs on the very first time CMake is run in a build directory, and the environment variables are only defined at configure time, not build time. On subsequent CMake runs, these environment variables are not set, opening up the opportunity for different behavior between the first and subsequent CMake runs. CMake 3.24 and above prefer to not set these environment variables when a language is enabled, even on the first run in a build directory.

The OLD behavior for this policy sets the relevant environment variable on the first run when a language is enabled. The NEW behavior for this policy does not set any such environment variables.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

LINK_LIBRARIES supports the $<LINK_ONLY:...> generator expression.

CMake 3.23 and below documented the $<LINK_ONLY:...> generator expression only for use in INTERFACE_LINK_LIBRARIES. When used in LINK_LIBRARIES, the content guarded inside $<LINK_ONLY:...> was always used, even when collecting non-linking usage requirements such as INTERFACE_COMPILE_DEFINITIONS.

CMake 3.24 and above prefer to support $<LINK_ONLY:...>, when used in LINK_LIBRARIES, by using the guarded content only for link dependencies and not other usage requirements.  This policy provides compatibility for projects that have not been updated to account for this change.

The OLD behavior for this policy is to use LINK_LIBRARIES content guarded by $<LINK_ONLY:...> even for non-linking usage requirements.  The NEW behavior for this policy is to use the guarded content only for link dependencies.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.24.

while() diagnoses condition evaluation errors.

CMake 3.23 and below accidentally tolerated errors encountered while evaluating the condition passed to the while() command (but not the if() command).  For example, the code

set(paren "(")
while(${paren})
endwhile()

creates an unbalanced parenthesis during condition evaluation.

CMake 3.24 and above prefer to diagnose such errors.  This policy provides compatibility for projects that have not been updated to fix their condition errors.

The OLD behavior for this policy is to ignore errors in while() conditions.  The NEW behavior for this policy is to diagnose errors in while() conditions.

This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.23.

Compiler id for MCST LCC compilers is now LCC, not GNU.

CMake 3.23 and above recognize MCST LCC compiler as a different from GNU, with its own command line and set of capabilities. CMake now prefers to present this to projects by setting the CMAKE_<LANG>_COMPILER_ID variable to LCC instead of GNU. However, existing projects may assume the compiler id for LCC is GNU as it was in CMake versions prior to 3.23. Therefore this policy determines for MCST LCC compiler which compiler id to report in the CMAKE_<LANG>_COMPILER_ID variable after language <LANG> is enabled by the project() or enable_language() command.  The policy must be set prior to the invocation of either command.

The OLD behavior for this policy is to use compiler id GNU (and set CMAKE_<LANG>_COMPILER_VERSION to the supported GNU compiler version.) NEW behavior for this policy is to use compiler id LCC, and set CMAKE_<LANG>_SIMULATE_ID to GNU, and CMAKE_<LANG>_SIMULATE_VERSION to the supported GNU compiler version.

This policy was introduced in CMake version 3.23. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0129 variable to control the warning.

NOTE:

Added in version 3.22.

When this policy is set to NEW:

• <LANG>_EXTENSIONS is initialized to CMAKE_<LANG>_EXTENSIONS if set, otherwise falling back to CMAKE_<LANG>_EXTENSIONS_DEFAULT.
• Extensions are correctly enabled/disabled if <LANG>_STANDARD is unset or satisfied by the default.
• Standard mode-affecting flags aren't added unless necessary to achieve the specified mode.

The OLD behavior:

• Initializes <LANG>_EXTENSIONS to CMAKE_<LANG>_EXTENSIONS if set, otherwise falling back to ON.
• Always adds a flag if <LANG>_STANDARD is set and <LANG>_STANDARD_REQUIRED is OFF.

• If <LANG>_STANDARD is unset:

  • Doesn't disable extensions even if <LANG>_EXTENSIONS is OFF.
  • Fails to enable extensions if <LANG>_EXTENSIONS is ON except for the IAR compiler.

Code may need to be updated for the NEW behavior in the following cases:

• If a standard mode flag previously overridden by CMake's and not used during compiler detection now takes effect due to CMake no longer adding one as the default detected is appropriate.

  Such code should be converted to either:

  • Use <LANG>_STANDARD and <LANG>_EXTENSIONS instead of manually adding flags.
  • Or ensure the manually-specified flags are used during compiler detection.

• If extensions were disabled without <LANG>_STANDARD being set CMake previously wouldn't actually disable extensions.

  Such code should be updated to not disable extensions if they are required.

• If extensions were enabled/disabled when <LANG>_STANDARD was satisfied by the compiler's default CMake previously wouldn't actually enable/disable extensions.

  Such code should be updated to set the correct extensions mode.

If compiler flags affecting the standard mode are used during compiler detection (for example in a toolchain file using CMAKE_<LANG>_FLAGS_INIT) then they will affect the detected default standard and extensions.

This policy was introduced in CMake version 3.22. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0128 variable to control the warning.

NOTE:

Added in version 3.22.

cmake_dependent_option() supports full Condition Syntax.

The <depends> parameter accepts a semicolon-separated list of conditions.  CMake 3.21 and lower evaluates each condition as if(${condition}), which does not properly handle conditions with nested paren groups.  CMake 3.22 and above instead prefer to evaluate each condition as if(<condition>), where <condition> is re-parsed as if literally written in a call to if().  This allows expressions like:

"A AND (B OR C)"

but requires expressions like:

"FOO MATCHES (UPPER|lower)"

to be re-written as:

"FOO MATCHES \"(UPPER|lower)\""

Policy CMP0127 provides compatibility for projects that have not been updated to expect the new behavior.

This policy was introduced in CMake version 3.22. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.21.

When this policy is set to NEW, the set(CACHE) command does not remove any normal variable of the same name from the current scope. The OLD behavior removes any normal variable of the same name from the current scope in the following situations:

• No cache variable of that name existed previously.
• A cache variable of that name existed previously, but it had no type. This can occur when the variable was set on the command line using a form like cmake -DMYVAR=blah instead of cmake -DMYVAR:STRING=blah.
• The FORCE or INTERNAL keywords were used when setting the cache variable.

Note that the NEW behavior has an important difference to the similar NEW behavior of policy CMP0077.  The set(CACHE) command always sets the cache variable if it did not exist previously, regardless of the CMP0126 policy setting.  The option() command will not set the cache variable if a non-cache variable of the same name already exists and CMP0077 is set to NEW.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0126 variable to control the warning.

The CMAKE_POLICY_DEFAULT_CMP0126 variable may be used to set the policy for a third-party project in a subdirectory without modifying it.

NOTE:

Added in version 3.21.

The find_file(), find_path(), find_library() and find_program() commands cache their result in the variable specified by their first argument.  Prior to CMake 3.21, if a cache variable of that name already existed before the call but the cache variable had no type, any non-cache variable of the same name would be discarded and the cache variable was always used (see also CMP0126 for a different but similar behavior).  This contradicts the convention that a non-cache variable should take precedence over a cache variable of the same name.  Such a situation can arise if a user sets a cache variable on the command line without specifying a type, such as cmake -DMYVAR=blah ... instead of cmake -DMYVAR:FILEPATH=blah.

Related to the above, if a cache variable of the specified name already exists and it does have a type, the various find_...() commands would return that value unchanged.  In particular, if it contained a relative path, it would not be converted to an absolute path in this situation.

When policy CMP0125 is set to OLD or is unset, the behavior is as described above.  When it is set to NEW, the behavior is as follows:

• If a non-cache variable of the specified name exists when the find_...() command is called, its value will be used regardless of whether a cache variable of the same name already exists or not.  A cache variable will not be created in this case if no such cache variable existed before. If a cache variable of the specified name did already exist, the cache will be updated to match the non-cache variable.
• The various find...() commands will always provide an absolute path in the result variable, except where a relative path provided by a cache or non-cache variable cannot be resolved to an existing path.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.21.

foreach() loop variables are only available in the loop scope.

CMake 3.20 and below always leave the loop variable set at the end of the loop, either to the value it had before the loop, if any, or to the empty string.  CMake 3.21 and above prefer to leave the loop variable in the state it had before the loop started, either set or unset.  This policy provides compatibility for projects that expect the loop variable to always be left set.

The OLD behavior for this policy is to set the loop variable at the end of the loop, either to its original value, or to an empty value. The NEW behavior for this policy is to restore the loop variable to the state it had before the loop started, either set or unset.

For example:

set(items a b c)

set(var1 "value")
unset(var2)

foreach(var1 IN LISTS items)
endforeach()

foreach(var2 IN LISTS items)
endforeach()

if(DEFINED var1)
  message("var1: ${var1}")
endif()
if(DEFINED var2)
  message("var2: ${var2}")
endif()

Under the OLD behavior, this code prints var1: value and var2:. Under the NEW behavior, this code prints only var1: value.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.21.

ARMClang cpu/arch compile and link flags must be set explicitly.

CMake 3.20 and lower automatically maps the CMAKE_SYSTEM_PROCESSOR variable and an undocumented CMAKE_SYSTEM_ARCH to compile and link options for ARMClang.  For example, the -mcpu=cortex-m33 flag is added when CMAKE_SYSTEM_PROCESSOR equals cortex-m33.  CMake requires projects to set either variable or it raises a fatal error.  However, the project may need to additionally specify CPU features using e.g. -mcpu=cortex-m33+nodsp, conflicting with the -mcpu=cortex-m33 added by CMake.  This results in either link errors or unusable binaries.

CMake 3.21 and above prefer instead to not add any cpu/arch compile and link flags automatically.  Instead, projects must specify them explicitly. This policy provides compatibility for projects that have not been updated.

The OLD behavior of this policy requires projects that use ARMClang to set either CMAKE_SYSTEM_PROCESSOR or CMAKE_SYSTEM_ARCH and it automatically adds a compile option -mcpu= or -march= and a link option --cpu= based on those variables.  The NEW behavior does not add compile or link options, and projects are responsible for setting correct options.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.21.

UseSWIG use library name conventions for CSharp language.

Starting with CMake 3.21, UseSWIG generates now a library using default naming conventions. This policy provides compatibility with projects that expect the legacy behavior.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.21.

The list() command now detects invalid indices.

Prior to CMake version 3.21, the list() command's GET, INSERT, SUBLIST, and REMOVE_AT subcommands did not detect invalid index arguments.

The OLD behavior of this policy is for invalid indices to be treated as their integer value (if any) at the start of the string. For example, 2good4you is a 2 and not_an_integer is a 0. The NEW behavior is for invalid indices to trigger an error.

This policy was introduced in CMake version 3.21. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.20.

The WriteCompilerDetectionHeader module is removed.

CMake versions 3.1 through 3.19 provide this module to generate a C++ compatibility layer by re-using information from CMake's table of preprocessor checks for cmake-compile-features(7).  However:

• Those granular features have been superseded by meta-features for Requiring Language Standards such as cxx_std_11.  Therefore no new granular feature checks will be added and projects will need to use other means to conditionally use new C++ features.
• The module exposes some of CMake's implementation details directly to C++ translation units.
• The module's approach effectively provides a header file with CMake, thus tying the version of the header to the version of CMake. Many projects found that the WriteCompilerDetectionHeader was best used by manually generating its header locally with a recent version of CMake and then bundling it with the project source so that it could be used with older CMake versions.

For reasons including the above, CMake 3.20 and above prefer to not provide the WriteCompilerDetectionHeader module.  This policy provides compatibility for projects that have not been ported away from it.  Projects using the module should be updated to stop using it. Alternatives include:

• Bundle a copy of the generated header in the project's source.
• Use a third-party alternative, such as the CC0-licensed Hedley.
• Drop support for compilers too old to provide the features natively.

The OLD behavior of this policy is for inclusion of the deprecated WriteCompilerDetectionHeader module to work.  The NEW behavior is for inclusion of the module to fail as if it does not exist.

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.20.

LANGUAGE source file property explicitly compiles as specified language.

The LANGUAGE source file property is documented to mean that the source file is written in the specified language.  In CMake 3.19 and below, setting this property causes CMake to compile the source file using the compiler for the specified language.  However, it only passes an explicit flag to tell the compiler to treat the source as the specified language for MSVC-like, XL, and Embarcadero compilers for the CXX language. CMake 3.20 and above prefer to also explicitly tell the compiler to use the specified language using a flag such as -x c on all compilers for which such flags are known.

This policy provides compatibility for projects that have not been updated to expect this behavior.  For example, some projects were setting the LANGUAGE property to C on assembly-language .S source files in order to compile them using the C compiler.  Such projects should be updated to use enable_language(ASM), for which CMake will often choose the C compiler as the assembler on relevant platforms anyway.

The OLD behavior for this policy is to interpret the LANGUAGE <LANG> property using its undocumented meaning to "use the <LANG> compiler". The NEW behavior for this policy is to interpret the LANGUAGE <LANG> property using its documented meaning to "compile as a <LANG> source".

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.20.

GENERATED sources may be used across directories without manual marking.

In CMake 3.19 and below, the GENERATED source file property, like other source file properties, was scoped in every directory separately. If a source file was generated in one directory, projects had to manually set the GENERATED property in another directory in order to use the file.

Whether or not a source file is generated is an all-or-nothing global property of the source: a source is either generated or it is not. CMake 3.20 and above prefer to allow source files generated in one directory to be used in other directories without manually marking them as GENERATED. Additionally, the GENERATED property may now be set only to boolean values, and may not be turned off once turned on.  This policy provides compatibility for projects that have not been updated for this behavior.

The OLD behavior of this policy is to allow generated files to be used only in directories in which their GENERATED property has been turned on. The NEW behavior of this policy is to allow generated files to be used in other directories without explicitly turning on the GENERATED property for those directories.

Added in version 3.30: Policy CMP0163 additionally makes the GENERATED source file property visible to get_property() and get_source_file_property() calls in other directories.

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns about setting the GENERATED property to a non-boolean value, and uses OLD behavior.

NOTE:

Added in version 3.20.

MSVC RTTI flag /GR is not added to CMAKE_CXX_FLAGS by default.

When using MSVC-like compilers in CMake 3.19 and below, the RTTI flag /GR is added to CMAKE_CXX_FLAGS by default.  This behavior is left from support for MSVC versions from Visual Studio 2003 and below that did not enable RTTI by default.  It is no longer necessary.  Furthermore, it is problematic for projects that want to change to /GR- programmatically.  In particular, it requires string editing of the CMAKE_CXX_FLAGS variable with knowledge of the CMake builtin default so it can be replaced.

CMake 3.20 and above prefer to leave out /GR from the value of CMAKE_CXX_FLAGS by default.

This policy provides compatibility with projects that have not been updated to expect the lack of the /GR flag.  The policy setting takes effect as of the first project() or enable_language() command that initializes CMAKE_CXX_FLAGS.

NOTE:

The OLD behavior for this policy is to place the MSVC /GR flag in the default CMAKE_CXX_FLAGS cache entry.  The NEW behavior for this policy is to not place the MSVC /GR flag in the default cache entry.

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.20.

Ninja generators transform DEPFILE s from add_custom_command().

In CMake 3.19 and below, files given to the DEPFILE argument of add_custom_command() were passed directly to Ninja's depfile variable without any path resolution. This meant that if add_custom_command() was called from a subdirectory (created by add_subdirectory()), the DEPFILE argument would have to be either an absolute path or a path relative to CMAKE_BINARY_DIR, rather than CMAKE_CURRENT_BINARY_DIR. In addition, no transformation was done on the file listed in DEPFILE, which meant that the paths within the DEPFILE had the same restrictions.

Starting with CMake 3.20, the DEPFILE argument is relative to CMAKE_CURRENT_BINARY_DIR (unless it is absolute), and the paths in the DEPFILE are also relative to CMAKE_CURRENT_BINARY_DIR. CMake automatically transforms the paths in the DEPFILE (unless they are absolute) after the custom command is run. The file listed in DEPFILE is not modified in any way. Instead, CMake writes the transformation to its own internal file, and passes this internal file to Ninja's depfile variable. This transformation happens regardless of whether or not DEPFILE is relative, and regardless of whether or not add_custom_command() is called from a subdirectory.

The OLD behavior for this policy is to pass the DEPFILE to Ninja unaltered. The NEW behavior for this policy is to transform the DEPFILE after running the custom command. The status of CMP0116 is recorded at the time of the custom command's creation, and you can have custom commands in the same directory with different values for CMP0116 by setting the policy before each custom command.

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default (unless DEPFILE is used in a subdirectory), and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0116 variable to control the warning.

NOTE:

Added in version 3.20.

Source file extensions must be explicit.

In CMake 3.19 and below, if a source file could not be found by the name specified, it would append a list of known extensions to the name to see if the file with the extension could be found. For example, this would allow the user to run:

add_executable(exe main)

and put main.c in the executable without specifying the extension.

Starting in CMake 3.20, CMake prefers all source files to have their extensions explicitly listed:

add_executable(exe main.c)

The OLD behavior for this policy is to implicitly append known extensions to source files if they can't be found. The NEW behavior of this policy is to not append known extensions and require them to be explicit.

This policy was introduced in CMake version 3.20. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.19.

ExternalProject step targets fully adopt their steps.

The ExternalProject_Add() STEP_TARGETS option, and the ExternalProject_Add_StepTargets() function, can be used to create build targets for individual steps of an external project.

In CMake 3.18 and below, step targets have some limitations:

• Step targets always depend on targets named by the ExternalProject_Add() DEPENDS option even though not all steps need them.  In order to allow step targets to be created without those dependencies, the ExternalProject_Add() INDEPENDENT_STEP_TARGETS option or the ExternalProject_Add_StepTargets() NO_DEPENDS option may be used.  However, adding such "independent" step targets makes sense only for specific steps such as download, update, and patch because they do not need any of the external project's build dependencies. Furthermore, it does not make sense to create independent step targets for steps that depend on non-independent steps.  Such rules are not enforced, and projects that do not follow them can generate build systems with confusing and generator-specific behavior.

• Step targets hold copies of the custom commands implementing their steps that are separate from the copies in the primary target created by ExternalProject_Add(), and the primary target does not depend on the step targets.  In parallel builds that drive the primary target and step targets concurrently, multiple copies of the steps' commands may run concurrently and race each other.

  Also, prior to policy CMP0113, the step targets generated by Makefile Generators also contain all the custom commands on which their step depends.  This can lead to repeated execution of those steps even in serial builds.

In CMake 3.19 and above, the ExternalProject module prefers a revised design to address these problems:

• Each step is classified as "independent" if it does not depend on other targets named by the ExternalProject_Add() DEPENDS. The predefined steps are automatically classified by default:

  • The download, update, and patch steps are independent.
  • The configure, build, test, and install steps are not.

  For custom steps, the ExternalProject_Add_Step() command provides an INDEPENDENT option to mark them as independent.  It is an error to mark a step as independent if it depends on other steps that are not.  Note that this use of the term "independent" refers only to independence from external targets and is orthogonal to a step's dependencies on other steps.

• Step targets created by the ExternalProject_Add() STEP_TARGETS option or the ExternalProject_Add_Step() function are now independent if and only if their steps are marked as independent. The ExternalProject_Add() INDEPENDENT_STEP_TARGETS option and ExternalProject_Add_StepTargets() NO_DEPENDS option are no longer allowed.

• Step targets, when created, are fully responsible for holding the custom commands implementing their steps.  The primary target created by ExternalProject_Add() depends on the step targets, and the step targets depend on each other.  The target-level dependencies match the file-level dependencies used by the custom commands for each step.

  When the ExternalProject_Add() UPDATE_DISCONNECTED or TEST_EXCLUDE_FROM_MAIN option is used, or the ExternalProject_Add_Step() EXCLUDE_FROM_MAIN option is used for a custom step, some step targets may be created automatically. These are needed to hold the steps commonly depended upon by the primary target and the disconnected step targets.

Policy CMP0114 provides compatibility for projects that have not been updated to expect the new behavior.  The OLD behavior for this policy is to use the above-documented behavior from 3.18 and below.  The NEW behavior for this policy is to use the above-documented behavior preferred by 3.19 and above.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.19.

Makefile Generators do not repeat custom commands from target dependencies.

Consider a chain of custom commands split across two dependent targets:

add_custom_command(OUTPUT output-not-created
  COMMAND ... DEPENDS ...)
set_property(SOURCE output-not-created PROPERTY SYMBOLIC 1)
add_custom_command(OUTPUT output-created
  COMMAND ... DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/output-not-created)
add_custom_target(first DEPENDS output-not-created)
add_custom_target(second DEPENDS output-created)
add_dependencies(second first)

In CMake 3.18 and lower, the Makefile generators put a copy of both custom commands in the Makefile for target second even though its dependency on target first ensures that the first custom command runs before the second. Running make second would cause the first custom command to run once in the first target and then again in the second target.

CMake 3.19 and above prefer to not duplicate custom commands in a target that are already generated in other targets on which the target depends (directly or indirectly).  This policy provides compatibility for projects that have not been updated to expect the new behavior.  In particular, projects that relied on the duplicate execution or that did not properly set the SYMBOLIC source file property may be affected.

The OLD behavior for this policy is to duplicate custom commands in dependent targets.  The NEW behavior of this policy is to not duplicate custom commands in dependent targets.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.19.

Target file component generator expressions do not add target dependencies.

The following target-based generator expressions that query for directory or file name components no longer add a dependency on the evaluated target.

• TARGET_FILE_NAME
• TARGET_FILE_DIR
• TARGET_LINKER_FILE_BASE_NAME
• TARGET_LINKER_FILE_NAME
• TARGET_LINKER_FILE_DIR
• TARGET_SONAME_FILE_NAME
• TARGET_SONAME_FILE_DIR
• TARGET_PDB_FILE_NAME
• TARGET_PDB_FILE_DIR
• TARGET_BUNDLE_DIR
• TARGET_BUNDLE_DIR_NAME
• TARGET_BUNDLE_CONTENT_DIR

In CMake 3.18 and lower a dependency on the evaluated target of the above generator expressions would always be added.  CMake 3.19 and above prefer to not add this dependency.  This policy provides compatibility for projects that have not been updated to expect the new behavior.  The policy setting is recorded on each target when it is created, and decides whether generator expressions referencing that target imply a dependency on it.

The OLD behavior for this policy is to add a dependency on the evaluated target for the above generator expressions.  The NEW behavior of this policy is to not add a dependency on the evaluated target for the above generator expressions.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0112 variable to control the warning.

NOTE:

Added in version 3.19.

An imported target missing its location property fails during generation.

Imported Targets for library files and executables require that their location on disk is specified in a target property such as IMPORTED_LOCATION, IMPORTED_IMPLIB, or a per-configuration equivalent.  If a needed location property is not set, CMake 3.18 and below generate the string <TARGET_NAME>-NOTFOUND in its place, which results in failures of the corresponding rules at build time.  CMake 3.19 and above prefer instead to raise an error during generation.  This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior of this policy is to generate the location of an imported unknown, static or shared library target as <TARGET_NAME>-NOTFOUND if not set. The NEW behavior is to raise an error.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.19.

add_test() supports arbitrary characters in test names.

add_test() can now (officially) create tests with whitespace and other special characters in its name.  Before CMake version 3.19 that was not allowed, however, it was possible to work around this limitation by explicitly putting escaped quotes around the test's name in the add_test command.

Although never officially supported several projects in the wild found and implemented this workaround.  However, the new change which officially allows the add_test command to support whitespace and other special characters in test names now breaks that workaround.  In order for these projects to work smoothly with newer CMake versions, this policy was introduced.

The OLD behavior of this policy is to still prevent add_test from handling whitespace and special characters properly (if not using the mentioned workaround).  The NEW behavior on the other hand allows names with whitespace and special characters for tests created by add_test.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.19.

find_program() requires permission to execute but not to read.

In CMake 3.18 and below, the find_program() command on UNIX would find files that are readable without requiring execute permission, and would not find files that are executable without read permission. In CMake 3.19 and above, find_program now prefers to require execute permission but not read permission.  This policy provides compatibility with projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is for find_program to require read permission but not execute permission. The NEW behavior for this policy is for find_program to require execute permission but not read permission.

This policy was introduced in CMake version 3.19. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.18.

A target is not allowed to link to itself even through an ALIAS target.

In CMake 3.17 and below, a target can link to a target aliased to itself.

The OLD behavior for this policy is to allow a target to link to a target aliased to itself.

The NEW behavior of this policy is to prevent a target to link to itself through an ALIAS target.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.18.

It is not allowed to create an ALIAS target with the same name as an another target.

In CMake 3.17 and below, an ALIAS target can overwrite silently an existing target with the same name.

The OLD behavior for this policy is to allow target overwrite.

The NEW behavior of this policy is to prevent target overwriting.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.18.

The Documentation module is removed.

The Documentation was added as a support mechanism for the VTK project and was tuned for that project. Instead of CMake providing this module with (now old) VTK patterns for cache variables and required packages, the module is now deprecated by CMake itself.

The OLD behavior of this policy is for Documentation to add cache variables and find VTK documentation dependent packages. The NEW behavior is to act as an empty module.

This policy was introduced in CMake version 3.18. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.18.

LINK_OPTIONS and INTERFACE_LINK_OPTIONS target properties are now used for the device link step.

In CMake 3.17 and below, link options are not used by the device link step.

The OLD behavior for this policy is to ignore the link options during the device link step.

The NEW behavior of this policy is to use the link options during the device link step.

This policy was introduced in CMake version 3.18. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.18.

Initialize CMAKE_CUDA_ARCHITECTURES when CMAKE_CUDA_COMPILER_ID is NVIDIA. Raise an error if CUDA_ARCHITECTURES is empty.

CMAKE_CUDA_ARCHITECTURES introduced in CMake 3.18 is used to initialize CUDA_ARCHITECTURES, which passes correct code generation flags to the CUDA compiler.

Previous to this users had to manually specify the code generation flags. This policy is for backwards compatibility with manually specifying code generation flags.

The OLD behavior for this policy is to not initialize CMAKE_CUDA_ARCHITECTURES when CMAKE_CUDA_COMPILER_ID is NVIDIA. Empty CUDA_ARCHITECTURES is allowed.

The NEW behavior of this policy is to initialize CMAKE_CUDA_ARCHITECTURES when CMAKE_CUDA_COMPILER_ID is NVIDIA and raise an error if CUDA_ARCHITECTURES is empty during generation.

If CUDA_ARCHITECTURES is set to a false value no architectures flags are passed to the compiler. This is intended to support packagers and the rare cases where full control over the passed flags is required.

This policy was introduced in CMake version 3.18. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

set_target_properties(tgt PROPERTIES CUDA_ARCHITECTURES "35;50;72")

Generates code for real and virtual architectures 30, 50 and 72.

set_property(TARGET tgt PROPERTY CUDA_ARCHITECTURES 70-real 72-virtual)

Generates code for real architecture 70 and virtual architecture 72.

set_property(TARGET tgt PROPERTY CUDA_ARCHITECTURES OFF)

CMake will not pass any architecture flags to the compiler.

Added in version 3.18.

Multiple calls to export() command with same FILE without APPEND is no longer allowed.

In CMake 3.17 and below, multiple calls to export() command with the same FILE without APPEND are accepted silently but only the last occurrence is taken into account during the generation.

The OLD behavior for this policy is to ignore the multiple occurrences of

export() command except the last one.

The NEW behavior of this policy is to raise an error on second call to export() command with same FILE without APPEND.

This policy was introduced in CMake version 3.18. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.17.

The mark_as_advanced() command no longer creates a cache entry if one does not already exist.

In CMake 3.16 and below, if a variable was not defined at all or just defined locally, the mark_as_advanced() command would create a new cache entry with an UNINITIALIZED type and no value. When a find_path() (or other similar find_ command) would next run, it would find this undefined cache entry and set it up with an empty string value. This process would end up deleting the local variable in the process (due to the way the cache works), effectively clearing any stored find_ results that were only available in the local scope.

The OLD behavior for this policy is to create the empty cache definition. The NEW behavior of this policy is to ignore variables which do not already exist in the cache.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0102 variable to control the warning.

NOTE:

Added in version 3.17.

target_compile_options() now always honors the BEFORE keyword.

In CMake 3.16 and below, the target_compile_options() command ignores the BEFORE keyword when inserting items into the COMPILE_OPTIONS target property (PRIVATE and PUBLIC items).  CMake 3.17 and later honors the BEFORE keyword in all cases. This policy provides compatibility for projects that have not been updated to expect the new behavior.

The behavior of inserting items into the INTERFACE_COMPILE_OPTIONS target property (PUBLIC and INTERFACE items) is not affected by this policy.  The BEFORE keyword has always been honored when adding items to INTERFACE_COMPILE_OPTIONS.

The OLD behavior for this policy is to not honor the BEFORE keyword when inserting into the COMPILE_OPTIONS property. The NEW behavior for this policy is to honor the BEFORE keyword in all cases.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.17.

Let AUTOMOC and AUTOUIC process header files that end with a .hh extension.

Since version 3.17, CMake processes header files that end with a .hh extension in AUTOMOC and AUTOUIC. In earlier CMake versions, these header files were ignored by AUTOMOC and AUTOUIC.

This policy affects how header files that end with a .hh extension get treated in AUTOMOC and AUTOUIC.

The OLD behavior for this policy is to ignore .hh header files in AUTOMOC and AUTOUIC.

The NEW behavior for this policy is to process .hh header files in AUTOMOC and AUTOUIC just like other header files.

NOTE:

# Source skip example:
set_property(SOURCE /path/to/file1.hh PROPERTY SKIP_AUTOMOC ON)
set_property(SOURCE /path/to/file2.hh PROPERTY SKIP_AUTOUIC ON)
set_property(SOURCE /path/to/file3.hh PROPERTY SKIP_AUTOGEN ON)

This policy was introduced in CMake version 3.17.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.17.

Link properties are transitive over private dependencies of static libraries.

In CMake 3.16 and below, evaluation of target properties INTERFACE_LINK_OPTIONS, INTERFACE_LINK_DIRECTORIES, and INTERFACE_LINK_DEPENDS during buildsystem generation does not follow private dependencies of static libraries, which appear in their INTERFACE_LINK_LIBRARIES guarded by LINK_ONLY generator expressions. Only the libraries themselves are propagated to link the dependent binary.

CMake 3.17 and later prefer to propagate all interface link properties. This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is to not propagate interface link properties. The NEW behavior of this policy is to propagate interface link properties.

Added in version 3.30: Policy CMP0166 makes TARGET_PROPERTY evaluation of these three transitive link properties follow private dependencies of static libraries too.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.17.

FindFLEX runs flex in directory CMAKE_CURRENT_BINARY_DIR when executing.

The module provides a FLEX_TARGET macro which generates FLEX output. In CMake 3.16 and below the macro would generate a custom command that runs flex in the current source directory.  CMake 3.17 and later prefer to run it in the build directory and use CMAKE_CURRENT_BINARY_DIR as the WORKING_DIRECTORY of its add_custom_command() invocation. This ensures that any implicitly generated file is written relative to the build tree rather than the source tree, unless the generated file is provided as absolute path.

This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is for FLEX_TARGET to use the current source directory for the WORKING_DIRECTORY and where to generate implicit files. The NEW behavior of this policy is to use the current binary directory for the WORKING_DIRECTORY relative to which implicit files are generated unless provided as absolute path.

This policy was introduced in CMake version 3.17. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.16.

ExternalProject_Add() with GIT_SUBMODULES "" initializes no submodules.

The commands provide a GIT_SUBMODULES option which controls what submodules to initialize and update. Starting with CMake 3.16, explicitly setting GIT_SUBMODULES to an empty string means no submodules will be initialized or updated.

This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is for GIT_SUBMODULES when set to an empty string to initialize and update all git submodules. The NEW behavior for this policy is for GIT_SUBMODULES when set to an empty string to initialize and update no git submodules.

This policy was introduced in CMake version 3.16. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

This policy also applies to FetchContent_Declare(), which uses the same download and update features as ExternalProject_Add().  However, due to an implementation deficiency present since the policy was first introduced, CMake 3.16 and later always uses the NEW behavior for FetchContent_Declare(), regardless of the policy setting. Formally, this forcing of NEW behavior for FetchContent_Declare() will continue to apply in future CMake releases.

NOTE:

The OLD behavior of a policy is deprecated by definition and may be removed in a future version of CMake.

Added in version 3.16.

The project() command preserves leading zeros in version components.

When a VERSION <major>[.<minor>[.<patch>[.<tweak>]]]] argument is given to the project() command, it stores the version string in the PROJECT_VERSION variable and stores individual integer version components in PROJECT_VERSION_{MAJOR,MINOR,PATCH,TWEAK} variables (see policy CMP0048).  CMake 3.15 and below dropped leading zeros from each component.  CMake 3.16 and higher prefer to preserve leading zeros.  This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior of this policy drops leading zeros in all components, e.g.  such that version 1.07.06 becomes 1.7.6.  The NEW behavior of this policy preserves the leading zeros in all components, such that version 1.07.06 remains unchanged.

This policy was introduced in CMake version 3.16. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.16.

RPATH entries are properly escaped in the intermediary CMake install script.

In CMake 3.15 and earlier, RPATH entries set via CMAKE_INSTALL_RPATH or via INSTALL_RPATH have not been escaped before being inserted into the cmake_install.cmake script. Dynamic linkers on ELF-based systems (e.g. Linux and FreeBSD) allow certain keywords in RPATH entries, such as ${ORIGIN} (More details are available in the ld.so man pages on those systems). The syntax of these keywords can match CMake's variable syntax. In order to not be substituted (usually to an empty string) already by the intermediary cmake_install.cmake script, the user had to double-escape such RPATH keywords, e.g. set(CMAKE_INSTALL_RPATH "\\\${ORIGIN}/../lib"). Since the intermediary cmake_install.cmake script is an implementation detail of CMake, CMake 3.16 and later will make sure RPATH entries are inserted literally by escaping any coincidental CMake syntax.

The OLD behavior of this policy is to not escape RPATH entries in the intermediary cmake_install.cmake script. The NEW behavior is to properly escape coincidental CMake syntax in RPATH entries when generating the intermediary cmake_install.cmake script.

This policy was introduced in CMake version 3.16. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns when it detects use of CMake-like syntax, and uses OLD behavior.

NOTE:

Added in version 3.15.

Modules FindPython3, FindPython2 and FindPython use LOCATION for lookup strategy.

Starting with CMake 3.15, Modules FindPython3, FindPython2 and FindPython set value LOCATION for, respectively, variables Python3_FIND_STRATEGY, Python2_FIND_STRATEGY and Python_FIND_STRATEGY. This policy provides compatibility with projects that expect the legacy behavior.

The OLD behavior for this policy set value VERSION for variables Python3_FIND_STRATEGY, Python2_FIND_STRATEGY and Python_FIND_STRATEGY.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.15.

FindBoost reports Boost_VERSION in x.y.z format.

In CMake 3.14 and below the module would report the Boost version number as specified in the preprocessor definition BOOST_VERSION in the boost/version.hpp file. In CMake 3.15 and later it is preferred that the reported version number matches the x.y.z format reported by the CMake package shipped with Boost 1.70.0 and later. The macro value is still reported in the Boost_VERSION_MACRO variable.

The OLD behavior for this policy is for FindBoost to report Boost_VERSION as specified in the preprocessor definition BOOST_VERSION in boost/version.hpp. The NEW behavior for this policy is for FindBoost to report Boost_VERSION in x.y.z format.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.15.

MSVC warning flags are not in CMAKE_<LANG>_FLAGS by default.

When using MSVC-like compilers in CMake 3.14 and below, warning flags like /W3 are added to CMAKE_<LANG>_FLAGS by default. This is problematic for projects that want to choose a different warning level programmatically.  In particular, it requires string editing of the CMAKE_<LANG>_FLAGS variables with knowledge of the CMake builtin defaults so they can be replaced.

CMake 3.15 and above prefer to leave out warning flags from the value of CMAKE_<LANG>_FLAGS by default.

This policy provides compatibility with projects that have not been updated to expect the lack of warning flags.  The policy setting takes effect as of the first project() or enable_language() command that initializes CMAKE_<LANG>_FLAGS for a given language <LANG>.

NOTE:

The OLD behavior for this policy is to place MSVC warning flags in the default CMAKE_<LANG>_FLAGS cache entries.  The NEW behavior for this policy is to not place MSVC warning flags in the default cache entries.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.15.

MSVC runtime library flags are selected by an abstraction.

Compilers targeting the MSVC ABI have flags to select the MSVC runtime library. Runtime library selection typically varies with build configuration because there is a separate runtime library for Debug builds.

In CMake 3.14 and below, MSVC runtime library selection flags are added to the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries by CMake automatically.  This allows users to edit their cache entries to adjust the flags.  However, the presence of such default flags is problematic for projects that want to choose a different runtime library programmatically. In particular, it requires string editing of the CMAKE_<LANG>_FLAGS_<CONFIG> variables with knowledge of the CMake builtin defaults so they can be replaced.

CMake 3.15 and above prefer to leave the MSVC runtime library selection flags out of the default CMAKE_<LANG>_FLAGS_<CONFIG> values and instead offer a first-class abstraction.  The CMAKE_MSVC_RUNTIME_LIBRARY variable and MSVC_RUNTIME_LIBRARY target property may be set to select the MSVC runtime library.  If they are not set then CMake uses the default value MultiThreaded$<$<CONFIG:Debug>:Debug>DLL which is equivalent to the original flags.

This policy provides compatibility with projects that have not been updated to be aware of the abstraction.  The policy setting takes effect as of the first project() or enable_language() command that enables a language whose compiler targets the MSVC ABI.

NOTE:

The OLD behavior for this policy is to place MSVC runtime library flags in the default CMAKE_<LANG>_FLAGS_<CONFIG> cache entries and ignore the CMAKE_MSVC_RUNTIME_LIBRARY abstraction. The NEW behavior for this policy is to not place MSVC runtime library flags in the default cache entries and use the abstraction instead.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.15.

export(PACKAGE) does not populate package registry by default.

In CMake 3.14 and below the export(PACKAGE) command populated the user package registry by default and users needed to set the CMAKE_EXPORT_NO_PACKAGE_REGISTRY to disable it, e.g. in automated build and packaging environments.  Since the user package registry is stored outside the build tree, this side effect should not be enabled by default. Therefore CMake 3.15 and above prefer that export(PACKAGE) does nothing unless an explicit CMAKE_EXPORT_PACKAGE_REGISTRY variable is set to enable it.  This policy provides compatibility with projects that have not been updated.

The OLD behavior for this policy is for export(PACKAGE) command to populate the user package registry unless CMAKE_EXPORT_NO_PACKAGE_REGISTRY is enabled. The NEW behavior is for export(PACKAGE) command to do nothing unless the CMAKE_EXPORT_PACKAGE_REGISTRY is enabled.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.15.

Compiler id for IBM Clang-based XL compilers is now XLClang.

CMake 3.15 and above recognize that IBM's Clang-based XL compilers that define __ibmxl__ are a new front-end distinct from xlc with a different command line and set of capabilities. CMake now prefers to present this to projects by setting the CMAKE_<LANG>_COMPILER_ID variable to XLClang instead of XL.  However, existing projects may assume the compiler id for Clang-based XL is just XL as it was in CMake versions prior to 3.15. Therefore this policy determines for Clang-based XL compilers which compiler id to report in the CMAKE_<LANG>_COMPILER_ID variable after language <LANG> is enabled by the project() or enable_language() command.  The policy must be set prior to the invocation of either command.

The OLD behavior for this policy is to use compiler id XL.  The NEW behavior for this policy is to use compiler id XLClang.

This policy was introduced in CMake version 3.15. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0089 variable to control the warning.

NOTE:

Added in version 3.14.

FindBISON runs bison in CMAKE_CURRENT_BINARY_DIR when executing.

The module provides a BISON_TARGET macro which generates BISON output. In CMake 3.13 and below the macro would generate a custom command that runs bison in the source directory.  CMake 3.14 and later prefer to run it in the build directory and use CMAKE_CURRENT_BINARY_DIR as the WORKING_DIRECTORY of its add_custom_command() invocation. This ensures that any implicitly generated file is written to the build tree rather than the source.

This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is for BISON_TARGET to use the current source directory for the WORKING_DIRECTORY and where to generate implicit files. The NEW behavior of this policy is to use the current binary directory for the WORKING_DIRECTORY and where to generate implicit files.

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.14.

install(CODE) and install(SCRIPT) support generator expressions.

In CMake 3.13 and earlier, install(CODE) and install(SCRIPT) did not evaluate generator expressions.  CMake 3.14 and later will evaluate generator expressions for install(CODE) and install(SCRIPT).

The OLD behavior of this policy is for install(CODE) and install(SCRIPT) to not evaluate generator expressions.  The NEW behavior is to evaluate generator expressions for install(CODE) and install(SCRIPT).

Note that it is the value of this policy setting at the end of the directory scope that is important, not its setting at the time of the call to install(CODE) or install(SCRIPT).  This has implications for calling these commands from places that have their own policy scope but not their own directory scope (e.g. from files brought in via include() rather than add_subdirectory()).

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.14.

UseSWIG honors SWIG_MODULE_NAME via -module flag.

Starting with CMake 3.14, UseSWIG passes option -module <module_name> to SWIG compiler if the file property SWIG_MODULE_NAME is specified. This policy provides compatibility with projects that expect the legacy behavior.

The OLD behavior for this policy is to never pass -module option. The NEW behavior is to pass -module option to SWIG compiler if SWIG_MODULE_NAME is specified.

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.14.

$<IN_LIST:...> handles empty list items.

In CMake 3.13 and lower, the $<IN_LIST:...> generator expression always returned 0 if the first argument was empty, even if the list contained an empty item. This behavior is inconsistent with the IN_LIST behavior of if(), which this generator expression is meant to emulate. CMake 3.14 and later handles this case correctly.

The OLD behavior of this policy is for $<IN_LIST:...> to always return 0 if the first argument is empty. The NEW behavior is to return 1 if the first argument is empty and the list contains an empty item.

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.14.

The FindQt module does not exist for find_package().

The existence of FindQt means that for Qt upstream to provide package config files that can be found by find_package(Qt), the consuming project has to explicitly specify find_package(Qt CONFIG). Removing this module gives Qt a path forward for exporting its own config files which can easily be found by consuming projects.

This policy pretends that CMake's internal FindQt module does not exist for find_package(). If a project really wants to use Qt 3 or 4, it can call find_package(Qt[34]), include(FindQt), or add FindQt to their CMAKE_MODULE_PATH.

The OLD behavior of this policy is for FindQt to exist for find_package(). The NEW behavior is to pretend that it doesn't exist for find_package().

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.14.

To control generation of Position Independent Executable (PIE) or not, some flags are required at link time.

CMake 3.13 and lower did not add these link flags when POSITION_INDEPENDENT_CODE is set.

The OLD behavior for this policy is to not manage PIE link flags. The NEW behavior is to add link flags if POSITION_INDEPENDENT_CODE is set:

• Set to TRUE: flags to produce a position independent executable are passed to the linker step. For example -pie for GCC.
• Set to FALSE: flags not to produce a position independent executable are passed to the linker step. For example -no-pie for GCC.
• Not set: no flags are passed to the linker step.

Since a given linker may not support PIE flags in all environments in which it is used, it is the project's responsibility to use the CheckPIESupported module to check for support to ensure that the POSITION_INDEPENDENT_CODE target property for executables will be honored at link time.

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Android platform has a special handling of PIE so it is not required to use the CheckPIESupported module to ensure flags are passed to the linker.

NOTE:

The OLD behavior of a policy is deprecated by definition and may be removed in a future version of CMake.

Behave like CMake 3.13 and do not apply any PIE flags at link stage.

cmake_minimum_required(VERSION 3.13)
project(foo)

# ...

add_executable(foo ...)
set_property(TARGET foo PROPERTY POSITION_INDEPENDENT_CODE TRUE)

Use the CheckPIESupported module to detect whether PIE is supported by the current linker and environment.  Apply PIE flags only if the linker supports them.

cmake_minimum_required(VERSION 3.14) # CMP0083 NEW
project(foo)

include(CheckPIESupported)
check_pie_supported()

# ...

add_executable(foo ...)
set_property(TARGET foo PROPERTY POSITION_INDEPENDENT_CODE TRUE)

Added in version 3.14.

Install rules from add_subdirectory() calls are interleaved with those in caller.

CMake 3.13 and lower ran the install rules from add_subdirectory() after all other install rules, even if add_subdirectory() was called before the other install rules.  CMake 3.14 and above prefer to interleave these add_subdirectory() install rules with the others so that they are run in the order they are declared.  This policy provides compatibility for projects that have not been updated to expect the new behavior.

The OLD behavior for this policy is to run the install rules from add_subdirectory() after the other install rules.  The NEW behavior for this policy is to run all install rules in the order they are declared.

This policy was introduced in CMake version 3.14. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0082 variable to control the warning.

NOTE:

Added in version 3.13.

Relative paths not allowed in LINK_DIRECTORIES target property.

CMake 3.12 and lower allowed the LINK_DIRECTORIES directory property to contain relative paths.  The base path for such relative entries is not well defined.  CMake 3.13 and later will issue a FATAL_ERROR if the LINK_DIRECTORIES target property (which is initialized by the LINK_DIRECTORIES directory property) contains a relative path.

The OLD behavior for this policy is not to warn about relative paths in the LINK_DIRECTORIES target property.  The NEW behavior for this policy is to issue a FATAL_ERROR if LINK_DIRECTORIES contains a relative path.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.13.

BundleUtilities cannot be included at configure time.

The macros provided by BundleUtilities are intended to be invoked at install time rather than at configure time, because they depend on the listed targets already existing at the time they are invoked. If they are invoked at configure time, the targets haven't been built yet, and the commands will fail.

This policy restricts the inclusion of BundleUtilities to cmake -P style scripts and install rules. Specifically, it looks for the presence of CMAKE_GENERATOR and throws a fatal error if it exists.

The OLD behavior of this policy is to allow BundleUtilities to be included at configure time. The NEW behavior of this policy is to disallow such inclusion.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.13.

target_link_libraries() allows use with targets in other directories.

Prior to CMake 3.13 the target_link_libraries() command did not accept targets not created in the calling directory as its first argument for calls that update the LINK_LIBRARIES of the target itself. It did accidentally accept targets from other directories on calls that only update the INTERFACE_LINK_LIBRARIES, but would simply add entries to the property as if the call were made in the original directory.  Thus link interface libraries specified this way were always looked up by generators in the scope of the original target rather than in the scope that called target_link_libraries().

CMake 3.13 now allows the target_link_libraries() command to be called from any directory to add link dependencies and link interface libraries to targets created in other directories.  The entries are added to LINK_LIBRARIES and INTERFACE_LINK_LIBRARIES using a special (internal) suffix to tell the generators to look up the names in the calling scope rather than the scope that created the target.

This policy provides compatibility with projects that already use target_link_libraries() with the INTERFACE keyword on a target in another directory to add INTERFACE_LINK_LIBRARIES entries to be looked up in the target's directory.  Such projects should be updated to be aware of the new scoping rules in that case.

The OLD behavior of this policy is to disallow target_link_libraries() calls naming targets from another directory except in the previously accidentally allowed case of using the INTERFACE keyword only.  The NEW behavior of this policy is to allow all such calls but use the new scoping rules.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.13.

UseSWIG generates standard target names.

Starting with CMake 3.13, UseSWIG generates now standard target names. This policy provides compatibility with projects that expect the legacy behavior.

The OLD behavior for this policy relies on UseSWIG_TARGET_NAME_PREFERENCE variable that can be used to specify an explicit preference.  The value may be one of:

• LEGACY: legacy strategy is applied. Variable SWIG_MODULE_<name>_REAL_NAME must be used to get real target name. This is the default if not specified.
• STANDARD: target name matches specified name.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.13.

option() honors normal variables.

The option() command is typically used to create a cache entry to allow users to set the option.  However, there are cases in which a normal (non-cached) variable of the same name as the option may be defined by the project prior to calling the option() command. For example, a project that embeds another project as a subdirectory may want to hard-code options of the subproject to build the way it needs.

For historical reasons in CMake 3.12 and below the option() command removes a normal (non-cached) variable of the same name when:

• a cache entry of the specified name does not exist at all, or
• a cache entry of the specified name exists but has not been given a type (e.g. via -D<name>=ON on the command line).

In both of these cases (typically on the first run in a new build tree), the option() command gives the cache entry type BOOL and removes any normal (non-cached) variable of the same name.  In the remaining case that the cache entry of the specified name already exists and has a type (typically on later runs in a build tree), the option() command changes nothing and any normal variable of the same name remains set.

In CMake 3.13 and above the option() command prefers to do nothing when a normal variable of the given name already exists. It does not create or update a cache entry or remove the normal variable. The new behavior is consistent between the first and later runs in a build tree.  This policy provides compatibility with projects that have not been updated to expect the new behavior.

When the option() command sees a normal variable of the given name:

• The OLD behavior for this policy is to proceed even when a normal variable of the same name exists.  If the cache entry does not already exist and have a type then it is created and/or given a type and the normal variable is removed.
• The NEW behavior for this policy is to do nothing when a normal variable of the same name exists.  The normal variable is not removed. The cache entry is not created or updated and is ignored if it exists.

See CMP0126 for a similar policy for the set(CACHE) command, but note that there are some differences in NEW behavior between the two policies.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

Use the CMAKE_POLICY_DEFAULT_CMP0077 variable to set the policy for a third-party project in a subdirectory without modifying it.

NOTE:

Added in version 3.13.

The target_sources() command converts relative paths to absolute.

In CMake 3.13 and above, the target_sources() command now converts relative source file paths to absolute paths in the following cases:

• Source files are added to the target's INTERFACE_SOURCES property.
• The target's SOURCE_DIR property differs from CMAKE_CURRENT_SOURCE_DIR.

A path that begins with a generator expression is always left unmodified.

This policy provides compatibility with projects that have not been updated to expect this behavior.  The OLD behavior for this policy is to leave all relative source file paths unmodified.  The NEW behavior of this policy is to convert relative paths to absolute according to above rules.

This policy was introduced in CMake version 3.13. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.12.

Include file check macros honor CMAKE_REQUIRED_LIBRARIES.

In CMake 3.12 and above, the

• check_include_file macro in the CheckIncludeFile module, the
• check_include_file_cxx macro in the CheckIncludeFileCXX module, and the
• check_include_files macro in the CheckIncludeFiles module

now prefer to link the check executable to the libraries listed in the CMAKE_REQUIRED_LIBRARIES variable.  This policy provides compatibility with projects that have not been updated to expect this behavior.

The OLD behavior for this policy is to ignore CMAKE_REQUIRED_LIBRARIES in the include file check macros.  The NEW behavior of this policy is to honor CMAKE_REQUIRED_LIBRARIES in the include file check macros.

This policy was introduced in CMake version 3.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.12.

find_package() uses <PackageName>_ROOT variables.

In CMake 3.12 and above the find_package(<PackageName>) command now searches prefixes specified by the <PackageName>_ROOT CMake variable and the <PackageName>_ROOT environment variable. Package roots are maintained as a stack so nested calls to all find_* commands inside find modules and config packages also search the roots as prefixes.  This policy provides compatibility with projects that have not been updated to avoid using <PackageName>_ROOT variables for other purposes.

The OLD behavior for this policy is to ignore <PackageName>_ROOT variables.  The NEW behavior for this policy is to use <PackageName>_ROOT variables.

This policy was introduced in CMake version 3.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.12.

Do not produce legacy _LIB_DEPENDS cache entries.

Ancient CMake versions once used <tgt>_LIB_DEPENDS cache entries to propagate library link dependencies.  This has long been done by other means, leaving the export_library_dependencies() command as the only user of these values.  That command has long been disallowed by policy CMP0033, but the <tgt>_LIB_DEPENDS cache entries were left for compatibility with possible non-standard uses by projects.

CMake 3.12 and above now prefer to not produce these cache entries at all.  This policy provides compatibility with projects that have not been updated to avoid using them.

The OLD behavior for this policy is to set <tgt>_LIB_DEPENDS cache entries.  The NEW behavior for this policy is to not set them.

This policy was introduced in CMake version 3.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.11.

FindOpenGL prefers GLVND by default when available.

The FindOpenGL module provides an OpenGL::GL target and an OPENGL_LIBRARIES variable for projects to use for legacy GL interfaces. When both a legacy GL library (e.g. libGL.so) and GLVND libraries for OpenGL and GLX (e.g. libOpenGL.so and libGLX.so) are available, the module must choose between them.  It documents an OpenGL_GL_PREFERENCE variable that can be used to specify an explicit preference.  When no such preference is set, the module must choose a default preference.

CMake 3.11 and above prefer to choose GLVND libraries.  This policy provides compatibility with projects that expect the legacy GL library to be used.

The OLD behavior for this policy is to set OpenGL_GL_PREFERENCE to LEGACY.  The NEW behavior for this policy is to set OpenGL_GL_PREFERENCE to GLVND.

This policy was introduced in CMake version 3.11. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.10.

Let AUTOMOC and AUTOUIC process GENERATED files.

Since version 3.10, CMake processes regular and GENERATED source files in AUTOMOC and AUTOUIC. In earlier CMake versions, only regular source files were processed. GENERATED source files were ignored silently.

This policy affects how source files that are GENERATED get treated in AUTOMOC and AUTOUIC.

The OLD behavior for this policy is to ignore GENERATED source files in AUTOMOC and AUTOUIC.

The NEW behavior for this policy is to process GENERATED source files in AUTOMOC and AUTOUIC just like regular source files.

NOTE:

Source skip example:

# ...
set_property(SOURCE /path/to/file1.h PROPERTY SKIP_AUTOMOC ON)
set_property(SOURCE /path/to/file2.h PROPERTY SKIP_AUTOUIC ON)
set_property(SOURCE /path/to/file3.h PROPERTY SKIP_AUTOGEN ON)
# ...

This policy was introduced in CMake version 3.10. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.10.

Define file(GENERATE) behavior for relative paths.

CMake 3.10 and newer define that relative paths given to INPUT and OUTPUT arguments of file(GENERATE) are interpreted relative to the current source and binary directories, respectively.  CMake 3.9 and lower did not define any behavior for relative paths but did not diagnose them either and accidentally treated them relative to the process working directory. Policy CMP0070 provides compatibility with projects that used the old undefined behavior.

This policy affects behavior of relative paths given to file(GENERATE). The OLD behavior for this policy is to treat the paths relative to the working directory of CMake.  The NEW behavior for this policy is to interpret relative paths with respect to the current source or binary directory of the caller.

This policy was introduced in CMake version 3.10. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.9.

INTERPROCEDURAL_OPTIMIZATION is enforced when enabled.

CMake 3.9 and newer prefer to add IPO flags whenever the INTERPROCEDURAL_OPTIMIZATION target property is enabled and produce an error if flags are not known to CMake for the current compiler. Since a given compiler may not support IPO flags in all environments in which it is used, it is now the project's responsibility to use the CheckIPOSupported module to check for support before enabling the INTERPROCEDURAL_OPTIMIZATION target property.  This approach allows a project to conditionally activate IPO when supported.  It also allows an end user to set the CMAKE_INTERPROCEDURAL_OPTIMIZATION variable in an environment known to support IPO even if the project does not enable the property.

Since CMake 3.8 and lower only honored INTERPROCEDURAL_OPTIMIZATION for the Intel compiler on Linux, some projects may unconditionally enable the target property.  Policy CMP0069 provides compatibility with such projects.

This policy takes effect whenever the IPO property is enabled.  The OLD behavior for this policy is to add IPO flags only for Intel compiler on Linux. The NEW behavior for this policy is to add IPO flags for the current compiler or produce an error if CMake does not know the flags.

This policy was introduced in CMake version 3.9. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Behave like CMake 3.8 and do not apply any IPO flags except for Intel compiler on Linux:

cmake_minimum_required(VERSION 3.8)
project(foo)

# ...

set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)

Use the CheckIPOSupported module to detect whether IPO is supported by the current compiler, environment, and CMake version. Produce a fatal error if support is not available:

cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
project(foo)

include(CheckIPOSupported)
check_ipo_supported()

# ...

set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)

Apply IPO flags only if compiler supports it:

cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
project(foo)

include(CheckIPOSupported)

# ...

check_ipo_supported(RESULT result)
if(result)
  set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
endif()

Apply IPO flags without any checks.  This may lead to build errors if IPO is not supported by the compiler in the current environment.  Produce an error if CMake does not know IPO flags for the current compiler:

cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
project(foo)

# ...

set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)

Added in version 3.9.

RPATH settings on macOS do not affect install_name.

CMake 3.9 and newer remove any effect the following settings may have on the install_name of a target on macOS:

• BUILD_WITH_INSTALL_RPATH target property
• SKIP_BUILD_RPATH target property
• CMAKE_SKIP_RPATH variable
• CMAKE_SKIP_INSTALL_RPATH variable

Previously, setting BUILD_WITH_INSTALL_RPATH had the effect of setting both the install_name of a target to INSTALL_NAME_DIR and the RPATH to INSTALL_RPATH.  In CMake 3.9, it only affects setting of RPATH.  However, if one wants INSTALL_NAME_DIR to apply to the target in the build tree, one may set BUILD_WITH_INSTALL_NAME_DIR.

If SKIP_BUILD_RPATH, CMAKE_SKIP_RPATH or CMAKE_SKIP_INSTALL_RPATH were used to strip the directory portion of the install_name of a target, one may set INSTALL_NAME_DIR="" instead.

The OLD behavior of this policy is to use the RPATH settings for install_name on macOS.  The NEW behavior of this policy is to ignore the RPATH settings for install_name on macOS.

This policy was introduced in CMake version 3.9. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.8.

Honor language standard in try_compile() source-file signature.

The try_compile() source file signature is intended to allow callers to check whether they will be able to compile a given source file with the current toolchain.  In order to match compiler behavior, any language standard mode should match.  However, CMake 3.7 and below did not do this.  CMake 3.8 and above prefer to honor the language standard settings for C, CXX (C++), and CUDA using the values of the variables:

• CMAKE_C_STANDARD
• CMAKE_C_STANDARD_REQUIRED
• CMAKE_C_EXTENSIONS
• CMAKE_CXX_STANDARD
• CMAKE_CXX_STANDARD_REQUIRED
• CMAKE_CXX_EXTENSIONS
• CMAKE_CUDA_STANDARD
• CMAKE_CUDA_STANDARD_REQUIRED
• CMAKE_CUDA_EXTENSIONS

This policy provides compatibility for projects that do not expect the language standard settings to be used automatically.

The OLD behavior of this policy is to ignore language standard setting variables when generating the try_compile test project. The NEW behavior of this policy is to honor language standard setting variables.

This policy was introduced in CMake version 3.8. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0067 variable to control the warning.

NOTE:

Added in version 3.7.

Honor per-config flags in try_compile() source-file signature.

The source file signature of the try_compile() command uses the value of the CMAKE_<LANG>_FLAGS variable in the test project so that the test compilation works as it would in the main project.  However, CMake 3.6 and below do not also honor config-specific compiler flags such as those in the CMAKE_<LANG>_FLAGS_DEBUG variable.  CMake 3.7 and above prefer to honor config-specific compiler flags too.  This policy provides compatibility for projects that do not expect config-specific compiler flags to be used.

The OLD behavior of this policy is to ignore config-specific flag variables like CMAKE_<LANG>_FLAGS_DEBUG and only use CMake's built-in defaults for the current compiler and platform.

The NEW behavior of this policy is to honor config-specific flag variables like CMAKE_<LANG>_FLAGS_DEBUG.

This policy was introduced in CMake version 3.7. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0066 variable to control the warning.

NOTE:

Added in version 3.4.

Do not add flags to export symbols from executables without the ENABLE_EXPORTS target property.

CMake 3.3 and below, for historical reasons, always linked executables on some platforms with flags like -rdynamic to export symbols from the executables for use by any plugins they may load via dlopen. CMake 3.4 and above prefer to do this only for executables that are explicitly marked with the ENABLE_EXPORTS target property.

The OLD behavior of this policy is to always use the additional link flags when linking executables regardless of the value of the ENABLE_EXPORTS target property.

The NEW behavior of this policy is to only use the additional link flags when linking executables if the ENABLE_EXPORTS target property is set to True.

This policy was introduced in CMake version 3.4. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0065 variable to control the warning.

NOTE:

Added in version 3.4.

Recognize TEST as a operator for the if() command.

The TEST operator was added to the if() command to determine if a given test name was created by the add_test() command.

The OLD behavior for this policy is to ignore the TEST operator. The NEW behavior is to interpret the TEST operator.

This policy was introduced in CMake version 3.4. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.3.

Honor visibility properties for all target types.

The <LANG>_VISIBILITY_PRESET and VISIBILITY_INLINES_HIDDEN target properties affect visibility of symbols during dynamic linking.  When first introduced these properties affected compilation of sources only in shared libraries, module libraries, and executables with the ENABLE_EXPORTS property set.  This was sufficient for the basic use cases of shared libraries and executables with plugins.  However, some sources may be compiled as part of static libraries or object libraries and then linked into a shared library later. CMake 3.3 and above prefer to honor these properties for sources compiled in all target types.  This policy preserves compatibility for projects expecting the properties to work only for some target types.

The OLD behavior for this policy is to ignore the visibility properties for static libraries, object libraries, and executables without exports. The NEW behavior for this policy is to honor the visibility properties for all target types.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.3.

Disallow install() of export() result.

The export() command generates a file containing Imported Targets, which is suitable for use from the build directory.  It is not suitable for installation because it contains absolute paths to buildsystem locations, and is particular to a single build configuration.

The install(EXPORT) generates and installs files which contain Imported Targets.  These files are generated with relative paths (unless the user specifies absolute paths), and are designed for multi-configuration use.  See Creating Packages for more.

CMake 3.3 no longer allows the use of the install(FILES) command with the result of the export() command.

The OLD behavior for this policy is to allow installing the result of an export() command.  The NEW behavior for this policy is not to allow installing the result of an export() command.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.3.

CTest does not by default tell make to ignore errors (-i).

The ctest_build() and build_command() commands no longer generate build commands for Makefile Generators with the -i option.  Previously this was done to help build as much of tested projects as possible.  However, this behavior is not consistent with other generators and also causes the return code of the make tool to be meaningless.

Of course users may still add this option manually by setting CTEST_BUILD_COMMAND or the MAKECOMMAND cache entry. See the CTest Build Step MakeCommand setting documentation for their effects.

The OLD behavior for this policy is to add -i to make calls in CTest.  The NEW behavior for this policy is to not add -i.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.

NOTE:

Added in version 3.3.

Link libraries by full path even in implicit directories.

Policy CMP0003 was introduced with the intention of always linking library files by full path when a full path is given to the target_link_libraries() command.  However, on some platforms (e.g. HP-UX) the compiler front-end adds alternative library search paths for the current architecture (e.g. /usr/lib/<arch> has alternatives to libraries in /usr/lib for the current architecture). On such platforms the find_library() may find a library such as /usr/lib/libfoo.so that does not belong to the current architecture.

Prior to policy CMP0003 projects would still build in such cases because the incorrect library path would be converted to -lfoo on the link line and the linker would find the proper library in the arch-specific search path provided by the compiler front-end implicitly. At the time we chose to remain compatible with such projects by always converting library files found in implicit link directories to -lfoo flags to ask the linker to search for them.  This approach allowed existing projects to continue to build while still linking to libraries outside implicit link directories via full path (such as those in the build tree).

CMake does allow projects to override this behavior by using an IMPORTED library target with its IMPORTED_LOCATION property set to the desired full path to a library file.  In fact, many Find Modules are learning to provide Imported Targets instead of just the traditional Foo_LIBRARIES variable listing library files.  However, this makes the link line generated for a library found by a Find Module depend on whether it is linked through an imported target or not, which is inconsistent. Furthermore, this behavior has been a source of confusion because the generated link line for a library file depends on its location.  It is also problematic for projects trying to link statically because flags like -Wl,-Bstatic -lfoo -Wl,-Bdynamic may be used to help the linker select libfoo.a instead of libfoo.so but then leak dynamic linking to following libraries.  (See the LINK_SEARCH_END_STATIC target property for a solution typically used for that problem.)

When the special case for libraries in implicit link directories was first introduced the list of implicit link directories was simply hard-coded (e.g. /lib, /usr/lib, and a few others).  Since that time, CMake has learned to detect the implicit link directories used by the compiler front-end.  If necessary, the find_library() command could be taught to use this information to help find libraries of the proper architecture.

For these reasons, CMake 3.3 and above prefer to drop the special case and link libraries by full path even when they are in implicit link directories.  Policy CMP0060 provides compatibility for existing projects.

The OLD behavior for this policy is to ask the linker to search for libraries whose full paths are known to be in implicit link directories. The NEW behavior for this policy is to link libraries by full path even if they are in implicit link directories.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0060 variable to control the warning.

NOTE:

Added in version 3.3.

Do not treat DEFINITIONS as a built-in directory property.

CMake 3.3 and above no longer make a list of definitions available through the DEFINITIONS directory property.  The COMPILE_DEFINITIONS directory property may be used instead.

The OLD behavior for this policy is to provide the list of flags given so far to the add_definitions() command.  The NEW behavior is to behave as a normal user-defined directory property.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.3.

Ninja requires custom command byproducts to be explicit.

When an intermediate file generated during the build is consumed by an expensive operation or a large tree of dependents, one may reduce the work needed for an incremental rebuild by updating the file timestamp only when its content changes.  With this approach the generation rule must have a separate output file that is always updated with a new timestamp that is newer than any dependencies of the rule so that the build tool re-runs the rule only when the input changes.  We refer to the separate output file as a rule's witness and the generated file as a rule's byproduct.

Byproducts may not be listed as outputs because their timestamps are allowed to be older than the inputs.  No build tools (like make) that existed when CMake was designed have a way to express byproducts. Therefore CMake versions prior to 3.2 had no way to specify them. Projects typically left byproducts undeclared in the rules that generate them.  For example:

add_custom_command(
  OUTPUT witness.txt
  COMMAND ${CMAKE_COMMAND} -E copy_if_different
          ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
          byproduct.txt # timestamp may not change
  COMMAND ${CMAKE_COMMAND} -E touch witness.txt
  DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
  )
add_custom_target(Provider DEPENDS witness.txt)
add_custom_command(
  OUTPUT generated.c
  COMMAND expensive-task -i byproduct.txt -o generated.c
  DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/byproduct.txt
  )
add_library(Consumer generated.c)
add_dependencies(Consumer Provider)

This works well for all generators except Ninja. The Ninja build tool sees a rule listing byproduct.txt as a dependency and no rule listing it as an output.  Ninja then complains that there is no way to satisfy the dependency and stops building even though there are order-only dependencies that ensure byproduct.txt will exist before its consumers need it.  See discussion of this problem in Ninja Issue 760 for further details on why Ninja works this way.

Instead of leaving byproducts undeclared in the rules that generate them, Ninja expects byproducts to be listed along with other outputs. Such rules may be marked with a restat option that tells Ninja to check the timestamps of outputs after the rules run.  This prevents byproducts whose timestamps do not change from causing their dependents to re-build unnecessarily.

Since the above approach does not tell CMake what custom command generates byproduct.txt, the Ninja generator does not have enough information to add the byproduct as an output of any rule. CMake 2.8.12 and above work around this problem and allow projects using the above approach to build by generating phony build rules to tell Ninja to tolerate such missing files.  However, this workaround prevents Ninja from diagnosing a dependency that is really missing.  It also works poorly in in-source builds where every custom command dependency, even on source files, needs to be treated this way because CMake does not have enough information to know which files are generated as byproducts of custom commands.

CMake 3.2 introduced the BYPRODUCTS option to the add_custom_command() and add_custom_target() commands.  This option allows byproducts to be specified explicitly:

add_custom_command(
  OUTPUT witness.txt
  BYPRODUCTS byproduct.txt # explicit byproduct specification
  COMMAND ${CMAKE_COMMAND} -E copy_if_different
          ${CMAKE_CURRENT_SOURCE_DIR}/input.txt
          byproduct.txt # timestamp may not change
...

The BYPRODUCTS option is used by the Ninja generator to list byproducts among the outputs of the custom commands that generate them, and is ignored by other generators.

CMake 3.3 and above prefer to require projects to specify custom command byproducts explicitly so that it can avoid using the phony rule workaround altogether.  Policy CMP0058 was introduced to provide compatibility with existing projects that still need the workaround.

This policy has no effect on generators other than Ninja. The OLD behavior for this policy is to generate Ninja phony rules for unknown dependencies in the build tree.  The NEW behavior for this policy is to not generate these and instead require projects to specify custom command BYPRODUCTS explicitly.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns when it sees unknown dependencies in out-of-source build trees, and uses OLD behavior.

The policy setting must be in scope at the end of the top-level CMakeLists.txt file of the project and has global effect.

NOTE:

Added in version 3.3.

Support new if() IN_LIST operator.

CMake 3.3 adds support for the new IN_LIST operator.

The OLD behavior for this policy is to ignore the IN_LIST operator. The NEW behavior is to interpret the IN_LIST operator.

This policy was introduced in CMake version 3.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.2.

Honor link flags in try_compile() source-file signature.

The try_compile() command source-file signature generates a CMakeLists.txt file to build the source file into an executable. In order to compile the source the same way as it might be compiled by the calling project, the generated project sets the value of the CMAKE_<LANG>_FLAGS variable to that in the calling project. The value of the CMAKE_EXE_LINKER_FLAGS variable may be needed in some cases too, but CMake 3.1 and lower did not set it in the generated project.  CMake 3.2 and above prefer to set it so that linker flags are honored as well as compiler flags.  This policy provides compatibility with the pre-3.2 behavior.

The OLD behavior for this policy is to not set the value of the CMAKE_EXE_LINKER_FLAGS variable in the generated test project.  The NEW behavior for this policy is to set the value of the CMAKE_EXE_LINKER_FLAGS variable in the test project to the same as it is in the calling project.

If the project code does not set the policy explicitly, users may set it on the command line by defining the CMAKE_POLICY_DEFAULT_CMP0056 variable in the cache.

This policy was introduced in CMake version 3.2. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0056 variable to control the warning.

NOTE:

Added in version 3.2.

Strict checking for the break() command.

CMake 3.1 and lower allowed calls to the break() command outside of a loop context and also ignored any given arguments. This was undefined behavior.

The OLD behavior for this policy is to allow break() to be placed outside of loop contexts and ignores any arguments.  The NEW behavior for this policy is to issue an error if a misplaced break or any arguments are found.

This policy was introduced in CMake version 3.2. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.1.

Only interpret if() arguments as variables or keywords when unquoted.

CMake 3.1 and above no longer implicitly dereference variables or interpret keywords in an if() command argument when it is a Quoted Argument or a Bracket Argument.

The OLD behavior for this policy is to dereference variables and interpret keywords even if they are quoted or bracketed. The NEW behavior is to not dereference variables or interpret keywords that have been quoted or bracketed.

Given the following partial example:

set(A E)
set(E "")

if("${A}" STREQUAL "")
  message("Result is TRUE before CMake 3.1 or when CMP0054 is OLD")
else()
  message("Result is FALSE in CMake 3.1 and above if CMP0054 is NEW")
endif()

After explicit expansion of variables this gives:

if("E" STREQUAL "")

With the policy set to OLD implicit expansion reduces this semantically to:

if("" STREQUAL "")

With the policy set to NEW the quoted arguments will not be further dereferenced:

if("E" STREQUAL "")

This policy was introduced in CMake version 3.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.1.

Simplify variable reference and escape sequence evaluation.

CMake 3.1 introduced a much faster implementation of evaluation of the Variable References and Escape Sequences documented in the cmake-language(7) manual.  While the behavior is identical to the legacy implementation in most cases, some corner cases were cleaned up to simplify the behavior.  Specifically:

• Expansion of @VAR@ reference syntax defined by the configure_file() and string(CONFIGURE) commands is no longer performed in other contexts.

• Literal ${VAR} reference syntax may contain only alphanumeric characters (A-Z, a-z, 0-9) and the characters _, ., /, -, and +. Note that $ is technically allowed in the NEW behavior, but is invalid for OLD behavior.  This is due to an oversight during the implementation of CMP0053 and its use as a literal variable reference is discouraged for this reason. Variables with other characters in their name may still be referenced indirectly, e.g.

  set(varname "otherwise & disallowed $ characters")
  message("${${varname}}")

• The setting of policy CMP0010 is not considered, so improper variable reference syntax is always an error.
• More characters are allowed to be escaped in variable names. Previously, only ()#" \@^ were valid characters to escape. Now any non-alphanumeric, non-semicolon, non-NUL character may be escaped following the escape_identity production in the Escape Sequences section of the cmake-language(7) manual.

The OLD behavior for this policy is to honor the legacy behavior for variable references and escape sequences.  The NEW behavior is to use the simpler variable expansion and escape sequence evaluation rules.

This policy was introduced in CMake version 3.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.1.

Reject source and build dirs in installed INTERFACE_INCLUDE_DIRECTORIES.

CMake 3.0 and lower allowed subdirectories of the source directory or build directory to be in the INTERFACE_INCLUDE_DIRECTORIES of installed and exported targets, if the directory was also a subdirectory of the installation prefix.  This makes the installation depend on the existence of the source dir or binary dir, and the installation will be broken if either are removed after installation.

See Include Directories and Usage Requirements for more on specifying include directories for targets.

The OLD behavior for this policy is to export the content of the INTERFACE_INCLUDE_DIRECTORIES with the source or binary directory.  The NEW behavior for this policy is to issue an error if such a directory is used.

This policy was introduced in CMake version 3.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Added in version 3.1.

List TARGET_OBJECTS in SOURCES target property.

CMake 3.0 and lower did not include the TARGET_OBJECTS generator expression when returning the SOURCES target property.

Configure-time CMake code is not able to handle generator expressions.  If using the SOURCES target property at configure time, it may be necessary to first remove generator expressions using the string(GENEX_STRIP) command.  Generate-time CMake code such as file(GENERATE) can handle the content without stripping.

The OLD behavior for this policy is to omit TARGET_OBJECTS expressions from the SOURCES target property.  The NEW behavior for this policy is to include TARGET_OBJECTS expressions in the output.

This policy was introduced in CMake version 3.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Disallow add_custom_command SOURCE signatures.

CMake 2.8.12 and lower allowed a signature for add_custom_command() which specified an input to a command.  This was undocumented behavior. Modern use of CMake associates custom commands with their output, rather than their input.

The OLD behavior for this policy is to allow the use of add_custom_command() SOURCE signatures.  The NEW behavior for this policy is to issue an error if such a signature is used.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Do not expand variables in target source entries.

CMake 2.8.12 and lower performed an extra layer of variable expansion when evaluating source file names:

set(a_source foo.c)
add_executable(foo \${a_source})

This was undocumented behavior.

The OLD behavior for this policy is to expand such variables when processing the target sources.  The NEW behavior for this policy is to issue an error if such variables need to be expanded.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The project() command manages VERSION variables.

CMake version 3.0 introduced the VERSION option of the project() command to specify a project version as well as the name.  In order to keep PROJECT_VERSION and related variables consistent with variable PROJECT_NAME it is necessary to set the VERSION variables to the empty string when no VERSION is given to project(). However, this can change behavior for existing projects that set VERSION variables themselves since project() may now clear them. This policy controls the behavior for compatibility with such projects.

The OLD behavior for this policy is to leave VERSION variables untouched. The NEW behavior for this policy is to set VERSION as documented by the project() command.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Use QCC compiler id for the qcc drivers on QNX.

CMake 3.0 and above recognize that the QNX qcc compiler driver is different from the GNU compiler. CMake now prefers to present this to projects by setting the CMAKE_<LANG>_COMPILER_ID variable to QCC instead of GNU.  However, existing projects may assume the compiler id for QNX qcc is just GNU as it was in CMake versions prior to 3.0. Therefore this policy determines for QNX qcc which compiler id to report in the CMAKE_<LANG>_COMPILER_ID variable after language <LANG> is enabled by the project() or enable_language() command.  The policy must be set prior to the invocation of either command.

The OLD behavior for this policy is to use the GNU compiler id for the qcc and QCC compiler drivers. The NEW behavior for this policy is to use the QCC compiler id for those drivers.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0047 variable to control the warning.

NOTE:

Error on non-existent dependency in add_dependencies.

CMake 2.8.12 and lower silently ignored non-existent dependencies listed in the add_dependencies() command.

The OLD behavior for this policy is to silently ignore non-existent dependencies. The NEW behavior for this policy is to report an error if non-existent dependencies are listed in the add_dependencies() command.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Error on non-existent target in get_target_property.

In CMake 2.8.12 and lower, the get_target_property() command accepted a non-existent target argument without issuing any error or warning.  The result variable is set to a -NOTFOUND value.

The OLD behavior for this policy is to issue no warning and set the result variable to a -NOTFOUND value.  The NEW behavior for this policy is to issue a FATAL_ERROR if the command is called with a non-existent target.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Case sensitive <LANG>_COMPILER_ID generator expressions

CMake 2.8.12 introduced the <LANG>_COMPILER_ID generator expressions to allow comparison of the CMAKE_<LANG>_COMPILER_ID with a test value.  The possible valid values are lowercase, but the comparison with the test value was performed case-insensitively.

The OLD behavior for this policy is to perform a case-insensitive comparison with the value in the <LANG>_COMPILER_ID expression. The NEW behavior for this policy is to perform a case-sensitive comparison with the value in the <LANG>_COMPILER_ID expression.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Ignore COMPILE_DEFINITIONS_<Config> properties

CMake 2.8.12 and lower allowed setting the COMPILE_DEFINITIONS_<CONFIG> target property and COMPILE_DEFINITIONS_<CONFIG> directory property to apply configuration-specific compile definitions.

Since CMake 2.8.10, the COMPILE_DEFINITIONS property has supported generator expressions for setting configuration-dependent content.  The continued existence of the suffixed variables is redundant, and causes a maintenance burden.  Population of the COMPILE_DEFINITIONS_DEBUG property may be replaced with a population of COMPILE_DEFINITIONS directly or via target_compile_definitions():

# Old Interfaces:
set_property(TARGET tgt APPEND PROPERTY
  COMPILE_DEFINITIONS_DEBUG DEBUG_MODE
)
set_property(DIRECTORY APPEND PROPERTY
  COMPILE_DEFINITIONS_DEBUG DIR_DEBUG_MODE
)

# New Interfaces:
set_property(TARGET tgt APPEND PROPERTY
  COMPILE_DEFINITIONS $<$<CONFIG:Debug>:DEBUG_MODE>
)
target_compile_definitions(tgt PRIVATE $<$<CONFIG:Debug>:DEBUG_MODE>)
set_property(DIRECTORY APPEND PROPERTY
  COMPILE_DEFINITIONS $<$<CONFIG:Debug>:DIR_DEBUG_MODE>
)

The OLD behavior for this policy is to consume the content of the suffixed COMPILE_DEFINITIONS_<CONFIG> target property when generating the compilation command. The NEW behavior for this policy is to ignore the content of the COMPILE_DEFINITIONS_<CONFIG> target property .

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

MACOSX_RPATH is enabled by default.

CMake 2.8.12 and newer has support for using @rpath in a target's install name.  This was enabled by setting the target property MACOSX_RPATH.  The @rpath in an install name is a more flexible and powerful mechanism than @executable_path or @loader_path for locating shared libraries.

CMake 3.0 and later prefer this property to be ON by default.  Projects wanting @rpath in a target's install name may remove any setting of the INSTALL_NAME_DIR and CMAKE_INSTALL_NAME_DIR variables.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Error on relative include with generator expression.

Diagnostics in CMake 2.8.12 and lower silently ignored an entry in the INTERFACE_INCLUDE_DIRECTORIES of a target if it contained a generator expression at any position.

The path entries in that target property should not be relative. High-level API should ensure that by adding either a source directory or a install directory prefix, as appropriate.

As an additional diagnostic, the INTERFACE_INCLUDE_DIRECTORIES generated on an IMPORTED target for the install location should not contain paths in the source directory or the build directory.

The OLD behavior for this policy is to ignore relative path entries if they contain a generator expression. The NEW behavior for this policy is to report an error if a generator expression appears in another location and the path is relative.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The target in the TARGET signature of add_custom_command() must exist and must be defined in the current directory.

CMake 2.8.12 and lower silently ignored a custom command created with the TARGET signature of add_custom_command() if the target is unknown or was defined outside the current directory.

The OLD behavior for this policy is to ignore custom commands for unknown targets.  The NEW behavior for this policy is to report an error if the target referenced in add_custom_command() is unknown or was defined outside the current directory.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Utility targets may not have link dependencies.

CMake 2.8.12 and lower allowed using utility targets in the left hand side position of the target_link_libraries() command. This is an indicator of a bug in user code.

The OLD behavior for this policy is to ignore attempts to set the link libraries of utility targets.  The NEW behavior for this policy is to report an error if an attempt is made to set the link libraries of a utility target.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Targets may not link directly to themselves.

CMake 2.8.12 and lower allowed a build target to link to itself directly with a target_link_libraries() call. This is an indicator of a bug in user code.

The OLD behavior for this policy is to ignore targets which list themselves in their own link implementation.  The NEW behavior for this policy is to report an error if a target attempts to link to itself.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Target names should not be reserved and should match a validity pattern.

CMake 2.8.12 and lower allowed creating targets using add_library(), add_executable() and add_custom_target() with unrestricted choice for the target name.  Newer cmake features such as cmake-generator-expressions(7) and some diagnostics expect target names to match a restricted pattern.

Target names may contain upper and lower case letters, numbers, the underscore character (_), dot(.), plus(+) and minus(-). As a special case, ALIAS and IMPORTED targets may contain two consecutive colons.

Target names reserved by one or more CMake generators are not allowed. Among others these include all, clean, help, and install.

Target names associated with optional features, such as test and package, may also be reserved.  CMake 3.10 and below always reserve them. CMake 3.11 and above reserve them only when the corresponding feature is enabled (e.g. by including the CTest or CPack modules).

The OLD behavior for this policy is to allow creating targets with reserved names or which do not match the validity pattern. The NEW behavior for this policy is to report an error if an add_* command is used with an invalid target name.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The build_name() command should not be called.

This command was added in May 2001 to compute a name for the current operating system and compiler combination.  The command has long been documented as discouraged and replaced by the CMAKE_SYSTEM and CMAKE_<LANG>_COMPILER variables.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The variable_requires() command should not be called.

This command was introduced in November 2001 to perform some conditional logic.  It has long been replaced by the if() command.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The utility_source() command should not be called.

This command was introduced in March 2001 to help build executables used to generate other files.  This approach has long been replaced by add_executable() combined with add_custom_command().

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The export_library_dependencies() command should not be called.

This command was added in January 2003 to export <tgt>_LIB_DEPENDS internal CMake cache entries to a file for installation with a project. This was used at the time to allow transitive link dependencies to work for applications outside of the original build tree of a project. The functionality has been superseded by the export() and install(EXPORT) commands.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The output_required_files() command should not be called.

This command was added in June 2001 to expose the then-current CMake implicit dependency scanner.  CMake's real implicit dependency scanner has evolved since then but is not exposed through this command.  The scanning capabilities of this command are very limited and this functionality is better achieved through dedicated outside tools.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The load_command() command should not be called.

This command was added in August 2002 to allow projects to add arbitrary commands implemented in C or C++.  However, it does not work when the toolchain in use does not match the ABI of the CMake process.  It has been mostly superseded by the macro() and function() commands.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The use_mangled_mesa() command should not be called.

This command was created in September 2001 to support VTK before modern CMake language and custom command capabilities.  VTK has not used it in years.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

The subdir_depends() command should not be called.

The implementation of this command has been empty since December 2001 but was kept in CMake for compatibility for a long time.

CMake >= 3.0 prefer that this command never be called. The OLD behavior for this policy is to allow the command to be called. The NEW behavior for this policy is to issue a FATAL_ERROR when the command is called.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Double colon in target name means ALIAS or IMPORTED target.

CMake 2.8.12 and lower allowed the use of targets and files with double colons in target_link_libraries(), with some buildsystem generators.

The use of double-colons is a common pattern used to namespace IMPORTED targets and ALIAS targets.  When computing the link dependencies of a target, the name of each dependency could either be a target, or a file on disk.  Previously, if a target was not found with a matching name, the name was considered to refer to a file on disk.  This can lead to confusing error messages if there is a typo in what should be a target name.

See also the LINK_LIBRARIES_ONLY_TARGETS target property.

The OLD behavior for this policy is to search for targets, then files on disk, even if the search term contains double-colons.  The NEW behavior for this policy is to issue a FATAL_ERROR if a link dependency contains double-colons but is not an IMPORTED target or an ALIAS target.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Conditionally linked imported targets with missing include directories.

CMake 2.8.11 introduced introduced the concept of INTERFACE_INCLUDE_DIRECTORIES, and a check at cmake time that the entries in the INTERFACE_INCLUDE_DIRECTORIES of an IMPORTED target actually exist.  CMake 2.8.11 also introduced generator expression support in the target_link_libraries() command.  However, if an imported target is linked as a result of a generator expression evaluation, the entries in the INTERFACE_INCLUDE_DIRECTORIES of that target were not checked for existence as they should be.

The OLD behavior of this policy is to report a warning if an entry in the INTERFACE_INCLUDE_DIRECTORIES of a generator-expression conditionally linked IMPORTED target does not exist.

The NEW behavior of this policy is to report an error if an entry in the INTERFACE_INCLUDE_DIRECTORIES of a generator-expression conditionally linked IMPORTED target does not exist.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Disallow use of the LOCATION property for build targets.

CMake 2.8.12 and lower allowed reading the LOCATION target property (and configuration-specific variants) to determine the eventual location of build targets.  This relies on the assumption that all necessary information is available at configure-time to determine the final location and filename of the target.  However, this property is not fully determined until later at generate-time.  At generate time, the $<TARGET_FILE> generator expression can be used to determine the eventual LOCATION of a target output.

Code which reads the LOCATION target property can be ported to use the $<TARGET_FILE> generator expression together with the file(GENERATE) subcommand to generate a file containing the target location.

The OLD behavior for this policy is to allow reading the LOCATION properties from build-targets.  The NEW behavior for this policy is to not to allow reading the LOCATION properties from build-targets.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Compiler id for Apple Clang is now AppleClang.

CMake 3.0 and above recognize that Apple Clang is a different compiler than upstream Clang and that they have different version numbers. CMake now prefers to present this to projects by setting the CMAKE_<LANG>_COMPILER_ID variable to AppleClang instead of Clang.  However, existing projects may assume the compiler id for Apple Clang is just Clang as it was in CMake versions prior to 3.0. Therefore this policy determines for Apple Clang which compiler id to report in the CMAKE_<LANG>_COMPILER_ID variable after language <LANG> is enabled by the project() or enable_language() command.  The policy must be set prior to the invocation of either command.

The OLD behavior for this policy is to use compiler id Clang.  The NEW behavior for this policy is to use compiler id AppleClang.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake does not warn by default, and uses OLD behavior.

See documentation of the CMAKE_POLICY_WARNING_CMP0025 variable to control the warning.

NOTE:

Disallow include export result.

CMake 2.8.12 and lower allowed use of the include() command with the result of the export() command.  This relies on the assumption that the export() command has an immediate effect at configure-time during a cmake run.  Certain properties of targets are not fully determined until later at generate-time, such as the link language and complete list of link libraries.  Future refactoring will change the effect of the export() command to be executed at generate-time.  Use ALIAS targets instead in cases where the goal is to refer to targets by another name.

The OLD behavior for this policy is to allow including the result of an export() command.  The NEW behavior for this policy is not to allow including the result of an export() command.

This policy was introduced in CMake version 3.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Plain and keyword target_link_libraries() signatures cannot be mixed.

CMake 2.8.12 introduced the target_link_libraries() signature using the PUBLIC, PRIVATE, and INTERFACE keywords to generalize the LINK_PUBLIC and LINK_PRIVATE keywords introduced in CMake 2.8.7. Use of signatures with any of these keywords sets the link interface of a target explicitly, even if empty.  This produces confusing behavior when used in combination with the historical behavior of the plain target_link_libraries() signature.  For example, consider the code:

target_link_libraries(mylib A)
target_link_libraries(mylib PRIVATE B)

After the first line the link interface has not been set explicitly so CMake would use the link implementation, A, as the link interface. However, the second line sets the link interface to empty.  In order to avoid this subtle behavior CMake now prefers to disallow mixing the plain and keyword signatures of target_link_libraries() for a single target.

The OLD behavior for this policy is to allow keyword and plain target_link_libraries() signatures to be mixed.  The NEW behavior for this policy is to not to allow mixing of the keyword and plain signatures.

This policy was introduced in CMake version 2.8.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

INTERFACE_LINK_LIBRARIES defines the link interface.

CMake 2.8.11 constructed the 'link interface' of a target from properties matching (IMPORTED_)?LINK_INTERFACE_LIBRARIES(_<CONFIG>)?. The modern way to specify config-sensitive content is to use generator expressions and the IMPORTED_ prefix makes uniform processing of the link interface with generator expressions impossible.  The INTERFACE_LINK_LIBRARIES target property was introduced as a replacement in CMake 2.8.12.  This new property is named consistently with the INTERFACE_COMPILE_DEFINITIONS, INTERFACE_INCLUDE_DIRECTORIES and INTERFACE_COMPILE_OPTIONS properties.  For in-build targets, CMake will use the INTERFACE_LINK_LIBRARIES property as the source of the link interface only if policy CMP0022 is NEW.  When exporting a target which has this policy set to NEW, only the INTERFACE_LINK_LIBRARIES property will be processed and generated for the IMPORTED target by default.  A new option to the install(EXPORT) and export commands allows export of the old-style properties for compatibility with downstream users of CMake versions older than 2.8.12.  The target_link_libraries() command will no longer populate the properties matching LINK_INTERFACE_LIBRARIES(_<CONFIG>)? if this policy is NEW.

Warning-free future-compatible code which works with CMake 2.8.7 onwards can be written by using the LINK_PRIVATE and LINK_PUBLIC keywords of target_link_libraries().

The OLD behavior for this policy is to ignore the INTERFACE_LINK_LIBRARIES property for in-build targets. The NEW behavior for this policy is to use the INTERFACE_LINK_LIBRARIES property for in-build targets, and ignore the old properties matching (IMPORTED_)?LINK_INTERFACE_LIBRARIES(_<CONFIG>)?.

This policy was introduced in CMake version 2.8.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Fatal error on relative paths in INCLUDE_DIRECTORIES target property.

CMake 2.8.10.2 and lower allowed the INCLUDE_DIRECTORIES target property to contain relative paths.  The base path for such relative entries is not well defined.  CMake 2.8.12 issues a FATAL_ERROR if the INCLUDE_DIRECTORIES property contains a relative path.

The OLD behavior for this policy is not to warn about relative paths in the INCLUDE_DIRECTORIES target property.  The NEW behavior for this policy is to issue a FATAL_ERROR if INCLUDE_DIRECTORIES contains a relative path.

This policy was introduced in CMake version 2.8.12. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Automatically link Qt executables to qtmain target on Windows.

CMake 2.8.10 and lower required users of Qt to always specify a link dependency to the qtmain.lib static library manually on Windows. CMake 2.8.11 gained the ability to evaluate generator expressions while determining the link dependencies from IMPORTED targets.  This allows CMake itself to automatically link executables which link to Qt to the qtmain.lib library when using IMPORTED Qt targets.  For applications already linking to qtmain.lib, this should have little impact.  For applications which supply their own alternative WinMain implementation and for applications which use the QAxServer library, this automatic linking will need to be disabled as per the documentation.

The OLD behavior for this policy is not to link executables to qtmain.lib automatically when they link to the QtCore IMPORTED target. The NEW behavior for this policy is to link executables to qtmain.lib automatically when they link to QtCore IMPORTED target.

This policy was introduced in CMake version 2.8.11. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Do not re-expand variables in include and link information.

CMake 2.8.10 and lower re-evaluated values given to the include_directories, link_directories, and link_libraries commands to expand any leftover variable references at the end of the configuration step.  This was for strict compatibility with VERY early CMake versions because all variable references are now normally evaluated during CMake language processing.  CMake 2.8.11 and higher prefer to skip the extra evaluation.

The OLD behavior for this policy is to re-evaluate the values for strict compatibility.  The NEW behavior for this policy is to leave the values untouched.

This policy was introduced in CMake version 2.8.11. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Ignore CMAKE_SHARED_LIBRARY_<Lang>_FLAGS variable.

CMake 2.8.8 and lower compiled sources in SHARED and MODULE libraries using the value of the undocumented CMAKE_SHARED_LIBRARY_<Lang>_FLAGS platform variable.  The variable contained platform-specific flags needed to compile objects for shared libraries.  Typically it included a flag such as -fPIC for position independent code but also included other flags needed on certain platforms.  CMake 2.8.9 and higher prefer instead to use the POSITION_INDEPENDENT_CODE target property to determine what targets should be position independent, and new undocumented platform variables to select flags while ignoring CMAKE_SHARED_LIBRARY_<Lang>_FLAGS completely.

The default for either approach produces identical compilation flags, but if a project modifies CMAKE_SHARED_LIBRARY_<Lang>_FLAGS from its original value this policy determines which approach to use.

The OLD behavior for this policy is to ignore the POSITION_INDEPENDENT_CODE property for all targets and use the modified value of CMAKE_SHARED_LIBRARY_<Lang>_FLAGS for SHARED and MODULE libraries.

The NEW behavior for this policy is to ignore CMAKE_SHARED_LIBRARY_<Lang>_FLAGS whether it is modified or not and honor the POSITION_INDEPENDENT_CODE target property.

This policy was introduced in CMake version 2.8.9. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Prefer files from the CMake module directory when including from there.

Starting with CMake 2.8.4, if a cmake-module shipped with CMake (i.e. located in the CMake module directory) calls include() or find_package(), the files located in the CMake module directory are preferred over the files in CMAKE_MODULE_PATH.  This makes sure that the modules belonging to CMake always get those files included which they expect, and against which they were developed and tested.  In all other cases, the files found in CMAKE_MODULE_PATH still take precedence over the ones in the CMake module directory.  The OLD behavior is to always prefer files from CMAKE_MODULE_PATH over files from the CMake modules directory.

This policy was introduced in CMake version 2.8.4. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

target_link_libraries() reports error if its only argument is not a target.

In CMake 2.8.2 and lower the target_link_libraries() command silently ignored if it was called with only one argument, and this argument wasn't a valid target.  In CMake 2.8.3 and above it reports an error in this case.

This policy was introduced in CMake version 2.8.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

In CMake 2.8.0 and lower the link_directories() command passed relative paths unchanged to the linker.  In CMake 2.8.1 and above the link_directories() command prefers to interpret relative paths with respect to CMAKE_CURRENT_SOURCE_DIR, which is consistent with include_directories() and other commands.  The OLD behavior for this policy is to use relative paths verbatim in the linker command.  The NEW behavior for this policy is to convert relative paths to absolute paths by appending the relative path to CMAKE_CURRENT_SOURCE_DIR.

This policy was introduced in CMake version 2.8.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Input directories must have CMakeLists.txt.

CMake versions before 2.8 silently ignored missing CMakeLists.txt files in directories referenced by add_subdirectory() or  subdirs(), treating them as if present but empty.  In CMake 2.8.0 and above this cmake_policy() determines whether or not the case is an error. The OLD behavior for this policy is to silently ignore the problem. The NEW behavior for this policy is to report an error.

This policy was introduced in CMake version 2.8.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Duplicate binary directories are not allowed.

CMake 2.6.3 and below silently permitted add_subdirectory() calls to create the same binary directory multiple times.  During build system generation files would be written and then overwritten in the build tree and could lead to strange behavior.  CMake 2.6.4 and above explicitly detect duplicate binary directories.  CMake 2.6.4 always considers this case an error.  In CMake 2.8.0 and above this policy determines whether or not the case is an error.  The OLD behavior for this policy is to allow duplicate binary directories.  The NEW behavior for this policy is to disallow duplicate binary directories with an error.

This policy was introduced in CMake version 2.8.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

if() recognizes numbers and boolean constants.

In CMake versions 2.6.4 and lower the if() command implicitly dereferenced arguments corresponding to variables, even those named like numbers or boolean constants, except for 0 and 1.  Numbers and boolean constants such as true, false, yes, no, on, off, y, n, notfound, ignore (all case insensitive) were recognized in some cases but not all.  For example, the code if(TRUE) might have evaluated as false. Numbers such as 2 were recognized only in boolean expressions like if(NOT 2) (leading to false) but not as a single-argument like if(2) (also leading to false).  Later versions of CMake prefer to treat numbers and boolean constants literally, so they should not be used as variable names.

The OLD behavior for this policy is to implicitly dereference variables named like numbers and boolean constants.  The NEW behavior for this policy is to recognize numbers and boolean constants without dereferencing variables with such names.

This policy was introduced in CMake version 2.8.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Included scripts do automatic cmake_policy() PUSH and POP.

In CMake 2.6.2 and below, CMake Policy settings in scripts loaded by the include() and find_package() commands would affect the includer.  Explicit invocations of cmake_policy(PUSH) and cmake_policy(POP) were required to isolate policy changes and protect the includer.  While some scripts intend to affect the policies of their includer, most do not.  In CMake 2.6.3 and above, include() and find_package() by default PUSH and POP an entry on the policy stack around an included script, but provide a NO_POLICY_SCOPE option to disable it.  This policy determines whether or not to imply NO_POLICY_SCOPE for compatibility.  The OLD behavior for this policy is to imply NO_POLICY_SCOPE for include() and find_package() commands. The NEW behavior for this policy is to allow the commands to do their default cmake_policy PUSH and POP.

This policy was introduced in CMake version 2.6.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Bad variable reference syntax is an error.

In CMake 2.6.2 and below, incorrect variable reference syntax such as a missing close-brace (${FOO) was reported but did not stop processing of CMake code.  This policy determines whether a bad variable reference is an error.  The OLD behavior for this policy is to warn about the error, leave the string untouched, and continue. The NEW behavior for this policy is to report an error.

If CMP0053 is set to NEW, this policy has no effect and is treated as always being NEW.

This policy was introduced in CMake version 2.6.3. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

FILE GLOB_RECURSE calls should not follow symlinks by default.

In CMake 2.6.1 and below, file(GLOB_RECURSE) calls would follow through symlinks, sometimes coming up with unexpectedly large result sets because of symlinks to top level directories that contain hundreds of thousands of files.

This policy determines whether or not to follow symlinks encountered during a file(GLOB_RECURSE) call.  The OLD behavior for this policy is to follow the symlinks.  The NEW behavior for this policy is not to follow the symlinks by default, but only if FOLLOW_SYMLINKS is given as an additional argument to the FILE command.

This policy was introduced in CMake version 2.6.2. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Libraries linked by full-path must have a valid library file name.

In CMake 2.4 and below it is possible to write code like

target_link_libraries(myexe /full/path/to/somelib)

where somelib is supposed to be a valid library file name such as libsomelib.a or somelib.lib.  For Makefile generators this produces an error at build time because the dependency on the full path cannot be found.  For Visual Studio Generators IDE and Xcode generators this used to work by accident because CMake would always split off the library directory and ask the linker to search for the library by name (-lsomelib or somelib.lib).  Despite the failure with Makefiles, some projects have code like this and build only with Visual Studio and/or Xcode. This version of CMake prefers to pass the full path directly to the native build tool, which will fail in this case because it does not name a valid library file.

This policy determines what to do with full paths that do not appear to name a valid library file.  The OLD behavior for this policy is to split the library name from the path and ask the linker to search for it.  The NEW behavior for this policy is to trust the given path and pass it directly to the native build tool unchanged.

This policy was introduced in CMake version 2.6.1. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

list command no longer ignores empty elements.

This policy determines whether the list command will ignore empty elements in the list.  CMake 2.4 and below list commands ignored all empty elements in the list.  For example, a;b;;c would have length 3 and not 4.  The OLD behavior for this policy is to ignore empty list elements.  The NEW behavior for this policy is to correctly count empty elements in a list.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Installing MACOSX_BUNDLE targets requires a BUNDLE DESTINATION.

This policy determines whether the install(TARGETS) command must be given a BUNDLE DESTINATION when asked to install a target with the MACOSX_BUNDLE property set.  CMake 2.4 and below did not distinguish application bundles from normal executables when installing targets. CMake 2.6 provides a BUNDLE option to the install(TARGETS) command that specifies rules specific to application bundles on the Mac. Projects should use this option when installing a target with the MACOSX_BUNDLE property set.

The OLD behavior for this policy is to fall back to the RUNTIME DESTINATION if a BUNDLE DESTINATION is not given.  The NEW behavior for this policy is to produce an error if a bundle target is installed without a BUNDLE DESTINATION.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Preprocessor definition values are now escaped automatically.

This policy determines whether or not CMake should generate escaped preprocessor definition values added via add_definitions.  CMake versions 2.4 and below assumed that only trivial values would be given for macros in add_definitions calls.  It did not attempt to escape non-trivial values such as string literals in generated build rules. CMake versions 2.6 and above support escaping of most values, but cannot assume the user has not added escapes already in an attempt to work around limitations in earlier versions.

The OLD behavior for this policy is to place definition values given to add_definitions directly in the generated build rules without attempting to escape anything.  The NEW behavior for this policy is to generate correct escapes for all native build tools automatically. See documentation of the COMPILE_DEFINITIONS target property for limitations of the escaping implementation.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Libraries linked may not have leading or trailing whitespace.

CMake versions 2.4 and below silently removed leading and trailing whitespace from libraries linked with code like

target_link_libraries(myexe " A ")

This could lead to subtle errors in user projects.

The OLD behavior for this policy is to silently remove leading and trailing whitespace.  The NEW behavior for this policy is to diagnose the existence of such whitespace as an error.  The setting for this policy used when checking the library names is that in effect when the target is created by an add_executable() or add_library() command.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Libraries linked via full path no longer produce linker search paths.

This policy affects how libraries whose full paths are NOT known are found at link time, but was created due to a change in how CMake deals with libraries whose full paths are known.  Consider the code

target_link_libraries(myexe /path/to/libA.so)

CMake 2.4 and below implemented linking to libraries whose full paths are known by splitting them on the link line into separate components consisting of the linker search path and the library name.  The example code might have produced something like

... -L/path/to -lA ...

in order to link to library A.  An analysis was performed to order multiple link directories such that the linker would find library A in the desired location, but there are cases in which this does not work. CMake versions 2.6 and above use the more reliable approach of passing the full path to libraries directly to the linker in most cases.  The example code now produces something like

... /path/to/libA.so ....

Unfortunately this change can break code like

target_link_libraries(myexe /path/to/libA.so B)

where B is meant to find /path/to/libB.so.  This code is wrong because the user is asking the linker to find library B but has not provided a linker search path (which may be added with the link_directories command).  However, with the old linking implementation the code would work accidentally because the linker search path added for library A allowed library B to be found.

In order to support projects depending on linker search paths added by linking to libraries with known full paths, the OLD behavior for this policy will add the linker search paths even though they are not needed for their own libraries.  When this policy is set to OLD, CMake will produce a link line such as

... -L/path/to /path/to/libA.so -lB ...

which will allow library B to be found as it was previously.  When this policy is set to NEW, CMake will produce a link line such as

... /path/to/libA.so -lB ...

which more accurately matches what the project specified.

The setting for this policy used when generating the link line is that in effect when the target is created by an add_executable or add_library command.  For the example described above, the code

cmake_policy(SET CMP0003 OLD) # or cmake_policy(VERSION 2.4)
add_executable(myexe myexe.c)
target_link_libraries(myexe /path/to/libA.so B)

will work and suppress the warning for this policy.  It may also be updated to work with the corrected linking approach:

cmake_policy(SET CMP0003 NEW) # or cmake_policy(VERSION 2.6)
link_directories(/path/to) # needed to find library B
add_executable(myexe myexe.c)
target_link_libraries(myexe /path/to/libA.so B)

Even better, library B may be specified with a full path:

add_executable(myexe myexe.c)
target_link_libraries(myexe /path/to/libA.so /path/to/libB.so)

When all items on the link line have known paths CMake does not check this policy so it has no effect.

Note that the warning for this policy will be issued for at most one target.  This avoids flooding users with messages for every target when setting the policy once will probably fix all targets.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

Logical target names must be globally unique.

Targets names created with add_executable(), add_library(), or add_custom_target() are logical build target names.  Logical target names must be globally unique because:

- Unique names may be referenced unambiguously both in CMake
  code and on make tool command lines.
- Logical names are used by Xcode and VS IDE generators
  to produce meaningful project names for the targets.

The logical name of executable and library targets does not have to correspond to the physical file names built.  Consider using the OUTPUT_NAME target property to create two targets with the same physical name while keeping logical names distinct.  Custom targets must simply have globally unique names (unless one uses the global property ALLOW_DUPLICATE_CUSTOM_TARGETS with a Makefiles generator).

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

CMAKE_BACKWARDS_COMPATIBILITY should no longer be used.

The behavior is to check CMAKE_BACKWARDS_COMPATIBILITY and present it to the user.  The NEW behavior is to ignore CMAKE_BACKWARDS_COMPATIBILITY completely.

In CMake 2.4 and below the variable CMAKE_BACKWARDS_COMPATIBILITY was used to request compatibility with earlier versions of CMake.  In CMake 2.6 and above all compatibility issues are handled by policies and the cmake_policy() command.  However, CMake must still check CMAKE_BACKWARDS_COMPATIBILITY for projects written for CMake 2.4 and below.

This policy was introduced in CMake version 2.6.0. It may be set by cmake_policy() or cmake_minimum_required(). If it is not set, CMake warns, and uses OLD behavior.

NOTE:

A minimum required CMake version must be specified.

CMake requires that projects specify the version of CMake to which they have been written.  This policy has been put in place so users trying to build the project may be told when they need to update their CMake.  Specifying a version also helps the project build with CMake versions newer than that specified.  Use the cmake_minimum_required() command at the top of your main CMakeLists.txt file:

cmake_minimum_required(VERSION <major>.<minor>)

where <major>.<minor> is the version of CMake you want to support (such as 3.14).  The command will ensure that at least the given version of CMake is running and help newer versions be compatible with the project.  See documentation of cmake_minimum_required() for details.

Note that the command invocation must appear in the CMakeLists.txt file itself; a call in an included file is not sufficient.  However, the  cmake_policy() command may be called to set policy CMP0000 to OLD or NEW behavior explicitly.  The OLD behavior is to silently ignore the missing invocation.  The NEW behavior is to issue an error instead of a warning.  An included file may set CMP0000 explicitly to affect how this policy is enforced for the main CMakeLists.txt file.

This policy was introduced in CMake version 2.6.0.

NOTE: