Provided by: cmake-data_3.30.3-1_all 
NAME
cmake-policies - CMake Policies Reference
INTRODUCTION
Policies in CMake are used to preserve backward compatible behavior across multiple releases. When a new
policy is introduced, newer CMake versions will begin to warn about the backward compatible behavior. It
is possible to disable the warning by explicitly requesting the OLD, or backward compatible behavior
using the cmake_policy() command. It is also possible to request NEW, or non-backward compatible
behavior for a policy, also avoiding the warning. Each policy can also be set to either NEW or OLD
behavior explicitly on the command line with the CMAKE_POLICY_DEFAULT_CMP<NNNN> variable.
A policy is a deprecation mechanism and not a reliable feature toggle. A policy should almost never be
set to OLD, except to silence warnings in an otherwise frozen or stable codebase, or temporarily as part
of a larger migration path. The OLD behavior of each policy is undesirable and will be replaced with an
error condition in a future release.
The cmake_minimum_required() command does more than report an error if a too-old version of CMake is used
to build a project. It also sets all policies introduced in that CMake version or earlier to NEW
behavior. To manage policies without increasing the minimum required CMake version, the if(POLICY)
command may be used:
if(POLICY CMP0990)
cmake_policy(SET CMP0990 NEW)
endif()
This has the effect of using the NEW behavior with newer CMake releases which users may be using and not
issuing a compatibility warning.
The setting of a policy is confined in some cases to not propagate to the parent scope. For example, if
the files read by the include() command or the find_package() command contain a use of cmake_policy(),
that policy setting will not affect the caller by default. Both commands accept an optional
NO_POLICY_SCOPE keyword to control this behavior.
The CMAKE_MINIMUM_REQUIRED_VERSION variable may also be used to determine whether to report an error on
use of deprecated macros or functions.
POLICIES INTRODUCED BY CMAKE 3.30
CMP0170
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0169
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:
Calling FetchContent_Populate() with the full population details as command arguments rather than just
a dependency name remains fully supported. Only the form calling FetchContent_Populate() with a single
argument (the name of a previously declared dependency) is deprecated with 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 warns, and uses OLD behavior.
NOTE:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0168
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0167
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0166
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0165
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0164
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0163
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0162
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.29
CMP0161
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0160
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0159
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0158
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0157
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:
Once the policy has taken effect at the top of a project, that choice must be used throughout the
tree. In projects that have nested projects in subdirectories, be sure to convert everything together.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0156
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.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.28
CMP0155
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0154
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0153
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0152
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.27
CMP0151
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0150
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0149
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:
This policy must be set before the first project() or enable_language() command invocation at the top
of the project. That is when Visual Studio Generators select a Windows SDK.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0148
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0147
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0146
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0145
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0144
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.26
CMP0143
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.25
CMP0142
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0141
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:
Once the policy has taken effect at the top of a project, that choice will be used throughout the
tree. In projects that have nested projects in subdirectories, be sure to confirm if everything is
working with the selected policy behavior.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0140
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.24
CMP0139
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0138
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0137
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0136
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:
Once the policy has taken effect at the top of a project, that choice must be used throughout the
tree. In projects that have nested projects in subdirectories, be sure to convert everything
together.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0135
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0134
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0133
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0132
Added in version 3.24.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0131
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 $<LINK_ONLY:...> even for
non-linking usage requirements. The NEW behavior for this policy is to use the guarded content only for
link dependencies.
This policy was introduced in CMake version 3.24. It may be set by cmake_policy() or
cmake_minimum_required(). If it is not set, CMake does not warn, and uses OLD behavior.
NOTE:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0130
Added in version 3.24.
while() diagnoses condition evaluation errors.
CMake 3.23 and below accidentally tolerated errors encountered while evaluating the condition passed to
the while() command (but not the if() command). For example, the code
set(paren "(")
while(${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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.23
CMP0129
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.22
CMP0128
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0127
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.21
CMP0126
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0125
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0124
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0123
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0122
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0121
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.20
CMP0120
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0119
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0118
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0117
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:
Once the policy has taken effect at the top of a project for a given language, that choice must be
used throughout the tree for that language. In projects that have nested projects in subdirectories,
be sure to convert everything together.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0116
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0115
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.19
CMP0114
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0113
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0112
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0111
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0110
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0109
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.18
CMP0108
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0107
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0106
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0105
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0104
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
Examples
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.
CMP0103
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.17
CMP0102
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0101
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0100
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:
To silence the CMP0100 warning source files can be excluded from AUTOMOC and AUTOUIC processing by
setting the source file properties SKIP_AUTOMOC, SKIP_AUTOUIC or SKIP_AUTOGEN.
# 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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0099
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0098
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.16
CMP0097
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.
CMP0096
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0095
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.15
CMP0094
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0093
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0092
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:
Once the policy has taken effect at the top of a project for a given language, that choice must be
used throughout the tree for that language. In projects that have nested projects in subdirectories,
be sure to convert everything together.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0091
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:
Once the policy has taken effect at the top of a project, that choice must be used throughout the
tree. In projects that have nested projects in subdirectories, be sure to convert everything
together.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0090
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0089
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.14
CMP0088
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0087
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0086
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0085
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0084
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0083
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.
Examples
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)
CMP0082
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.13
CMP0081
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0080
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0079
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0078
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0077
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0076
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.12
CMP0075
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0074
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0073
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.11
CMP0072
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.10
CMP0071
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:
To silence the CMP0071 warning source files can be excluded from AUTOMOC and AUTOUIC processing by
setting the source file properties SKIP_AUTOMOC, SKIP_AUTOUIC or SKIP_AUTOGEN.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0070
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.9
CMP0069
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
Examples
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)
CMP0068
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.8
CMP0067
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.7
CMP0066
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.4
CMP0065
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0064
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.3
CMP0063
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0062
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0061
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0060
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0059
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0058
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.
Introducing Byproducts
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0057
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.2
CMP0056
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0055
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.1
CMP0054
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0053
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0052
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0051
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 3.0
CMP0050
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0049
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0048
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0047
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0046
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0045
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0044
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0043
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0042
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0041
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0040
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0039
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0038
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0037
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0036
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0035
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0034
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0033
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0032
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0031
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0030
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 OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0029
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0028
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0027
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0026
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0025
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0024
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 2.8
CMP0023
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0022
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0021
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0020
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0019
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0018
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0017
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0016
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0015
link_directories() treats paths relative to the source dir.
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0014
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0013
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0012
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
POLICIES INTRODUCED BY CMAKE 2.6
CMP0011
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0010
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0009
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0008
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0007
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0006
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0005
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0004
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0003
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0002
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0001
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
CMP0000
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:
The OLD behavior of a policy is deprecated by definition and may be removed in a future version of
CMake.
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