NAME
cmakepolicies - Reference of CMake policies.
DESCRIPTION
The "cmake" executable is the CMake command-line interface. It may be
used to configure projects in scripts. Project configuration settings
may be specified on the command line with the -D option. The -i option
will cause cmake to interactively prompt for such settings.
CMake is a cross-platform build system generator. Projects specify
their build process with platform-independent CMake listfiles included
in each directory of a source tree with the name CMakeLists.txt. Users
build a project by using CMake to generate a build system for a native
tool on their platform.
POLICIES
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 "2.6"). 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.
CMP0001
CMAKE_BACKWARDS_COMPATIBILITY should no longer be used.
The OLD 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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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 VS 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 VS 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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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.
This policy was introduced in CMake version 2.6.3. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
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 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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
CMP0015
link_directories() treats paths relative to the source dir.
In CMake 2.6.4 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. CMake
version 2.8.2 warns when the policy is not set and uses OLD
behavior. Use the cmake_policy command to set it to OLD or NEW
explicitly.
COPYRIGHT
Copyright 2000-2009 Kitware, Inc., Insight Software Consortium. All
rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
Neither the names of Kitware, Inc., the Insight Software Consortium,
nor the names of their contributors may be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
SEE ALSO
ccmake(1), cpack(1), ctest(1), cmakecommands(1), cmakecompat(1),
cmakemodules(1), cmakeprops(1), cmakevars(1)
The following resources are available to get help using CMake:
Home Page
http://www.cmake.org
The primary starting point for learning about CMake.
Frequently Asked Questions
http://www.cmake.org/Wiki/CMake_FAQ
A Wiki is provided containing answers to frequently asked
questions.
Online Documentation
http://www.cmake.org/HTML/Documentation.html
Links to available documentation may be found on this web page.
Mailing List
http://www.cmake.org/HTML/MailingLists.html
For help and discussion about using cmake, a mailing list is
provided at cmake@cmake.org. The list is member-post-only but
one may sign up on the CMake web page. Please first read the
full documentation at http://www.cmake.org before posting
questions to the list.
Summary of helpful links:
Home: http://www.cmake.org
Docs: http://www.cmake.org/HTML/Documentation.html
Mail: http://www.cmake.org/HTML/MailingLists.html
FAQ: http://www.cmake.org/Wiki/CMake_FAQ