Merge branch 'release-4.0'

[kiteware-cmake.git] / Modules / ExternalProject.cmake

# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.

include_guard(GLOBAL)

#[=======================================================================[.rst:
ExternalProject
---------------

.. only:: html

   .. contents::

External Project Definition
^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. command:: ExternalProject_Add

  The ``ExternalProject_Add()`` function creates a custom target to drive
  download, update/patch, configure, build, install and test steps of an
  external project:

  .. code-block:: cmake

    ExternalProject_Add(<name> [<option>...])

  The individual steps within the process can be driven independently if
  required (e.g. for CDash submission) and extra custom steps can be defined,
  along with the ability to control the step dependencies. The directory
  structure used for the management of the external project can also be
  customized. The function supports a large number of options which can be used
  to tailor the external project behavior.

Directory Options
"""""""""""""""""

Most of the time, the default directory layout is sufficient. It is largely
an implementation detail that the main project usually doesn't need to
change. In some circumstances, however, control over the directory layout
can be useful or necessary. The directory options are potentially more
useful from the point of view that the main build can use the
:command:`ExternalProject_Get_Property` command to retrieve their values,
thereby allowing the main project to refer to build artifacts of the
external project.

``PREFIX <dir>``
  Root directory for the external project. Unless otherwise noted below,
  all other directories associated with the external project will be
  created under here.

``TMP_DIR <dir>``
  Directory in which to store temporary files.

``STAMP_DIR <dir>``
  Directory in which to store the timestamps of each step. Log files from
  individual steps are also created in here unless overridden by LOG_DIR
  (see *Logging Options* below).

``LOG_DIR <dir>``
  .. versionadded:: 3.14

  Directory in which to store the logs of each step.

``DOWNLOAD_DIR <dir>``
  Directory in which to store downloaded files before unpacking them. This
  directory is only used by the URL download method, all other download
  methods use ``SOURCE_DIR`` directly instead.

``SOURCE_DIR <dir>``
  Source directory into which downloaded contents will be unpacked, or for
  non-URL download methods, the directory in which the repository should be
  checked out, cloned, etc. If no download method is specified, this must
  point to an existing directory where the external project has already
  been unpacked or cloned/checked out.

  .. note::
      If a download method is specified, any existing contents of the source
      directory may be deleted. Only the URL download method checks whether
      this directory is either missing or empty before initiating the
      download, stopping with an error if it is not empty. All other
      download methods silently discard any previous contents of the source
      directory.

``BINARY_DIR <dir>``
  Specify the build directory location. This option is ignored if
  ``BUILD_IN_SOURCE`` is enabled.

``INSTALL_DIR <dir>``
  Installation prefix to be placed in the ``<INSTALL_DIR>`` placeholder.
  This does not actually configure the external project to install to
  the given prefix. That must be done by passing appropriate arguments
  to the external project configuration step, e.g. using ``<INSTALL_DIR>``.

If any of the above ``..._DIR`` options are not specified, their defaults
are computed as follows. If the ``PREFIX`` option is given or the
``EP_PREFIX`` directory property is set, then an external project is built
and installed under the specified prefix::

  TMP_DIR      = <prefix>/tmp
  STAMP_DIR    = <prefix>/src/<name>-stamp
  DOWNLOAD_DIR = <prefix>/src
  SOURCE_DIR   = <prefix>/src/<name>
  BINARY_DIR   = <prefix>/src/<name>-build
  INSTALL_DIR  = <prefix>
  LOG_DIR      = <STAMP_DIR>

Otherwise, if the ``EP_BASE`` directory property is set then components
of an external project are stored under the specified base::

  TMP_DIR      = <base>/tmp/<name>
  STAMP_DIR    = <base>/Stamp/<name>
  DOWNLOAD_DIR = <base>/Download/<name>
  SOURCE_DIR   = <base>/Source/<name>
  BINARY_DIR   = <base>/Build/<name>
  INSTALL_DIR  = <base>/Install/<name>
  LOG_DIR      = <STAMP_DIR>

If no ``PREFIX``, ``EP_PREFIX``, or ``EP_BASE`` is specified, then the
default is to set ``PREFIX`` to ``<name>-prefix``. Relative paths are
interpreted with respect to :variable:`CMAKE_CURRENT_BINARY_DIR` at the
point where ``ExternalProject_Add()`` is called.

Download Step Options
"""""""""""""""""""""

A download method can be omitted if the ``SOURCE_DIR`` option is used to
point to an existing non-empty directory. Otherwise, one of the download
methods below must be specified (multiple download methods should not be
given) or a custom ``DOWNLOAD_COMMAND`` provided.

``DOWNLOAD_COMMAND <cmd>...``
  Overrides the command used for the download step
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). If this option is specified, all other download options will
  be ignored. Providing an empty string for ``<cmd>`` effectively disables
  the download step.

URL
~~~

``URL <url1> [<url2>...]``
  List of paths and/or URL(s) of the external project's source. When more
  than one URL is given, they are tried in turn until one succeeds. A URL
  may be an ordinary path in the local file system (in which case it
  must be the only URL provided) or any downloadable URL supported by the
  :command:`file(DOWNLOAD)` command. A local filesystem path may refer to
  either an existing directory or to an archive file, whereas a URL is
  expected to point to a file which can be treated as an archive. When an
  archive is used, it will be unpacked automatically unless the
  ``DOWNLOAD_NO_EXTRACT`` option is set to prevent it. The archive type
  is determined by inspecting the actual content rather than using logic
  based on the file extension.

  .. versionchanged:: 3.7
    Multiple URLs are allowed.

``URL_HASH <algo>=<hashValue>``
  Hash of the archive file to be downloaded. The argument should be of
  the form ``<algo>=<hashValue>`` where ``algo`` can be any of the hashing
  algorithms supported by the :command:`file()` command. Specifying this
  option is strongly recommended for URL downloads, as it ensures the
  integrity of the downloaded content. It is also used as a check for a
  previously downloaded file, allowing connection to the remote location
  to be avoided altogether if the local directory already has a file from
  an earlier download that matches the specified hash.

``URL_MD5 <md5>``
  Equivalent to ``URL_HASH MD5=<md5>``.

``DOWNLOAD_NAME <fname>``
  File name to use for the downloaded file. If not given, the end of the
  URL is used to determine the file name. This option is rarely needed,
  the default name is generally suitable and is not normally used outside
  of code internal to the ``ExternalProject`` module.

``DOWNLOAD_EXTRACT_TIMESTAMP <bool>``
  .. versionadded:: 3.24

  When specified with a true value, the timestamps of the extracted
  files will match those in the archive. When false, the timestamps of
  the extracted files will reflect the time at which the extraction
  was performed. If the download URL changes, timestamps based off
  those in the archive can result in dependent targets not being rebuilt
  when they potentially should have been. Therefore, unless the file
  timestamps are significant to the project in some way, use a false
  value for this option. If ``DOWNLOAD_EXTRACT_TIMESTAMP`` is not given,
  the default is false. See policy :policy:`CMP0135`.

``DOWNLOAD_NO_EXTRACT <bool>``
  .. versionadded:: 3.6

  Allows the extraction part of the download step to be disabled by
  passing a boolean true value for this option. If this option is not
  given, the downloaded contents will be unpacked automatically if
  required. If extraction has been disabled, the full path to the
  downloaded file is available as ``<DOWNLOADED_FILE>`` in subsequent
  steps or as the property ``DOWNLOADED_FILE`` with the
  :command:`ExternalProject_Get_Property` command.

``DOWNLOAD_NO_PROGRESS <bool>``
  Can be used to disable logging the download progress. If this option is
  not given, download progress messages will be logged.

``TIMEOUT <seconds>``
  Maximum time allowed for file download operations.

``INACTIVITY_TIMEOUT <seconds>``
  .. versionadded:: 3.19

  Terminate the operation after a period of inactivity.

``HTTP_USERNAME <username>``
  .. versionadded:: 3.7

  Username for the download operation if authentication is required.

``HTTP_PASSWORD <password>``
  .. versionadded:: 3.7

  Password for the download operation if authentication is required.

``HTTP_HEADER <header1> [<header2>...]``
  .. versionadded:: 3.7

  Provides an arbitrary list of HTTP headers for the download operation.
  This can be useful for accessing content in systems like AWS, etc.

``TLS_VERSION <min>``
  .. versionadded:: 3.30

  Specify minimum TLS version for ``https://`` URLs.  If this option is
  not provided, the value of the :variable:`CMAKE_TLS_VERSION` variable
  or the :envvar:`CMAKE_TLS_VERSION` environment variable will be used
  instead (see :command:`file(DOWNLOAD)`).

  This option also applies to ``git clone`` invocations, although the
  default behavior is different.  If none of the ``TLS_VERSION`` option,
  :variable:`CMAKE_TLS_VERSION` variable, or :envvar:`CMAKE_TLS_VERSION`
  environment variable is specified, the behavior will be determined by
  git's default or a ``http.sslVersion`` git config option the user may
  have set at a global level.

``TLS_VERIFY <bool>``
  Specifies whether certificate verification should be performed for
  ``https://`` URLs.  If this option is not provided, the value of the
  :variable:`CMAKE_TLS_VERIFY` variable or the :envvar:`CMAKE_TLS_VERIFY`
  environment variable will be used instead (see :command:`file(DOWNLOAD)`).
  If neither of those is set, certificate verification will not be performed.
  In situations where ``URL_HASH`` cannot be provided, this option can
  be an alternative verification measure.

  This option also applies to ``git clone`` invocations, although the
  default behavior is different.  If none of the ``TLS_VERIFY`` option,
  :variable:`CMAKE_TLS_VERIFY` variable, or :envvar:`CMAKE_TLS_VERIFY`
  environment variable is specified, the behavior will be determined by
  git's default (true) or a ``http.sslVerify`` git config option the
  user may have set at a global level.

  .. versionchanged:: 3.6

    Previously this option did not apply to ``git clone`` invocations.

  .. versionchanged:: 3.30

    Previously the :envvar:`CMAKE_TLS_VERIFY` environment variable
    was not checked.

``TLS_CAINFO <file>``
  Specify a custom certificate authority file to use if ``TLS_VERIFY``
  is enabled. If this option is not specified, the value of the
  :variable:`CMAKE_TLS_CAINFO` variable will be used instead (see
  :command:`file(DOWNLOAD)`)

``NETRC <level>``
  .. versionadded:: 3.11

  Specify whether the ``.netrc`` file is to be used for operation.
  If this option is not specified, the value of the
  :variable:`CMAKE_NETRC` variable will be used instead
  (see :command:`file(DOWNLOAD)`).  Valid levels are:

  ``IGNORED``
    The ``.netrc`` file is ignored.
    This is the default.
  ``OPTIONAL``
    The ``.netrc`` file is optional, and information in the URL
    is preferred.  The file will be scanned to find which ever
    information is not specified in the URL.
  ``REQUIRED``
    The ``.netrc`` file is required, and information in the URL
    is ignored.

``NETRC_FILE <file>``
  .. versionadded:: 3.11

  Specify an alternative ``.netrc`` file to the one in your home directory
  if the ``NETRC`` level is ``OPTIONAL`` or ``REQUIRED``. If this option
  is not specified, the value of the :variable:`CMAKE_NETRC_FILE` variable
  will be used instead (see :command:`file(DOWNLOAD)`)

.. versionadded:: 3.1
  Added support for `tbz2`, `.tar.xz`, `.txz`, and `.7z` extensions.

Git
~~~

NOTE: A git version of 1.6.5 or later is required if this download method
is used.

``GIT_REPOSITORY <url>``
  URL of the git repository. Any URL understood by the ``git`` command
  may be used.

  .. versionchanged:: 3.27
    A relative URL will be resolved based on the parent project's
    remote, subject to :policy:`CMP0150`.  See the policy documentation
    for how the remote is selected, including conditions where the
    remote selection can fail.  Local filesystem remotes should
    always use absolute paths.

``GIT_TAG <tag>``
  Git branch name, tag or commit hash. Note that branch names and tags
  should generally be specified as remote names (i.e. ``origin/myBranch``
  rather than simply ``myBranch``). This ensures that if the remote end
  has its tag moved or branch rebased or history rewritten, the local
  clone will still be updated correctly. In general, however, specifying
  a commit hash should be preferred for a number of reasons:

  - If the local clone already has the commit corresponding to the hash,
    no ``git fetch`` needs to be performed to check for changes each time
    CMake is re-run. This can result in a significant speed up if many
    external projects are being used.
  - Using a specific git hash ensures that the main project's own history
    is fully traceable to a specific point in the external project's
    evolution. If a branch or tag name is used instead, then checking out
    a specific commit of the main project doesn't necessarily pin the
    whole build to a specific point in the life of the external project.
    The lack of such deterministic behavior makes the main project lose
    traceability and repeatability.

  If ``GIT_SHALLOW`` is enabled then ``GIT_TAG`` works only with
  branch names and tags.  A commit hash is not allowed.

  Note that if not provided, ``GIT_TAG`` defaults to ``master``, not the
  default Git branch name.

``GIT_REMOTE_NAME <name>``
  The optional name of the remote. If this option is not specified, it
  defaults to ``origin``.

``GIT_SUBMODULES <module>...``
  Specific git submodules that should also be updated. If this option is
  not provided, all git submodules will be updated.

  .. versionchanged:: 3.16
    When :policy:`CMP0097` is set to ``NEW``, if this value is set
    to an empty string then no submodules are initialized or updated.

``GIT_SUBMODULES_RECURSE <bool>``
  .. versionadded:: 3.17

  Specify whether git submodules (if any) should update recursively by
  passing the ``--recursive`` flag to ``git submodule update``.
  If not specified, the default is on.

``GIT_SHALLOW <bool>``
  .. versionadded:: 3.6

  When this option is enabled, the ``git clone`` operation will be given
  the ``--depth 1`` option. This performs a shallow clone, which avoids
  downloading the whole history and instead retrieves just the commit
  denoted by the ``GIT_TAG`` option.

``GIT_PROGRESS <bool>``
  .. versionadded:: 3.8

  When enabled, this option instructs the ``git clone`` operation to
  report its progress by passing it the ``--progress`` option. Without
  this option, the clone step for large projects may appear to make the
  build stall, since nothing will be logged until the clone operation
  finishes. While this option can be used to provide progress to prevent
  the appearance of the build having stalled, it may also make the build
  overly noisy if lots of external projects are used.

``GIT_CONFIG <option1> [<option2>...]``
  .. versionadded:: 3.8

  Specify a list of config options to pass to ``git clone``. Each option
  listed will be transformed into its own ``--config <option>`` on the
  ``git clone`` command line, with each option required to be in the
  form ``key=value``.

``GIT_REMOTE_UPDATE_STRATEGY <strategy>``
  .. versionadded:: 3.18

  When ``GIT_TAG`` refers to a remote branch, this option can be used to
  specify how the update step behaves.  The ``<strategy>`` must be one of
  the following:

  ``CHECKOUT``
    Ignore the local branch and always checkout the branch specified by
    ``GIT_TAG``.

  ``REBASE``
    Try to rebase the current branch to the one specified by ``GIT_TAG``.
    If there are local uncommitted changes, they will be stashed first
    and popped again after rebasing.  If rebasing or popping stashed
    changes fail, abort the rebase and halt with an error.
    When ``GIT_REMOTE_UPDATE_STRATEGY`` is not present, this is the
    default strategy unless the default has been overridden with
    ``CMAKE_EP_GIT_REMOTE_UPDATE_STRATEGY`` (see below).
    Note that if the branch specified in ``GIT_TAG`` is different to
    the upstream branch currently being tracked, it is not safe to
    perform a rebase. In that situation, ``REBASE`` will silently be
    treated as ``CHECKOUT`` instead.

  ``REBASE_CHECKOUT``
    Same as ``REBASE`` except if the rebase fails, an annotated tag will
    be created at the original ``HEAD`` position from before the rebase
    and then checkout ``GIT_TAG`` just like the ``CHECKOUT`` strategy.
    The message stored on the annotated tag will give information about
    what was attempted and the tag name will include a timestamp so that
    each failed run will add a new tag.  This strategy ensures no changes
    will be lost, but updates should always succeed if ``GIT_TAG`` refers
    to a valid ref unless there are uncommitted changes that cannot be
    popped successfully.

  The variable ``CMAKE_EP_GIT_REMOTE_UPDATE_STRATEGY`` can be set to
  override the default strategy.  This variable should not be set by a
  project, it is intended for the user to set.  It is primarily intended
  for use in continuous integration scripts to ensure that when history
  is rewritten on a remote branch, the build doesn't end up with
  unintended changes or failed builds resulting from conflicts during
  rebase operations.

Subversion
~~~~~~~~~~

``SVN_REPOSITORY <url>``
  URL of the Subversion repository.

``SVN_REVISION -r<rev>``
  Revision to checkout from the Subversion repository.

``SVN_USERNAME <username>``
  Username for the Subversion checkout and update.

``SVN_PASSWORD <password>``
  Password for the Subversion checkout and update.

``SVN_TRUST_CERT <bool>``
  Specifies whether to trust the Subversion server site certificate. If
  enabled, the ``--trust-server-cert`` option is passed to the ``svn``
  checkout and update commands.

Mercurial
~~~~~~~~~

``HG_REPOSITORY <url>``
  URL of the mercurial repository.

``HG_TAG <tag>``
  Mercurial branch name, tag or commit id.

CVS
~~~

``CVS_REPOSITORY <cvsroot>``
  CVSROOT of the CVS repository.

``CVS_MODULE <mod>``
  Module to checkout from the CVS repository.

``CVS_TAG <tag>``
  Tag to checkout from the CVS repository.

Update Step Options
"""""""""""""""""""

Whenever CMake is re-run, by default the external project's sources will be
updated if the download method supports updates (e.g. a git repository
would be checked if the ``GIT_TAG`` does not refer to a specific commit).

``UPDATE_COMMAND <cmd>...``
  Overrides the download method's update step with a custom command.
  The command may use
  :manual:`generator expressions <cmake-generator-expressions(7)>`.

``UPDATE_DISCONNECTED <bool>``
  .. versionadded:: 3.2

  When enabled, this option causes the update step to be skipped (but see
  below for changed behavior where this is not the case). It does not
  prevent the download step. The update step can still be
  added as a step target (see :command:`ExternalProject_Add_StepTargets`)
  and called manually. This is useful if you want to allow developers to
  build the project when disconnected from the network (the network may
  still be needed for the download step though).

  .. versionchanged:: 3.27

    When ``UPDATE_DISCONNECTED`` is true, the update step will be executed
    if any details about the update or download step are changed.
    Furthermore, if using the git download/update method, the update
    logic will be modified to skip attempts to contact the remote.
    If the ``GIT_TAG`` mentions a ref that is not known locally, the
    update step will halt with a fatal error.

  When this option is present, it is generally advisable to make the value
  a cache variable under the developer's control rather than hard-coding
  it. If this option is not present, the default value is taken from the
  ``EP_UPDATE_DISCONNECTED`` directory property. If that is also not
  defined, updates are performed as normal. The ``EP_UPDATE_DISCONNECTED``
  directory property is intended as a convenience for controlling the
  ``UPDATE_DISCONNECTED`` behavior for an entire section of a project's
  directory hierarchy and may be a more convenient method of giving
  developers control over whether or not to perform updates (assuming the
  project also provides a cache variable or some other convenient method
  for setting the directory property).

  This may cause a step target to be created automatically for the
  ``download`` step.  See policy :policy:`CMP0114`.

Patch Step Options
""""""""""""""""""

``PATCH_COMMAND <cmd>...``
  Specifies a custom command to patch the sources after an update. By
  default, no patch command is defined. Note that it can be quite difficult
  to define an appropriate patch command that performs robustly, especially
  for download methods such as git where changing the ``GIT_TAG`` will not
  discard changes from a previous patch, but the patch command will be
  called again after updating to the new tag.

Configure Step Options
""""""""""""""""""""""

The configure step is run after the download and update steps. By default,
the external project is assumed to be a CMake project, but this can be
overridden if required.

``CONFIGURE_COMMAND <cmd>...``
  The default configure command runs CMake with a few options based on
  the main project.  The options added are typically only those needed to
  use the same generator as the main project, but the ``CMAKE_GENERATOR``
  option can be given to override this.  The project is responsible for
  adding any toolchain details, flags or other settings it wants to
  reuse from the main project or otherwise specify (see ``CMAKE_ARGS``,
  ``CMAKE_CACHE_ARGS`` and ``CMAKE_CACHE_DEFAULT_ARGS`` below).

  For non-CMake external projects, the ``CONFIGURE_COMMAND`` option must
  be used to override the default configure command
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). For projects that require no configure step, specify this
  option with an empty string as the command to execute.

``CMAKE_COMMAND /.../cmake``
  Specify an alternative cmake executable for the configure step (use an
  absolute path). This is generally not recommended, since it is
  usually desirable to use the same CMake version throughout the whole
  build. This option is ignored if a custom configure command has been
  specified with ``CONFIGURE_COMMAND``.

``CMAKE_GENERATOR <gen>``
  Override the CMake generator used for the configure step. Without this
  option, the same generator as the main build will be used. This option is
  ignored if a custom configure command has been specified with the
  ``CONFIGURE_COMMAND`` option.

``CMAKE_GENERATOR_PLATFORM <platform>``
  .. versionadded:: 3.1

  Pass a generator-specific platform name to the CMake command (see
  :variable:`CMAKE_GENERATOR_PLATFORM`). It is an error to provide this
  option without the ``CMAKE_GENERATOR`` option.

``CMAKE_GENERATOR_TOOLSET <toolset>``
  Pass a generator-specific toolset name to the CMake command (see
  :variable:`CMAKE_GENERATOR_TOOLSET`). It is an error to provide this
  option without the ``CMAKE_GENERATOR`` option.

``CMAKE_GENERATOR_INSTANCE <instance>``
  .. versionadded:: 3.11

  Pass a generator-specific instance selection to the CMake command (see
  :variable:`CMAKE_GENERATOR_INSTANCE`). It is an error to provide this
  option without the ``CMAKE_GENERATOR`` option.

``CMAKE_ARGS <arg>...``
  The specified arguments are passed to the :program:`cmake` command line.
  They can be any argument the :program:`cmake` command understands, not just
  cache values defined by ``-D...`` arguments (see also
  :manual:`CMake Options <cmake(1)>`).

  .. versionadded:: 3.3
    Arguments may use
    :manual:`generator expressions <cmake-generator-expressions(7)>`.

``CMAKE_CACHE_ARGS <arg>...``
  This is an alternate way of specifying cache variables where command line
  length issues may become a problem. The arguments are expected to be in
  the form ``-Dvar:STRING=value``, which are then transformed into
  CMake :command:`set` commands with the ``FORCE`` option used. These
  ``set()`` commands are written to a pre-load script which is then applied
  using the :manual:`cmake -C <cmake(1)>` command line option.

  .. versionadded:: 3.3
    Arguments may use
    :manual:`generator expressions <cmake-generator-expressions(7)>`.

``CMAKE_CACHE_DEFAULT_ARGS <arg>...``
  .. versionadded:: 3.2

  This is the same as the ``CMAKE_CACHE_ARGS`` option except the ``set()``
  commands do not include the ``FORCE`` keyword. This means the values act
  as initial defaults only and will not override any variables already set
  from a previous run. Use this option with care, as it can lead to
  different behavior depending on whether the build starts from a fresh
  build directory or reuses previous build contents.

  .. versionadded:: 3.15
    If the CMake generator is the ``Green Hills MULTI`` and not overridden,
    the original project's settings for the GHS toolset and target system
    customization cache variables are propagated into the external project.

``SOURCE_SUBDIR <dir>``
  .. versionadded:: 3.7

  When no ``CONFIGURE_COMMAND`` option is specified, the configure step
  assumes the external project has a ``CMakeLists.txt`` file at the top of
  its source tree (i.e. in ``SOURCE_DIR``). The ``SOURCE_SUBDIR`` option
  can be used to point to an alternative directory within the source tree
  to use as the top of the CMake source tree instead. This must be a
  relative path and it will be interpreted as being relative to
  ``SOURCE_DIR``.

  .. versionadded:: 3.14
    When ``BUILD_IN_SOURCE`` option is enabled, the ``BUILD_COMMAND``
    is used to point to an alternative directory within the source tree.

``CONFIGURE_HANDLED_BY_BUILD <bool>``
  .. versionadded:: 3.20

  Enabling this option relaxes the dependencies of the configure step on
  other external projects to order-only. This means the configure step will
  be executed after its external project dependencies are built but it will
  not be marked dirty when one of its external project dependencies is
  rebuilt. This option can be enabled when the build step is smart enough
  to figure out if the configure step needs to be rerun. CMake and Meson are
  examples of build systems whose build step is smart enough to know if the
  configure step needs to be rerun.

Build Step Options
""""""""""""""""""

If the configure step assumed the external project uses CMake as its build
system, the build step will also. Otherwise, the build step will assume a
Makefile-based build and simply run ``make`` with no arguments as the
default build step. This can be overridden with custom build commands if
required.

If both the main project and the external project use make as their build
tool, the build step of the external project is invoked as a recursive
make using ``$(MAKE)``.  This will communicate some build tool settings
from the main project to the external project.  If either the main project
or external project is not using make, no build tool settings will be
passed to the external project other than those established by the
configure step (i.e. running ``ninja -v`` in the main project will not
pass ``-v`` to the external project's build step, even if it also uses
``ninja`` as its build tool).

``BUILD_COMMAND <cmd>...``
  Overrides the default build command
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). If this option is not given, the default build command will
  be chosen to integrate with the main build in the most appropriate way
  (e.g. using recursive ``make`` for Makefile generators or
  :option:`cmake --build` if the project uses a CMake build). This option
  can be specified with an empty string as the command to make the build
  step do nothing.

``BUILD_IN_SOURCE <bool>``
  When this option is enabled, the build will be done directly within the
  external project's source tree. This should generally be avoided, the use
  of a separate build directory is usually preferred, but it can be useful
  when the external project assumes an in-source build. The ``BINARY_DIR``
  option should not be specified if building in-source.

``BUILD_ALWAYS <bool>``
  Enabling this option forces the build step to always be run. This can be
  the easiest way to robustly ensure that the external project's own build
  dependencies are evaluated rather than relying on the default
  success timestamp-based method. This option is not normally needed unless
  developers are expected to modify something the external project's build
  depends on in a way that is not detectable via the step target
  dependencies (e.g. ``SOURCE_DIR`` is used without a download method and
  developers might modify the sources in ``SOURCE_DIR``).

``BUILD_BYPRODUCTS <file>...``
  .. versionadded:: 3.2

  Specifies files that will be generated by the build command but which
  might or might not have their modification time updated by subsequent
  builds. This may also be required to explicitly declare dependencies
  when using the :generator:`Ninja` generator.
  These ultimately get passed through as ``BYPRODUCTS`` to the
  build step's own underlying call to :command:`add_custom_command`, which
  has additional documentation.

``BUILD_JOB_SERVER_AWARE <bool>``
  .. versionadded:: 3.28

  Specifies that the build step is aware of the GNU Make job server.
  See the :command:`add_custom_command` documentation of its
  ``JOB_SERVER_AWARE`` option for details.  This option is relevant
  only when an explicit ``BUILD_COMMAND`` is specified.

Install Step Options
""""""""""""""""""""

If the configure step assumed the external project uses CMake as its build
system, the install step will also. Otherwise, the install step will assume
a Makefile-based build and simply run ``make install`` as the default build
step. This can be overridden with custom install commands if required.

``INSTALL_COMMAND <cmd>...``
  The external project's own install step is invoked as part of the main
  project's *build*. It is done after the external project's build step
  and may be before or after the external project's test step (see the
  ``TEST_BEFORE_INSTALL`` option below). The external project's install
  rules are not part of the main project's install rules, so if anything
  from the external project should be installed as part of the main build,
  these need to be specified in the main build as additional
  :command:`install` commands. The default install step builds the
  ``install`` target of the external project, but this can be overridden
  with a custom command using this option
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). Passing an empty string as the ``<cmd>`` makes the install
  step do nothing.

``INSTALL_BYPRODUCTS <file>...``
  .. versionadded:: 3.26

  Specifies files that will be generated by the install command but which
  might or might not have their modification time updated by subsequent
  installs. This may also be required to explicitly declare dependencies
  when using the :generator:`Ninja` generator.
  These ultimately get passed through as ``BYPRODUCTS`` to the
  install step's own underlying call to :command:`add_custom_command`, which
  has additional documentation.

``INSTALL_JOB_SERVER_AWARE <bool>``
  .. versionadded:: 4.0

  Specifies that the install step is aware of the GNU Make job server.
  See the :command:`add_custom_command` documentation of its
  ``JOB_SERVER_AWARE`` option for details.  This option is relevant
  only when an explicit ``INSTALL_COMMAND`` is specified.

.. note::
  If the :envvar:`CMAKE_INSTALL_MODE` environment variable is set when the
  main project is built, it will only have an effect if the following
  conditions are met:

  * The main project's configure step assumed the external project uses
    CMake as its build system.
  * The external project's install command actually runs. Note that due
    to the way ``ExternalProject`` may use timestamps internally, if
    nothing the install step depends on needs to be re-executed, the
    install command might also not need to run.

  Note also that ``ExternalProject`` does not check whether the
  :envvar:`CMAKE_INSTALL_MODE` environment variable changes from one run
  to another.

Test Step Options
"""""""""""""""""

The test step is only defined if at least one of the following ``TEST_...``
options are provided.

``TEST_COMMAND <cmd>...``
  Overrides the default test command
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). If this option is not given, the default behavior of the test
  step is to build the external project's own ``test`` target. This option
  can be specified with ``<cmd>`` as an empty string, which allows the test
  step to still be defined, but it will do nothing. Do not specify any of
  the other ``TEST_...`` options if providing an empty string as the test
  command, but prefer to omit all ``TEST_...`` options altogether if the
  test step target is not needed.

``TEST_BEFORE_INSTALL <bool>``
  When this option is enabled, the test step will be executed before the
  install step. The default behavior is for the test step to run after the
  install step.

``TEST_AFTER_INSTALL <bool>``
  This option is mainly useful as a way to indicate that the test step is
  desired but all default behavior is sufficient. Specifying this option
  with a boolean true value ensures the test step is defined and that it
  comes after the install step. If both ``TEST_BEFORE_INSTALL`` and
  ``TEST_AFTER_INSTALL`` are enabled, the latter is silently ignored.

``TEST_EXCLUDE_FROM_MAIN <bool>``
  .. versionadded:: 3.2

  If enabled, the main build's default ALL target will not depend on the
  test step. This can be a useful way of ensuring the test step is defined
  but only gets invoked when manually requested.
  This may cause a step target to be created automatically for either
  the ``install`` or ``build`` step.  See policy :policy:`CMP0114`.

Output Logging Options
""""""""""""""""""""""

Each of the following ``LOG_...`` options can be used to wrap the relevant
step in a script to capture its output to files. The log files will be
created in ``LOG_DIR`` if supplied or otherwise the ``STAMP_DIR``
directory with step-specific file names.

``LOG_DOWNLOAD <bool>``
  When enabled, the output of the download step is logged to files.

``LOG_UPDATE <bool>``
  When enabled, the output of the update step is logged to files.

``LOG_PATCH <bool>``
  .. versionadded:: 3.14

  When enabled, the output of the patch step is logged to files.

``LOG_CONFIGURE <bool>``
  When enabled, the output of the configure step is logged to files.

``LOG_BUILD <bool>``
  When enabled, the output of the build step is logged to files.

``LOG_INSTALL <bool>``
  When enabled, the output of the install step is logged to files.

``LOG_TEST <bool>``
  When enabled, the output of the test step is logged to files.

``LOG_MERGED_STDOUTERR <bool>``
  .. versionadded:: 3.14

  When enabled, stdout and stderr will be merged for any step whose
  output is being logged to files.

``LOG_OUTPUT_ON_FAILURE <bool>``
  .. versionadded:: 3.14

  This option only has an effect if at least one of the other ``LOG_<step>``
  options is enabled.  If an error occurs for a step which has logging to
  file enabled, that step's output will be printed to the console if
  ``LOG_OUTPUT_ON_FAILURE`` is set to true.  For cases where a large amount
  of output is recorded, just the end of that output may be printed to the
  console.

Terminal Access Options
"""""""""""""""""""""""

.. versionadded:: 3.4

Steps can be given direct access to the terminal in some cases. Giving a
step access to the terminal may allow it to receive terminal input if
required, such as for authentication details not provided by other options.
With the :generator:`Ninja` generator, these options place the steps in the
``console`` :prop_gbl:`job pool <JOB_POOLS>`. Each step can be given access
to the terminal individually via the following options:

``USES_TERMINAL_DOWNLOAD <bool>``
  Give the download step access to the terminal.

``USES_TERMINAL_UPDATE <bool>``
  Give the update step access to the terminal.

``USES_TERMINAL_PATCH <bool>``
  .. versionadded:: 3.23

  Give the patch step access to the terminal.

``USES_TERMINAL_CONFIGURE <bool>``
  Give the configure step access to the terminal.

``USES_TERMINAL_BUILD <bool>``
  Give the build step access to the terminal.

``USES_TERMINAL_INSTALL <bool>``
  Give the install step access to the terminal.

``USES_TERMINAL_TEST <bool>``
  Give the test step access to the terminal.

Target Options
""""""""""""""

``DEPENDS <targets>...``
  Specify other targets on which the external project depends. The other
  targets will be brought up to date before any of the external project's
  steps are executed. Because the external project uses additional custom
  targets internally for each step, the ``DEPENDS`` option is the most
  convenient way to ensure all of those steps depend on the other targets.
  Simply doing
  :command:`add_dependencies(\<name\> \<targets\>) <add_dependencies>` will
  not make any of the steps dependent on ``<targets>``.

``EXCLUDE_FROM_ALL <bool>``
  When enabled, this option excludes the external project from the default
  ALL target of the main build.

``STEP_TARGETS <step-target>...``
  Generate custom targets for the specified steps. This is required if the
  steps need to be triggered manually or if they need to be used as
  dependencies of other targets. If this option is not specified, the
  default value is taken from the ``EP_STEP_TARGETS`` directory property.
  See :command:`ExternalProject_Add_StepTargets` below for further
  discussion of the effects of this option.

``INDEPENDENT_STEP_TARGETS <step-target>...``
  .. deprecated:: 3.19
    This is allowed only if policy :policy:`CMP0114` is not set to ``NEW``.

  Generates custom targets for the specified steps and prevent these targets
  from having the usual dependencies applied to them. If this option is not
  specified, the default value is taken from the
  ``EP_INDEPENDENT_STEP_TARGETS`` directory property. This option is mostly
  useful for allowing individual steps to be driven independently, such as
  for a CDash setup where each step should be initiated and reported
  individually rather than as one whole build. See
  :command:`ExternalProject_Add_StepTargets` below for further discussion
  of the effects of this option.

Miscellaneous Options
"""""""""""""""""""""

``LIST_SEPARATOR <sep>``
  For any of the various ``..._COMMAND`` options, and ``CMAKE_ARGS``,
  ``ExternalProject`` will replace ``<sep>`` with ``;`` in the specified
  command lines. This can be used to ensure a command has a literal ``;`` in it
  where direct usage would otherwise be interpreted as argument separators to
  CMake APIs instead. Note that the separator should be chosen to avoid being
  confused for non-list-separator usages of the sequence. For example, using
  ``LIST_SEPARATOR`` allows for passing list values to CMake cache variables on
  the command line:

  .. code-block:: cmake

    ExternalProject_Add(example
      ... # Download options, etc.
      LIST_SEPARATOR ","
      CMAKE_ARGS "-DCMAKE_PREFIX_PATH:STRING=${first_prefix},${second_prefix}"
    )

``COMMAND <cmd>...``
  Any of the other ``..._COMMAND`` options can have additional commands
  appended to them by following them with as many ``COMMAND ...`` options
  as needed
  (:manual:`generator expressions <cmake-generator-expressions(7)>` are
  supported). For example:

  .. code-block:: cmake

    ExternalProject_Add(example
      ... # Download options, etc.
      BUILD_COMMAND ${CMAKE_COMMAND} -E echo "Starting $<CONFIG> build"
      COMMAND       ${CMAKE_COMMAND} --build <BINARY_DIR> --config $<CONFIG>
      COMMAND       ${CMAKE_COMMAND} -E echo "$<CONFIG> build complete"
    )

It should also be noted that each build step is created via a call to
:command:`ExternalProject_Add_Step`. See that command's documentation for the
automatic substitutions that are supported for some options.

Obtaining Project Properties
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. command:: ExternalProject_Get_Property

  The ``ExternalProject_Get_Property()`` function retrieves external project
  target properties:

  .. code-block:: cmake

    ExternalProject_Get_Property(<name> <prop1> [<prop2>...])

  The function stores property values in variables of the same name. Property
  names correspond to the keyword argument names of ``ExternalProject_Add()``.
  For example, the source directory might be retrieved like so:

  .. code-block:: cmake

    ExternalProject_Get_property(myExtProj SOURCE_DIR)
    message("Source dir of myExtProj = ${SOURCE_DIR}")

Explicit Step Management
^^^^^^^^^^^^^^^^^^^^^^^^

The ``ExternalProject_Add()`` function on its own is often sufficient for
incorporating an external project into the main build. Certain scenarios
require additional work to implement desired behavior, such as adding in a
custom step or making steps available as manually triggerable targets. The
``ExternalProject_Add_Step()``, ``ExternalProject_Add_StepTargets()`` and
``ExternalProject_Add_StepDependencies`` functions provide the lower level
control needed to implement such step-level capabilities.

.. command:: ExternalProject_Add_Step

  The ``ExternalProject_Add_Step()`` function specifies an additional custom
  step for an external project defined by an earlier call to
  :command:`ExternalProject_Add`:

  .. code-block:: cmake

    ExternalProject_Add_Step(<name> <step> [<option>...])

  ``<name>`` is the same as the name passed to the original call to
  :command:`ExternalProject_Add`. The specified ``<step>`` must not be one of
  the pre-defined steps (``mkdir``, ``download``, ``update``,
  ``patch``, ``configure``, ``build``, ``install`` or ``test``). The supported
  options are:

  ``COMMAND <cmd>...``
    The command line to be executed by this custom step
    (:manual:`generator expressions <cmake-generator-expressions(7)>` are
    supported). This option can be repeated multiple times to specify multiple
    commands to be executed in order.

  ``COMMENT "<text>..."``
    Text to be printed when the custom step executes.

  ``DEPENDEES <step>...``
    Other steps (custom or pre-defined) on which this step depends.

  ``DEPENDERS <step>...``
    Other steps (custom or pre-defined) that depend on this new custom step.

  ``DEPENDS <file>...``
    Files on which this custom step depends.

  ``INDEPENDENT <bool>``
    .. versionadded:: 3.19

    Specifies whether this step is independent of the external dependencies
    specified by the :command:`ExternalProject_Add`'s ``DEPENDS`` option.
    The default is ``FALSE``.  Steps marked as independent may depend only
    on other steps marked independent.  See policy :policy:`CMP0114`.

    Note that this use of the term "independent" refers only to independence
    from external targets specified by the ``DEPENDS`` option and is
    orthogonal to a step's dependencies on other steps.

    If a step target is created for an independent step by the
    :command:`ExternalProject_Add` ``STEP_TARGETS`` option or by the
    :command:`ExternalProject_Add_StepTargets` function, it will not depend
    on the external targets, but may depend on targets for other steps.

  ``BYPRODUCTS <file>...``
    .. versionadded:: 3.2

    Files that will be generated by this custom step but which might or might
    not have their modification time updated by subsequent builds.
    This may also be required to explicitly declare dependencies
    when using the :generator:`Ninja` generator. This list of
    files will ultimately be passed through as the ``BYPRODUCTS`` option to the
    :command:`add_custom_command` used to implement the custom step internally,
    which has additional documentation.

  ``ALWAYS <bool>``
    When enabled, this option specifies that the custom step should always be
    run (i.e. that it is always considered out of date).

  ``JOB_SERVER_AWARE <bool>``
    .. versionadded:: 3.28

    Specifies that the custom step is aware of the GNU Make job server.
    See the :command:`add_custom_command` documentation of its
    ``JOB_SERVER_AWARE`` option for details.

  ``EXCLUDE_FROM_MAIN <bool>``
    When enabled, this option specifies that the external project's main target
    does not depend on the custom step.
    This may cause step targets to be created automatically for the steps on
    which this step depends.  See policy :policy:`CMP0114`.

  ``WORKING_DIRECTORY <dir>``
    Specifies the working directory to set before running the custom step's
    command. If this option is not specified, the directory will be the value
    of the :variable:`CMAKE_CURRENT_BINARY_DIR` at the point where
    ``ExternalProject_Add_Step()`` was called.

  ``LOG <bool>``
    If set, this causes the output from the custom step to be captured to files
    in the external project's ``LOG_DIR`` if supplied or ``STAMP_DIR``.

  ``USES_TERMINAL <bool>``
    If enabled, this gives the custom step direct access to the terminal if
    possible.

  The command line, comment, working directory and byproducts of every
  standard and custom step are processed to replace the tokens
  ``<SOURCE_DIR>``, ``<SOURCE_SUBDIR>``, ``<BINARY_DIR>``, ``<INSTALL_DIR>``
  ``<TMP_DIR>``, ``<DOWNLOAD_DIR>`` and ``<DOWNLOADED_FILE>`` with their
  corresponding property values defined in the original call to
  :command:`ExternalProject_Add`.

  .. versionadded:: 3.3
    Token replacement is extended to byproducts.

  .. versionadded:: 3.11
    The ``<DOWNLOAD_DIR>`` substitution token.

.. command:: ExternalProject_Add_StepTargets

  The ``ExternalProject_Add_StepTargets()`` function generates targets for the
  steps listed. The name of each created target will be of the form
  ``<name>-<step>``:

  .. code-block:: cmake

    ExternalProject_Add_StepTargets(<name> <step1> [<step2>...])

  Creating a target for a step allows it to be used as a dependency of another
  target or to be triggered manually. Having targets for specific steps also
  allows them to be driven independently of each other by specifying targets on
  build command lines. For example, you may be submitting to a sub-project
  based dashboard where you want to drive the configure portion of the build,
  then submit to the dashboard, followed by the build portion, followed
  by tests. If you invoke a custom target that depends on a step halfway
  through the step dependency chain, then all the previous steps will also run
  to ensure everything is up to date.

  Internally, :command:`ExternalProject_Add` calls
  :command:`ExternalProject_Add_Step` to create each step. If any
  ``STEP_TARGETS`` were specified, then ``ExternalProject_Add_StepTargets()``
  will also be called after :command:`ExternalProject_Add_Step`.  Even if a
  step is not mentioned in the ``STEP_TARGETS`` option,
  ``ExternalProject_Add_StepTargets()`` can still be called later to manually
  define a target for the step.

  The ``STEP_TARGETS`` option for :command:`ExternalProject_Add` is generally
  the easiest way to ensure targets are created for specific steps of interest.
  For custom steps, ``ExternalProject_Add_StepTargets()`` must be called
  explicitly if a target should also be created for that custom step.
  An alternative to these two options is to populate the ``EP_STEP_TARGETS``
  directory property.  It acts as a default for the step target options and
  can save having to repeatedly specify the same set of step targets when
  multiple external projects are being defined.

  .. versionadded:: 3.19
    If :policy:`CMP0114` is set to ``NEW``, step targets 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.
    The targets for steps created with :command:`ExternalProject_Add_Step`'s
    ``INDEPENDENT`` option do not depend on the external targets specified
    by :command:`ExternalProject_Add`'s ``DEPENDS`` option.  The predefined
    steps ``mkdir``, ``download``, ``update``, and ``patch`` are independent.

  If :policy:`CMP0114` is not ``NEW``, the following deprecated behavior
  is available:

  * A deprecated ``NO_DEPENDS`` option may be specified immediately after the
    ``<name>`` and before the first step.
    If the ``NO_DEPENDS`` option is specified, the step target will not depend
    on the dependencies of the external project (i.e. on any dependencies of the
    ``<name>`` custom target created by :command:`ExternalProject_Add`). This is
    usually safe for the ``download``, ``update`` and ``patch`` steps, since
    they do not typically require that the dependencies are updated and built.
    Using ``NO_DEPENDS`` for any of the other pre-defined steps, however, may
    break parallel builds. Only use ``NO_DEPENDS`` where it is certain that the
    named steps genuinely do not have dependencies. For custom steps, consider
    whether or not the custom commands require the dependencies to be
    configured, built and installed.

  * The ``INDEPENDENT_STEP_TARGETS`` option for :command:`ExternalProject_Add`,
    or the ``EP_INDEPENDENT_STEP_TARGETS`` directory property, tells the
    function to call ``ExternalProject_Add_StepTargets()`` internally
    using the ``NO_DEPENDS`` option for the specified steps.

.. command:: ExternalProject_Add_StepDependencies

  .. versionadded:: 3.2

  The ``ExternalProject_Add_StepDependencies()`` function can be used to add
  dependencies to a step. The dependencies added must be targets CMake already
  knows about (these can be ordinary executable or library targets, custom
  targets or even step targets of another external project):

  .. code-block:: cmake

    ExternalProject_Add_StepDependencies(<name> <step> <target1> [<target2>...])

  This function takes care to set both target and file level dependencies and
  will ensure that parallel builds will not break. It should be used instead of
  :command:`add_dependencies` whenever adding a dependency for some of the step
  targets generated by the ``ExternalProject`` module.

Examples
^^^^^^^^

The following example shows how to download and build a hypothetical project
called *FooBar* from github:

.. code-block:: cmake

  include(ExternalProject)
  ExternalProject_Add(foobar
    GIT_REPOSITORY    git@github.com:FooCo/FooBar.git
    GIT_TAG           origin/release/1.2.3
  )

For the sake of the example, also define a second hypothetical external project
called *SecretSauce*, which is downloaded from a web server. Two URLs are given
to take advantage of a faster internal network if available, with a fallback to
a slower external server. The project is a typical ``Makefile`` project with no
configure step, so some of the default commands are overridden. The build is
only required to build the *sauce* target:

.. code-block:: cmake

  find_program(MAKE_EXE NAMES gmake nmake make)
  ExternalProject_Add(secretsauce
    URL               http://intranet.somecompany.com/artifacts/sauce-2.7.tgz
                      https://www.somecompany.com/downloads/sauce-2.7.zip
    URL_HASH          MD5=d41d8cd98f00b204e9800998ecf8427e
    CONFIGURE_COMMAND ""
    BUILD_COMMAND     ${MAKE_EXE} sauce
  )

Suppose the build step of ``secretsauce`` requires that ``foobar`` must already
be built. This could be enforced like so:

.. code-block:: cmake

  ExternalProject_Add_StepDependencies(secretsauce build foobar)

Another alternative would be to create a custom target for ``foobar``'s build
step and make ``secretsauce`` depend on that rather than the whole ``foobar``
project. This would mean ``foobar`` only needs to be built, it doesn't need to
run its install or test steps before ``secretsauce`` can be built. The
dependency can also be defined along with the ``secretsauce`` project:

.. code-block:: cmake

  ExternalProject_Add_StepTargets(foobar build)
  ExternalProject_Add(secretsauce
    URL               http://intranet.somecompany.com/artifacts/sauce-2.7.tgz
                      https://www.somecompany.com/downloads/sauce-2.7.zip
    URL_HASH          MD5=d41d8cd98f00b204e9800998ecf8427e
    CONFIGURE_COMMAND ""
    BUILD_COMMAND     ${MAKE_EXE} sauce
    DEPENDS           foobar-build
  )

Instead of calling :command:`ExternalProject_Add_StepTargets`, the target could
be defined along with the ``foobar`` project itself:

.. code-block:: cmake

  ExternalProject_Add(foobar
    GIT_REPOSITORY git@github.com:FooCo/FooBar.git
    GIT_TAG        origin/release/1.2.3
    STEP_TARGETS   build
  )

If many external projects should have the same set of step targets, setting a
directory property may be more convenient. The ``build`` step target could be
created automatically by setting the ``EP_STEP_TARGETS`` directory property
before creating the external projects with :command:`ExternalProject_Add`:

.. code-block:: cmake

  set_property(DIRECTORY PROPERTY EP_STEP_TARGETS build)

Lastly, suppose that ``secretsauce`` provides a script called ``makedoc`` which
can be used to generate its own documentation. Further suppose that the script
expects the output directory to be provided as the only parameter and that it
should be run from the ``secretsauce`` source directory. A custom step and a
custom target to trigger the script can be defined like so:

.. code-block:: cmake

  ExternalProject_Add_Step(secretsauce docs
    COMMAND           <SOURCE_DIR>/makedoc <BINARY_DIR>
    WORKING_DIRECTORY <SOURCE_DIR>
    COMMENT           "Building secretsauce docs"
    ALWAYS            TRUE
    EXCLUDE_FROM_MAIN TRUE
  )
  ExternalProject_Add_StepTargets(secretsauce docs)

The custom step could then be triggered from the main build like so::

  cmake --build . --target secretsauce-docs

#]=======================================================================]

include(${CMAKE_CURRENT_LIST_DIR}/ExternalProject/shared_internal_commands.cmake)

define_property(DIRECTORY PROPERTY "EP_BASE" INHERITED)
define_property(DIRECTORY PROPERTY "EP_PREFIX" INHERITED)
define_property(DIRECTORY PROPERTY "EP_STEP_TARGETS" INHERITED)
define_property(DIRECTORY PROPERTY "EP_INDEPENDENT_STEP_TARGETS" INHERITED)
define_property(DIRECTORY PROPERTY "EP_UPDATE_DISCONNECTED" INHERITED)

# file(TO_CMAKE_PATH) will interpret a platform-specific character as a path
# separator, and if its input contains that character, it will treat the input
# as a list. Sometimes we have a string that we know is always a single path,
# but it may contain the separator character. To prevent it being treated as a
# list of paths, this function masks the separator character while calling
# file(TO_CMAKE_PATH).
function(_ep_to_single_cmake_path out_var input)
  if(WIN32)
    set(unsafe_char ";")
  else()
    set(unsafe_char ":")
  endif()

  string(REPLACE "${unsafe_char}" "__EP_MARKER__" safe_input "${input}")
  file(TO_CMAKE_PATH "${safe_input}" converted_input)
  string(REPLACE "__EP_MARKER__" "${unsafe_char}" output "${converted_input}")

  set(${out_var} "${output}" PARENT_SCOPE)
endfunction()

function(_ep_set_directories name)
  get_property(prefix TARGET ${name} PROPERTY _EP_PREFIX)
  if(NOT prefix)
    get_property(prefix DIRECTORY PROPERTY EP_PREFIX)
    if(NOT prefix)
      get_property(base DIRECTORY PROPERTY EP_BASE)
      if(NOT base)
        set(prefix "${name}-prefix")
      endif()
    endif()
  endif()
  if(prefix)
    _ep_to_single_cmake_path(prefix "${prefix}")
    set(tmp_default "${prefix}/tmp")
    set(download_default "${prefix}/src")
    set(source_default "${prefix}/src/${name}")
    set(binary_default "${prefix}/src/${name}-build")
    set(stamp_default "${prefix}/src/${name}-stamp")
    set(install_default "${prefix}")
  else()
    _ep_to_single_cmake_path(base "${base}")
    set(tmp_default "${base}/tmp/${name}")
    set(download_default "${base}/Download/${name}")
    set(source_default "${base}/Source/${name}")
    set(binary_default "${base}/Build/${name}")
    set(stamp_default "${base}/Stamp/${name}")
    set(install_default "${base}/Install/${name}")
  endif()
  get_property(build_in_source TARGET ${name} PROPERTY _EP_BUILD_IN_SOURCE)
  if(build_in_source)
    get_property(have_binary_dir TARGET ${name} PROPERTY _EP_BINARY_DIR SET)
    if(have_binary_dir)
      message(FATAL_ERROR
        "External project ${name} has both BINARY_DIR and BUILD_IN_SOURCE!"
      )
    endif()
  endif()
  set(top "${CMAKE_CURRENT_BINARY_DIR}")

  # Apply defaults and convert to absolute paths.
  set(places stamp download source binary install tmp)
  foreach(var IN LISTS places)
    string(TOUPPER "${var}" VAR)
    get_property(${var}_dir TARGET ${name} PROPERTY _EP_${VAR}_DIR)
    if(NOT ${var}_dir)
      set(${var}_dir "${${var}_default}")
    endif()
    if(NOT IS_ABSOLUTE "${${var}_dir}")
      get_filename_component(${var}_dir "${top}/${${var}_dir}" ABSOLUTE)
    endif()
    _ep_to_single_cmake_path(${var}_dir "${${var}_dir}")
    set_property(TARGET ${name} PROPERTY _EP_${VAR}_DIR "${${var}_dir}")
    set(_EP_${VAR}_DIR "${${var}_dir}" PARENT_SCOPE)
  endforeach()

  # Special case for default log directory based on stamp directory.
  get_property(log_dir TARGET ${name} PROPERTY _EP_LOG_DIR)
  if(NOT log_dir)
    get_property(log_dir TARGET ${name} PROPERTY _EP_STAMP_DIR)
  endif()
  if(NOT IS_ABSOLUTE "${log_dir}")
    get_filename_component(log_dir "${top}/${log_dir}" ABSOLUTE)
  endif()
  _ep_to_single_cmake_path(log_dir "${log_dir}")
  set_property(TARGET ${name} PROPERTY _EP_LOG_DIR "${log_dir}")
  set(_EP_LOG_DIR "${log_dir}" PARENT_SCOPE)

  get_property(source_subdir TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR)
  if(NOT source_subdir)
    set_property(TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR "")
    set(_EP_SOURCE_SUBDIR "" PARENT_SCOPE)
  elseif(IS_ABSOLUTE "${source_subdir}")
    message(FATAL_ERROR
      "External project ${name} has non-relative SOURCE_SUBDIR!"
    )
  else()
    # Prefix with a slash so that when appended to the source directory, it
    # behaves as expected.
    _ep_to_single_cmake_path(source_subdir "${source_subdir}")
    set_property(TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR "/${source_subdir}")
    set(_EP_SOURCE_SUBDIR "/${source_subdir}" PARENT_SCOPE)
  endif()
  if(build_in_source)
    get_property(source_dir TARGET ${name} PROPERTY _EP_SOURCE_DIR)
    if(source_subdir)
      set_property(TARGET ${name} PROPERTY
        _EP_BINARY_DIR "${source_dir}/${source_subdir}"
      )
      set(_EP_BINARY_DIR "${source_dir}/${source_subdir}" PARENT_SCOPE)
    else()
      set_property(TARGET ${name} PROPERTY
        _EP_BINARY_DIR "${source_dir}"
      )
      set(_EP_BINARY_DIR "${source_dir}" PARENT_SCOPE)
    endif()
  endif()

  # This script will be used both here and by the mkdir step. We create the
  # directories now at configure time and ensure they exist again at build
  # time (since somebody might remove one of the required directories and try
  # to rebuild without re-running cmake). They need to exist now at makefile
  # generation time for Borland make and wmake so that CMake may generate
  # makefiles with "cd C:\short\paths\with\no\spaces" commands in them.
  set(script_filename "${tmp_dir}/${name}-mkdirs.cmake")
  configure_file(
    ${CMAKE_CURRENT_FUNCTION_LIST_DIR}/ExternalProject/mkdirs.cmake.in
    ${script_filename}
    @ONLY
  )
  unset(cfgdir) # do not leak into mkdirs.cmake script
  include(${script_filename})
endfunction()


# IMPORTANT: this MUST be a macro and not a function because of the
# in-place replacements that occur in each ${var}
#
macro(_ep_replace_location_tags target_name)
  set(vars ${ARGN})
  foreach(var IN LISTS vars)
    if(var)
      foreach(dir IN ITEMS
        SOURCE_DIR
        SOURCE_SUBDIR
        BINARY_DIR
        INSTALL_DIR
        TMP_DIR
        DOWNLOAD_DIR
        DOWNLOADED_FILE
        LOG_DIR
      )
        get_property(val TARGET ${target_name} PROPERTY _EP_${dir})
        string(REPLACE "<${dir}>" "${val}" ${var} "${${var}}")
      endforeach()
    endif()
  endforeach()
endmacro()


function(_ep_command_line_to_initial_cache
  var
  args
  force
)
  set(script_initial_cache "")
  set(regex "^([^:]+):([^=]+)=(.*)$")
  set(setArg "")
  set(forceArg "")
  if(force)
    set(forceArg "FORCE")
  endif()
  foreach(line IN LISTS args)
    if("${line}" MATCHES "^-D(.*)")
      set(line "${CMAKE_MATCH_1}")
      if(NOT "${setArg}" STREQUAL "")
        # This is required to build up lists in variables, or complete an entry
        string(APPEND setArg
          "${accumulator}\" CACHE ${type} \"Initial cache\" ${forceArg})"
        )
        string(APPEND script_initial_cache "\n${setArg}")
        set(accumulator "")
        set(setArg "")
      endif()
      if("${line}" MATCHES "${regex}")
        set(name "${CMAKE_MATCH_1}")
        set(type "${CMAKE_MATCH_2}")
        set(value "${CMAKE_MATCH_3}")
        set(setArg "set(${name} \"${value}")
      else()
        message(WARNING "Line '${line}' does not match regex. Ignoring.")
      endif()
    else()
      # Assume this is a list to append to the last var
      string(APPEND accumulator ";${line}")
    endif()
  endforeach()
  # Catch the final line of the args
  if(NOT "${setArg}" STREQUAL "")
    string(APPEND setArg
      "${accumulator}\" CACHE ${type} \"Initial cache\" ${forceArg})"
    )
    string(APPEND script_initial_cache "\n${setArg}")
  endif()
  set(${var} ${script_initial_cache} PARENT_SCOPE)
endfunction()


function(_ep_write_initial_cache
  target_name
  script_filename
  script_initial_cache
)
  # Write out values into an initial cache, that will be passed to CMake with -C
  # Replace location tags.
  _ep_replace_location_tags(${target_name} script_initial_cache)
  _ep_replace_location_tags(${target_name} script_filename)
  # Replace list separators.
  get_property(sep TARGET ${target_name} PROPERTY _EP_LIST_SEPARATOR)
  if(sep AND script_initial_cache)
    string(REPLACE "${sep}" ";" script_initial_cache "${script_initial_cache}")
  endif()
  # Write out the initial cache file to the location specified.
  file(GENERATE OUTPUT "${script_filename}" CONTENT "${script_initial_cache}")
endfunction()


function(ExternalProject_Get_Property name)
  foreach(var IN LISTS ARGN)
    string(TOUPPER "${var}" VAR)
    get_property(is_set TARGET ${name} PROPERTY _EP_${VAR} SET)
    if(NOT is_set)
      message(FATAL_ERROR "External project \"${name}\" has no ${var}")
    endif()
    get_property(${var} TARGET ${name} PROPERTY _EP_${VAR})
    set(${var} "${${var}}" PARENT_SCOPE)
  endforeach()
endfunction()


function(_ep_get_configure_command_id
  name
  cfg_cmd_id_var
)
  get_target_property(cmd ${name} _EP_CONFIGURE_COMMAND)

  if(cmd STREQUAL "")
    # Explicit empty string means no configure step for this project
    set(${cfg_cmd_id_var} "none" PARENT_SCOPE)
  else()
    if(NOT cmd)
      # Default is "use cmake":
      set(${cfg_cmd_id_var} "cmake" PARENT_SCOPE)
    else()
      # Otherwise we have to analyze the value:
      if(cmd MATCHES "^[^;]*/configure")
        set(${cfg_cmd_id_var} "configure" PARENT_SCOPE)
      elseif(cmd MATCHES "^[^;]*/cmake" AND NOT cmd MATCHES ";-[PE];")
        set(${cfg_cmd_id_var} "cmake" PARENT_SCOPE)
      elseif(cmd MATCHES "config")
        set(${cfg_cmd_id_var} "configure" PARENT_SCOPE)
      else()
        set(${cfg_cmd_id_var} "unknown:${cmd}" PARENT_SCOPE)
      endif()
    endif()
  endif()
endfunction()


function(_ep_get_build_command
  name
  step
  cmd_var
)
  set(cmd "")
  set(args)
  _ep_get_configure_command_id(${name} cfg_cmd_id)
  if(cfg_cmd_id STREQUAL "cmake")
    # Adding a CMake project as an External Project.  Select command based on generator
    get_property(cmake_generator TARGET ${name} PROPERTY _EP_CMAKE_GENERATOR)
    # cmake_generator is the CMake generator of the ExternalProject target being added
    # CMAKE_GENERATOR is the CMake generator of the Current Project
    if("${CMAKE_GENERATOR}" MATCHES "Make" AND
       ("${cmake_generator}" MATCHES "Make" OR NOT cmake_generator))
      # The project uses the same Makefile generator.  Use recursive make.
      set(cmd "$(MAKE)")
      if(step STREQUAL "INSTALL")
        set(args install)
      endif()
      if("x${step}x" STREQUAL "xTESTx")
        set(args test)
      endif()
    else()
      # Drive the project with "cmake --build".
      if(NOT cmake_generator)
        # If there is no CMake Generator defined on the ExternalProject,
        # use the same Generator as the current project
        set(cmake_generator "${CMAKE_GENERATOR}")
      endif()
      get_target_property(cmake_command ${name} _EP_CMAKE_COMMAND)
      if(cmake_command)
        set(cmd "${cmake_command}")
      else()
        set(cmd "${CMAKE_COMMAND}")
      endif()
      set(args --build ".")
      get_property(_isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
      if(_isMultiConfig)
        if (CMAKE_CFG_INTDIR AND
            NOT CMAKE_CFG_INTDIR STREQUAL "." AND
            NOT CMAKE_CFG_INTDIR MATCHES "\\$")
          # CMake 3.4 and below used the CMAKE_CFG_INTDIR placeholder value
          # provided by multi-configuration generators.  Some projects were
          # taking advantage of that undocumented implementation detail to
          # specify a specific configuration here.  They should use
          # BUILD_COMMAND to change the default command instead, but for
          # compatibility honor the value.
          set(config ${CMAKE_CFG_INTDIR})
          message(AUTHOR_WARNING
            "CMAKE_CFG_INTDIR should not be set by project code.\n"
            "To get a non-default build command, use the BUILD_COMMAND option."
          )
        else()
          set(config $<CONFIG>)
        endif()
        list(APPEND args --config ${config})
      endif()
      if(step STREQUAL "INSTALL")
        if("${cmake_generator}" MATCHES "Green Hills MULTI")
          list(APPEND args --target INSTALL)
        else()
          list(APPEND args --target install)
        endif()
      endif()
      # But for "TEST" drive the project with corresponding "ctest".
      if("x${step}x" STREQUAL "xTESTx")
        string(REGEX REPLACE "^(.*/)cmake([^/]*)$" "\\1ctest\\2" cmd "${cmd}")
        set(args "")
        if(_isMultiConfig)
          list(APPEND args -C ${config})
        endif()
      endif()
    endif()
  else()
    # Non-CMake project.  Guess "make" and "make install" and "make test".
    if("${CMAKE_GENERATOR}" MATCHES "Makefiles")
      # Try to get the parallel arguments
      set(cmd "$(MAKE)")
    else()
      set(cmd "make")
    endif()
    if(step STREQUAL "INSTALL")
      set(args install)
    endif()
    if("x${step}x" STREQUAL "xTESTx")
      set(args test)
    endif()
  endif()

  # Use user-specified arguments instead of default arguments, if any.
  get_property(have_args TARGET ${name} PROPERTY _EP_${step}_ARGS SET)
  if(have_args)
    get_target_property(args ${name} _EP_${step}_ARGS)
  endif()

  if(NOT "${args}" STREQUAL "")
    # args could have empty items, so we must quote it to prevent them
    # from being silently removed
    list(APPEND cmd "${args}")
  endif()
  set(${cmd_var} "${cmd}" PARENT_SCOPE)
endfunction()


function(_ep_write_log_script
  name
  step
  cmd_var
)
  ExternalProject_Get_Property(${name} log_dir)
  ExternalProject_Get_Property(${name} stamp_dir)
  set(command "${${cmd_var}}")

  set(make "")
  set(code_cygpath_make "")
  if(command MATCHES "^\\$\\(MAKE\\)")
    # GNU make recognizes the string "$(MAKE)" as recursive make, so
    # ensure that it appears directly in the makefile.
    string(REGEX REPLACE "^\\$\\(MAKE\\)" "\${make}" command "${command}")
    set(make "-Dmake=$(MAKE)")

    if(WIN32 AND NOT CYGWIN)
      set(code_cygpath_make "
if(\${make} MATCHES \"^/\")
  execute_process(
    COMMAND cygpath -w \${make}
    OUTPUT_VARIABLE cygpath_make
    ERROR_VARIABLE cygpath_make
    RESULT_VARIABLE cygpath_error
    OUTPUT_STRIP_TRAILING_WHITESPACE
  )
  if(NOT cygpath_error)
    set(make \${cygpath_make})
  endif()
endif()
")
    endif()
  endif()

  set(config "")
  if("${CMAKE_CFG_INTDIR}" MATCHES "^\\$")
    string(REPLACE "${CMAKE_CFG_INTDIR}" "\${config}" command "${command}")
    set(config "-Dconfig=${CMAKE_CFG_INTDIR}")
  endif()

  # Wrap multiple 'COMMAND' lines up into a second-level wrapper
  # script so all output can be sent to one log file.
  if(command MATCHES "(^|;)COMMAND;")
    set(code_execute_process "
${code_cygpath_make}
execute_process(COMMAND \${command} RESULT_VARIABLE result)
if(result)
  set(msg \"Command failed (\${result}):\\n\")
  foreach(arg IN LISTS command)
    set(msg \"\${msg} '\${arg}'\")
  endforeach()
  message(FATAL_ERROR \"\${msg}\")
endif()
")
    set(code "")
    set(cmd "")
    set(sep "")
    foreach(arg IN LISTS command)
      if("x${arg}" STREQUAL "xCOMMAND")
        if(NOT "x${cmd}" STREQUAL "x")
          string(APPEND code "set(command \"${cmd}\")${code_execute_process}")
        endif()
        set(cmd "")
        set(sep "")
      else()
        string(APPEND cmd "${sep}${arg}")
        set(sep ";")
      endif()
    endforeach()
    string(APPEND code "set(command \"${cmd}\")${code_execute_process}")
    file(GENERATE
      OUTPUT "${stamp_dir}/${name}-${step}-$<CONFIG>-impl.cmake"
      CONTENT "${code}"
    )
    set(command
      ${CMAKE_COMMAND}
      "-Dmake=\${make}"
      "-Dconfig=\${config}"
      -P ${stamp_dir}/${name}-${step}-$<CONFIG>-impl.cmake
    )
  endif()

  # Wrap the command in a script to log output to files.
  set(script ${stamp_dir}/${name}-${step}-$<CONFIG>.cmake)
  set(logbase ${log_dir}/${name}-${step})
  get_property(log_merged
    TARGET ${name}
    PROPERTY _EP_LOG_MERGED_STDOUTERR
  )
  get_property(log_output_on_failure
    TARGET ${name}
    PROPERTY _EP_LOG_OUTPUT_ON_FAILURE
  )
  if (log_merged)
    set(stdout_log "${logbase}.log")
    set(stderr_log "${logbase}.log")
  else()
    set(stdout_log "${logbase}-out.log")
    set(stderr_log "${logbase}-err.log")
  endif()
  set(code "
cmake_minimum_required(VERSION \${CMAKE_VERSION}) # this file comes with cmake
${code_cygpath_make}
set(command \"${command}\")
set(log_merged \"${log_merged}\")
set(log_output_on_failure \"${log_output_on_failure}\")
set(stdout_log \"${stdout_log}\")
set(stderr_log \"${stderr_log}\")
execute_process(
  COMMAND \${command}
  RESULT_VARIABLE result
  OUTPUT_FILE \"\${stdout_log}\"
  ERROR_FILE \"\${stderr_log}\"
)
macro(read_up_to_max_size log_file output_var)
  file(SIZE \${log_file} determined_size)
  set(max_size 10240)
  if (determined_size GREATER max_size)
    math(EXPR seek_position \"\${determined_size} - \${max_size}\")
    file(READ \${log_file} \${output_var} OFFSET \${seek_position})
    set(\${output_var} \"...skipping to end...\\n\${\${output_var}}\")
  else()
    file(READ \${log_file} \${output_var})
  endif()
endmacro()
if(result)
  set(msg \"Command failed: \${result}\\n\")
  foreach(arg IN LISTS command)
    set(msg \"\${msg} '\${arg}'\")
  endforeach()
  if (\${log_merged})
    set(msg \"\${msg}\\nSee also\\n  \${stderr_log}\")
  else()
    set(msg \"\${msg}\\nSee also\\n  ${logbase}-*.log\")
  endif()
  if (\${log_output_on_failure})
    message(SEND_ERROR \"\${msg}\")
    if (\${log_merged})
      read_up_to_max_size(\"\${stderr_log}\" error_log_contents)
      message(STATUS \"Log output is:\\n\${error_log_contents}\")
    else()
      read_up_to_max_size(\"\${stdout_log}\" out_log_contents)
      read_up_to_max_size(\"\${stderr_log}\" err_log_contents)
      message(STATUS \"stdout output is:\\n\${out_log_contents}\")
      message(STATUS \"stderr output is:\\n\${err_log_contents}\")
    endif()
    message(FATAL_ERROR \"Stopping after outputting logs.\")
  else()
    message(FATAL_ERROR \"\${msg}\")
  endif()
else()
  if(NOT \"${CMAKE_GENERATOR}\" MATCHES \"Ninja\")
    set(msg \"${name} ${step} command succeeded.  See also ${logbase}-*.log\")
    message(STATUS \"\${msg}\")
  endif()
endif()
")
  file(GENERATE OUTPUT "${script}" CONTENT "${code}")
  set(command ${CMAKE_COMMAND} ${make} ${config} -P ${script})
  set(${cmd_var} "${command}" PARENT_SCOPE)
endfunction()


# On multi-config generators, provide a placeholder for a per-config subdir.
# On single-config generators, this is empty.
function(_ep_get_configuration_subdir_genex suffix_var)
  set(suffix "")
  get_property(_isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
  if(_isMultiConfig)
    if(CMAKE_GENERATOR STREQUAL "Xcode")
      # The Xcode generator does not support per-config sources,
      # so use the underlying build system's placeholder instead.
      # FIXME(#23652): We have no test for the use case requiring
      # CMAKE_CFG_INTDIR for XCODE_EMIT_EFFECTIVE_PLATFORM_NAME,
      # but $<CONFIG> does not work.
      set(suffix "/${CMAKE_CFG_INTDIR}")
    else()
      set(suffix "/$<CONFIG>")
    endif()
  endif()
  set(${suffix_var} "${suffix}" PARENT_SCOPE)
endfunction()


function(_ep_get_step_stampfile
  name
  step
  stampfile_var
)
  ExternalProject_Get_Property(${name} stamp_dir)

  _ep_get_configuration_subdir_genex(cfgdir)
  set(stampfile "${stamp_dir}${cfgdir}/${name}-${step}")

  set(${stampfile_var} "${stampfile}" PARENT_SCOPE)
endfunction()


function(_ep_get_complete_stampfile
  name
  stampfile_var
)
  set(cmf_dir ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles)
  _ep_get_configuration_subdir_genex(cfgdir)
  set(stampfile "${cmf_dir}${cfgdir}/${name}-complete")

  set(${stampfile_var} ${stampfile} PARENT_SCOPE)
endfunction()


function(_ep_step_add_target
  name
  step
  no_deps
)
  if(TARGET ${name}-${step})
    return()
  endif()
  get_property(cmp0114 TARGET ${name} PROPERTY _EP_CMP0114)
  _ep_get_step_stampfile(${name} ${step} stamp_file)
  cmake_policy(PUSH)
  if(cmp0114 STREQUAL "NEW")
    # To implement CMP0114 NEW behavior with Makefile generators,
    # we need CMP0113 NEW behavior.
    cmake_policy(SET CMP0113 NEW)
  endif()
  add_custom_target(${name}-${step} DEPENDS ${stamp_file})
  cmake_policy(POP)
  set_target_properties(${name}-${step} PROPERTIES
    _EP_IS_EXTERNAL_PROJECT_STEP 1
    LABELS "${name}"
    FOLDER "ExternalProjectTargets/${name}"
  )

  if(cmp0114 STREQUAL "NEW")
    # Add target-level dependencies for the step.
    get_property(exclude_from_main
      TARGET ${name}
      PROPERTY _EP_${step}_EXCLUDE_FROM_MAIN
    )
    if(NOT exclude_from_main)
      add_dependencies(${name} ${name}-${step})
    endif()
    _ep_step_add_target_dependencies(${name} ${step} ${step})
    _ep_step_add_target_dependents(${name} ${step} ${step})

    get_property(independent TARGET ${name} PROPERTY _EP_${step}_INDEPENDENT)
  else()
    if(no_deps AND "${step}" MATCHES "^(configure|build|install|test)$")
      message(AUTHOR_WARNING
        "Using NO_DEPENDS for \"${step}\" step  might break parallel builds"
      )
    endif()
    set(independent ${no_deps})
  endif()

  # Depend on other external projects (target-level).
  if(NOT independent)
    get_property(deps TARGET ${name} PROPERTY _EP_DEPENDS)
    foreach(arg IN LISTS deps)
      add_dependencies(${name}-${step} ${arg})
    endforeach()
  endif()
endfunction()


function(_ep_step_add_target_dependencies
  name
  step
  node
)
  get_property(dependees
    TARGET ${name}
    PROPERTY _EP_${node}_INTERNAL_DEPENDEES
  )
  list(REMOVE_DUPLICATES dependees)
  foreach(dependee IN LISTS dependees)
    get_property(exclude_from_main
      TARGET ${name}
      PROPERTY _EP_${step}_EXCLUDE_FROM_MAIN
    )
    get_property(dependee_dependers
      TARGET ${name}
      PROPERTY _EP_${dependee}_INTERNAL_DEPENDERS
    )
    if(exclude_from_main OR dependee_dependers MATCHES ";")
      # The step on which our step target depends itself has
      # dependents in multiple targes.  It needs a step target too
      # so that there is a unique place for its custom command.
      _ep_step_add_target("${name}" "${dependee}" "FALSE")
    endif()

    if(TARGET ${name}-${dependee})
      add_dependencies(${name}-${step} ${name}-${dependee})
    else()
      _ep_step_add_target_dependencies(${name} ${step} ${dependee})
    endif()
  endforeach()
endfunction()


function(_ep_step_add_target_dependents
  name
  step
  node
)
  get_property(dependers
    TARGET ${name}
    PROPERTY _EP_${node}_INTERNAL_DEPENDERS
  )
  list(REMOVE_DUPLICATES dependers)
  foreach(depender IN LISTS dependers)
    if(TARGET ${name}-${depender})
      add_dependencies(${name}-${depender} ${name}-${step})
    else()
      _ep_step_add_target_dependents(${name} ${step} ${depender})
    endif()
  endforeach()
endfunction()


function(ExternalProject_Add_StepTargets name)
  get_property(cmp0114 TARGET ${name} PROPERTY _EP_CMP0114)
  set(steps ${ARGN})
  if(ARGC GREATER 1 AND "${ARGV1}" STREQUAL "NO_DEPENDS")
    set(no_deps 1)
    list(REMOVE_AT steps 0)
  else()
    set(no_deps 0)
  endif()
  if(cmp0114 STREQUAL "NEW")
    if(no_deps)
      message(FATAL_ERROR
        "The 'NO_DEPENDS' option is no longer allowed.  "
        "It has been superseded by the per-step 'INDEPENDENT' option.  "
        "See policy CMP0114."
      )
    endif()
  elseif(cmp0114 STREQUAL "")
    cmake_policy(GET_WARNING CMP0114 _cmp0114_warning)
    string(APPEND _cmp0114_warning "\n"
      "ExternalProject target '${name}' would depend on the targets for "
      "step(s) '${steps}' under policy CMP0114, but this is being left out "
      "for compatibility since the policy is not set."
    )
    if(no_deps)
      string(APPEND _cmp0114_warning "  "
        "Also, the NO_DEPENDS option is deprecated in favor of policy CMP0114."
      )
    endif()
    message(AUTHOR_WARNING "${_cmp0114_warning}")
  endif()
  foreach(step IN LISTS steps)
    _ep_step_add_target("${name}" "${step}" "${no_deps}")
  endforeach()
endfunction()


# While this function is referenced in shared_internal_commands.cmake in a few
# places, all of those code paths will only be reached by calling one of the
# functions defined in this file. Keep it here, since it is part of the public
# interface of ExternalProject.
function(ExternalProject_Add_Step name step)
  get_property(cmp0114 TARGET ${name} PROPERTY _EP_CMP0114)
  _ep_get_complete_stampfile(${name} complete_stamp_file)
  _ep_get_step_stampfile(${name} ${step} stamp_file)

  set(keywords
    COMMAND
    COMMENT
    DEPENDEES
    DEPENDERS
    DEPENDS
    INDEPENDENT
    BYPRODUCTS
    ALWAYS
    JOB_SERVER_AWARE
    EXCLUDE_FROM_MAIN
    WORKING_DIRECTORY
    LOG
    USES_TERMINAL
  )
  _ep_parse_arguments(
    ExternalProject_Add_Step
    "${keywords}"
    ${name}
    _EP_${step}_
    "${ARGN}"
  )

  get_property(independent
    TARGET ${name}
    PROPERTY _EP_${step}_INDEPENDENT
  )
  if(independent STREQUAL "")
    set(independent FALSE)
    set_property(TARGET ${name} PROPERTY
      _EP_${step}_INDEPENDENT "${independent}"
    )
  endif()

  get_property(exclude_from_main
    TARGET ${name}
    PROPERTY _EP_${step}_EXCLUDE_FROM_MAIN
  )
  if(NOT exclude_from_main)
    add_custom_command(APPEND
      OUTPUT ${complete_stamp_file}
      DEPENDS ${stamp_file}
    )
  endif()

  # Steps depending on this step.
  get_property(dependers TARGET ${name} PROPERTY _EP_${step}_DEPENDERS)
  set_property(TARGET ${name} APPEND PROPERTY
    _EP_${step}_INTERNAL_DEPENDERS ${dependers}
  )
  foreach(depender IN LISTS dependers)
    set_property(TARGET ${name} APPEND PROPERTY
      _EP_${depender}_INTERNAL_DEPENDEES ${step}
    )
    _ep_get_step_stampfile(${name} ${depender} depender_stamp_file)
    add_custom_command(APPEND
      OUTPUT ${depender_stamp_file}
      DEPENDS ${stamp_file}
    )
    if(cmp0114 STREQUAL "NEW" AND NOT independent)
      get_property(dep_independent
        TARGET ${name}
        PROPERTY _EP_${depender}_INDEPENDENT
      )
      if(dep_independent)
        message(FATAL_ERROR
          "ExternalProject '${name}' step '${depender}' is marked INDEPENDENT "
          "but depends on step '${step}' that is not marked INDEPENDENT."
        )
      endif()
    endif()
  endforeach()

  # Dependencies on files.
  get_property(depends TARGET ${name} PROPERTY _EP_${step}_DEPENDS)

  # Byproducts of the step.
  get_property(byproducts TARGET ${name} PROPERTY _EP_${step}_BYPRODUCTS)

  # Dependencies on steps.
  get_property(dependees TARGET ${name} PROPERTY _EP_${step}_DEPENDEES)
  set_property(TARGET ${name} APPEND PROPERTY
    _EP_${step}_INTERNAL_DEPENDEES ${dependees}
  )
  foreach(dependee IN LISTS dependees)
    set_property(TARGET ${name} APPEND PROPERTY
      _EP_${dependee}_INTERNAL_DEPENDERS ${step}
    )
    _ep_get_step_stampfile(${name} ${dependee} dependee_stamp_file)
    list(APPEND depends ${dependee_stamp_file})
    if(cmp0114 STREQUAL "NEW" AND independent)
      get_property(dep_independent
        TARGET ${name}
        PROPERTY _EP_${dependee}_INDEPENDENT
      )
      if(NOT dep_independent)
        message(FATAL_ERROR
          "ExternalProject '${name}' step '${step}' is marked INDEPENDENT "
          "but depends on step '${dependee}' that is not marked INDEPENDENT."
        )
      endif()
    endif()
  endforeach()

  # The command to run.
  get_property(command TARGET ${name} PROPERTY _EP_${step}_COMMAND)
  if(command)
    set(comment "Performing ${step} step for '${name}'")
  else()
    set(comment "No ${step} step for '${name}'")
  endif()
  get_property(work_dir
    TARGET ${name}
    PROPERTY _EP_${step}_WORKING_DIRECTORY
  )

  # Replace list separators.
  get_property(sep
    TARGET ${name}
    PROPERTY _EP_LIST_SEPARATOR
  )
  if(sep AND command)
    string(REPLACE "${sep}" "\\;" command "${command}")
  endif()

  # Replace location tags.
  _ep_replace_location_tags(
    ${name}
    comment
    command
    work_dir
    byproducts
  )

  if(NOT "x${work_dir}" STREQUAL "x")
    set(maybe_WORKING_DIRECTORY "WORKING_DIRECTORY [==[${work_dir}]==]")
  else()
    set(maybe_WORKING_DIRECTORY "")
  endif()

  # Custom comment?
  get_property(comment_set
    TARGET ${name}
    PROPERTY _EP_${step}_COMMENT
    SET
  )
  if(comment_set)
    get_property(comment
      TARGET ${name}
      PROPERTY _EP_${step}_COMMENT
    )
  endif()

  # Uses terminal?
  get_property(uses_terminal
    TARGET ${name}
    PROPERTY _EP_${step}_USES_TERMINAL
  )
  if(uses_terminal)
    set(maybe_USES_TERMINAL USES_TERMINAL)
  else()
    set(maybe_USES_TERMINAL "")
  endif()

  # Run every time?
  get_property(always
    TARGET ${name}
    PROPERTY _EP_${step}_ALWAYS
  )
  if(always)
    set(maybe_COMMAND_touch "")
    # Mark stamp files for all configs as SYMBOLIC since we do not create them.
    # Remove any existing stamp in case the option changed in an existing tree.
    get_property(_isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
    if(_isMultiConfig)
      _ep_get_configuration_subdir_genex(cfgdir)
      foreach(cfg IN LISTS CMAKE_CONFIGURATION_TYPES)
        string(REPLACE "${cfgdir}" "/${cfg}"
          stamp_file_config "${stamp_file}"
        )
        set_property(SOURCE ${stamp_file_config} PROPERTY SYMBOLIC 1)
        file(REMOVE ${stamp_file_config})
      endforeach()
      if(CMAKE_GENERATOR STREQUAL "Xcode")
        # See Xcode case in _ep_get_configuration_subdir_genex.
        set_property(SOURCE ${stamp_file} PROPERTY SYMBOLIC 1)
      endif()
    else()
      set_property(SOURCE ${stamp_file} PROPERTY SYMBOLIC 1)
      file(REMOVE ${stamp_file})
    endif()
  else()
    set(maybe_COMMAND_touch "COMMAND \${CMAKE_COMMAND} -E touch \${stamp_file}")
  endif()

  get_property(job_server_aware
    TARGET ${name}
    PROPERTY _EP_${step}_JOB_SERVER_AWARE
  )
  if(job_server_aware)
    set(maybe_JOB_SERVER_AWARE "JOB_SERVER_AWARE 1")
  else()
    set(maybe_JOB_SERVER_AWARE "")
  endif()

  # Wrap with log script?
  get_property(log TARGET ${name} PROPERTY _EP_${step}_LOG)
  if(command AND log)
    _ep_write_log_script(${name} ${step} command)
  endif()

  if("${command}" STREQUAL "")
    # Some generators (i.e. Xcode) will not generate a file level target
    # if no command is set, and therefore the dependencies on this
    # target will be broken.
    # The empty command is replaced by an echo command here in order to
    # avoid this issue.
    set(command ${CMAKE_COMMAND} -E echo_append)
  endif()

  set(__cmdQuoted)
  foreach(__item IN LISTS command)
    string(APPEND __cmdQuoted " [==[${__item}]==]")
  endforeach()
  cmake_language(EVAL CODE "
    add_custom_command(
      OUTPUT \${stamp_file}
      BYPRODUCTS \${byproducts}
      COMMENT [===[${comment}]===]
      COMMAND ${__cmdQuoted}
      DEPENDS \${depends}
      VERBATIM
      ${maybe_COMMAND_touch}
      ${maybe_JOB_SERVER_AWARE}
      ${maybe_WORKING_DIRECTORY}
      ${maybe_USES_TERMINAL}
    )"
  )
  set_property(TARGET ${name} APPEND PROPERTY _EP_STEPS ${step})

  # Add custom "step target"?
  get_property(step_targets
    TARGET ${name}
    PROPERTY _EP_STEP_TARGETS
  )
  if(NOT step_targets)
    get_property(step_targets
      DIRECTORY
      PROPERTY EP_STEP_TARGETS
    )
  endif()
  foreach(st IN LISTS step_targets)
    if("${st}" STREQUAL "${step}")
      _ep_step_add_target("${name}" "${step}" "FALSE")
      break()
    endif()
  endforeach()

  get_property(independent_step_targets
    TARGET ${name} PROPERTY
    _EP_INDEPENDENT_STEP_TARGETS
  )
  if(NOT independent_step_targets)
    get_property(independent_step_targets
      DIRECTORY
      PROPERTY EP_INDEPENDENT_STEP_TARGETS
    )
  endif()
  if(cmp0114 STREQUAL "NEW")
    if(independent_step_targets)
      message(FATAL_ERROR
        "ExternalProject '${name}' option 'INDEPENDENT_STEP_TARGETS' is set to"
        "\n  ${independent_step_targets}\n"
        "but the option is no longer allowed.  "
        "It has been superseded by the per-step 'INDEPENDENT' option.  "
        "See policy CMP0114."
      )
    endif()
  else()
    if(independent_step_targets AND cmp0114 STREQUAL "")
      get_property(warned
        TARGET ${name}
        PROPERTY _EP_CMP0114_WARNED_INDEPENDENT_STEP_TARGETS
      )
      if(NOT warned)
        set_property(TARGET ${name} PROPERTY
          _EP_CMP0114_WARNED_INDEPENDENT_STEP_TARGETS 1
        )
        cmake_policy(GET_WARNING CMP0114 _cmp0114_warning)
        string(APPEND _cmp0114_warning
          "\n"
          "ExternalProject '${name}' option INDEPENDENT_STEP_TARGETS is set to"
          "\n  ${independent_step_targets}\n"
          "but the option is deprecated in favor of policy CMP0114."
        )
        message(AUTHOR_WARNING "${_cmp0114_warning}")
      endif()
    endif()
    foreach(st IN LISTS independent_step_targets)
      if("${st}" STREQUAL "${step}")
        _ep_step_add_target("${name}" "${step}" "TRUE")
        break()
      endif()
    endforeach()
  endif()
endfunction()


function(ExternalProject_Add_StepDependencies name step)
  set(dependencies ${ARGN})

  # Sanity checks on "name" and "step".
  if(NOT TARGET ${name})
    message(FATAL_ERROR
      "Cannot find target \"${name}\". Perhaps it has not yet been created "
      "using ExternalProject_Add."
    )
  endif()

  get_property(type TARGET ${name} PROPERTY TYPE)
  if(NOT type STREQUAL "UTILITY")
    message(FATAL_ERROR
      "Target \"${name}\" was not generated by ExternalProject_Add."
    )
  endif()

  get_property(is_ep TARGET ${name} PROPERTY _EP_IS_EXTERNAL_PROJECT)
  if(NOT is_ep)
    message(FATAL_ERROR
      "Target \"${name}\" was not generated by ExternalProject_Add."
    )
  endif()

  get_property(steps TARGET ${name} PROPERTY _EP_STEPS)
  list(FIND steps ${step} is_step)
  if(is_step LESS 0)
    message(FATAL_ERROR
      "External project \"${name}\" does not have a step \"${step}\"."
    )
  endif()

  if(TARGET ${name}-${step})
    get_property(type TARGET ${name}-${step} PROPERTY TYPE)
    if(NOT type STREQUAL "UTILITY")
      message(FATAL_ERROR
        "Target \"${name}-${step}\" was not generated by "
        "ExternalProject_Add_StepTargets."
      )
    endif()
    get_property(is_ep_step
      TARGET ${name}-${step}
      PROPERTY _EP_IS_EXTERNAL_PROJECT_STEP
    )
    if(NOT is_ep_step)
      message(FATAL_ERROR
        "Target \"${name}-${step}\" was not generated by "
        "ExternalProject_Add_StepTargets."
      )
    endif()
  endif()

  # Always add file-level dependency, but add target-level dependency
  # only if the target exists for that step.
  _ep_get_step_stampfile(${name} ${step} stamp_file)
  foreach(dep IN LISTS dependencies)
    add_custom_command(APPEND
      OUTPUT ${stamp_file}
      DEPENDS ${dep}
    )
  endforeach()
  if(TARGET ${name}-${step})
    add_dependencies(${name}-${step} ${dependencies})
  endif()

endfunction()


function(_ep_add_mkdir_command name)
  ExternalProject_Get_Property(${name} tmp_dir)
  set(script_filename "${tmp_dir}/${name}-mkdirs.cmake")
  _ep_get_configuration_subdir_genex(cfgdir)

  ExternalProject_Add_Step(${name} mkdir
    INDEPENDENT TRUE
    COMMENT "Creating directories for '${name}'"
    COMMAND ${CMAKE_COMMAND} -Dcfgdir=${cfgdir} -P ${script_filename}
  )
endfunction()


function(_ep_get_file_deps var name)
  set(file_deps)

  get_property(deps
    TARGET ${name}
    PROPERTY _EP_DEPENDS
  )
  foreach(dep IN LISTS deps)
    get_property(dep_type
      TARGET ${dep}
      PROPERTY TYPE
    )
    if(dep_type STREQUAL "UTILITY")
      get_property(is_ep
        TARGET ${dep}
        PROPERTY _EP_IS_EXTERNAL_PROJECT
      )
      if(is_ep)
        _ep_get_step_stampfile(${dep} "done" done_stamp_file)
        list(APPEND file_deps ${done_stamp_file})
      endif()
    endif()
  endforeach()

  set("${var}" "${file_deps}" PARENT_SCOPE)
endfunction()


function(_ep_extract_configure_command var name)
  get_property(cmd_set
    TARGET ${name}
    PROPERTY _EP_CONFIGURE_COMMAND
    SET
  )
  if(cmd_set)
    get_property(cmd
      TARGET ${name}
      PROPERTY _EP_CONFIGURE_COMMAND
    )
  else()
    get_target_property(cmake_command ${name} _EP_CMAKE_COMMAND)
    if(cmake_command)
      set(cmd "${cmake_command}")
    else()
      set(cmd "${CMAKE_COMMAND}")
    endif()

    get_property(cmake_args
      TARGET ${name}
      PROPERTY _EP_CMAKE_ARGS
    )
    list(APPEND cmd ${cmake_args})

    # If there are any CMAKE_CACHE_ARGS or CMAKE_CACHE_DEFAULT_ARGS,
    # write an initial cache and use it
    get_property(cmake_cache_args
      TARGET ${name}
      PROPERTY _EP_CMAKE_CACHE_ARGS
    )
    get_property(cmake_cache_default_args
      TARGET ${name}
      PROPERTY _EP_CMAKE_CACHE_DEFAULT_ARGS
    )

    set(has_cmake_cache_args 0)
    if(NOT "${cmake_cache_args}" STREQUAL "")
      set(has_cmake_cache_args 1)
    endif()

    set(has_cmake_cache_default_args 0)
    if(NOT "${cmake_cache_default_args}" STREQUAL "")
      set(has_cmake_cache_default_args 1)
    endif()

    get_target_property(cmake_generator ${name}
      _EP_CMAKE_GENERATOR
    )
    get_target_property(cmake_generator_instance ${name}
      _EP_CMAKE_GENERATOR_INSTANCE
    )
    get_target_property(cmake_generator_platform ${name}
      _EP_CMAKE_GENERATOR_PLATFORM
    )
    get_target_property(cmake_generator_toolset ${name}
      _EP_CMAKE_GENERATOR_TOOLSET
    )
    if(cmake_generator)
      list(APPEND cmd "-G${cmake_generator}")
      if(cmake_generator_platform)
        list(APPEND cmd "-A${cmake_generator_platform}")
      endif()
      if(cmake_generator_toolset)
        list(APPEND cmd "-T${cmake_generator_toolset}")
      endif()
      if(cmake_generator_instance)
        list(APPEND cmd
          "-DCMAKE_GENERATOR_INSTANCE:INTERNAL=${cmake_generator_instance}"
        )
      endif()
    else()
      if(CMAKE_EXTRA_GENERATOR)
        list(APPEND cmd "-G${CMAKE_EXTRA_GENERATOR} - ${CMAKE_GENERATOR}")
      else()
        list(APPEND cmd "-G${CMAKE_GENERATOR}")
        # GreenHills needs to know about the compiler and toolset.
        # Be sure to update the similar section in
        # FetchContent.cmake:__FetchContent_directPopulate()
        if("${CMAKE_GENERATOR}" MATCHES "Green Hills MULTI")
          set(has_cmake_cache_default_args 1)
          list(APPEND cmake_cache_default_args
            "-DGHS_TARGET_PLATFORM:STRING=${GHS_TARGET_PLATFORM}"
            "-DGHS_PRIMARY_TARGET:STRING=${GHS_PRIMARY_TARGET}"
            "-DGHS_TOOLSET_ROOT:STRING=${GHS_TOOLSET_ROOT}"
            "-DGHS_OS_ROOT:STRING=${GHS_OS_ROOT}"
            "-DGHS_OS_DIR:STRING=${GHS_OS_DIR}"
            "-DGHS_BSP_NAME:STRING=${GHS_BSP_NAME}"
          )
        endif()
      endif()
      if(cmake_generator_platform)
        message(FATAL_ERROR
          "Option CMAKE_GENERATOR_PLATFORM not allowed without "
          "CMAKE_GENERATOR."
        )
      endif()
      if(CMAKE_GENERATOR_PLATFORM)
        list(APPEND cmd "-A${CMAKE_GENERATOR_PLATFORM}")
      endif()
      if(cmake_generator_toolset)
        message(FATAL_ERROR
          "Option CMAKE_GENERATOR_TOOLSET not allowed without CMAKE_GENERATOR."
        )
      endif()
      if(CMAKE_GENERATOR_TOOLSET)
        list(APPEND cmd "-T${CMAKE_GENERATOR_TOOLSET}")
      endif()
      if(cmake_generator_instance)
        message(FATAL_ERROR
          "Option CMAKE_GENERATOR_INSTANCE not allowed without CMAKE_GENERATOR."
        )
      endif()
      if(CMAKE_GENERATOR_INSTANCE)
        list(APPEND cmd
          "-DCMAKE_GENERATOR_INSTANCE:INTERNAL=${CMAKE_GENERATOR_INSTANCE}"
        )
      endif()
    endif()

    if(has_cmake_cache_args OR has_cmake_cache_default_args)
      set(_ep_cache_args_script "<TMP_DIR>/${name}-cache-$<CONFIG>.cmake")
      if(has_cmake_cache_args)
        _ep_command_line_to_initial_cache(
          script_initial_cache_force
          "${cmake_cache_args}"
          1
        )
      endif()
      if(has_cmake_cache_default_args)
        _ep_command_line_to_initial_cache(
          script_initial_cache_default
          "${cmake_cache_default_args}"
          0
        )
      endif()
      _ep_write_initial_cache(
        ${name}
        "${_ep_cache_args_script}"
        "${script_initial_cache_force}${script_initial_cache_default}"
      )
      list(APPEND cmd "-C${_ep_cache_args_script}")
      _ep_replace_location_tags(${name} _ep_cache_args_script)
      set(_ep_cache_args_script
        "${_ep_cache_args_script}"
        PARENT_SCOPE
      )
    endif()

    list(APPEND cmd -S "<SOURCE_DIR><SOURCE_SUBDIR>" -B "<BINARY_DIR>")
  endif()

  set("${var}" "${cmd}" PARENT_SCOPE)
endfunction()


# TODO: Make sure external projects use the proper compiler
function(_ep_add_configure_command name)
  ExternalProject_Get_Property(${name} binary_dir tmp_dir)

  set(file_deps)
  get_property(configure_handled_by_build
    TARGET ${name}
    PROPERTY _EP_CONFIGURE_HANDLED_BY_BUILD
  )
  if(NOT configure_handled_by_build)
    # Depend on other external projects (file-level)
    _ep_get_file_deps(file_deps ${name})
  endif()

  _ep_extract_configure_command(cmd ${name})

  # If anything about the configure command changes, (command itself, cmake
  # used, cmake args or cmake generator) then re-run the configure step.
  # Fixes issue https://gitlab.kitware.com/cmake/cmake/-/issues/10258
  #
  configure_file(
    ${CMAKE_CURRENT_FUNCTION_LIST_DIR}/ExternalProject/cfgcmd.txt.in
    ${tmp_dir}/${name}-cfgcmd.txt
    @ONLY
  )
  list(APPEND file_deps ${tmp_dir}/${name}-cfgcmd.txt)
  list(APPEND file_deps ${_ep_cache_args_script})

  _ep_get_update_disconnected(update_disconnected ${name})
  if(update_disconnected)
    set(dependees patch_disconnected)
  else()
    set(dependees patch)
  endif()

  get_property(log
    TARGET ${name}
    PROPERTY _EP_LOG_CONFIGURE
  )
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  get_property(uses_terminal
    TARGET ${name}
    PROPERTY _EP_USES_TERMINAL_CONFIGURE
  )
  if(uses_terminal)
    set(uses_terminal USES_TERMINAL 1)
  else()
    set(uses_terminal "")
  endif()

  set(__cmdQuoted)
  foreach(__item IN LISTS cmd)
    string(APPEND __cmdQuoted " [==[${__item}]==]")
  endforeach()
  cmake_language(EVAL CODE "
    ExternalProject_Add_Step(${name} configure
      INDEPENDENT FALSE
      COMMAND ${__cmdQuoted}
      WORKING_DIRECTORY \${binary_dir}
      DEPENDEES \${dependees}
      DEPENDS \${file_deps}
      ${log}
      ${uses_terminal}
    )"
  )
endfunction()


function(_ep_add_build_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  set(file_deps)
  get_property(configure_handled_by_build
    TARGET ${name}
    PROPERTY _EP_CONFIGURE_HANDLED_BY_BUILD
  )
  if(configure_handled_by_build)
    # Depend on other external projects (file-level)
    _ep_get_file_deps(file_deps ${name})
  endif()

  get_property(cmd_set
    TARGET ${name}
    PROPERTY _EP_BUILD_COMMAND
    SET
  )
  if(cmd_set)
    get_property(cmd
      TARGET ${name}
      PROPERTY _EP_BUILD_COMMAND
    )
  else()
    _ep_get_build_command(${name} BUILD cmd)
  endif()

  get_property(log
    TARGET ${name}
    PROPERTY _EP_LOG_BUILD
  )
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  get_property(uses_terminal
    TARGET ${name}
    PROPERTY _EP_USES_TERMINAL_BUILD
  )
  if(uses_terminal)
    set(uses_terminal USES_TERMINAL 1)
  else()
    set(uses_terminal "")
  endif()

  get_property(build_always
    TARGET ${name}
    PROPERTY _EP_BUILD_ALWAYS
  )
  if(build_always)
    set(always 1)
  else()
    set(always 0)
  endif()

  get_property(build_byproducts
    TARGET ${name}
    PROPERTY _EP_BUILD_BYPRODUCTS
  )

  get_property(build_job_server_aware
    TARGET ${name}
    PROPERTY _EP_BUILD_JOB_SERVER_AWARE
  )
  if(build_job_server_aware)
    set(maybe_JOB_SERVER_AWARE "JOB_SERVER_AWARE 1")
  else()
    set(maybe_JOB_SERVER_AWARE "")
  endif()


  set(__cmdQuoted)
  foreach(__item IN LISTS cmd)
    string(APPEND __cmdQuoted " [==[${__item}]==]")
  endforeach()
  cmake_language(EVAL CODE "
    ExternalProject_Add_Step(${name} build
      INDEPENDENT FALSE
      COMMAND ${__cmdQuoted}
      BYPRODUCTS \${build_byproducts}
      WORKING_DIRECTORY \${binary_dir}
      DEPENDEES configure
      DEPENDS \${file_deps}
      ALWAYS \${always}
      ${maybe_JOB_SERVER_AWARE}
      ${log}
      ${uses_terminal}
    )"
  )
endfunction()


function(_ep_add_install_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  get_property(cmd_set
    TARGET ${name}
    PROPERTY _EP_INSTALL_COMMAND
    SET
  )
  if(cmd_set)
    get_property(cmd
      TARGET ${name}
      PROPERTY _EP_INSTALL_COMMAND
    )
  else()
    _ep_get_build_command(${name} INSTALL cmd)
  endif()

  get_property(log
    TARGET ${name}
    PROPERTY _EP_LOG_INSTALL
  )
  if(log)
    set(log LOG 1)
  else()
    set(log "")
  endif()

  get_property(uses_terminal
    TARGET ${name}
    PROPERTY _EP_USES_TERMINAL_INSTALL
  )
  if(uses_terminal)
    set(uses_terminal USES_TERMINAL 1)
  else()
    set(uses_terminal "")
  endif()

  # With BUILD_ALWAYS+BUILD_BYPRODUCTS, Ninja restats the
  # build step outputs and may not consider this step to
  # be out-of-date.  Explicitly mark it out-of-date too.
  get_property(build_always
    TARGET ${name}
    PROPERTY _EP_BUILD_ALWAYS
  )
  if(build_always)
    set(always 1)
  else()
    set(always 0)
  endif()

  get_property(install_byproducts
    TARGET ${name}
    PROPERTY _EP_INSTALL_BYPRODUCTS
  )

  get_property(install_job_server_aware
    TARGET ${name}
    PROPERTY _EP_INSTALL_JOB_SERVER_AWARE
  )
  if(install_job_server_aware)
    set(maybe_JOB_SERVER_AWARE "JOB_SERVER_AWARE 1")
  else()
    set(maybe_JOB_SERVER_AWARE "")
  endif()

  set(__cmdQuoted)
  foreach(__item IN LISTS cmd)
    string(APPEND __cmdQuoted " [==[${__item}]==]")
  endforeach()
  cmake_language(EVAL CODE "
    ExternalProject_Add_Step(${name} install
      INDEPENDENT FALSE
      COMMAND ${__cmdQuoted}
      BYPRODUCTS \${install_byproducts}
      WORKING_DIRECTORY \${binary_dir}
      DEPENDEES build
      ALWAYS \${always}
      ${maybe_JOB_SERVER_AWARE}
      ${log}
      ${uses_terminal}
    )"
  )
endfunction()


function(_ep_add_test_command name)
  ExternalProject_Get_Property(${name} binary_dir)

  get_property(before TARGET ${name} PROPERTY _EP_TEST_BEFORE_INSTALL)
  get_property(after TARGET ${name} PROPERTY _EP_TEST_AFTER_INSTALL)
  get_property(exclude TARGET ${name} PROPERTY _EP_TEST_EXCLUDE_FROM_MAIN)
  get_property(cmd_set TARGET ${name} PROPERTY _EP_TEST_COMMAND SET)

  # Only actually add the test step if one of the test related properties is
  # explicitly set. (i.e. the test step is omitted unless requested...)
  #
  if(cmd_set OR before OR after OR exclude)
    if(cmd_set)
      get_property(cmd
        TARGET ${name}
        PROPERTY _EP_TEST_COMMAND
      )
    else()
      _ep_get_build_command(${name} TEST cmd)
    endif()

    if(before)
      set(dependees_args DEPENDEES build)
    else()
      set(dependees_args DEPENDEES install)
    endif()

    if(exclude)
      set(dependers_args "")
      set(exclude_args EXCLUDE_FROM_MAIN 1)
    else()
      if(before)
        set(dependers_args DEPENDERS install)
      else()
        set(dependers_args "")
      endif()
      set(exclude_args "")
    endif()

    get_property(log
      TARGET ${name}
      PROPERTY _EP_LOG_TEST
    )
    if(log)
      set(log LOG 1)
    else()
      set(log "")
    endif()

    get_property(uses_terminal
      TARGET ${name}
      PROPERTY _EP_USES_TERMINAL_TEST
    )
    if(uses_terminal)
      set(uses_terminal USES_TERMINAL 1)
    else()
      set(uses_terminal "")
    endif()

    set(__cmdQuoted)
    foreach(__item IN LISTS cmd)
      string(APPEND __cmdQuoted " [==[${__item}]==]")
    endforeach()
    cmake_language(EVAL CODE "
      ExternalProject_Add_Step(${name} test
        INDEPENDENT FALSE
        COMMAND ${__cmdQuoted}
        WORKING_DIRECTORY \${binary_dir}
        ${dependees_args}
        ${dependers_args}
        ${exclude_args}
        ${log}
        ${uses_terminal}
      )"
    )
  endif()
endfunction()


function(ExternalProject_Add name)
  cmake_policy(GET CMP0097 _EP_CMP0097
    PARENT_SCOPE # undocumented, do not use outside of CMake
  )
  cmake_policy(GET CMP0114 cmp0114
    PARENT_SCOPE # undocumented, do not use outside of CMake
  )
  if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12 AND
     NOT cmp0114 STREQUAL "NEW")
    message(AUTHOR_WARNING
      "Policy CMP0114 is not set to NEW.  "
      "In order to support the Xcode \"new build system\", "
      "this project must be updated to set policy CMP0114 to NEW."
      "\n"
      "Since CMake is generating for the Xcode \"new build system\", "
      "ExternalProject_Add will use policy CMP0114's NEW behavior anyway, "
      "but the generated build system may not match what the project intends."
    )
    set(cmp0114 "NEW")
  endif()
  cmake_policy(GET CMP0135 _EP_CMP0135
    PARENT_SCOPE # undocumented, do not use outside of CMake
  )

  _ep_get_configuration_subdir_genex(cfgdir)

  # Add a custom target for the external project.
  set(cmf_dir ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles)
  _ep_get_complete_stampfile(${name} complete_stamp_file)

  cmake_policy(PUSH)
  if(cmp0114 STREQUAL "NEW")
    # To implement CMP0114 NEW behavior with Makefile generators,
    # we need CMP0113 NEW behavior.
    cmake_policy(SET CMP0113 NEW)
  endif()
  # The "ALL" option to add_custom_target just tells it to not set the
  # EXCLUDE_FROM_ALL target property. Later, if the EXCLUDE_FROM_ALL
  # argument was passed, we explicitly set it for the target.
  add_custom_target(${name} ALL DEPENDS ${complete_stamp_file})
  cmake_policy(POP)
  set_target_properties(${name} PROPERTIES
    _EP_IS_EXTERNAL_PROJECT 1
    LABELS ${name}
    FOLDER "ExternalProjectTargets/${name}"
    _EP_CMP0114 "${cmp0114}"
  )

  _ep_get_add_keywords(keywords)
  _ep_parse_arguments(
    ExternalProject_Add
    "${keywords}"
    ${name}
    _EP_
    "${ARGN}"
  )
  _ep_set_directories(${name})
  _ep_get_step_stampfile(${name} "done" done_stamp_file)
  _ep_get_step_stampfile(${name} "install" install_stamp_file)

  # Set the EXCLUDE_FROM_ALL target property if required.
  get_property(exclude_from_all
    TARGET ${name}
    PROPERTY _EP_EXCLUDE_FROM_ALL
  )
  if(exclude_from_all)
    set_property(TARGET ${name} PROPERTY EXCLUDE_FROM_ALL TRUE)
  endif()

  get_property(repo TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
  if(NOT repo STREQUAL "")
    cmake_policy(GET CMP0150 cmp0150
      PARENT_SCOPE # undocumented, do not use outside of CMake
    )
    get_property(source_dir TARGET ${name} PROPERTY _EP_SOURCE_DIR)
    get_filename_component(work_dir "${source_dir}" PATH)
    _ep_resolve_git_remote(resolved_git_repository "${repo}" "${cmp0150}" "${work_dir}")
    set_property(TARGET ${name} PROPERTY _EP_GIT_REPOSITORY ${resolved_git_repository})
    set(_EP_GIT_REPOSITORY "${resolved_git_repository}")
  endif()

  # The 'complete' step depends on all other steps and creates a
  # 'done' mark.  A dependent external project's 'configure' step
  # depends on the 'done' mark so that it rebuilds when this project
  # rebuilds.  It is important that 'done' is not the output of any
  # custom command so that CMake does not propagate build rules to
  # other external project targets, which may cause problems during
  # parallel builds.  However, the Ninja generator needs to see the entire
  # dependency graph, and can cope with custom commands belonging to
  # multiple targets, so we add the 'done' mark as an output for Ninja only.
  set(complete_outputs ${complete_stamp_file})
  if(${CMAKE_GENERATOR} MATCHES "Ninja")
    set(complete_outputs ${complete_outputs} ${done_stamp_file})
  endif()

  add_custom_command(
    OUTPUT ${complete_outputs}
    COMMENT "Completed '${name}'"
    COMMAND ${CMAKE_COMMAND} -E make_directory ${cmf_dir}${cfgdir}
    COMMAND ${CMAKE_COMMAND} -E touch ${complete_stamp_file}
    COMMAND ${CMAKE_COMMAND} -E touch ${done_stamp_file}
    DEPENDS ${install_stamp_file}
    VERBATIM
  )

  # Depend on other external projects (target-level).
  get_property(deps
    TARGET ${name}
    PROPERTY _EP_DEPENDS
  )
  foreach(arg IN LISTS deps)
    add_dependencies(${name} ${arg})
  endforeach()

  # Set up custom build steps based on the target properties.
  # Each step depends on the previous one.
  #
  # The target depends on the output of the final step.
  # (Already set up above in the DEPENDS of the add_custom_target command.)
  #
  _ep_add_mkdir_command(${name})
  _ep_add_download_command(${name})
  _ep_add_update_command(${name})
  _ep_add_patch_command(${name})
  _ep_add_configure_command(${name})
  _ep_add_build_command(${name})
  _ep_add_install_command(${name})

  # Test is special in that it might depend on build, or it might depend
  # on install.
  #
  _ep_add_test_command(${name})
endfunction()