CMake/Modules/ExternalProject.cmake

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

#[=======================================================================[.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 overriden by LOG_DIR
      (see *Logging Options* below).

    ``LOG_DIR <dir>``
      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 Download*
      ``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.

      ``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_NO_EXTRACT <bool>``
        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.

      ``HTTP_USERNAME <username>``
        Username for the download operation if authentication is required.

      ``HTTP_PASSWORD <password>``
        Password for the download operation if authentication is required.

      ``HTTP_HEADER <header1> [<header2>...]``
        Provides an arbitrary list of HTTP headers for the download operation.
        This can be useful for accessing content in systems like AWS, etc.

      ``TLS_VERIFY <bool>``
        Specifies whether certificate verification should be performed for
        https URLs. If this option is not provided, the default behavior is
        determined by the ``CMAKE_TLS_VERIFY`` variable (see
        :command:`file(DOWNLOAD)`). If that is also not set, certificate
        verification will not be performed. In situations where ``URL_HASH``
        cannot be provided, this option can be an alternative verification
        measure.

      ``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
        ``CMAKE_TLS_CAINFO`` variable will be used instead (see
        :command:`file(DOWNLOAD)`)

      ``NETRC <level>``
        Specify whether the ``.netrc`` file is to be used for operation.
        If this option is not specified, the value of the ``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>``
        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 ``CMAKE_NETRC_FILE`` variable will
        be used instead (see :command:`file(DOWNLOAD)`)

    *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.

      ``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.

      ``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.

      ``GIT_SHALLOW <bool>``
        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>``
        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>...]``
        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``.

    *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/Patch 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>``
      When enabled, this option causes the update step to be skipped. It does
      not, however, 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).

      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).

    ``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 options based on the main
      project. For non-CMake external projects, the ``CONFIGURE_COMMAND``
      option must be used to override this behavior
      (: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>``
      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>``
      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 ``cmake`` command line. They
      can be any argument the ``cmake`` command understands, not just cache
      values defined by ``-D...`` arguments (see also
      :manual:`CMake Options <cmake(1)>`). In addition, 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. Arguments
      may use :manual:`generator expressions <cmake-generator-expressions(7)>`.

    ``CMAKE_CACHE_DEFAULT_ARGS <arg>...``
      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 re-uses previous build contents.

      If the CMake generator is the ``Green Hills MULTI`` and not overridden then
      the orginal projects settings for the GHS toolset and target system
      customization cache variables are propagated into the external project.

    ``SOURCE_SUBDIR <dir>``
      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``.  When ``BUILD_IN_SOURCE 1`` is specified, the
      ``BUILD_COMMAND`` is used to point to an alternative directory within the
      source tree.

  **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.

    ``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
      ``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>...``
      Specifies files that will be generated by the build command but which
      might or might not have their modification time updated by subsequent
      builds. These ultimately get passed through as ``BYPRODUCTS`` to the
      build step's own underlying call to :command:`add_custom_command`.

  **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.

  **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>``
      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.

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

    ``LOG_OUTPUT_ON_FAILURE <bool>``
      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:**
    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_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_Step` below for further discussion of
      the effects of this option.

    ``INDEPENDENT_STEP_TARGETS <step-target>...``
      Generate 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_Step` below for further discussion of the
      effects of this option.

  **Miscellaneous Options:**
    ``LIST_SEPARATOR <sep>``
      For any of the various ``..._COMMAND`` options, replace ``;`` with
      ``<sep>`` in the specified command lines. This can be useful where list
      variables may be given in commands where they should end up as
      space-separated arguments (``<sep>`` would be a single space character
      string in this case).

    ``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``, ``skip-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.

  ``BYPRODUCTS <file>...``
    Files that will be generated by this custom step but which might or might
    not have their modification time updated by subsequent builds. 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.

  ``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).

  ``EXCLUDE_FROM_MAIN <bool>``
    When enabled, this option specifies that the external project's main target
    does not depend on the custom step.

  ``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`.

.. 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> [NO_DEPENDS] <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.

  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.

  Internally, :command:`ExternalProject_Add` calls
  :command:`ExternalProject_Add_Step` to create each step. If any
  ``STEP_TARGETS`` or ``INDEPENDENT_STEP_TARGETS`` were specified, then
  ``ExternalProject_Add_StepTargets()`` will also be called after
  :command:`ExternalProject_Add_Step`. ``INDEPENDENT_STEP_TARGETS`` have the
  ``NO_DEPENDS`` option set, whereas ``STEP_TARGETS`` do not. Other than that,
  the two options result in ``ExternalProject_Add_StepTargets()`` being called
  in the same way. Even if a step is not mentioned in either of those two
  options, ``ExternalProject_Add_StepTargets()`` can still be called later to
  manually define a target for the step.

  The ``STEP_TARGETS`` and ``INDEPENDENT_STEP_TARGETS`` options for
  :command:`ExternalProject_Add` are 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`` and
  ``EP_INDEPENDENT_STEP_TARGETS`` directory properties. These act as defaults
  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.

.. command:: ExternalProject_Add_StepDependencies

  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    [email protected]: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 [email protected]: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

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

cmake_policy(PUSH)
cmake_policy(SET CMP0054 NEW) # if() quoted variables not dereferenced

# Pre-compute a regex to match documented keywords for each command.
math(EXPR _ep_documentation_line_count "${CMAKE_CURRENT_LIST_LINE} - 4")
file(STRINGS "${CMAKE_CURRENT_LIST_FILE}" lines
     LIMIT_COUNT ${_ep_documentation_line_count}
     REGEX "^\\.\\. command:: [A-Za-z0-9_]+|^ +``[A-Z0-9_]+ [^`]*``$")
foreach(line IN LISTS lines)
  if("${line}" MATCHES "^\\.\\. command:: ([A-Za-z0-9_]+)")
    if(_ep_func)
      string(APPEND _ep_keywords_${_ep_func} ")$")
    endif()
    set(_ep_func "${CMAKE_MATCH_1}")
    #message("function [${_ep_func}]")
    set(_ep_keywords_${_ep_func} "^(")
    set(_ep_keyword_sep)
  elseif("${line}" MATCHES "^ +``([A-Z0-9_]+) [^`]*``$")
    set(_ep_key "${CMAKE_MATCH_1}")
    # COMMAND should never be included as a keyword,
    # for ExternalProject_Add(), as it is treated as a
    # special case by argument parsing as an extension
    # of a previous ..._COMMAND
    if("x${_ep_key}x" STREQUAL "xCOMMANDx" AND
       "x${_ep_func}x" STREQUAL "xExternalProject_Addx")
      continue()
    endif()
    #message("  keyword [${_ep_key}]")
    string(APPEND _ep_keywords_${_ep_func}
      "${_ep_keyword_sep}${_ep_key}")
    set(_ep_keyword_sep "|")
  endif()
endforeach()
if(_ep_func)
  string(APPEND _ep_keywords_${_ep_func} ")$")
endif()

# Save regex matching supported hash algorithm names.
set(_ep_hash_algos "MD5|SHA1|SHA224|SHA256|SHA384|SHA512|SHA3_224|SHA3_256|SHA3_384|SHA3_512")
set(_ep_hash_regex "^(${_ep_hash_algos})=([0-9A-Fa-f]+)$")

set(_ExternalProject_SELF "${CMAKE_CURRENT_LIST_FILE}")
get_filename_component(_ExternalProject_SELF_DIR "${_ExternalProject_SELF}" PATH)

function(_ep_parse_arguments f name ns args)
  # Transfer the arguments to this function into target properties for the
  # new custom target we just added so that we can set up all the build steps
  # correctly based on target properties.
  #
  # We loop through ARGN and consider the namespace starting with an
  # upper-case letter followed by at least two more upper-case letters,
  # numbers or underscores to be keywords.

  if(NOT DEFINED _ExternalProject_SELF)
    message(FATAL_ERROR "error: ExternalProject module must be explicitly included before using ${f} function")
  endif()

  set(key)

  foreach(arg IN LISTS args)
    set(is_value 1)

    if(arg MATCHES "^[A-Z][A-Z0-9_][A-Z0-9_]+$" AND
        NOT (("x${arg}x" STREQUAL "x${key}x") AND ("x${key}x" STREQUAL "xCOMMANDx")) AND
        NOT arg MATCHES "^(TRUE|FALSE)$")
      if(_ep_keywords_${f} AND arg MATCHES "${_ep_keywords_${f}}")
        set(is_value 0)
      endif()
    endif()

    if(is_value)
      if(key)
        # Value
        if(NOT arg STREQUAL "")
          set_property(TARGET ${name} APPEND PROPERTY ${ns}${key} "${arg}")
        else()
          get_property(have_key TARGET ${name} PROPERTY ${ns}${key} SET)
          if(have_key)
            get_property(value TARGET ${name} PROPERTY ${ns}${key})
            set_property(TARGET ${name} PROPERTY ${ns}${key} "${value};${arg}")
          else()
            set_property(TARGET ${name} PROPERTY ${ns}${key} "${arg}")
          endif()
        endif()
      else()
        # Missing Keyword
        message(AUTHOR_WARNING "value '${arg}' with no previous keyword in ${f}")
      endif()
    else()
      set(key "${arg}")
    endif()
  endforeach()
endfunction()


define_property(DIRECTORY PROPERTY "EP_BASE" INHERITED
  BRIEF_DOCS "Base directory for External Project storage."
  FULL_DOCS
  "See documentation of the ExternalProject_Add() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_PREFIX" INHERITED
  BRIEF_DOCS "Top prefix for External Project storage."
  FULL_DOCS
  "See documentation of the ExternalProject_Add() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_STEP_TARGETS" INHERITED
  BRIEF_DOCS
  "List of ExternalProject steps that automatically get corresponding targets"
  FULL_DOCS
  "These targets will be dependent on the main target dependencies. "
  "See documentation of the ExternalProject_Add_StepTargets() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_INDEPENDENT_STEP_TARGETS" INHERITED
  BRIEF_DOCS
  "List of ExternalProject steps that automatically get corresponding targets"
  FULL_DOCS
  "These targets will not be dependent on the main target dependencies. "
  "See documentation of the ExternalProject_Add_StepTargets() function in the "
  "ExternalProject module."
  )

define_property(DIRECTORY PROPERTY "EP_UPDATE_DISCONNECTED" INHERITED
  BRIEF_DOCS "Never update automatically from the remote repo."
  FULL_DOCS
  "See documentation of the ExternalProject_Add() function in the "
  "ExternalProject module."
  )

function(_ep_write_gitclone_script script_filename source_dir git_EXECUTABLE git_repository git_tag git_remote_name git_submodules git_shallow git_progress git_config src_name work_dir gitclone_infofile gitclone_stampfile tls_verify)
  if(NOT GIT_VERSION_STRING VERSION_LESS 1.8.5)
    # Use `git checkout <tree-ish> --` to avoid ambiguity with a local path.
    set(git_checkout_explicit-- "--")
  else()
    # Use `git checkout <branch>` even though this risks ambiguity with a
    # local path.  Unfortunately we cannot use `git checkout <tree-ish> --`
    # because that will not search for remote branch names, a common use case.
    set(git_checkout_explicit-- "")
  endif()
  if("${git_tag}" STREQUAL "")
    message(FATAL_ERROR "Tag for git checkout should not be empty.")
  endif()

  set(git_clone_options)
  if(git_shallow)
    if(NOT GIT_VERSION_STRING VERSION_LESS 1.7.10)
      list(APPEND git_clone_options "--depth 1 --no-single-branch")
    else()
      list(APPEND git_clone_options "--depth 1")
    endif()
  endif()
  if(git_progress)
    list(APPEND git_clone_options --progress)
  endif()
  foreach(config IN LISTS git_config)
    list(APPEND git_clone_options --config ${config})
  endforeach()
  if(NOT ${git_remote_name} STREQUAL "origin")
    list(APPEND git_clone_options --origin \"${git_remote_name}\")
  endif()

  string (REPLACE ";" " " git_clone_options "${git_clone_options}")

  set(git_options)
  # disable cert checking if explicitly told not to do it
  if(NOT "x${tls_verify}" STREQUAL "x" AND NOT tls_verify)
    set(git_options
      -c http.sslVerify=false)
  endif()
  string (REPLACE ";" " " git_options "${git_options}")

  file(WRITE ${script_filename}
"
if(NOT \"${gitclone_infofile}\" IS_NEWER_THAN \"${gitclone_stampfile}\")
  message(STATUS \"Avoiding repeated git clone, stamp file is up to date: '${gitclone_stampfile}'\")
  return()
endif()

execute_process(
  COMMAND \${CMAKE_COMMAND} -E remove_directory \"${source_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to remove directory: '${source_dir}'\")
endif()

# try the clone 3 times in case there is an odd git clone issue
set(error_code 1)
set(number_of_tries 0)
while(error_code AND number_of_tries LESS 3)
  execute_process(
    COMMAND \"${git_EXECUTABLE}\" ${git_options} clone ${git_clone_options} \"${git_repository}\" \"${src_name}\"
    WORKING_DIRECTORY \"${work_dir}\"
    RESULT_VARIABLE error_code
    )
  math(EXPR number_of_tries \"\${number_of_tries} + 1\")
endwhile()
if(number_of_tries GREATER 1)
  message(STATUS \"Had to git clone more than once:
          \${number_of_tries} times.\")
endif()
if(error_code)
  message(FATAL_ERROR \"Failed to clone repository: '${git_repository}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" ${git_options} checkout ${git_tag} ${git_checkout_explicit--}
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to checkout tag: '${git_tag}'\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" ${git_options} submodule update --recursive --init ${git_submodules}
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to update submodules in: '${work_dir}/${src_name}'\")
endif()

# Complete success, update the script-last-run stamp file:
#
execute_process(
  COMMAND \${CMAKE_COMMAND} -E copy
    \"${gitclone_infofile}\"
    \"${gitclone_stampfile}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to copy script-last-run stamp file: '${gitclone_stampfile}'\")
endif()

"
)

endfunction()

function(_ep_write_hgclone_script script_filename source_dir hg_EXECUTABLE hg_repository hg_tag src_name work_dir hgclone_infofile hgclone_stampfile)
  if("${hg_tag}" STREQUAL "")
    message(FATAL_ERROR "Tag for hg checkout should not be empty.")
  endif()
  file(WRITE ${script_filename}
"
if(NOT \"${hgclone_infofile}\" IS_NEWER_THAN \"${hgclone_stampfile}\")
  message(STATUS \"Avoiding repeated hg clone, stamp file is up to date: '${hgclone_stampfile}'\")
  return()
endif()

execute_process(
  COMMAND \${CMAKE_COMMAND} -E remove_directory \"${source_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to remove directory: '${source_dir}'\")
endif()

execute_process(
  COMMAND \"${hg_EXECUTABLE}\" clone -U \"${hg_repository}\" \"${src_name}\"
  WORKING_DIRECTORY \"${work_dir}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to clone repository: '${hg_repository}'\")
endif()

execute_process(
  COMMAND \"${hg_EXECUTABLE}\" update ${hg_tag}
  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to checkout tag: '${hg_tag}'\")
endif()

# Complete success, update the script-last-run stamp file:
#
execute_process(
  COMMAND \${CMAKE_COMMAND} -E copy
    \"${hgclone_infofile}\"
    \"${hgclone_stampfile}\"
  RESULT_VARIABLE error_code
  )
if(error_code)
  message(FATAL_ERROR \"Failed to copy script-last-run stamp file: '${hgclone_stampfile}'\")
endif()

"
)

endfunction()


function(_ep_write_gitupdate_script script_filename git_EXECUTABLE git_tag git_remote_name git_submodules git_repository work_dir)
  if("${git_tag}" STREQUAL "")
    message(FATAL_ERROR "Tag for git checkout should not be empty.")
  endif()
  if(NOT GIT_VERSION_STRING VERSION_LESS 1.7.6)
    set(git_stash_save_options --all --quiet)
  else()
    set(git_stash_save_options --quiet)
  endif()
  file(WRITE ${script_filename}
"
execute_process(
  COMMAND \"${git_EXECUTABLE}\" rev-list --max-count=1 HEAD
  WORKING_DIRECTORY \"${work_dir}\"
  RESULT_VARIABLE error_code
  OUTPUT_VARIABLE head_sha
  OUTPUT_STRIP_TRAILING_WHITESPACE
  )
if(error_code)
  message(FATAL_ERROR \"Failed to get the hash for HEAD\")
endif()

execute_process(
  COMMAND \"${git_EXECUTABLE}\" show-ref ${git_tag}
  WORKING_DIRECTORY \"${work_dir}\"
  OUTPUT_VARIABLE show_ref_output
  )
# If a remote ref is asked for, which can possibly move around,
# we must always do a fetch and checkout.
if(\"\${show_ref_output}\" MATCHES \"remotes\")
  set(is_remote_ref 1)
else()
  set(is_remote_ref 0)
endif()

# Tag is in the form <remote>/<tag> (i.e. origin/master) we must strip
# the remote from the tag.
if(\"\${show_ref_output}\" MATCHES \"refs/remotes/${git_tag}\")
  string(REGEX MATCH \"^([^/]+)/(.+)$\" _unused \"${git_tag}\")
  set(git_remote \"\${CMAKE_MATCH_1}\")
  set(git_tag \"\${CMAKE_MATCH_2}\")
else()
  set(git_remote \"${git_remote_name}\")
  set(git_tag \"${git_tag}\")
endif()

# This will fail if the tag does not exist (it probably has not been fetched
# yet).
execute_process(
  COMMAND \"${git_EXECUTABLE}\" rev-list --max-count=1 ${git_tag}
  WORKING_DIRECTORY \"${work_dir}\"
  RESULT_VARIABLE error_code
  OUTPUT_VARIABLE tag_sha
  OUTPUT_STRIP_TRAILING_WHITESPACE
  )

# Is the hash checkout out that we want?
if(error_code OR is_remote_ref OR NOT (\"\${tag_sha}\" STREQUAL \"\${head_sha}\"))
  execute_process(
    COMMAND \"${git_EXECUTABLE}\" fetch
    WORKING_DIRECTORY \"${work_dir}\"
    RESULT_VARIABLE error_code
    )
  if(error_code)
    message(FATAL_ERROR \"Failed to fetch repository '${git_repository}'\")
  endif()

  if(is_remote_ref)
    # Check if stash is needed
    execute_process(
      COMMAND \"${git_EXECUTABLE}\" status --porcelain
      WORKING_DIRECTORY \"${work_dir}\"
      RESULT_VARIABLE error_code
      OUTPUT_VARIABLE repo_status
      )
    if(error_code)
      message(FATAL_ERROR \"Failed to get the status\")
    endif()
    string(LENGTH \"\${repo_status}\" need_stash)

    # If not in clean state, stash changes in order to be able to be able to
    # perform git pull --rebase
    if(need_stash)
      execute_process(
        COMMAND \"${git_EXECUTABLE}\" stash save ${git_stash_save_options}
        WORKING_DIRECTORY \"${work_dir}\"
        RESULT_VARIABLE error_code
        )
      if(error_code)
        message(FATAL_ERROR \"Failed to stash changes\")
      endif()
    endif()

    # Pull changes from the remote branch
    execute_process(
      COMMAND \"${git_EXECUTABLE}\" rebase \${git_remote}/\${git_tag}
      WORKING_DIRECTORY \"${work_dir}\"
      RESULT_VARIABLE error_code
      )
    if(error_code)
      # Rebase failed: Restore previous state.
      execute_process(
        COMMAND \"${git_EXECUTABLE}\" rebase --abort
        WORKING_DIRECTORY \"${work_dir}\"
      )
      if(need_stash)
        execute_process(
          COMMAND \"${git_EXECUTABLE}\" stash pop --index --quiet
          WORKING_DIRECTORY \"${work_dir}\"
          )
      endif()
      message(FATAL_ERROR \"\\nFailed to rebase in: '${work_dir}/${src_name}'.\\nYou will have to resolve the conflicts manually\")
    endif()

    if(need_stash)
      execute_process(
        COMMAND \"${git_EXECUTABLE}\" stash pop --index --quiet
        WORKING_DIRECTORY \"${work_dir}\"
        RESULT_VARIABLE error_code
        )
      if(error_code)
        # Stash pop --index failed: Try again dropping the index
        execute_process(
          COMMAND \"${git_EXECUTABLE}\" reset --hard --quiet
          WORKING_DIRECTORY \"${work_dir}\"
          RESULT_VARIABLE error_code
          )
        execute_process(
          COMMAND \"${git_EXECUTABLE}\" stash pop --quiet
          WORKING_DIRECTORY \"${work_dir}\"
          RESULT_VARIABLE error_code
          )
        if(error_code)
          # Stash pop failed: Restore previous state.
          execute_process(
            COMMAND \"${git_EXECUTABLE}\" reset --hard --quiet \${head_sha}
            WORKING_DIRECTORY \"${work_dir}\"
          )
          execute_process(
            COMMAND \"${git_EXECUTABLE}\" stash pop --index --quiet
            WORKING_DIRECTORY \"${work_dir}\"
          )
          message(FATAL_ERROR \"\\nFailed to unstash changes in: '${work_dir}/${src_name}'.\\nYou will have to resolve the conflicts manually\")
        endif()
      endif()
    endif()
  else()
    execute_process(
      COMMAND \"${git_EXECUTABLE}\" checkout ${git_tag}
      WORKING_DIRECTORY \"${work_dir}\"
      RESULT_VARIABLE error_code
      )
    if(error_code)
      message(FATAL_ERROR \"Failed to checkout tag: '${git_tag}'\")
    endif()
  endif()

  execute_process(
    COMMAND \"${git_EXECUTABLE}\" submodule update --recursive --init ${git_submodules}
    WORKING_DIRECTORY \"${work_dir}/${src_name}\"
    RESULT_VARIABLE error_code
    )
  if(error_code)
    message(FATAL_ERROR \"Failed to update submodules in: '${work_dir}/${src_name}'\")
  endif()
endif()

"
)

endfunction(_ep_write_gitupdate_script)

function(_ep_write_downloadfile_script script_filename REMOTE LOCAL timeout no_progress hash tls_verify tls_cainfo userpwd http_headers netrc netrc_file)
  if(timeout)
    set(TIMEOUT_ARGS TIMEOUT ${timeout})
    set(TIMEOUT_MSG "${timeout} seconds")
  else()
    set(TIMEOUT_ARGS "# no TIMEOUT")
    set(TIMEOUT_MSG "none")
  endif()

  if(no_progress)
    set(SHOW_PROGRESS "")
  else()
    set(SHOW_PROGRESS "SHOW_PROGRESS")
  endif()

  if("${hash}" MATCHES "${_ep_hash_regex}")
    set(ALGO "${CMAKE_MATCH_1}")
    string(TOLOWER "${CMAKE_MATCH_2}" EXPECT_VALUE)
  else()
    set(ALGO "")
    set(EXPECT_VALUE "")
  endif()

  set(TLS_VERIFY_CODE "")
  set(TLS_CAINFO_CODE "")
  set(NETRC_CODE "")
  set(NETRC_FILE_CODE "")

  # check for curl globals in the project
  if(DEFINED CMAKE_TLS_VERIFY)
    set(TLS_VERIFY_CODE "set(CMAKE_TLS_VERIFY ${CMAKE_TLS_VERIFY})")
  endif()
  if(DEFINED CMAKE_TLS_CAINFO)
    set(TLS_CAINFO_CODE "set(CMAKE_TLS_CAINFO \"${CMAKE_TLS_CAINFO}\")")
  endif()
  if(DEFINED CMAKE_NETRC)
    set(NETRC_CODE "set(CMAKE_NETRC \"${CMAKE_NETRC}\")")
  endif()
  if(DEFINED CMAKE_NETRC_FILE)
    set(NETRC_FILE_CODE "set(CMAKE_NETRC_FILE \"${CMAKE_NETRC_FILE}\")")
  endif()

  # now check for curl locals so that the local values
  # will override the globals

  # check for tls_verify argument
  string(LENGTH "${tls_verify}" tls_verify_len)
  if(tls_verify_len GREATER 0)
    set(TLS_VERIFY_CODE "set(CMAKE_TLS_VERIFY ${tls_verify})")
  endif()
  # check for tls_cainfo argument
  string(LENGTH "${tls_cainfo}" tls_cainfo_len)
  if(tls_cainfo_len GREATER 0)
    set(TLS_CAINFO_CODE "set(CMAKE_TLS_CAINFO \"${tls_cainfo}\")")
  endif()
  # check for netrc argument
  string(LENGTH "${netrc}" netrc_len)
  if(netrc_len GREATER 0)
    set(NETRC_CODE "set(CMAKE_NETRC \"${netrc}\")")
  endif()
  # check for netrc_file argument
  string(LENGTH "${netrc_file}" netrc_file_len)
  if(netrc_file_len GREATER 0)
    set(NETRC_FILE_CODE "set(CMAKE_NETRC_FILE \"${netrc_file}\")")
  endif()

  if(userpwd STREQUAL ":")
    set(USERPWD_ARGS)
  else()
    set(USERPWD_ARGS USERPWD "${userpwd}")
  endif()

  set(HTTP_HEADERS_ARGS "")
  if(NOT http_headers STREQUAL "")
    foreach(header ${http_headers})
      set(
          HTTP_HEADERS_ARGS
          "HTTPHEADER \"${header}\"\n        ${HTTP_HEADERS_ARGS}"
      )
    endforeach()
  endif()

  # Used variables:
  # * TLS_VERIFY_CODE
  # * TLS_CAINFO_CODE
  # * ALGO
  # * EXPECT_VALUE
  # * REMOTE
  # * LOCAL
  # * SHOW_PROGRESS
  # * TIMEOUT_ARGS
  # * TIMEOUT_MSG
  # * USERPWD_ARGS
  # * HTTP_HEADERS_ARGS
  configure_file(
      "${_ExternalProject_SELF_DIR}/ExternalProject-download.cmake.in"
      "${script_filename}"
      @ONLY
  )
endfunction()

function(_ep_write_verifyfile_script script_filename LOCAL hash)
  if("${hash}" MATCHES "${_ep_hash_regex}")
    set(ALGO "${CMAKE_MATCH_1}")
    string(TOLOWER "${CMAKE_MATCH_2}" EXPECT_VALUE)
  else()
    set(ALGO "")
    set(EXPECT_VALUE "")
  endif()

  # Used variables:
  # * ALGO
  # * EXPECT_VALUE
  # * LOCAL
  configure_file(
      "${_ExternalProject_SELF_DIR}/ExternalProject-verify.cmake.in"
      "${script_filename}"
      @ONLY
  )
endfunction()


function(_ep_write_extractfile_script script_filename name filename directory)
  set(args "")

  if(filename MATCHES "(\\.|=)(7z|tar\\.bz2|tar\\.gz|tar\\.xz|tbz2|tgz|txz|zip)$")
    set(args xfz)
  endif()

  if(filename MATCHES "(\\.|=)tar$")
    set(args xf)
  endif()

  if(args STREQUAL "")
    message(SEND_ERROR "error: do not know how to extract '${filename}' -- known types are .7z, .tar, .tar.bz2, .tar.gz, .tar.xz, .tbz2, .tgz, .txz and .zip")
    return()
  endif()

  file(WRITE ${script_filename}
"# Make file names absolute:
#
get_filename_component(filename \"${filename}\" ABSOLUTE)
get_filename_component(directory \"${directory}\" ABSOLUTE)

message(STATUS \"extracting...
     src='\${filename}'
     dst='\${directory}'\")

if(NOT EXISTS \"\${filename}\")
  message(FATAL_ERROR \"error: file to extract does not exist: '\${filename}'\")
endif()

# Prepare a space for extracting:
#
set(i 1234)
while(EXISTS \"\${directory}/../ex-${name}\${i}\")
  math(EXPR i \"\${i} + 1\")
endwhile()
set(ut_dir \"\${directory}/../ex-${name}\${i}\")
file(MAKE_DIRECTORY \"\${ut_dir}\")

# Extract it:
#
message(STATUS \"extracting... [tar ${args}]\")
execute_process(COMMAND \${CMAKE_COMMAND} -E tar ${args} \${filename}
  WORKING_DIRECTORY \${ut_dir}
  RESULT_VARIABLE rv)

if(NOT rv EQUAL 0)
  message(STATUS \"extracting... [error clean up]\")
  file(REMOVE_RECURSE \"\${ut_dir}\")
  message(FATAL_ERROR \"error: extract of '\${filename}' failed\")
endif()

# Analyze what came out of the tar file:
#
message(STATUS \"extracting... [analysis]\")
file(GLOB contents \"\${ut_dir}/*\")
list(REMOVE_ITEM contents \"\${ut_dir}/.DS_Store\")
list(LENGTH contents n)
if(NOT n EQUAL 1 OR NOT IS_DIRECTORY \"\${contents}\")
  set(contents \"\${ut_dir}\")
endif()

# Move \"the one\" directory to the final directory:
#
message(STATUS \"extracting... [rename]\")
file(REMOVE_RECURSE \${directory})
get_filename_component(contents \${contents} ABSOLUTE)
file(RENAME \${contents} \${directory})

# Clean up:
#
message(STATUS \"extracting... [clean up]\")
file(REMOVE_RECURSE \"\${ut_dir}\")

message(STATUS \"extracting... done\")
"
)

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)
    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 "${prefix}")
  else()
    set(tmp_default "${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 ${places})
    string(TOUPPER "${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()
    set_property(TARGET ${name} PROPERTY _EP_${VAR}_DIR "${${var}_dir}")
  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()
  set_property(TARGET ${name} PROPERTY _EP_LOG_DIR "${log_dir}")

  get_property(source_subdir TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR)
  if(NOT source_subdir)
    set_property(TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR "")
  elseif(IS_ABSOLUTE "${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.
    set_property(TARGET ${name} PROPERTY _EP_SOURCE_SUBDIR "/${source_subdir}")
  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}")
    else()
      set_property(TARGET ${name} PROPERTY _EP_BINARY_DIR "${source_dir}")
    endif()
  endif()

  # Make the directories at CMake configure time *and* add a custom command
  # to make them at build time. They need to exist 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.
  #
  # Additionally, the add_custom_command is still used in case somebody
  # removes one of the necessary directories and tries to rebuild without
  # re-running cmake.
  foreach(var ${places})
    string(TOUPPER "${var}" VAR)
    get_property(dir TARGET ${name} PROPERTY _EP_${VAR}_DIR)
    file(MAKE_DIRECTORY "${dir}")
    if(NOT EXISTS "${dir}")
      message(FATAL_ERROR "dir '${dir}' does not exist after file(MAKE_DIRECTORY)")
    endif()
  endforeach()
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 ${vars})
    if(${var})
      foreach(dir 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 ${args})
    if("${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)
  # 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 ${ARGN})
    string(TOUPPER "${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")
    # CMake project.  Select build command based on generator.
    get_target_property(cmake_generator ${name} _EP_CMAKE_GENERATOR)
    if("${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".
      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 ${config})
      endif()
      if(step STREQUAL "INSTALL")
        list(APPEND args --target install)
      endif()
      # But for "TEST" drive the project with corresponding "ctest".
      if("x${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()

  list(APPEND cmd ${args})
  set(${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 3.13)
${code_cygpath_make}
set(command \"${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  ${logbase}-*.log\")
  endif()
  if (\${log_output_on_failure})
    message(SEND_ERROR \"\${msg}\")
    if (\${log_merged})
      read_up_to_max_size(\"\${stderr_log}\" error_log_contents)
      message(STATUS \"Log output is:\\n\${error_log_contents}\")
    else()
      read_up_to_max_size(\"\${stdout_log}\" out_log_contents)
      read_up_to_max_size(\"\${stderr_log}\" err_log_contents)
      message(STATUS \"stdout output is:\\n\${out_log_contents}\")
      message(STATUS \"stderr output is:\\n\${err_log_contents}\")
    endif()
    message(FATAL_ERROR \"Stopping after outputting logs.\")
  else()
    message(FATAL_ERROR \"\${msg}\")
  endif()
else()
  set(msg \"${name} ${step} command succeeded.  See also ${logbase}-*.log\")
  message(STATUS \"\${msg}\")
endif()
")
  file(GENERATE OUTPUT "${script}" CONTENT "${code}")
  set(command ${CMAKE_COMMAND} ${make} ${config} -P ${script})
  set(${cmd_var} "${command}" PARENT_SCOPE)
endfunction()

# This module used to use "/${CMAKE_CFG_INTDIR}" directly and produced
# makefiles with "/./" in paths for custom command dependencies. Which
# resulted in problems with parallel make -j invocations.
#
# This function was added so that the suffix (search below for ${cfgdir}) is
# only set to "/${CMAKE_CFG_INTDIR}" when ${CMAKE_CFG_INTDIR} is not going to
# be "." (multi-configuration build systems like Visual Studio and Xcode...)
#
function(_ep_get_configuration_subdir_suffix suffix_var)
  set(suffix "")
  get_property(_isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
  if(_isMultiConfig)
    set(suffix "/${CMAKE_CFG_INTDIR}")
  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_suffix(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 ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles)
  _ep_get_configuration_subdir_suffix(cfgdir)
  set(stampfile "${cmf_dir}${cfgdir}/${name}-complete")

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


function(ExternalProject_Add_StepTargets name)
  set(steps ${ARGN})
  if(ARGC GREATER 1 AND "${ARGV1}" STREQUAL "NO_DEPENDS")
    set(no_deps 1)
    list(REMOVE_AT steps 0)
  endif()
  foreach(step ${steps})
    if(no_deps  AND  "${step}" MATCHES "^(configure|build|install|test)$")
      message(AUTHOR_WARNING "Using NO_DEPENDS for \"${step}\" step  might break parallel builds")
    endif()
    _ep_get_step_stampfile(${name} ${step} stamp_file)
    add_custom_target(${name}-${step}
      DEPENDS ${stamp_file})
    set_property(TARGET ${name}-${step} PROPERTY _EP_IS_EXTERNAL_PROJECT_STEP 1)
    set_property(TARGET ${name}-${step} PROPERTY LABELS ${name})
    set_property(TARGET ${name}-${step} PROPERTY FOLDER "ExternalProjectTargets/${name}")

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


function(ExternalProject_Add_Step name step)
  _ep_get_complete_stampfile(${name} complete_stamp_file)
  _ep_get_step_stampfile(${name} ${step} stamp_file)

  _ep_parse_arguments(ExternalProject_Add_Step
                      ${name} _EP_${step}_ "${ARGN}")

  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)
  foreach(depender IN LISTS dependers)
    _ep_get_step_stampfile(${name} ${depender} depender_stamp_file)
    add_custom_command(APPEND
      OUTPUT ${depender_stamp_file}
      DEPENDS ${stamp_file}
      )
  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)
  foreach(dependee IN LISTS dependees)
    _ep_get_step_stampfile(${name} ${dependee} dependee_stamp_file)
    list(APPEND depends ${dependee_stamp_file})
  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)

  # 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(uses_terminal USES_TERMINAL)
  else()
    set(uses_terminal "")
  endif()

  # Run every time?
  get_property(always TARGET ${name} PROPERTY _EP_${step}_ALWAYS)
  if(always)
    set_property(SOURCE ${stamp_file} PROPERTY SYMBOLIC 1)
    set(touch)
    # Remove any existing stamp in case the option changed in an existing tree.
    get_property(_isMultiConfig GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
    if(_isMultiConfig)
      foreach(cfg ${CMAKE_CONFIGURATION_TYPES})
        string(REPLACE "/${CMAKE_CFG_INTDIR}" "/${cfg}" stamp_file_config "${stamp_file}")
        file(REMOVE ${stamp_file_config})
      endforeach()
    else()
      file(REMOVE ${stamp_file})
    endif()
  else()
    set(touch ${CMAKE_COMMAND} -E touch ${stamp_file})
  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()

  add_custom_command(
    OUTPUT ${stamp_file}
    BYPRODUCTS ${byproducts}
    COMMENT ${comment}
    COMMAND ${command}
    COMMAND ${touch}
    DEPENDS ${depends}
    WORKING_DIRECTORY ${work_dir}
    VERBATIM
    ${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 ${step_targets})
    if("${st}" STREQUAL "${step}")
      ExternalProject_Add_StepTargets(${name} ${step})
      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()
  foreach(st ${independent_step_targets})
    if("${st}" STREQUAL "${step}")
      ExternalProject_Add_StepTargets(${name} NO_DEPENDS ${step})
      break()
    endif()
  endforeach()
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 ${step} is_step)
  if(NOT is_step)
    message(FATAL_ERROR "External project \"${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 ${dependencies})
    add_custom_command(APPEND
      OUTPUT ${stamp_file}
      DEPENDS ${dep})
    if(TARGET ${name}-${step})
      foreach(dep ${dependencies})
        add_dependencies(${name}-${step} ${dep})
      endforeach()
    endif()
  endforeach()

endfunction()


function(_ep_add_mkdir_command name)
  ExternalProject_Get_Property(${name}
    source_dir binary_dir install_dir stamp_dir download_dir tmp_dir log_dir)

  _ep_get_configuration_subdir_suffix(cfgdir)

  ExternalProject_Add_Step(${name} mkdir
    COMMENT "Creating directories for '${name}'"
    COMMAND ${CMAKE_COMMAND} -E make_directory ${source_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${binary_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${install_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${tmp_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${stamp_dir}${cfgdir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${download_dir}
    COMMAND ${CMAKE_COMMAND} -E make_directory ${log_dir}
    )
endfunction()


function(_ep_is_dir_empty dir empty_var)
  file(GLOB gr "${dir}/*")
  if("${gr}" STREQUAL "")
    set(${empty_var} 1 PARENT_SCOPE)
  else()
    set(${empty_var} 0 PARENT_SCOPE)
  endif()
endfunction()


function(_ep_add_download_command name)
  ExternalProject_Get_Property(${name} source_dir stamp_dir download_dir tmp_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_DOWNLOAD_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_DOWNLOAD_COMMAND)
  get_property(cvs_repository TARGET ${name} PROPERTY _EP_CVS_REPOSITORY)
  get_property(svn_repository TARGET ${name} PROPERTY _EP_SVN_REPOSITORY)
  get_property(git_repository TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
  get_property(hg_repository  TARGET ${name} PROPERTY _EP_HG_REPOSITORY )
  get_property(url TARGET ${name} PROPERTY _EP_URL)
  get_property(fname TARGET ${name} PROPERTY _EP_DOWNLOAD_NAME)

  # TODO: Perhaps file:// should be copied to download dir before extraction.
  string(REGEX REPLACE "file://" "" url "${url}")

  set(depends)
  set(comment)
  set(work_dir)

  if(cmd_set)
    set(work_dir ${download_dir})
  elseif(cvs_repository)
    find_package(CVS QUIET)
    if(NOT CVS_EXECUTABLE)
      message(FATAL_ERROR "error: could not find cvs for checkout of ${name}")
    endif()

    get_target_property(cvs_module ${name} _EP_CVS_MODULE)
    if(NOT cvs_module)
      message(FATAL_ERROR "error: no CVS_MODULE")
    endif()

    get_property(cvs_tag TARGET ${name} PROPERTY _EP_CVS_TAG)

    set(repository ${cvs_repository})
    set(module ${cvs_module})
    set(tag ${cvs_tag})
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-cvsinfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)
    set(comment "Performing download step (CVS checkout) for '${name}'")
    set(cmd ${CVS_EXECUTABLE} -d ${cvs_repository} -q co ${cvs_tag} -d ${src_name} ${cvs_module})
    list(APPEND depends ${stamp_dir}/${name}-cvsinfo.txt)
  elseif(svn_repository)
    find_package(Subversion QUIET)
    if(NOT Subversion_SVN_EXECUTABLE)
      message(FATAL_ERROR "error: could not find svn for checkout of ${name}")
    endif()

    get_property(svn_revision TARGET ${name} PROPERTY _EP_SVN_REVISION)
    get_property(svn_username TARGET ${name} PROPERTY _EP_SVN_USERNAME)
    get_property(svn_password TARGET ${name} PROPERTY _EP_SVN_PASSWORD)
    get_property(svn_trust_cert TARGET ${name} PROPERTY _EP_SVN_TRUST_CERT)

    set(repository "${svn_repository} user=${svn_username} password=${svn_password}")
    set(module)
    set(tag ${svn_revision})
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-svninfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)
    set(comment "Performing download step (SVN checkout) for '${name}'")
    set(svn_user_pw_args "")
    if(DEFINED svn_username)
      set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
    endif()
    if(DEFINED svn_password)
      set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
    endif()
    if(svn_trust_cert)
      set(svn_trust_cert_args --trust-server-cert)
    endif()
    set(cmd ${Subversion_SVN_EXECUTABLE} co ${svn_repository} ${svn_revision}
      --non-interactive ${svn_trust_cert_args} ${svn_user_pw_args} ${src_name})
    list(APPEND depends ${stamp_dir}/${name}-svninfo.txt)
  elseif(git_repository)
    unset(CMAKE_MODULE_PATH) # Use CMake builtin find module
    find_package(Git QUIET)
    if(NOT GIT_EXECUTABLE)
      message(FATAL_ERROR "error: could not find git for clone of ${name}")
    endif()

    # The git submodule update '--recursive' flag requires git >= v1.6.5
    #
    if(GIT_VERSION_STRING VERSION_LESS 1.6.5)
      message(FATAL_ERROR "error: git version 1.6.5 or later required for 'git submodule update --recursive': GIT_VERSION_STRING='${GIT_VERSION_STRING}'")
    endif()

    get_property(git_tag TARGET ${name} PROPERTY _EP_GIT_TAG)
    if(NOT git_tag)
      set(git_tag "master")
    endif()
    get_property(git_submodules TARGET ${name} PROPERTY _EP_GIT_SUBMODULES)

    get_property(git_remote_name TARGET ${name} PROPERTY _EP_GIT_REMOTE_NAME)
    if(NOT git_remote_name)
      set(git_remote_name "origin")
    endif()

    get_property(tls_verify TARGET ${name} PROPERTY _EP_TLS_VERIFY)
    if("x${tls_verify}" STREQUAL "x" AND DEFINED CMAKE_TLS_VERIFY)
      set(tls_verify "${CMAKE_TLS_VERIFY}")
    endif()
    get_property(git_shallow TARGET ${name} PROPERTY _EP_GIT_SHALLOW)
    get_property(git_progress TARGET ${name} PROPERTY _EP_GIT_PROGRESS)
    get_property(git_config TARGET ${name} PROPERTY _EP_GIT_CONFIG)

    # For the download step, and the git clone operation, only the repository
    # should be recorded in a configured RepositoryInfo file. If the repo
    # changes, the clone script should be run again. But if only the tag
    # changes, avoid running the clone script again. Let the 'always' running
    # update step checkout the new tag.
    #
    set(repository ${git_repository})
    set(module)
    set(tag ${git_remote_name})
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-gitinfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)

    # Since git clone doesn't succeed if the non-empty source_dir exists,
    # create a cmake script to invoke as download command.
    # The script will delete the source directory and then call git clone.
    #
    _ep_write_gitclone_script(${tmp_dir}/${name}-gitclone.cmake ${source_dir}
      ${GIT_EXECUTABLE} ${git_repository} ${git_tag} ${git_remote_name} "${git_submodules}" "${git_shallow}" "${git_progress}" "${git_config}" ${src_name} ${work_dir}
      ${stamp_dir}/${name}-gitinfo.txt ${stamp_dir}/${name}-gitclone-lastrun.txt "${tls_verify}"
      )
    set(comment "Performing download step (git clone) for '${name}'")
    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-gitclone.cmake)
    list(APPEND depends ${stamp_dir}/${name}-gitinfo.txt)
  elseif(hg_repository)
    find_package(Hg QUIET)
    if(NOT HG_EXECUTABLE)
      message(FATAL_ERROR "error: could not find hg for clone of ${name}")
    endif()

    get_property(hg_tag TARGET ${name} PROPERTY _EP_HG_TAG)
    if(NOT hg_tag)
      set(hg_tag "tip")
    endif()

    # For the download step, and the hg clone operation, only the repository
    # should be recorded in a configured RepositoryInfo file. If the repo
    # changes, the clone script should be run again. But if only the tag
    # changes, avoid running the clone script again. Let the 'always' running
    # update step checkout the new tag.
    #
    set(repository ${hg_repository})
    set(module)
    set(tag)
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-hginfo.txt"
      @ONLY
      )

    get_filename_component(src_name "${source_dir}" NAME)
    get_filename_component(work_dir "${source_dir}" PATH)

    # Since hg clone doesn't succeed if the non-empty source_dir exists,
    # create a cmake script to invoke as download command.
    # The script will delete the source directory and then call hg clone.
    #
    _ep_write_hgclone_script(${tmp_dir}/${name}-hgclone.cmake ${source_dir}
      ${HG_EXECUTABLE} ${hg_repository} ${hg_tag} ${src_name} ${work_dir}
      ${stamp_dir}/${name}-hginfo.txt ${stamp_dir}/${name}-hgclone-lastrun.txt
      )
    set(comment "Performing download step (hg clone) for '${name}'")
    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-hgclone.cmake)
    list(APPEND depends ${stamp_dir}/${name}-hginfo.txt)
  elseif(url)
    get_filename_component(work_dir "${source_dir}" PATH)
    get_property(hash TARGET ${name} PROPERTY _EP_URL_HASH)
    if(hash AND NOT "${hash}" MATCHES "${_ep_hash_regex}")
      message(FATAL_ERROR "URL_HASH is set to\n  ${hash}\n"
        "but must be ALGO=value where ALGO is\n  ${_ep_hash_algos}\n"
        "and value is a hex string.")
    endif()
    get_property(md5 TARGET ${name} PROPERTY _EP_URL_MD5)
    if(md5 AND NOT "MD5=${md5}" MATCHES "${_ep_hash_regex}")
      message(FATAL_ERROR "URL_MD5 is set to\n  ${md5}\nbut must be a hex string.")
    endif()
    if(md5 AND NOT hash)
      set(hash "MD5=${md5}")
    endif()
    set(repository "external project URL")
    set(module "${url}")
    set(tag "${hash}")
    configure_file(
      "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
      "${stamp_dir}/${name}-urlinfo.txt"
      @ONLY
      )
    list(APPEND depends ${stamp_dir}/${name}-urlinfo.txt)

    list(LENGTH url url_list_length)
    if(NOT "${url_list_length}" STREQUAL "1")
      foreach(entry ${url})
        if(NOT "${entry}" MATCHES "^[a-z]+://")
          message(FATAL_ERROR "At least one entry of URL is a path (invalid in a list)")
        endif()
      endforeach()
      if("x${fname}" STREQUAL "x")
        list(GET url 0 fname)
      endif()
    endif()

    if(IS_DIRECTORY "${url}")
      get_filename_component(abs_dir "${url}" ABSOLUTE)
      set(comment "Performing download step (DIR copy) for '${name}'")
      set(cmd   ${CMAKE_COMMAND} -E remove_directory ${source_dir}
        COMMAND ${CMAKE_COMMAND} -E copy_directory ${abs_dir} ${source_dir})
    else()
      get_property(no_extract TARGET "${name}" PROPERTY _EP_DOWNLOAD_NO_EXTRACT SET)
      if("${url}" MATCHES "^[a-z]+://")
        # TODO: Should download and extraction be different steps?
        if("x${fname}" STREQUAL "x")
          set(fname "${url}")
        endif()
        if("${fname}" MATCHES [[([^/\?#]+(\.|=)(7z|tar|tar\.bz2|tar\.gz|tar\.xz|tbz2|tgz|txz|zip))([/?#].*)?$]])
          set(fname "${CMAKE_MATCH_1}")
        elseif(no_extract)
          get_filename_component(fname "${fname}" NAME)
        else()
          # Fall back to a default file name.  The actual file name does not
          # matter because it is used only internally and our extraction tool
          # inspects the file content directly.  If it turns out the wrong URL
          # was given that will be revealed during the build which is an easier
          # place for users to diagnose than an error here anyway.
          set(fname "archive.tar")
        endif()
        string(REPLACE ";" "-" fname "${fname}")
        set(file ${download_dir}/${fname})
        get_property(timeout TARGET ${name} PROPERTY _EP_TIMEOUT)
        get_property(no_progress TARGET ${name} PROPERTY _EP_DOWNLOAD_NO_PROGRESS)
        get_property(tls_verify TARGET ${name} PROPERTY _EP_TLS_VERIFY)
        get_property(tls_cainfo TARGET ${name} PROPERTY _EP_TLS_CAINFO)
        get_property(netrc TARGET ${name} PROPERTY _EP_NETRC)
        get_property(netrc_file TARGET ${name} PROPERTY _EP_NETRC_FILE)
        get_property(http_username TARGET ${name} PROPERTY _EP_HTTP_USERNAME)
        get_property(http_password TARGET ${name} PROPERTY _EP_HTTP_PASSWORD)
        get_property(http_headers TARGET ${name} PROPERTY _EP_HTTP_HEADER)
        set(download_script "${stamp_dir}/download-${name}.cmake")
        _ep_write_downloadfile_script("${download_script}" "${url}" "${file}" "${timeout}" "${no_progress}" "${hash}" "${tls_verify}" "${tls_cainfo}" "${http_username}:${http_password}" "${http_headers}" "${netrc}" "${netrc_file}")
        set(cmd ${CMAKE_COMMAND} -P "${download_script}"
          COMMAND)
        if (no_extract)
          set(steps "download and verify")
        else ()
          set(steps "download, verify and extract")
        endif ()
        set(comment "Performing download step (${steps}) for '${name}'")
        file(WRITE "${stamp_dir}/verify-${name}.cmake" "") # already verified by 'download_script'
      else()
        set(file "${url}")
        if (no_extract)
          set(steps "verify")
        else ()
          set(steps "verify and extract")
        endif ()
        set(comment "Performing download step (${steps}) for '${name}'")
        _ep_write_verifyfile_script("${stamp_dir}/verify-${name}.cmake" "${file}" "${hash}")
      endif()
      list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/verify-${name}.cmake)
      if (NOT no_extract)
        _ep_write_extractfile_script("${stamp_dir}/extract-${name}.cmake" "${name}" "${file}" "${source_dir}")
        list(APPEND cmd COMMAND ${CMAKE_COMMAND} -P ${stamp_dir}/extract-${name}.cmake)
      else ()
        set_property(TARGET ${name} PROPERTY _EP_DOWNLOADED_FILE ${file})
      endif ()
    endif()
  else()
    _ep_is_dir_empty("${source_dir}" empty)
    if(${empty})
      message(SEND_ERROR
        "No download info given for '${name}' and its source directory:\n"
        " ${source_dir}\n"
        "is not an existing non-empty directory.  Please specify one of:\n"
        " * SOURCE_DIR with an existing non-empty directory\n"
        " * DOWNLOAD_COMMAND\n"
        " * URL\n"
        " * GIT_REPOSITORY\n"
        " * SVN_REPOSITORY\n"
        " * HG_REPOSITORY\n"
        " * CVS_REPOSITORY and CVS_MODULE"
        )
    endif()
  endif()

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

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

  ExternalProject_Add_Step(${name} download
    COMMENT ${comment}
    COMMAND ${cmd}
    WORKING_DIRECTORY ${work_dir}
    DEPENDS ${depends}
    DEPENDEES mkdir
    ${log}
    ${uses_terminal}
    )
endfunction()


function(_ep_add_update_command name)
  ExternalProject_Get_Property(${name} source_dir tmp_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_UPDATE_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_UPDATE_COMMAND)
  get_property(cvs_repository TARGET ${name} PROPERTY _EP_CVS_REPOSITORY)
  get_property(svn_repository TARGET ${name} PROPERTY _EP_SVN_REPOSITORY)
  get_property(git_repository TARGET ${name} PROPERTY _EP_GIT_REPOSITORY)
  get_property(hg_repository  TARGET ${name} PROPERTY _EP_HG_REPOSITORY )
  get_property(update_disconnected_set TARGET ${name} PROPERTY _EP_UPDATE_DISCONNECTED SET)
  if(update_disconnected_set)
    get_property(update_disconnected TARGET ${name} PROPERTY _EP_UPDATE_DISCONNECTED)
  else()
    get_property(update_disconnected DIRECTORY PROPERTY EP_UPDATE_DISCONNECTED)
  endif()

  set(work_dir)
  set(comment)
  set(always)

  if(cmd_set)
    set(work_dir ${source_dir})
    if(NOT "x${cmd}" STREQUAL "x")
      set(always 1)
    endif()
  elseif(cvs_repository)
    if(NOT CVS_EXECUTABLE)
      message(FATAL_ERROR "error: could not find cvs for update of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (CVS update) for '${name}'")
    get_property(cvs_tag TARGET ${name} PROPERTY _EP_CVS_TAG)
    set(cmd ${CVS_EXECUTABLE} -d ${cvs_repository} -q up -dP ${cvs_tag})
    set(always 1)
  elseif(svn_repository)
    if(NOT Subversion_SVN_EXECUTABLE)
      message(FATAL_ERROR "error: could not find svn for update of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (SVN update) for '${name}'")
    get_property(svn_revision TARGET ${name} PROPERTY _EP_SVN_REVISION)
    get_property(svn_username TARGET ${name} PROPERTY _EP_SVN_USERNAME)
    get_property(svn_password TARGET ${name} PROPERTY _EP_SVN_PASSWORD)
    get_property(svn_trust_cert TARGET ${name} PROPERTY _EP_SVN_TRUST_CERT)
    set(svn_user_pw_args "")
    if(DEFINED svn_username)
      set(svn_user_pw_args ${svn_user_pw_args} "--username=${svn_username}")
    endif()
    if(DEFINED svn_password)
      set(svn_user_pw_args ${svn_user_pw_args} "--password=${svn_password}")
    endif()
    if(svn_trust_cert)
      set(svn_trust_cert_args --trust-server-cert)
    endif()
    set(cmd ${Subversion_SVN_EXECUTABLE} up ${svn_revision}
      --non-interactive ${svn_trust_cert_args} ${svn_user_pw_args})
    set(always 1)
  elseif(git_repository)
    unset(CMAKE_MODULE_PATH) # Use CMake builtin find module
    find_package(Git QUIET)
    if(NOT GIT_EXECUTABLE)
      message(FATAL_ERROR "error: could not find git for fetch of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step for '${name}'")
    get_property(git_tag TARGET ${name} PROPERTY _EP_GIT_TAG)
    if(NOT git_tag)
      set(git_tag "master")
    endif()
    get_property(git_remote_name TARGET ${name} PROPERTY _EP_GIT_REMOTE_NAME)
    if(NOT git_remote_name)
      set(git_remote_name "origin")
    endif()
    get_property(git_submodules TARGET ${name} PROPERTY _EP_GIT_SUBMODULES)
    _ep_write_gitupdate_script(${tmp_dir}/${name}-gitupdate.cmake
      ${GIT_EXECUTABLE} ${git_tag} ${git_remote_name} "${git_submodules}" ${git_repository} ${work_dir}
      )
    set(cmd ${CMAKE_COMMAND} -P ${tmp_dir}/${name}-gitupdate.cmake)
    set(always 1)
  elseif(hg_repository)
    if(NOT HG_EXECUTABLE)
      message(FATAL_ERROR "error: could not find hg for pull of ${name}")
    endif()
    set(work_dir ${source_dir})
    set(comment "Performing update step (hg pull) for '${name}'")
    get_property(hg_tag TARGET ${name} PROPERTY _EP_HG_TAG)
    if(NOT hg_tag)
      set(hg_tag "tip")
    endif()
    if("${HG_VERSION_STRING}" STREQUAL "2.1")
      message(WARNING "Mercurial 2.1 does not distinguish an empty pull from a failed pull:
 http://mercurial.selenic.com/wiki/UpgradeNotes#A2.1.1:_revert_pull_return_code_change.2C_compile_issue_on_OS_X
 http://thread.gmane.org/gmane.comp.version-control.mercurial.devel/47656
Update to Mercurial >= 2.1.1.
")
    endif()
    set(cmd ${HG_EXECUTABLE} pull
      COMMAND ${HG_EXECUTABLE} update ${hg_tag}
      )
    set(always 1)
  endif()

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

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

  ExternalProject_Add_Step(${name} update
    COMMENT ${comment}
    COMMAND ${cmd}
    ALWAYS ${always}
    EXCLUDE_FROM_MAIN ${update_disconnected}
    WORKING_DIRECTORY ${work_dir}
    DEPENDEES download
    ${log}
    ${uses_terminal}
    )

  if(update_disconnected)
    _ep_get_step_stampfile(${name} skip-update skip-update_stamp_file)
    string(REPLACE "Performing" "Skipping" comment "${comment}")
    ExternalProject_Add_Step(${name} skip-update
      COMMENT ${comment}
      ALWAYS ${always}
      EXCLUDE_FROM_MAIN 1
      WORKING_DIRECTORY ${work_dir}
      DEPENDEES download
      ${log}
      ${uses_terminal}
    )
    set_property(SOURCE ${skip-update_stamp_file} PROPERTY SYMBOLIC 1)
  endif()

endfunction()


function(_ep_add_patch_command name)
  ExternalProject_Get_Property(${name} source_dir)

  get_property(cmd_set TARGET ${name} PROPERTY _EP_PATCH_COMMAND SET)
  get_property(cmd TARGET ${name} PROPERTY _EP_PATCH_COMMAND)

  set(work_dir)

  if(cmd_set)
    set(work_dir ${source_dir})
  endif()

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

  ExternalProject_Add_Step(${name} patch
    COMMAND ${cmd}
    WORKING_DIRECTORY ${work_dir}
    DEPENDEES download
    ${log}
    )
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}")
        if("${CMAKE_GENERATOR}" MATCHES "Green Hills MULTI")
          set(has_cmake_cache_default_args 1)
          set(cmake_cache_default_args ${cmake_cache_default_args}
            "-DGHS_TARGET_PLATFORM:STRING=${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}")
    endif()

    list(APPEND cmd "<SOURCE_DIR><SOURCE_SUBDIR>")
  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)

  # Depend on other external projects (file-level).
  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()

  _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
  #
  if(NOT EXISTS ${tmp_dir}/${name}-cfgcmd.txt.in)
    file(WRITE ${tmp_dir}/${name}-cfgcmd.txt.in "cmd='\@cmd\@'\n")
  endif()
  configure_file(${tmp_dir}/${name}-cfgcmd.txt.in ${tmp_dir}/${name}-cfgcmd.txt)
  list(APPEND file_deps ${tmp_dir}/${name}-cfgcmd.txt)
  list(APPEND file_deps ${_ep_cache_args_script})

  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()

  get_property(update_disconnected_set TARGET ${name} PROPERTY _EP_UPDATE_DISCONNECTED SET)
  if(update_disconnected_set)
    get_property(update_disconnected TARGET ${name} PROPERTY _EP_UPDATE_DISCONNECTED)
  else()
    get_property(update_disconnected DIRECTORY PROPERTY EP_UPDATE_DISCONNECTED)
  endif()
  if(update_disconnected)
    set(update_dep skip-update)
  else()
    set(update_dep update)
  endif()

  ExternalProject_Add_Step(${name} configure
    COMMAND ${cmd}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES ${update_dep} patch
    DEPENDS ${file_deps}
    ${log}
    ${uses_terminal}
    )
endfunction()


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

  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)

  ExternalProject_Add_Step(${name} build
    COMMAND ${cmd}
    BYPRODUCTS ${build_byproducts}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES configure
    ALWAYS ${always}
    ${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()

  ExternalProject_Add_Step(${name} install
    COMMAND ${cmd}
    WORKING_DIRECTORY ${binary_dir}
    DEPENDEES build
    ${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()

    ExternalProject_Add_Step(${name} test
      COMMAND ${cmd}
      WORKING_DIRECTORY ${binary_dir}
      ${dependees_args}
      ${dependers_args}
      ${exclude_args}
      ${log}
      ${uses_terminal}
      )
  endif()
endfunction()


function(ExternalProject_Add name)
  _ep_get_configuration_subdir_suffix(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)

  # 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})
  set_property(TARGET ${name} PROPERTY _EP_IS_EXTERNAL_PROJECT 1)
  set_property(TARGET ${name} PROPERTY LABELS ${name})
  set_property(TARGET ${name} PROPERTY FOLDER "ExternalProjectTargets/${name}")

  _ep_parse_arguments(ExternalProject_Add ${name} _EP_ "${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()

  # 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()

cmake_policy(POP)