path: root/Help/manual/cmake-file-api.7.rst

.. cmake-manual-description: CMake File-Based API

cmake-file-api(7)
*****************

.. only:: html

   .. contents::

Introduction
============

CMake provides a file-based API that clients may use to get semantic
information about the buildsystems CMake generates.  Clients may use
the API by writing query files to a specific location in a build tree
to request zero or more `Object Kinds`_.  When CMake generates the
buildsystem in that build tree it will read the query files and write
reply files for the client to read.

The file-based API uses a ``<build>/.cmake/api/`` directory at the top
of a build tree.  The API is versioned to support changes to the layout
of files within the API directory.  API file layout versioning is
orthogonal to the versioning of `Object Kinds`_ used in replies.
This version of CMake supports only one API version, `API v1`_.

API v1
======

API v1 is housed in the ``<build>/.cmake/api/v1/`` directory.
It has the following subdirectories:

``query/``
  Holds query files written by clients.
  These may be `v1 Shared Stateless Query Files`_,
  `v1 Client Stateless Query Files`_, or `v1 Client Stateful Query Files`_.

``reply/``
  Holds reply files written by CMake whenever it runs to generate a build
  system.  These are indexed by a `v1 Reply Index File`_ file that may
  reference additional `v1 Reply Files`_.  CMake owns all reply files.
  Clients must never remove them.

  Clients may look for and read a reply index file at any time.
  Clients may optionally create the ``reply/`` directory at any time
  and monitor it for the appearance of a new reply index file.

v1 Shared Stateless Query Files
-------------------------------

Shared stateless query files allow clients to share requests for
major versions of the `Object Kinds`_ and get all requested versions
recognized by the CMake that runs.

Clients may create shared requests by creating empty files in the
``v1/query/`` directory.  The form is::

  <build>/.cmake/api/v1/query/<kind>-v<major>

where ``<kind>`` is one of the `Object Kinds`_, ``-v`` is literal,
and ``<major>`` is the major version number.

Files of this form are stateless shared queries not owned by any specific
client.  Once created they should not be removed without external client
coordination or human intervention.

v1 Client Stateless Query Files
-------------------------------

Client stateless query files allow clients to create owned requests for
major versions of the `Object Kinds`_ and get all requested versions
recognized by the CMake that runs.

Clients may create owned requests by creating empty files in
client-specific query subdirectories.  The form is::

  <build>/.cmake/api/v1/query/client-<client>/<kind>-v<major>

where ``client-`` is literal, ``<client>`` is a string uniquely
identifying the client, ``<kind>`` is one of the `Object Kinds`_,
``-v`` is literal, and ``<major>`` is the major version number.
Each client must choose a unique ``<client>`` identifier via its
own means.

Files of this form are stateless queries owned by the client ``<client>``.
The owning client may remove them at any time.

v1 Client Stateful Query Files
------------------------------

Stateful query files allow clients to request a list of versions of
each of the `Object Kinds`_ and get only the most recent version
recognized by the CMake that runs.

Clients may create owned stateful queries by creating ``query.json``
files in client-specific query subdirectories.  The form is::

  <build>/.cmake/api/v1/query/client-<client>/query.json

where ``client-`` is literal, ``<client>`` is a string uniquely
identifying the client, and ``query.json`` is literal.  Each client
must choose a unique ``<client>`` identifier via its own means.

``query.json`` files are stateful queries owned by the client ``<client>``.
The owning client may update or remove them at any time.  When a
given client installation is updated it may then update the stateful
query it writes to build trees to request newer object versions.
This can be used to avoid asking CMake to generate multiple object
versions unnecessarily.

A ``query.json`` file must contain a JSON object:

.. code-block:: json

  {
    "requests": [
      { "kind": "<kind>" , "version": 1 },
      { "kind": "<kind>" , "version": { "major": 1, "minor": 2 } },
      { "kind": "<kind>" , "version": [2, 1] },
      { "kind": "<kind>" , "version": [2, { "major": 1, "minor": 2 }] },
      { "kind": "<kind>" , "version": 1, "client": {} },
      { "kind": "..." }
    ],
    "client": {}
  }

The members are:

``requests``
  A JSON array containing zero or more requests.  Each request is
  a JSON object with members:

  ``kind``
    Specifies one of the `Object Kinds`_ to be included in the reply.

  ``version``
    Indicates the version(s) of the object kind that the client
    understands.  Versions have major and minor components following
    semantic version conventions.  The value must be

    * a JSON integer specifying a (non-negative) major version number, or
    * a JSON object containing ``major`` and (optionally) ``minor``
      members specifying non-negative integer version components, or
    * a JSON array whose elements are each one of the above.

  ``client``
    Optional member reserved for use by the client.  This value is
    preserved in the reply written for the client in the
    `v1 Reply Index File`_ but is otherwise ignored.  Clients may use
    this to pass custom information with a request through to its reply.

  For each requested object kind CMake will choose the *first* version
  that it recognizes for that kind among those listed in the request.
  The response will use the selected *major* version with the highest
  *minor* version known to the running CMake for that major version.
  Therefore clients should list all supported major versions in
  preferred order along with the minimal minor version required
  for each major version.

``client``
  Optional member reserved for use by the client.  This value is
  preserved in the reply written for the client in the
  `v1 Reply Index File`_ but is otherwise ignored.  Clients may use
  this to pass custom information with a query through to its reply.

Other ``query.json`` top-level members are reserved for future use.
If present they are ignored for forward compatibility.

v1 Reply Index File
-------------------

CMake writes an ``index-*.json`` file to the ``v1/reply/`` directory
whenever it runs to generate a build system.  Clients must read the
reply index file first and may read other `v1 Reply Files`_ only by
following references.  The form of the reply index file name is::

  <build>/.cmake/api/v1/reply/index-<unspecified>.json

where ``index-`` is literal and ``<unspecified>`` is an unspecified
name selected by CMake.  Whenever a new index file is generated it
is given a new name and any old one is deleted.  During the short
time between these steps there may be multiple index files present;
the one with the largest name in lexicographic order is the current
index file.

The reply index file contains a JSON object:

.. code-block:: json

  {
    "cmake": {
      "version": {
        "major": 3, "minor": 14, "patch": 0, "suffix": "",
        "string": "3.14.0", "isDirty": false
      },
      "paths": {
        "cmake": "/prefix/bin/cmake",
        "ctest": "/prefix/bin/ctest",
        "cpack": "/prefix/bin/cpack",
        "root": "/prefix/share/cmake-3.14"
      },
      "generator": {
        "multiConfig": false,
        "name": "Unix Makefiles"
      }
    },
    "objects": [
      { "kind": "<kind>",
        "version": { "major": 1, "minor": 0 },
        "jsonFile": "<file>" },
      { "...": "..." }
    ],
    "reply": {
      "<kind>-v<major>": { "kind": "<kind>",
                           "version": { "major": 1, "minor": 0 },
                           "jsonFile": "<file>" },
      "<unknown>": { "error": "unknown query file" },
      "...": {},
      "client-<client>": {
        "<kind>-v<major>": { "kind": "<kind>",
                             "version": { "major": 1, "minor": 0 },
                             "jsonFile": "<file>" },
        "<unknown>": { "error": "unknown query file" },
        "...": {},
        "query.json": {
          "requests": [ {}, {}, {} ],
          "responses": [
            { "kind": "<kind>",
              "version": { "major": 1, "minor": 0 },
              "jsonFile": "<file>" },
            { "error": "unknown query file" },
            { "...": {} }
          ],
          "client": {}
        }
      }
    }
  }

The members are:

``cmake``
  A JSON object containing information about the instance of CMake that
  generated the reply.  It contains members:

  ``version``
    A JSON object specifying the version of CMake with members:

    ``major``, ``minor``, ``patch``
      Integer values specifying the major, minor, and patch version components.
    ``suffix``
      A string specifying the version suffix, if any, e.g. ``g0abc3``.
    ``string``
      A string specifying the full version in the format
      ``<major>.<minor>.<patch>[-<suffix>]``.
    ``isDirty``
      A boolean indicating whether the version was built from a version
      controlled source tree with local modifications.

  ``paths``
    A JSON object specifying paths to things that come with CMake.
    It has members for :program:`cmake`, :program:`ctest`, and :program:`cpack`
    whose values are JSON strings specifying the absolute path to each tool,
    represented with forward slashes.  It also has a ``root`` member for
    the absolute path to the directory containing CMake resources like the
    ``Modules/`` directory (see :variable:`CMAKE_ROOT`).

  ``generator``
    A JSON object describing the CMake generator used for the build.
    It has members:

    ``multiConfig``
      A boolean specifying whether the generator supports multiple output
      configurations.
    ``name``
      A string specifying the name of the generator.
    ``platform``
      If the generator supports :variable:`CMAKE_GENERATOR_PLATFORM`,
      this is a string specifying the generator platform name.

``objects``
  A JSON array listing all versions of all `Object Kinds`_ generated
  as part of the reply.  Each array entry is a
  `v1 Reply File Reference`_.

``reply``
  A JSON object mirroring the content of the ``query/`` directory
  that CMake loaded to produce the reply.  The members are of the form

  ``<kind>-v<major>``
    A member of this form appears for each of the
    `v1 Shared Stateless Query Files`_ that CMake recognized as a
    request for object kind ``<kind>`` with major version ``<major>``.
    The value is a `v1 Reply File Reference`_ to the corresponding
    reply file for that object kind and version.

  ``<unknown>``
    A member of this form appears for each of the
    `v1 Shared Stateless Query Files`_ that CMake did not recognize.
    The value is a JSON object with a single ``error`` member
    containing a string with an error message indicating that the
    query file is unknown.

  ``client-<client>``
    A member of this form appears for each client-owned directory
    holding `v1 Client Stateless Query Files`_.
    The value is a JSON object mirroring the content of the
    ``query/client-<client>/`` directory.  The members are of the form:

    ``<kind>-v<major>``
      A member of this form appears for each of the
      `v1 Client Stateless Query Files`_ that CMake recognized as a
      request for object kind ``<kind>`` with major version ``<major>``.
      The value is a `v1 Reply File Reference`_ to the corresponding
      reply file for that object kind and version.

    ``<unknown>``
      A member of this form appears for each of the
      `v1 Client Stateless Query Files`_ that CMake did not recognize.
      The value is a JSON object with a single ``error`` member
      containing a string with an error message indicating that the
      query file is unknown.

    ``query.json``
      This member appears for clients using
      `v1 Client Stateful Query Files`_.
      If the ``query.json`` file failed to read or parse as a JSON object,
      this member is a JSON object with a single ``error`` member
      containing a string with an error message.  Otherwise, this member
      is a JSON object mirroring the content of the ``query.json`` file.
      The members are:

      ``client``
        A copy of the ``query.json`` file ``client`` member, if it exists.

      ``requests``
        A copy of the ``query.json`` file ``requests`` member, if it exists.

      ``responses``
        If the ``query.json`` file ``requests`` member is missing or invalid,
        this member is a JSON object with a single ``error`` member
        containing a string with an error message.  Otherwise, this member
        contains a JSON array with a response for each entry of the
        ``requests`` array, in the same order.  Each response is

        * a JSON object with a single ``error`` member containing a string
          with an error message, or
        * a `v1 Reply File Reference`_ to the corresponding reply file for
          the requested object kind and selected version.

After reading the reply index file, clients may read the other
`v1 Reply Files`_ it references.

v1 Reply File Reference
^^^^^^^^^^^^^^^^^^^^^^^

The reply index file represents each reference to another reply file
using a JSON object with members:

``kind``
  A string specifying one of the `Object Kinds`_.
``version``
  A JSON object with members ``major`` and ``minor`` specifying
  integer version components of the object kind.
``jsonFile``
  A JSON string specifying a path relative to the reply index file
  to another JSON file containing the object.

v1 Reply Files
--------------

Reply files containing specific `Object Kinds`_ are written by CMake.
The names of these files are unspecified and must not be interpreted
by clients.  Clients must first read the `v1 Reply Index File`_ and
follow references to the names of the desired response objects.

Reply files (including the index file) will never be replaced by
files of the same name but different content.  This allows a client
to read the files concurrently with a running CMake that may generate
a new reply.  However, after generating a new reply CMake will attempt
to remove reply files from previous runs that it did not just write.
If a client attempts to read a reply file referenced by the index but
finds the file missing, that means a concurrent CMake has generated
a new reply.  The client may simply start again by reading the new
reply index file.

.. _`file-api object kinds`:

Object Kinds
============

The CMake file-based API reports semantic information about the build
system using the following kinds of JSON objects.  Each kind of object
is versioned independently using semantic versioning with major and
minor components.  Every kind of object has the form:

.. code-block:: json

  {
    "kind": "<kind>",
    "version": { "major": 1, "minor": 0 },
    "...": {}
  }

The ``kind`` member is a string specifying the object kind name.
The ``version`` member is a JSON object with ``major`` and ``minor``
members specifying integer components of the object kind's version.
Additional top-level members are specific to each object kind.

Object Kind "codemodel"
-----------------------

The ``codemodel`` object kind describes the build system structure as
modeled by CMake.

There is only one ``codemodel`` object major version, version 2.
Version 1 does not exist to avoid confusion with that from
:manual:`cmake-server(7)` mode.

"codemodel" version 2
^^^^^^^^^^^^^^^^^^^^^

``codemodel`` object version 2 is a JSON object:

.. code-block:: json

  {
    "kind": "codemodel",
    "version": { "major": 2, "minor": 5 },
    "paths": {
      "source": "/path/to/top-level-source-dir",
      "build": "/path/to/top-level-build-dir"
    },
    "configurations": [
      {
        "name": "Debug",
        "directories": [
          {
            "source": ".",
            "build": ".",
            "childIndexes": [ 1 ],
            "projectIndex": 0,
            "targetIndexes": [ 0 ],
            "hasInstallRule": true,
            "minimumCMakeVersion": {
              "string": "3.14"
            },
            "jsonFile": "<file>"
          },
          {
            "source": "sub",
            "build": "sub",
            "parentIndex": 0,
            "projectIndex": 0,
            "targetIndexes": [ 1 ],
            "minimumCMakeVersion": {
              "string": "3.14"
            },
            "jsonFile": "<file>"
          }
        ],
        "projects": [
          {
            "name": "MyProject",
            "directoryIndexes": [ 0, 1 ],
            "targetIndexes": [ 0, 1 ]
          }
        ],
        "targets": [
          {
            "name": "MyExecutable",
            "directoryIndex": 0,
            "projectIndex": 0,
            "jsonFile": "<file>"
          },
          {
            "name": "MyLibrary",
            "directoryIndex": 1,
            "projectIndex": 0,
            "jsonFile": "<file>"
          }
        ]
      }
    ]
  }

The members specific to ``codemodel`` objects are:

``paths``
  A JSON object containing members:

  ``source``
    A string specifying the absolute path to the top-level source directory,
    represented with forward slashes.

  ``build``
    A string specifying the absolute path to the top-level build directory,
    represented with forward slashes.

``configurations``
  A JSON array of entries corresponding to available build configurations.
  On single-configuration generators there is one entry for the value
  of the :variable:`CMAKE_BUILD_TYPE` variable.  For multi-configuration
  generators there is an entry for each configuration listed in the
  :variable:`CMAKE_CONFIGURATION_TYPES` variable.
  Each entry is a JSON object containing members:

  ``name``
    A string specifying the name of the configuration, e.g. ``Debug``.

  ``directories``
    A JSON array of entries each corresponding to a build system directory
    whose source directory contains a ``CMakeLists.txt`` file.  The first
    entry corresponds to the top-level directory.  Each entry is a
    JSON object containing members:

    ``source``
      A string specifying the path to the source directory, represented
      with forward slashes.  If the directory is inside the top-level
      source directory then the path is specified relative to that
      directory (with ``.`` for the top-level source directory itself).
      Otherwise the path is absolute.

    ``build``
      A string specifying the path to the build directory, represented
      with forward slashes.  If the directory is inside the top-level
      build directory then the path is specified relative to that
      directory (with ``.`` for the top-level build directory itself).
      Otherwise the path is absolute.

    ``parentIndex``
      Optional member that is present when the directory is not top-level.
      The value is an unsigned integer 0-based index of another entry in
      the main ``directories`` array that corresponds to the parent
      directory that added this directory as a subdirectory.

    ``childIndexes``
      Optional member that is present when the directory has subdirectories.
      The value is a JSON array of entries corresponding to child directories
      created by the :command:`add_subdirectory` or :command:`subdirs`
      command.  Each entry is an unsigned integer 0-based index of another
      entry in the main ``directories`` array.

    ``projectIndex``
      An unsigned integer 0-based index into the main ``projects`` array
      indicating the build system project to which the this directory belongs.

    ``targetIndexes``
      Optional member that is present when the directory itself has targets,
      excluding those belonging to subdirectories.  The value is a JSON
      array of entries corresponding to the targets.  Each entry is an
      unsigned integer 0-based index into the main ``targets`` array.

    ``minimumCMakeVersion``
      Optional member present when a minimum required version of CMake is
      known for the directory.  This is the ``<min>`` version given to the
      most local call to the :command:`cmake_minimum_required(VERSION)`
      command in the directory itself or one of its ancestors.
      The value is a JSON object with one member:

      ``string``
        A string specifying the minimum required version in the format::

          <major>.<minor>[.<patch>[.<tweak>]][<suffix>]

        Each component is an unsigned integer and the suffix may be an
        arbitrary string.

    ``hasInstallRule``
      Optional member that is present with boolean value ``true`` when
      the directory or one of its subdirectories contains any
      :command:`install` rules, i.e. whether a ``make install``
      or equivalent rule is available.

    ``jsonFile``
      A JSON string specifying a path relative to the codemodel file
      to another JSON file containing a
      `"codemodel" version 2 "directory" object`_.

      This field was added in codemodel version 2.3.

  ``projects``
    A JSON array of entries corresponding to the top-level project
    and sub-projects defined in the build system.  Each (sub-)project
    corresponds to a source directory whose ``CMakeLists.txt`` file
    calls the :command:`project` command with a project name different
    from its parent directory.  The first entry corresponds to the
    top-level project.

    Each entry is a JSON object containing members:

    ``name``
      A string specifying the name given to the :command:`project` command.

    ``parentIndex``
      Optional member that is present when the project is not top-level.
      The value is an unsigned integer 0-based index of another entry in
      the main ``projects`` array that corresponds to the parent project
      that added this project as a sub-project.

    ``childIndexes``
      Optional member that is present when the project has sub-projects.
      The value is a JSON array of entries corresponding to the sub-projects.
      Each entry is an unsigned integer 0-based index of another
      entry in the main ``projects`` array.

    ``directoryIndexes``
      A JSON array of entries corresponding to build system directories
      that are part of the project.  The first entry corresponds to the
      top-level directory of the project.  Each entry is an unsigned
      integer 0-based index into the main ``directories`` array.

    ``targetIndexes``
      Optional member that is present when the project itself has targets,
      excluding those belonging to sub-projects.  The value is a JSON
      array of entries corresponding to the targets.  Each entry is an
      unsigned integer 0-based index into the main ``targets`` array.

  ``targets``
    A JSON array of entries corresponding to the build system targets.
    Such targets are created by calls to :command:`add_executable`,
    :command:`add_library`, and :command:`add_custom_target`, excluding
    imported targets and interface libraries (which do not generate any
    build rules).  Each entry is a JSON object containing members:

    ``name``
      A string specifying the target name.

    ``id``
      A string uniquely identifying the target.  This matches the ``id``
      field in the file referenced by ``jsonFile``.

    ``directoryIndex``
      An unsigned integer 0-based index into the main ``directories`` array
      indicating the build system directory in which the target is defined.

    ``projectIndex``
      An unsigned integer 0-based index into the main ``projects`` array
      indicating the build system project in which the target is defined.

    ``jsonFile``
      A JSON string specifying a path relative to the codemodel file
      to another JSON file containing a
      `"codemodel" version 2 "target" object`_.

"codemodel" version 2 "directory" object
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

A codemodel "directory" object is referenced by a `"codemodel" version 2`_
object's ``directories`` array.  Each "directory" object is a JSON object
with members:

``paths``
  A JSON object containing members:

  ``source``
    A string specifying the path to the source directory, represented
    with forward slashes.  If the directory is inside the top-level
    source directory then the path is specified relative to that
    directory (with ``.`` for the top-level source directory itself).
    Otherwise the path is absolute.

  ``build``
    A string specifying the path to the build directory, represented
    with forward slashes.  If the directory is inside the top-level
    build directory then the path is specified relative to that
    directory (with ``.`` for the top-level build directory itself).
    Otherwise the path is absolute.

``installers``
  A JSON array of entries corresponding to :command:`install` rules.
  Each entry is a JSON object containing members:

  ``component``
    A string specifying the component selected by the corresponding
    :command:`install` command invocation.

  ``destination``
    Optional member that is present for specific ``type`` values below.
    The value is a string specifying the install destination path.
    The path may be absolute or relative to the install prefix.

  ``paths``
    Optional member that is present for specific ``type`` values below.
    The value is a JSON array of entries corresponding to the paths
    (files or directories) to be installed.  Each entry is one of:

    * A string specifying the path from which a file or directory
      is to be installed.  The portion of the path not preceded by
      a ``/`` also specifies the path (name) to which the file
      or directory is to be installed under the destination.

    * A JSON object with members:

      ``from``
        A string specifying the path from which a file or directory
        is to be installed.

      ``to``
        A string specifying the path to which the file or directory
        is to be installed under the destination.

    In both cases the paths are represented with forward slashes.  If
    the "from" path is inside the top-level directory documented by the
    corresponding ``type`` value, then the path is specified relative
    to that directory.  Otherwise the path is absolute.

  ``type``
    A string specifying the type of installation rule.  The value is one
    of the following, with some variants providing additional members:

    ``file``
      An :command:`install(FILES)` or :command:`install(PROGRAMS)` call.
      The ``destination`` and ``paths`` members are populated, with paths
      under the top-level *source* directory expressed relative to it.
      The ``isOptional`` member may exist.
      This type has no additional members.

    ``directory``
      An :command:`install(DIRECTORY)` call.
      The ``destination`` and ``paths`` members are populated, with paths
      under the top-level *source* directory expressed relative to it.
      The ``isOptional`` member may exist.
      This type has no additional members.

    ``target``
      An :command:`install(TARGETS)` call.
      The ``destination`` and ``paths`` members are populated, with paths
      under the top-level *build* directory expressed relative to it.
      The ``isOptional`` member may exist.
      This type has additional members ``targetId``, ``targetIndex``,
      ``targetIsImportLibrary``, and ``targetInstallNamelink``.

    ``export``
      An :command:`install(EXPORT)` call.
      The ``destination`` and ``paths`` members are populated, with paths
      under the top-level *build* directory expressed relative to it.
      The ``paths`` entries refer to files generated automatically by
      CMake for installation, and their actual values are considered
      private implementation details.
      This type has additional members ``exportName`` and ``exportTargets``.

    ``script``
      An :command:`install(SCRIPT)` call.
      This type has additional member ``scriptFile``.

    ``code``
      An :command:`install(CODE)` call.
      This type has no additional members.

    ``importedRuntimeArtifacts``
      An :command:`install(IMPORTED_RUNTIME_ARTIFACTS)` call.
      The ``destination`` member is populated. The ``isOptional`` member may
      exist. This type has no additional members.

    ``runtimeDependencySet``
      An :command:`install(RUNTIME_DEPENDENCY_SET)` call or an
      :command:`install(TARGETS)` call with ``RUNTIME_DEPENDENCIES``. The
      ``destination`` member is populated. This type has additional members
      ``runtimeDependencySetName`` and ``runtimeDependencySetType``.

    ``fileSet``
      An :command:`install(TARGETS)` call with ``FILE_SET``.
      The ``destination`` and ``paths`` members are populated.
      The ``isOptional`` member may exist.
      This type has additional members ``fileSetName``, ``fileSetType``,
      ``fileSetDirectories``, and ``fileSetTarget``.

      This type was added in codemodel version 2.4.

  ``isExcludeFromAll``
    Optional member that is present with boolean value ``true`` when
    :command:`install` is called with the ``EXCLUDE_FROM_ALL`` option.

  ``isForAllComponents``
    Optional member that is present with boolean value ``true`` when
    :command:`install(SCRIPT|CODE)` is called with the
    ``ALL_COMPONENTS`` option.

  ``isOptional``
    Optional member that is present with boolean value ``true`` when
    :command:`install` is called with the ``OPTIONAL`` option.
    This is allowed when ``type`` is ``file``, ``directory``, or ``target``.

  ``targetId``
    Optional member that is present when ``type`` is ``target``.
    The value is a string uniquely identifying the target to be installed.
    This matches the ``id`` member of the target in the main
    "codemodel" object's ``targets`` array.

  ``targetIndex``
    Optional member that is present when ``type`` is ``target``.
    The value is an unsigned integer 0-based index into the main "codemodel"
    object's ``targets`` array for the target to be installed.

  ``targetIsImportLibrary``
    Optional member that is present when ``type`` is ``target`` and
    the installer is for a Windows DLL import library file or for an
    AIX linker import file.  If present, it has boolean value ``true``.

  ``targetInstallNamelink``
    Optional member that is present when ``type`` is ``target`` and
    the installer corresponds to a target that may use symbolic links
    to implement the :prop_tgt:`VERSION` and :prop_tgt:`SOVERSION`
    target properties.
    The value is a string indicating how the installer is supposed to
    handle the symlinks: ``skip`` means the installer should skip the
    symlinks and install only the real file, and ``only`` means the
    installer should install only the symlinks and not the real file.
    In all cases the ``paths`` member lists what it actually installs.

  ``exportName``
    Optional member that is present when ``type`` is ``export``.
    The value is a string specifying the name of the export.

  ``exportTargets``
    Optional member that is present when ``type`` is ``export``.
    The value is a JSON array of entries corresponding to the targets
    included in the export.  Each entry is a JSON object with members:

    ``id``
      A string uniquely identifying the target.  This matches
      the ``id`` member of the target in the main "codemodel"
      object's ``targets`` array.

    ``index``
      An unsigned integer 0-based index into the main "codemodel"
      object's ``targets`` array for the target.

  ``runtimeDependencySetName``
    Optional member that is present when ``type`` is ``runtimeDependencySet``
    and the installer was created by an
    :command:`install(RUNTIME_DEPENDENCY_SET)` call. The value is a string
    specifying the name of the runtime dependency set that was installed.

  ``runtimeDependencySetType``
    Optional member that is present when ``type`` is ``runtimeDependencySet``.
    The value is a string with one of the following values:

    ``library``
      Indicates that this installer installs dependencies that are not macOS
      frameworks.

    ``framework``
      Indicates that this installer installs dependencies that are macOS
      frameworks.

  ``fileSetName``
    Optional member that is present when ``type`` is ``fileSet``. The value is
    a string with the name of the file set.

    This field was added in codemodel version 2.4.

  ``fileSetType``
    Optional member that is present when ``type`` is ``fileSet``. The value is
    a string with the type of the file set.

    This field was added in codemodel version 2.4.

  ``fileSetDirectories``
    Optional member that is present when ``type`` is ``fileSet``. The value
    is a list of strings with the file set's base directories (determined by
    genex-evaluation of :prop_tgt:`HEADER_DIRS` or
    :prop_tgt:`HEADER_DIRS_<NAME>`).

    This field was added in codemodel version 2.4.

  ``fileSetTarget``
    Optional member that is present when ``type`` is ``fileSet``. The value
    is a JSON object with members:

    ``id``
      A string uniquely identifying the target.  This matches
      the ``id`` member of the target in the main "codemodel"
      object's ``targets`` array.

    ``index``
      An unsigned integer 0-based index into the main "codemodel"
      object's ``targets`` array for the target.

    This field was added in codemodel version 2.4.

  ``scriptFile``
    Optional member that is present when ``type`` is ``script``.
    The value is a string specifying the path to the script file on disk,
    represented with forward slashes.  If the file is inside the top-level
    source directory then the path is specified relative to that directory.
    Otherwise the path is absolute.

  ``backtrace``
    Optional member that is present when a CMake language backtrace to
    the :command:`install` or other command invocation that added this
    installer is available.  The value is an unsigned integer 0-based
    index into the ``backtraceGraph`` member's ``nodes`` array.

``backtraceGraph``
  A `"codemodel" version 2 "backtrace graph"`_ whose nodes are referenced
  from ``backtrace`` members elsewhere in this "directory" object.

"codemodel" version 2 "target" object
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

A codemodel "target" object is referenced by a `"codemodel" version 2`_
object's ``targets`` array.  Each "target" object is a JSON object
with members:

``name``
  A string specifying the logical name of the target.

``id``
  A string uniquely identifying the target.  The format is unspecified
  and should not be interpreted by clients.

``type``
  A string specifying the type of the target.  The value is one of
  ``EXECUTABLE``, ``STATIC_LIBRARY``, ``SHARED_LIBRARY``,
  ``MODULE_LIBRARY``, ``OBJECT_LIBRARY``, ``INTERFACE_LIBRARY``,
  or ``UTILITY``.

``backtrace``
  Optional member that is present when a CMake language backtrace to
  the command in the source code that created the target is available.
  The value is an unsigned integer 0-based index into the
  ``backtraceGraph`` member's ``nodes`` array.

``folder``
  Optional member that is present when the :prop_tgt:`FOLDER` target
  property is set.  The value is a JSON object with one member:

  ``name``
    A string specifying the name of the target folder.

``paths``
  A JSON object containing members:

  ``source``
    A string specifying the path to the target's source directory,
    represented with forward slashes.  If the directory is inside the
    top-level source directory then the path is specified relative to
    that directory (with ``.`` for the top-level source directory itself).
    Otherwise the path is absolute.

  ``build``
    A string specifying the path to the target's build directory,
    represented with forward slashes.  If the directory is inside the
    top-level build directory then the path is specified relative to
    that directory (with ``.`` for the top-level build directory itself).
    Otherwise the path is absolute.

``nameOnDisk``
  Optional member that is present for executable and library targets
  that are linked or archived into a single primary artifact.
  The value is a string specifying the file name of that artifact on disk.

``artifacts``
  Optional member that is present for executable and library targets
  that produce artifacts on disk meant for consumption by dependents.
  The value is a JSON array of entries corresponding to the artifacts.
  Each entry is a JSON object containing one member:

  ``path``
    A string specifying the path to the file on disk, represented with
    forward slashes.  If the file is inside the top-level build directory
    then the path is specified relative to that directory.
    Otherwise the path is absolute.

``isGeneratorProvided``
  Optional member that is present with boolean value ``true`` if the
  target is provided by CMake's build system generator rather than by
  a command in the source code.

``install``
  Optional member that is present when the target has an :command:`install`
  rule.  The value is a JSON object with members:

  ``prefix``
    A JSON object specifying the installation prefix.  It has one member:

    ``path``
      A string specifying the value of :variable:`CMAKE_INSTALL_PREFIX`.

  ``destinations``
    A JSON array of entries specifying an install destination path.
    Each entry is a JSON object with members:

    ``path``
      A string specifying the install destination path.  The path may
      be absolute or relative to the install prefix.

    ``backtrace``
      Optional member that is present when a CMake language backtrace to
      the :command:`install` command invocation that specified this
      destination is available.  The value is an unsigned integer 0-based
      index into the ``backtraceGraph`` member's ``nodes`` array.

``link``
  Optional member that is present for executables and shared library
  targets that link into a runtime binary.  The value is a JSON object
  with members describing the link step:

  ``language``
    A string specifying the language (e.g. ``C``, ``CXX``, ``Fortran``)
    of the toolchain is used to invoke the linker.

  ``commandFragments``
    Optional member that is present when fragments of the link command
    line invocation are available.  The value is a JSON array of entries
    specifying ordered fragments.  Each entry is a JSON object with members:

    ``fragment``
      A string specifying a fragment of the link command line invocation.
      The value is encoded in the build system's native shell format.

    ``role``
      A string specifying the role of the fragment's content:

      * ``flags``: link flags.
      * ``libraries``: link library file paths or flags.
      * ``libraryPath``: library search path flags.
      * ``frameworkPath``: macOS framework search path flags.

  ``lto``
    Optional member that is present with boolean value ``true``
    when link-time optimization (a.k.a. interprocedural optimization
    or link-time code generation) is enabled.

  ``sysroot``
    Optional member that is present when the :variable:`CMAKE_SYSROOT_LINK`
    or :variable:`CMAKE_SYSROOT` variable is defined.  The value is a
    JSON object with one member:

    ``path``
      A string specifying the absolute path to the sysroot, represented
      with forward slashes.

``archive``
  Optional member that is present for static library targets.  The value
  is a JSON object with members describing the archive step:

  ``commandFragments``
    Optional member that is present when fragments of the archiver command
    line invocation are available.  The value is a JSON array of entries
    specifying the fragments.  Each entry is a JSON object with members:

    ``fragment``
      A string specifying a fragment of the archiver command line invocation.
      The value is encoded in the build system's native shell format.

    ``role``
      A string specifying the role of the fragment's content:

      * ``flags``: archiver flags.

  ``lto``
    Optional member that is present with boolean value ``true``
    when link-time optimization (a.k.a. interprocedural optimization
    or link-time code generation) is enabled.

``dependencies``
  Optional member that is present when the target depends on other targets.
  The value is a JSON array of entries corresponding to the dependencies.
  Each entry is a JSON object with members:

  ``id``
    A string uniquely identifying the target on which this target depends.
    This matches the main ``id`` member of the other target.

  ``backtrace``
    Optional member that is present when a CMake language backtrace to
    the :command:`add_dependencies`, :command:`target_link_libraries`,
    or other command invocation that created this dependency is
    available.  The value is an unsigned integer 0-based index into
    the ``backtraceGraph`` member's ``nodes`` array.

``fileSets``
  A JSON array of entries corresponding to the target's file sets. Each entry
  is a JSON object with members:

  ``name``
    A string specifying the name of the file set.

  ``type``
    A string specifying the type of the file set.  See
    :command:`target_sources` supported file set types.

  ``visibility``
    A string specifying the visibility of the file set; one of ``PUBLIC``,
    ``PRIVATE``, or ``INTERFACE``.

  ``baseDirectories``
    A JSON array of strings specifying the base directories containing sources
    in the file set.

  This field was added in codemodel version 2.5.

``sources``
  A JSON array of entries corresponding to the target's source files.
  Each entry is a JSON object with members:

  ``path``
    A string specifying the path to the source file on disk, represented
    with forward slashes.  If the file is inside the top-level source
    directory then the path is specified relative to that directory.
    Otherwise the path is absolute.

  ``compileGroupIndex``
    Optional member that is present when the source is compiled.
    The value is an unsigned integer 0-based index into the
    ``compileGroups`` array.

  ``sourceGroupIndex``
    Optional member that is present when the source is part of a source
    group either via the :command:`source_group` command or by default.
    The value is an unsigned integer 0-based index into the
    ``sourceGroups`` array.

  ``isGenerated``
    Optional member that is present with boolean value ``true`` if
    the source is :prop_sf:`GENERATED`.

  ``fileSetIndex``
    Optional member that is present when the source is part of a file set.
    The value is an unsigned integer 0-based index into the ``fileSets``
    array.

    This field was added in codemodel version 2.5.

  ``backtrace``
    Optional member that is present when a CMake language backtrace to
    the :command:`target_sources`, :command:`add_executable`,
    :command:`add_library`, :command:`add_custom_target`, or other
    command invocation that added this source to the target is
    available.  The value is an unsigned integer 0-based index into
    the ``backtraceGraph`` member's ``nodes`` array.

``sourceGroups``
  Optional member that is present when sources are grouped together by
  the :command:`source_group` command or by default.  The value is a
  JSON array of entries corresponding to the groups.  Each entry is
  a JSON object with members:

  ``name``
    A string specifying the name of the source group.

  ``sourceIndexes``
    A JSON array listing the sources belonging to the group.
    Each entry is an unsigned integer 0-based index into the
    main ``sources`` array for the target.

``compileGroups``
  Optional member that is present when the target has sources that compile.
  The value is a JSON array of entries corresponding to groups of sources
  that all compile with the same settings.  Each entry is a JSON object
  with members:

  ``sourceIndexes``
    A JSON array listing the sources belonging to the group.
    Each entry is an unsigned integer 0-based index into the
    main ``sources`` array for the target.

  ``language``
    A string specifying the language (e.g. ``C``, ``CXX``, ``Fortran``)
    of the toolchain is used to compile the source file.

  ``languageStandard``
    Optional member that is present when the language standard is set
    explicitly (e.g. via :prop_tgt:`CXX_STANDARD`) or implicitly by
    compile features.  Each entry is a JSON object with two members:

    ``backtraces``
      Optional member that is present when a CMake language backtrace to
      the ``<LANG>_STANDARD`` setting is available.  If the language
      standard was set implicitly by compile features those are used as
      the backtrace(s).  It's possible for multiple compile features to
      require the same language standard so there could be multiple
      backtraces. The value is a JSON array with each entry being an
      unsigned integer 0-based index into the ``backtraceGraph``
      member's ``nodes`` array.

    ``standard``
      String representing the language standard.

    This field was added in codemodel version 2.2.

  ``compileCommandFragments``
    Optional member that is present when fragments of the compiler command
    line invocation are available.  The value is a JSON array of entries
    specifying ordered fragments.  Each entry is a JSON object with
    one member:

    ``fragment``
      A string specifying a fragment of the compile command line invocation.
      The value is encoded in the build system's native shell format.

  ``includes``
    Optional member that is present when there are include directories.
    The value is a JSON array with an entry for each directory.  Each
    entry is a JSON object with members:

    ``path``
      A string specifying the path to the include directory,
      represented with forward slashes.

    ``isSystem``
      Optional member that is present with boolean value ``true`` if
      the include directory is marked as a system include directory.

    ``backtrace``
      Optional member that is present when a CMake language backtrace to
      the :command:`target_include_directories` or other command invocation
      that added this include directory is available.  The value is
      an unsigned integer 0-based index into the ``backtraceGraph``
      member's ``nodes`` array.

  ``precompileHeaders``
    Optional member that is present when :command:`target_precompile_headers`
    or other command invocations set :prop_tgt:`PRECOMPILE_HEADERS` on the
    target.  The value is a JSON array with an entry for each header.  Each
    entry is a JSON object with members:

    ``header``
      Full path to the precompile header file.

    ``backtrace``
      Optional member that is present when a CMake language backtrace to
      the :command:`target_precompile_headers` or other command invocation
      that added this precompiled header is available.  The value is an
      unsigned integer 0-based index into the ``backtraceGraph`` member's
      ``nodes`` array.

    This field was added in codemodel version 2.1.

  ``defines``
    Optional member that is present when there are preprocessor definitions.
    The value is a JSON array with an entry for each definition.  Each
    entry is a JSON object with members:

    ``define``
      A string specifying the preprocessor definition in the format
      ``<name>[=<value>]``, e.g. ``DEF`` or ``DEF=1``.

    ``backtrace``
      Optional member that is present when a CMake language backtrace to
      the :command:`target_compile_definitions` or other command invocation
      that added this preprocessor definition is available.  The value is
      an unsigned integer 0-based index into the ``backtraceGraph``
      member's ``nodes`` array.

  ``sysroot``
    Optional member that is present when the
    :variable:`CMAKE_SYSROOT_COMPILE` or :variable:`CMAKE_SYSROOT`
    variable is defined.  The value is a JSON object with one member:

    ``path``
      A string specifying the absolute path to the sysroot, represented
      with forward slashes.

``backtraceGraph``
  A `"codemodel" version 2 "backtrace graph"`_ whose nodes are referenced
  from ``backtrace`` members elsewhere in this "target" object.

"codemodel" version 2 "backtrace graph"
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The ``backtraceGraph`` member of a `"codemodel" version 2 "directory" object`_,
or `"codemodel" version 2 "target" object`_ is a JSON object describing a
graph of backtraces.  Its nodes are referenced from ``backtrace`` members
elsewhere in the containing object.  The backtrace graph object members are:

``nodes``
  A JSON array listing nodes in the backtrace graph.  Each entry
  is a JSON object with members:

  ``file``
    An unsigned integer 0-based index into the backtrace ``files`` array.

  ``line``
    An optional member present when the node represents a line within
    the file.  The value is an unsigned integer 1-based line number.

  ``command``
    An optional member present when the node represents a command
    invocation within the file.  The value is an unsigned integer
    0-based index into the backtrace ``commands`` array.

  ``parent``
    An optional member present when the node is not the bottom of
    the call stack.  The value is an unsigned integer 0-based index
    of another entry in the backtrace ``nodes`` array.

``commands``
  A JSON array listing command names referenced by backtrace nodes.
  Each entry is a string specifying a command name.

``files``
  A JSON array listing CMake language files referenced by backtrace nodes.
  Each entry is a string specifying the path to a file, represented
  with forward slashes.  If the file is inside the top-level source
  directory then the path is specified relative to that directory.
  Otherwise the path is absolute.

.. _`file-api configureLog`:

Object Kind "configureLog"
--------------------------

The ``configureLog`` object kind describes the location and contents of
a :manual:`cmake-configure-log(7)` file.

There is only one ``configureLog`` object major version, version 1.

"configureLog" version 1
^^^^^^^^^^^^^^^^^^^^^^^^

``configureLog`` object version 1 is a JSON object:

.. code-block:: json

  {
    "kind": "configureLog",
    "version": { "major": 1, "minor": 0 },
    "path": "/path/to/top-level-build-dir/CMakeFiles/CMakeConfigureLog.yaml",
    "eventKindNames": [ "try_compile-v1", "try_run-v1" ]
  }

The members specific to ``configureLog`` objects are:

``path``
  A string specifying the path to the configure log file.
  Clients must read the log file from this path, which may be
  different than the path documented by :manual:`cmake-configure-log(7)`.
  The log file may not exist if no events are logged.

``eventKindNames``
  A JSON array whose entries are each a JSON string naming one
  of the :manual:`cmake-configure-log(7)` versioned event kinds.
  At most one version of each configure log event kind will be listed.
  Although the configure log may contain other (versioned) event kinds,
  clients must ignore those that are not listed in this field.

Object Kind "cache"
-------------------

The ``cache`` object kind lists cache entries.  These are the
:ref:`CMake Language Variables` stored in the persistent cache
(``CMakeCache.txt``) for the build tree.

There is only one ``cache`` object major version, version 2.
Version 1 does not exist to avoid confusion with that from
:manual:`cmake-server(7)` mode.

"cache" version 2
^^^^^^^^^^^^^^^^^

``cache`` object version 2 is a JSON object:

.. code-block:: json

  {
    "kind": "cache",
    "version": { "major": 2, "minor": 0 },
    "entries": [
      {
        "name": "BUILD_SHARED_LIBS",
        "value": "ON",
        "type": "BOOL",
        "properties": [
          {
            "name": "HELPSTRING",
            "value": "Build shared libraries"
          }
        ]
      },
      {
        "name": "CMAKE_GENERATOR",
        "value": "Unix Makefiles",
        "type": "INTERNAL",
        "properties": [
          {
            "name": "HELPSTRING",
            "value": "Name of generator."
          }
        ]
      }
    ]
  }

The members specific to ``cache`` objects are:

``entries``
  A JSON array whose entries are each a JSON object specifying a
  cache entry.  The members of each entry are:

  ``name``
    A string specifying the name of the entry.

  ``value``
    A string specifying the value of the entry.

  ``type``
    A string specifying the type of the entry used by
    :manual:`cmake-gui(1)` to choose a widget for editing.

  ``properties``
    A JSON array of entries specifying associated
    :ref:`cache entry properties <Cache Entry Properties>`.
    Each entry is a JSON object containing members:

    ``name``
      A string specifying the name of the cache entry property.

    ``value``
      A string specifying the value of the cache entry property.

Object Kind "cmakeFiles"
------------------------

The ``cmakeFiles`` object kind lists files used by CMake while
configuring and generating the build system.  These include the
``CMakeLists.txt`` files as well as included ``.cmake`` files.

There is only one ``cmakeFiles`` object major version, version 1.

"cmakeFiles" version 1
^^^^^^^^^^^^^^^^^^^^^^

``cmakeFiles`` object version 1 is a JSON object:

.. code-block:: json

  {
    "kind": "cmakeFiles",
    "version": { "major": 1, "minor": 0 },
    "paths": {
      "build": "/path/to/top-level-build-dir",
      "source": "/path/to/top-level-source-dir"
    },
    "inputs": [
      {
        "path": "CMakeLists.txt"
      },
      {
        "isGenerated": true,
        "path": "/path/to/top-level-build-dir/.../CMakeSystem.cmake"
      },
      {
        "isExternal": true,
        "path": "/path/to/external/third-party/module.cmake"
      },
      {
        "isCMake": true,
        "isExternal": true,
        "path": "/path/to/cmake/Modules/CMakeGenericSystem.cmake"
      }
    ]
  }

The members specific to ``cmakeFiles`` objects are:

``paths``
  A JSON object containing members:

  ``source``
    A string specifying the absolute path to the top-level source directory,
    represented with forward slashes.

  ``build``
    A string specifying the absolute path to the top-level build directory,
    represented with forward slashes.

``inputs``
  A JSON array whose entries are each a JSON object specifying an input
  file used by CMake when configuring and generating the build system.
  The members of each entry are:

  ``path``
    A string specifying the path to an input file to CMake, represented
    with forward slashes.  If the file is inside the top-level source
    directory then the path is specified relative to that directory.
    Otherwise the path is absolute.

  ``isGenerated``
    Optional member that is present with boolean value ``true``
    if the path specifies a file that is under the top-level
    build directory and the build is out-of-source.
    This member is not available on in-source builds.

  ``isExternal``
    Optional member that is present with boolean value ``true``
    if the path specifies a file that is not under the top-level
    source or build directories.

  ``isCMake``
    Optional member that is present with boolean value ``true``
    if the path specifies a file in the CMake installation.

Object Kind "toolchains"
------------------------

The ``toolchains`` object kind lists properties of the toolchains used during
the build.  These include the language, compiler path, ID, and version.

There is only one ``toolchains`` object major version, version 1.

"toolchains" version 1
^^^^^^^^^^^^^^^^^^^^^^

``toolchains`` object version 1 is a JSON object:

.. code-block:: json

  {
    "kind": "toolchains",
    "version": { "major": 1, "minor": 0 },
    "toolchains": [
      {
        "language": "C",
        "compiler": {
          "path": "/usr/bin/cc",
          "id": "GNU",
          "version": "9.3.0",
          "implicit": {
            "includeDirectories": [
              "/usr/lib/gcc/x86_64-linux-gnu/9/include",
              "/usr/local/include",
              "/usr/include/x86_64-linux-gnu",
              "/usr/include"
            ],
            "linkDirectories": [
              "/usr/lib/gcc/x86_64-linux-gnu/9",
              "/usr/lib/x86_64-linux-gnu",
              "/usr/lib",
              "/lib/x86_64-linux-gnu",
              "/lib"
            ],
            "linkFrameworkDirectories": [],
            "linkLibraries": [ "gcc", "gcc_s", "c", "gcc", "gcc_s" ]
          }
        },
        "sourceFileExtensions": [ "c", "m" ]
      },
      {
        "language": "CXX",
        "compiler": {
          "path": "/usr/bin/c++",
          "id": "GNU",
          "version": "9.3.0",
          "implicit": {
            "includeDirectories": [
              "/usr/include/c++/9",
              "/usr/include/x86_64-linux-gnu/c++/9",
              "/usr/include/c++/9/backward",
              "/usr/lib/gcc/x86_64-linux-gnu/9/include",
              "/usr/local/include",
              "/usr/include/x86_64-linux-gnu",
              "/usr/include"
            ],
            "linkDirectories": [
              "/usr/lib/gcc/x86_64-linux-gnu/9",
              "/usr/lib/x86_64-linux-gnu",
              "/usr/lib",
              "/lib/x86_64-linux-gnu",
              "/lib"
            ],
            "linkFrameworkDirectories": [],
            "linkLibraries": [
              "stdc++", "m", "gcc_s", "gcc", "c", "gcc_s", "gcc"
            ]
          }
        },
        "sourceFileExtensions": [
          "C", "M", "c++", "cc", "cpp", "cxx", "mm", "CPP"
        ]
      }
    ]
  }

The members specific to ``toolchains`` objects are:

``toolchains``
  A JSON array whose entries are each a JSON object specifying a toolchain
  associated with a particular language. The members of each entry are:

  ``language``
    A JSON string specifying the toolchain language, like C or CXX. Language
    names are the same as language names that can be passed to the
    :command:`project` command. Because CMake only supports a single toolchain
    per language, this field can be used as a key.

  ``compiler``
    A JSON object containing members:

    ``path``
      Optional member that is present when the
      :variable:`CMAKE_<LANG>_COMPILER` variable is defined for the current
      language. Its value is a JSON string holding the path to the compiler.

    ``id``
      Optional member that is present when the
      :variable:`CMAKE_<LANG>_COMPILER_ID` variable is defined for the current
      language. Its value is a JSON string holding the ID (GNU, MSVC, etc.) of
      the compiler.

    ``version``
      Optional member that is present when the
      :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable is defined for the
      current language. Its value is a JSON string holding the version of the
      compiler.

    ``target``
      Optional member that is present when the
      :variable:`CMAKE_<LANG>_COMPILER_TARGET` variable is defined for the
      current language. Its value is a JSON string holding the cross-compiling
      target of the compiler.

    ``implicit``
      A JSON object containing members:

      ``includeDirectories``
        Optional member that is present when the
        :variable:`CMAKE_<LANG>_IMPLICIT_INCLUDE_DIRECTORIES` variable is
        defined for the current language. Its value is a JSON array of JSON
        strings where each string holds a path to an implicit include
        directory for the compiler.

      ``linkDirectories``
        Optional member that is present when the
        :variable:`CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES` variable is
        defined for the current language. Its value is a JSON array of JSON
        strings where each string holds a path to an implicit link directory
        for the compiler.

      ``linkFrameworkDirectories``
        Optional member that is present when the
        :variable:`CMAKE_<LANG>_IMPLICIT_LINK_FRAMEWORK_DIRECTORIES` variable
        is defined for the current language. Its value is a JSON array of JSON
        strings where each string holds a path to an implicit link framework
        directory for the compiler.

      ``linkLibraries``
        Optional member that is present when the
        :variable:`CMAKE_<LANG>_IMPLICIT_LINK_LIBRARIES` variable is defined
        for the current language. Its value is a JSON array of JSON strings
        where each string holds a path to an implicit link library for the
        compiler.

  ``sourceFileExtensions``
    Optional member that is present when the
    :variable:`CMAKE_<LANG>_SOURCE_FILE_EXTENSIONS` variable is defined for
    the current language. Its value is a JSON array of JSON strings where each
    each string holds a file extension (without the leading dot) for the
    language.