CMake/Help/command/project.rst

project
-------

Set the name of the project.

Synopsis
^^^^^^^^

.. code-block:: cmake

 project(<PROJECT-NAME> [<language-name>...])
 project(<PROJECT-NAME>
         [VERSION <major>[.<minor>[.<patch>[.<tweak>]]]]
         [DESCRIPTION <project-description-string>]
         [HOMEPAGE_URL <url-string>]
         [LANGUAGES <language-name>...])

Sets the name of the project, and stores it in the variable
:variable:`PROJECT_NAME`. When called from the top-level
``CMakeLists.txt`` also stores the project name in the
variable :variable:`CMAKE_PROJECT_NAME`.

Also sets the variables:

:variable:`PROJECT_SOURCE_DIR`, :variable:`<PROJECT-NAME>_SOURCE_DIR`
  Absolute path to the source directory for the project.

:variable:`PROJECT_BINARY_DIR`, :variable:`<PROJECT-NAME>_BINARY_DIR`
  Absolute path to the binary directory for the project.

:variable:`PROJECT_IS_TOP_LEVEL`, :variable:`<PROJECT-NAME>_IS_TOP_LEVEL`
  .. versionadded:: 3.21

  Boolean value indicating whether the project is top-level.

Further variables are set by the optional arguments described in `Options`_
further below. Where an option is not given, its corresponding variable is
set to the empty string.

Note that variables of the form ``<name>_SOURCE_DIR`` and ``<name>_BINARY_DIR``
may also be set by other commands before ``project()`` is called (see the
:command:`FetchContent_MakeAvailable` command for one example).
Projects should not rely on ``<PROJECT-NAME>_SOURCE_DIR`` or
``<PROJECT-NAME>_BINARY_DIR`` holding a particular value outside of the scope
of the call to ``project()`` or one of its child scopes.

.. versionchanged:: 3.30.3
  ``<PROJECT-NAME>_SOURCE_DIR``, ``<PROJECT-NAME>_BINARY_DIR``, and
  ``<PROJECT-NAME>_IS_TOP_LEVEL`` are always set as non-cache variables by
  ``project(<PROJECT-NAME> ...)``.

.. versionchanged:: 3.30.4
  The variables ``<PROJECT-NAME>_SOURCE_DIR``, ``<PROJECT-NAME>_BINARY_DIR``,
  and ``<PROJECT-NAME>_IS_TOP_LEVEL`` are only set as non-cache variables if
  they are already set as cache or non-cache variables when
  ``project(<PROJECT-NAME> ...)`` is called.
  Note that this logic is flawed, as it can result in different behavior
  between the first and subsequent runs because cache variables won't exist
  on the first run, but they will on subsequent runs.

.. versionchanged:: 3.30.5
  The variables ``<PROJECT-NAME>_SOURCE_DIR``, ``<PROJECT-NAME>_BINARY_DIR``,
  and ``<PROJECT-NAME>_IS_TOP_LEVEL`` are only set as non-cache variables if
  they are already set as non-cache variables when
  ``project(<PROJECT-NAME> ...)`` is called.
  Unlike the flawed behavior of 3.30.4, non-cache variables will not be set
  if only cache variables of the same name are set.

Options
^^^^^^^

The options are:

``VERSION <version>``
  Optional; may not be used unless policy :policy:`CMP0048` is
  set to ``NEW``.

  Takes a ``<version>`` argument composed of non-negative integer components,
  i.e. ``<major>[.<minor>[.<patch>[.<tweak>]]]``,
  and sets the variables

  * :variable:`PROJECT_VERSION`,
    :variable:`<PROJECT-NAME>_VERSION`
  * :variable:`PROJECT_VERSION_MAJOR`,
    :variable:`<PROJECT-NAME>_VERSION_MAJOR`
  * :variable:`PROJECT_VERSION_MINOR`,
    :variable:`<PROJECT-NAME>_VERSION_MINOR`
  * :variable:`PROJECT_VERSION_PATCH`,
    :variable:`<PROJECT-NAME>_VERSION_PATCH`
  * :variable:`PROJECT_VERSION_TWEAK`,
    :variable:`<PROJECT-NAME>_VERSION_TWEAK`.

  .. versionadded:: 3.12
    When the ``project()`` command is called from the top-level
    ``CMakeLists.txt``, then the version is also stored in the variable
    :variable:`CMAKE_PROJECT_VERSION`.

``DESCRIPTION <project-description-string>``
  .. versionadded:: 3.9

  Optional.
  Sets the variables

  * :variable:`PROJECT_DESCRIPTION`, :variable:`<PROJECT-NAME>_DESCRIPTION`

  to ``<project-description-string>``.
  It is recommended that this description is a relatively short string,
  usually no more than a few words.

  When the ``project()`` command is called from the top-level ``CMakeLists.txt``,
  then the description is also stored in the variable :variable:`CMAKE_PROJECT_DESCRIPTION`.

  .. versionadded:: 3.12
    Added the ``<PROJECT-NAME>_DESCRIPTION`` variable.

``HOMEPAGE_URL <url-string>``
  .. versionadded:: 3.12

  Optional.
  Sets the variables

  * :variable:`PROJECT_HOMEPAGE_URL`, :variable:`<PROJECT-NAME>_HOMEPAGE_URL`

  to ``<url-string>``, which should be the canonical home URL for the project.

  When the ``project()`` command is called from the top-level ``CMakeLists.txt``,
  then the URL also is stored in the variable :variable:`CMAKE_PROJECT_HOMEPAGE_URL`.

``LANGUAGES <language-name>...``
  Optional.
  Can also be specified without ``LANGUAGES`` keyword per the first, short signature.

  Selects which programming languages are needed to build the project.

.. include:: SUPPORTED_LANGUAGES.txt

By default ``C`` and ``CXX`` are enabled if no language options are given.
Specify language ``NONE``, or use the ``LANGUAGES`` keyword and list no languages,
to skip enabling any languages.

The variables set through the ``VERSION``, ``DESCRIPTION`` and ``HOMEPAGE_URL``
options are intended for use as default values in package metadata and documentation.

.. _`Code Injection`:

Code Injection
^^^^^^^^^^^^^^

A number of variables can be defined by the user to specify files to include
at different points during the execution of the ``project()`` command.
The following outlines the steps performed during a ``project()`` call:

* .. versionadded:: 3.15
    For every ``project()`` call regardless of the project
    name, include the file(s) and module(s) named by
    :variable:`CMAKE_PROJECT_INCLUDE_BEFORE`, if set.

* .. versionadded:: 3.17
    If the ``project()`` command specifies ``<PROJECT-NAME>`` as its project
    name, include the file(s) and module(s) named by
    :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE_BEFORE`, if set.

* Set the various project-specific variables detailed in the `Synopsis`_
  and `Options`_ sections above.

* For the very first ``project()`` call only:

  * If :variable:`CMAKE_TOOLCHAIN_FILE` is set, read it at least once.
    It may be read multiple times and it may also be read again when
    enabling languages later (see below).

  * Set the variables describing the host and target platforms.
    Language-specific variables might or might not be set at this point.
    On the first run, the only language-specific variables that might be
    defined are those a toolchain file may have set. On subsequent runs,
    language-specific variables cached from a previous run may be set.

  * .. versionadded:: 3.24
      Include each file listed in :variable:`CMAKE_PROJECT_TOP_LEVEL_INCLUDES`,
      if set. The variable is ignored by CMake thereafter.

* Enable any languages specified in the call, or the default languages if
  none were provided. The toolchain file may be re-read when enabling a
  language for the first time.

* .. versionadded:: 3.15
    For every ``project()`` call regardless of the project
    name, include the file(s) and module(s) named by
    :variable:`CMAKE_PROJECT_INCLUDE`, if set.

* If the ``project()`` command specifies ``<PROJECT-NAME>`` as its project
  name, include the file(s) and module(s) named by
  :variable:`CMAKE_PROJECT_<PROJECT-NAME>_INCLUDE`, if set.

Usage
^^^^^

The top-level ``CMakeLists.txt`` file for a project must contain a
literal, direct call to the ``project()`` command; loading one
through the :command:`include` command is not sufficient.  If no such
call exists, CMake will issue a warning and pretend there is a
``project(Project)`` at the top to enable the default languages
(``C`` and ``CXX``).

.. note::
  Call the ``project()`` command near the top of the top-level
  ``CMakeLists.txt``, but *after* calling :command:`cmake_minimum_required`.
  It is important to establish version and policy settings before invoking
  other commands whose behavior they may affect and for this reason the
  ``project()`` command will issue a warning if this order is not kept.
  See also policy :policy:`CMP0000`.