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89 lines
3.2 KiB
89 lines
3.2 KiB
cmake_minimum_required
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----------------------
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Require a minimum version of cmake.
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.. code-block:: cmake
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cmake_minimum_required(VERSION <min>[...<policy_max>] [FATAL_ERROR])
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.. versionadded:: 3.12
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The optional ``<policy_max>`` version.
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Sets the minimum required version of cmake for a project.
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Also updates the policy settings as explained below.
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``<min>`` and the optional ``<policy_max>`` are each CMake versions of the
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form ``major.minor[.patch[.tweak]]``, and the ``...`` is literal.
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If the running version of CMake is lower than the ``<min>`` required
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version it will stop processing the project and report an error.
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The optional ``<policy_max>`` version, if specified, must be at least the
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``<min>`` version and affects policy settings as described in `Policy Settings`_.
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If the running version of CMake is older than 3.12, the extra ``...``
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dots will be seen as version component separators, resulting in the
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``...<max>`` part being ignored and preserving the pre-3.12 behavior
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of basing policies on ``<min>``.
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This command will set the value of the
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:variable:`CMAKE_MINIMUM_REQUIRED_VERSION` variable to ``<min>``.
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The ``FATAL_ERROR`` option is accepted but ignored by CMake 2.6 and
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higher. It should be specified so CMake versions 2.4 and lower fail
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with an error instead of just a warning.
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.. note::
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Call the ``cmake_minimum_required()`` command at the beginning of
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the top-level ``CMakeLists.txt`` file even before calling the
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:command:`project` command. It is important to establish version
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and policy settings before invoking other commands whose behavior
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they may affect. See also policy :policy:`CMP0000`.
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Calling ``cmake_minimum_required()`` inside a :command:`function`
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limits some effects to the function scope when invoked. For example,
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the :variable:`CMAKE_MINIMUM_REQUIRED_VERSION` variable won't be set
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in the calling scope. Functions do not introduce their own policy
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scope though, so policy settings of the caller *will* be affected
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(see below). Due to this mix of things that do and do not affect the
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calling scope, calling ``cmake_minimum_required()`` inside a function
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is generally discouraged.
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.. _`Policy Settings`:
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Policy Settings
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^^^^^^^^^^^^^^^
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The ``cmake_minimum_required(VERSION)`` command implicitly invokes the
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:command:`cmake_policy(VERSION)` command to specify that the current
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project code is written for the given range of CMake versions.
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All policies known to the running version of CMake and introduced
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in the ``<min>`` (or ``<max>``, if specified) version or earlier will
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be set to use ``NEW`` behavior. All policies introduced in later
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versions will be unset. This effectively requests behavior preferred
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as of a given CMake version and tells newer CMake versions to warn
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about their new policies.
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When a ``<min>`` version higher than 2.4 is specified the command
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implicitly invokes
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.. code-block:: cmake
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cmake_policy(VERSION <min>[...<max>])
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which sets CMake policies based on the range of versions specified.
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When a ``<min>`` version 2.4 or lower is given the command implicitly
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invokes
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.. code-block:: cmake
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cmake_policy(VERSION 2.4[...<max>])
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which enables compatibility features for CMake 2.4 and lower.
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.. include:: DEPRECATED_POLICY_VERSIONS.txt
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See Also
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^^^^^^^^
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* :command:`cmake_policy`
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