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CMake Source Code Guide
***********************
The following is a guide to the CMake source code for developers.
See documentation on `CMake Development`_ for more information.
.. _`CMake Development`: README.rst
C++ Code Style
==============
We use `clang-format`_ version **6.0** to define our style for C++ code in
the CMake source tree. See the `.clang-format`_ configuration file for our
style settings. Use the `Utilities/Scripts/clang-format.bash`_ script to
format source code. It automatically runs ``clang-format`` on the set of
source files for which we enforce style. The script also has options to
format only a subset of files, such as those that are locally modified.
.. _`clang-format`: http://clang.llvm.org/docs/ClangFormat.html
.. _`.clang-format`: ../../.clang-format
.. _`Utilities/Scripts/clang-format.bash`: ../../Utilities/Scripts/clang-format.bash
C++ Subset Permitted
====================
CMake requires compiling as C++11 in order to support building on older
toolchains. However, to facilitate development, some standard library
features from more recent C++ standards are supported through a compatibility
layer. These features are defined under the namespace ``cm`` and headers
are accessible under the ``cm/`` directory. The headers under ``cm/`` can
be used in place of the standard ones when extended features are needed.
For example ``<cm/memory>`` can be used in place of ``<memory>``.
Available features are:
* From ``C++14``:
* ``<cm/iterator>``:
``cm::make_reverse_iterator``, ``cm::cbegin``, ``cm::cend``,
``cm::rbegin``, ``cm::rend``, ``cm::crbegin``, ``cm::crend``
* ``<cm/memory>``:
``cm::make_unique``
* ``<cm/shared_mutex>``:
``cm::shared_lock``
* ``<cm/type_traits>``:
``cm::enable_if_t``
* From ``C++17``:
* ``<cm/algorithm>``:
``cm::clamp``
* ``<cm/iterator>``:
``cm::size``, ``cm::empty``, ``cm::data``
* ``<cm/optional>``:
``cm::nullopt_t``, ``cm::nullopt``, ``cm::optional``,
``cm::make_optional``, ``cm::bad_optional_access``
* ``<cm/shared_mutex>``:
``cm::shared_mutex``
* ``<cm/string_view>``:
``cm::string_view``
* ``<cm/type_traits>``:
``cm::bool_constant``, ``cm::invoke_result_t``, ``cm::invoke_result``,
``cm::void_t``
* ``<cm/utility>``:
``cm::in_place_t``, ``cm::in_place``
* From ``C++20``:
* ``<cm/deque>``:
``cm::erase``, ``cm::erase_if``
* ``<cm/list>``:
``cm::erase``, ``cm::erase_if``
* ``<cm/map>`` :
``cm::erase_if``
* ``<cm/set>`` :
``cm::erase_if``
* ``<cm/string>``:
``cm::erase``, ``cm::erase_if``
* ``<cm/unordered_map>``:
``cm::erase_if``
* ``<cm/unordered_set>``:
``cm::erase_if``
* ``<cm/vector>``:
``cm::erase``, ``cm::erase_if``
Additionally, some useful non-standard extensions to the C++ standard library
are available in headers under the directory ``cmext/`` in namespace ``cm``.
These are:
* ``<cmext/algorithm>``:
* ``cm::append``:
Append elements to a sequential container.
* ``cm::contains``:
Checks if element or key is contained in container.
* ``<cmext/iterator>``:
* ``cm::is_terator``:
Checks if a type is an iterator type.
* ``cm::is_input_iterator``:
Checks if a type is an input iterator type.
* ``cm::is_range``:
Checks if a type is a range type: functions ``std::begin()`` and
``std::end()`` apply.
* ``cm::is_input_range``:
Checks if a type is an input range type: functions ``std::begin()`` and
``std::end()`` apply and return an input iterator.
* ``<cmext/memory>``:
* ``cm::static_reference_cast``:
Apply a ``static_cast`` to a smart pointer.
* ``cm::dynamic_reference_cast``:
Apply a ``dynamic_cast`` to a smart pointer.
* ``<cmext/type_traits>``:
* ``cm::is_container``:
Checks if a type is a container type.
* ``cm::is_associative_container``:
Checks if a type is an associative container type.
* ``cm::is_unordered_associative_container``:
Checks if a type is an unordered associative container type.
* ``cm::is_sequence_container``:
Checks if a type is a sequence container type.
* ``cm::is_unique_ptr``:
Checks if a type is a ``std::unique_ptr`` type.
Dynamic Memory Management
=========================
To ensure efficient memory management, i.e. no memory leaks, it is required
to use smart pointers. Any dynamic memory allocation must be handled by a
smart pointer such as ``std::unique_ptr`` or ``std::shared_ptr``.
It is allowed to pass raw pointers between objects to enable objects sharing.
A raw pointer **must** not be deleted. Only the object(s) owning the smart
pointer are allowed to delete dynamically allocated memory.
Source Tree Layout
==================
The CMake source tree is organized as follows.
* ``Auxiliary/``:
Shell and editor integration files.
* ``Help/``:
Documentation. See the `CMake Documentation Guide`_.
* ``Help/dev/``:
Developer documentation.
* ``Help/release/dev/``:
Release note snippets for development since last release.
* ``Licenses/``:
License files for third-party libraries in binary distributions.
* ``Modules/``:
CMake language modules installed with CMake.
* ``Packaging/``:
Files used for packaging CMake itself for distribution.
* ``Source/``:
Source code of CMake itself.
* ``Templates/``:
Files distributed with CMake as implementation details for generators,
packagers, etc.
* ``Tests/``:
The test suite. See `Tests/README.rst`_.
* ``Utilities/``:
Scripts, third-party source code.
* ``Utilities/std/cm``:
Support files for various C++ standards.
* ``Utilities/std/cmext``:
Extensions to the C++ STL.
* ``Utilities/Sphinx/``:
Sphinx configuration to build CMake user documentation.
* ``Utilities/Release/``:
Scripts used to package CMake itself for distribution on ``cmake.org``.
See `Utilities/Release/README.rst`_.
.. _`CMake Documentation Guide`: documentation.rst
.. _`Tests/README.rst`: ../../Tests/README.rst
.. _`Utilities/Release/README.rst`: ../../Utilities/Release/README.rst
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