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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 **3.8** 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 supports compiling as C++98 in addition to C++11 and C++14.
In order to support building on older toolchains some constructs
need to be handled with care:
* Use ``CM_AUTO_PTR`` instead of ``std::auto_ptr``.
The ``std::auto_ptr`` template is deprecated in C++11. We want to use it
so we can build on C++98 compilers but we do not want to turn off compiler
warnings about deprecated interfaces in general. Use the ``CM_AUTO_PTR``
macro instead.
* Use ``CM_EQ_DELETE;`` instead of ``= delete;``.
Defining functions as *deleted* is not supported in C++98. Using
``CM_EQ_DELETE`` will delete the functions if the compiler supports it and
give them no implementation otherwise. Calling such a function will lead
to compiler errors if the compiler supports *deleted* functions and linker
errors otherwise.
* Use ``CM_DISABLE_COPY(Class)`` to mark classes as non-copyable.
The ``CM_DISABLE_COPY`` macro should be used in the private section of a
class to make sure that attempts to copy or assign an instance of the class
lead to compiler errors even if the compiler does not support *deleted*
functions. As a guideline, all polymorphic classes should be made
non-copyable in order to avoid slicing. Classes that are composed of or
derived from non-copyable classes must also be made non-copyable explicitly
with ``CM_DISABLE_COPY``.
* Use ``size_t`` instead of ``std::size_t``.
Various implementations have differing implementation of ``size_t``.
When assigning the result of ``.size()`` on a container for example,
the result should be assigned to ``size_t`` not to ``std::size_t``,
``unsigned int`` or similar types.
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