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Diffstat (limited to 'Help/manual/cmake-developer.7.rst')
| -rw-r--r-- | Help/manual/cmake-developer.7.rst | 586 |
1 files changed, 10 insertions, 576 deletions
diff --git a/Help/manual/cmake-developer.7.rst b/Help/manual/cmake-developer.7.rst index c3bbf28..b949464 100644 --- a/Help/manual/cmake-developer.7.rst +++ b/Help/manual/cmake-developer.7.rst @@ -10,579 +10,20 @@ cmake-developer(7) Introduction ============ -This manual is intended for reference by developers modifying the CMake -source tree itself, and by those authoring externally-maintained modules. +This manual is intended for reference by developers working with +:manual:`cmake-language(7)` code, whether writing their own modules, +authoring their own build systems, or working on CMake itself. See https://cmake.org/get-involved/ to get involved in development of -CMake upstream. - -Adding Compile Features -======================= - -CMake reports an error if a compiler whose features are known does not report -support for a particular requested feature. A compiler is considered to have -known features if it reports support for at least one feature. - -When adding a new compile feature to CMake, it is therefore necessary to list -support for the feature for all CompilerIds which already have one or more -feature supported, if the new feature is available for any version of the -compiler. - -When adding the first supported feature to a particular CompilerId, it is -necessary to list support for all features known to cmake (See -:variable:`CMAKE_C_COMPILE_FEATURES` and -:variable:`CMAKE_CXX_COMPILE_FEATURES` as appropriate), where available for -the compiler. Ensure that the ``CMAKE_<LANG>_STANDARD_DEFAULT`` is set to -the computed internal variable ``CMAKE_<LANG>_STANDARD_COMPUTED_DEFAULT`` -for compiler versions which should be supported. - -It is sensible to record the features for the most recent version of a -particular CompilerId first, and then work backwards. It is sensible to -try to create a continuous range of versions of feature releases of the -compiler. Gaps in the range indicate incorrect features recorded for -intermediate releases. - -Generally, features are made available for a particular version if the -compiler vendor documents availability of the feature with that -version. Note that sometimes partially implemented features appear to -be functional in previous releases (such as ``cxx_constexpr`` in GNU 4.6, -though availability is documented in GNU 4.7), and sometimes compiler vendors -document availability of features, though supporting infrastructure is -not available (such as ``__has_feature(cxx_generic_lambdas)`` indicating -non-availability in Clang 3.4, though it is documented as available, and -fixed in Clang 3.5). Similar cases for other compilers and versions -need to be investigated when extending CMake to support them. - -When a vendor releases a new version of a known compiler which supports -a previously unsupported feature, and there are already known features for -that compiler, the feature should be listed as supported in CMake for -that version of the compiler as soon as reasonably possible. - -Standard-specific/compiler-specific variables such -``CMAKE_CXX98_COMPILE_FEATURES`` are deliberately not documented. They -only exist for the compiler-specific implementation of adding the ``-std`` -compile flag for compilers which need that. - -Help -==== - -The ``Help`` directory contains CMake help manual source files. -They are written using the `reStructuredText`_ markup syntax and -processed by `Sphinx`_ to generate the CMake help manuals. - -.. _`reStructuredText`: http://docutils.sourceforge.net/docs/ref/rst/introduction.html -.. _`Sphinx`: http://sphinx-doc.org - -Markup Constructs ------------------ - -In addition to using Sphinx to generate the CMake help manuals, we -also use a C++-implemented document processor to print documents for -the ``--help-*`` command-line help options. It supports a subset of -reStructuredText markup. When authoring or modifying documents, -please verify that the command-line help looks good in addition to the -Sphinx-generated html and man pages. - -The command-line help processor supports the following constructs -defined by reStructuredText, Sphinx, and a CMake extension to Sphinx. - -.. - Note: This list must be kept consistent with the cmRST implementation. - -CMake Domain directives - Directives defined in the `CMake Domain`_ for defining CMake - documentation objects are printed in command-line help output as - if the lines were normal paragraph text with interpretation. - -CMake Domain interpreted text roles - Interpreted text roles defined in the `CMake Domain`_ for - cross-referencing CMake documentation objects are replaced by their - link text in command-line help output. Other roles are printed - literally and not processed. - -``code-block`` directive - Add a literal code block without interpretation. The command-line - help processor prints the block content without the leading directive - line and with common indentation replaced by one space. - -``include`` directive - Include another document source file. The command-line help - processor prints the included document inline with the referencing - document. - -literal block after ``::`` - A paragraph ending in ``::`` followed by a blank line treats - the following indented block as literal text without interpretation. - The command-line help processor prints the ``::`` literally and - prints the block content with common indentation replaced by one - space. - -``note`` directive - Call out a side note. The command-line help processor prints the - block content as if the lines were normal paragraph text with - interpretation. - -``parsed-literal`` directive - Add a literal block with markup interpretation. The command-line - help processor prints the block content without the leading - directive line and with common indentation replaced by one space. - -``productionlist`` directive - Render context-free grammar productions. The command-line help - processor prints the block content as if the lines were normal - paragraph text with interpretation. - -``replace`` directive - Define a ``|substitution|`` replacement. - The command-line help processor requires a substitution replacement - to be defined before it is referenced. - -``|substitution|`` reference - Reference a substitution replacement previously defined by - the ``replace`` directive. The command-line help processor - performs the substitution and replaces all newlines in the - replacement text with spaces. - -``toctree`` directive - Include other document sources in the Table-of-Contents - document tree. The command-line help processor prints - the referenced documents inline as part of the referencing - document. - -Inline markup constructs not listed above are printed literally in the -command-line help output. We prefer to use inline markup constructs that -look correct in source form, so avoid use of \\-escapes in favor of inline -literals when possible. - -Explicit markup blocks not matching directives listed above are removed from -command-line help output. Do not use them, except for plain ``..`` comments -that are removed by Sphinx too. - -Note that nested indentation of blocks is not recognized by the -command-line help processor. Therefore: - -* Explicit markup blocks are recognized only when not indented - inside other blocks. - -* Literal blocks after paragraphs ending in ``::`` but not - at the top indentation level may consume all indented lines - following them. - -Try to avoid these cases in practice. - -CMake Domain ------------- - -CMake adds a `Sphinx Domain`_ called ``cmake``, also called the -"CMake Domain". It defines several "object" types for CMake -documentation: - -``command`` - A CMake language command. - -``generator`` - A CMake native build system generator. - See the :manual:`cmake(1)` command-line tool's ``-G`` option. - -``manual`` - A CMake manual page, like this :manual:`cmake-developer(7)` manual. - -``module`` - A CMake module. - See the :manual:`cmake-modules(7)` manual - and the :command:`include` command. - -``policy`` - A CMake policy. - See the :manual:`cmake-policies(7)` manual - and the :command:`cmake_policy` command. - -``prop_cache, prop_dir, prop_gbl, prop_sf, prop_inst, prop_test, prop_tgt`` - A CMake cache, directory, global, source file, installed file, test, - or target property, respectively. See the :manual:`cmake-properties(7)` - manual and the :command:`set_property` command. - -``variable`` - A CMake language variable. - See the :manual:`cmake-variables(7)` manual - and the :command:`set` command. - -Documentation objects in the CMake Domain come from two sources. -First, the CMake extension to Sphinx transforms every document named -with the form ``Help/<type>/<file-name>.rst`` to a domain object with -type ``<type>``. The object name is extracted from the document title, -which is expected to be of the form:: - - <object-name> - ------------- - -and to appear at or near the top of the ``.rst`` file before any other -lines starting in a letter, digit, or ``<``. If no such title appears -literally in the ``.rst`` file, the object name is the ``<file-name>``. -If a title does appear, it is expected that ``<file-name>`` is equal -to ``<object-name>`` with any ``<`` and ``>`` characters removed. - -Second, the CMake Domain provides directives to define objects inside -other documents: - -.. code-block:: rst - - .. command:: <command-name> - - This indented block documents <command-name>. - - .. variable:: <variable-name> - - This indented block documents <variable-name>. - -Object types for which no directive is available must be defined using -the first approach above. - -.. _`Sphinx Domain`: http://sphinx-doc.org/domains.html - -Cross-References ----------------- - -Sphinx uses reStructuredText interpreted text roles to provide -cross-reference syntax. The `CMake Domain`_ provides for each -domain object type a role of the same name to cross-reference it. -CMake Domain roles are inline markup of the forms:: - - :type:`name` - :type:`text <name>` - -where ``type`` is the domain object type and ``name`` is the -domain object name. In the first form the link text will be -``name`` (or ``name()`` if the type is ``command``) and in -the second form the link text will be the explicit ``text``. -For example, the code: - -.. code-block:: rst - - * The :command:`list` command. - * The :command:`list(APPEND)` sub-command. - * The :command:`list() command <list>`. - * The :command:`list(APPEND) sub-command <list>`. - * The :variable:`CMAKE_VERSION` variable. - * The :prop_tgt:`OUTPUT_NAME_<CONFIG>` target property. - -produces: - -* The :command:`list` command. -* The :command:`list(APPEND)` sub-command. -* The :command:`list() command <list>`. -* The :command:`list(APPEND) sub-command <list>`. -* The :variable:`CMAKE_VERSION` variable. -* The :prop_tgt:`OUTPUT_NAME_<CONFIG>` target property. - -Note that CMake Domain roles differ from Sphinx and reStructuredText -convention in that the form ``a<b>``, without a space preceding ``<``, -is interpreted as a name instead of link text with an explicit target. -This is necessary because we use ``<placeholders>`` frequently in -object names like ``OUTPUT_NAME_<CONFIG>``. The form ``a <b>``, -with a space preceding ``<``, is still interpreted as a link text -with an explicit target. - -Style ------ - -Style: Section Headers -^^^^^^^^^^^^^^^^^^^^^^ - -When marking section titles, make the section decoration line as long as -the title text. Use only a line below the title, not above. For -example: - -.. code-block:: rst - - Title Text - ---------- - -Capitalize the first letter of each non-minor word in the title. - -The section header underline character hierarchy is - -* ``#``: Manual group (part) in the master document -* ``*``: Manual (chapter) title -* ``=``: Section within a manual -* ``-``: Subsection or `CMake Domain`_ object document title -* ``^``: Subsubsection or `CMake Domain`_ object document section -* ``"``: Paragraph or `CMake Domain`_ object document subsection - -Style: Whitespace -^^^^^^^^^^^^^^^^^ - -Use two spaces for indentation. Use two spaces between sentences in -prose. - -Style: Line Length -^^^^^^^^^^^^^^^^^^ - -Prefer to restrict the width of lines to 75-80 columns. This is not a -hard restriction, but writing new paragraphs wrapped at 75 columns -allows space for adding minor content without significant re-wrapping of -content. - -Style: Prose -^^^^^^^^^^^^ - -Use American English spellings in prose. - -Style: Starting Literal Blocks -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Prefer to mark the start of literal blocks with ``::`` at the end of -the preceding paragraph. In cases where the following block gets -a ``code-block`` marker, put a single ``:`` at the end of the preceding -paragraph. - -Style: CMake Command Signatures -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -Command signatures should be marked up as plain literal blocks, not as -cmake ``code-blocks``. - -Signatures are separated from preceding content by a section header. -That is, use: - -.. code-block:: rst - - ... preceding paragraph. - - Normal Libraries - ^^^^^^^^^^^^^^^^ - - :: - - add_library(<lib> ...) - - This signature is used for ... - -Signatures of commands should wrap optional parts with square brackets, -and should mark list of optional arguments with an ellipsis (``...``). -Elements of the signature which are specified by the user should be -specified with angle brackets, and may be referred to in prose using -``inline-literal`` syntax. - -Style: Boolean Constants -^^^^^^^^^^^^^^^^^^^^^^^^ - -Use "``OFF``" and "``ON``" for boolean values which can be modified by -the user, such as :prop_tgt:`POSITION_INDEPENDENT_CODE`. Such properties -may be "enabled" and "disabled". Use "``True``" and "``False``" for -inherent values which can't be modified after being set, such as the -:prop_tgt:`IMPORTED` property of a build target. - -Style: Inline Literals -^^^^^^^^^^^^^^^^^^^^^^ - -Mark up references to keywords in signatures, file names, and other -technical terms with ``inline-literal`` syntax, for example: - -.. code-block:: rst - - If ``WIN32`` is used with :command:`add_executable`, the - :prop_tgt:`WIN32_EXECUTABLE` target property is enabled. That command - creates the file ``<name>.exe`` on Windows. - -Style: Cross-References -^^^^^^^^^^^^^^^^^^^^^^^ - -Mark up linkable references as links, including repeats. -An alternative, which is used by wikipedia -(`<http://en.wikipedia.org/wiki/WP:REPEATLINK>`_), -is to link to a reference only once per article. That style is not used -in CMake documentation. - -Style: Referencing CMake Concepts -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -If referring to a concept which corresponds to a property, and that -concept is described in a high-level manual, prefer to link to the -manual section instead of the property. For example: - -.. code-block:: rst - - This command creates an :ref:`Imported Target <Imported Targets>`. - -instead of: - -.. code-block:: rst - - This command creates an :prop_tgt:`IMPORTED` target. - -The latter should be used only when referring specifically to the -property. - -References to manual sections are not automatically created by creating -a section, but code such as: - -.. code-block:: rst - - .. _`Imported Targets`: - -creates a suitable anchor. Use an anchor name which matches the name -of the corresponding section. Refer to the anchor using a -cross-reference with specified text. - -Imported Targets need the ``IMPORTED`` term marked up with care in -particular because the term may refer to a command keyword -(``IMPORTED``), a target property (:prop_tgt:`IMPORTED`), or a -concept (:ref:`Imported Targets`). - -Where a property, command or variable is related conceptually to others, -by for example, being related to the buildsystem description, generator -expressions or Qt, each relevant property, command or variable should -link to the primary manual, which provides high-level information. Only -particular information relating to the command should be in the -documentation of the command. - -Style: Referencing CMake Domain Objects -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - -When referring to `CMake Domain`_ objects such as properties, variables, -commands etc, prefer to link to the target object and follow that with -the type of object it is. For example: - -.. code-block:: rst - - Set the :prop_tgt:`AUTOMOC` target property to ``ON``. - -Instead of - -.. code-block:: rst - - Set the target property :prop_tgt:`AUTOMOC` to ``ON``. - -The ``policy`` directive is an exception, and the type us usually -referred to before the link: - -.. code-block:: rst - - If policy :prop_tgt:`CMP0022` is set to ``NEW`` the behavior is ... - -However, markup self-references with ``inline-literal`` syntax. -For example, within the :command:`add_executable` command -documentation, use - -.. code-block:: rst - - ``add_executable`` - -not - -.. code-block:: rst - - :command:`add_executable` - -which is used elsewhere. - -Modules -======= - -The ``Modules`` directory contains CMake-language ``.cmake`` module files. - -Module Documentation --------------------- - -To document CMake module ``Modules/<module-name>.cmake``, modify -``Help/manual/cmake-modules.7.rst`` to reference the module in the -``toctree`` directive, in sorted order, as:: - - /module/<module-name> - -Then add the module document file ``Help/module/<module-name>.rst`` -containing just the line:: - - .. cmake-module:: ../../Modules/<module-name>.cmake - -The ``cmake-module`` directive will scan the module file to extract -reStructuredText markup from comment blocks that start in ``.rst:``. -At the top of ``Modules/<module-name>.cmake``, begin with the following -license notice: - -.. code-block:: cmake - - # Distributed under the OSI-approved BSD 3-Clause License. See accompanying - # file Copyright.txt or https://cmake.org/licensing for details. - -After this notice, add a *BLANK* line. Then, add documentation using -a :ref:`Line Comment` block of the form: - -.. code-block:: cmake - - #.rst: - # <module-name> - # ------------- - # - # <reStructuredText documentation of module> - -or a :ref:`Bracket Comment` of the form: - -:: - - #[[.rst: - <module-name> - ------------- - - <reStructuredText documentation of module> - #]] - -Any number of ``=`` may be used in the opening and closing brackets -as long as they match. Content on the line containing the closing -bracket is excluded if and only if the line starts in ``#``. - -Additional such ``.rst:`` comments may appear anywhere in the module file. -All such comments must start with ``#`` in the first column. - -For example, a ``Modules/Findxxx.cmake`` module may contain: - -:: - - # Distributed under the OSI-approved BSD 3-Clause License. See accompanying - # file Copyright.txt or https://cmake.org/licensing for details. - - #.rst: - # FindXxx - # ------- - # - # This is a cool module. - # This module does really cool stuff. - # It can do even more than you think. - # - # It even needs two paragraphs to tell you about it. - # And it defines the following variables: - # - # * VAR_COOL: this is great isn't it? - # * VAR_REALLY_COOL: cool right? - - <code> - - #[========================================[.rst: - .. command:: xxx_do_something - - This command does something for Xxx:: - - xxx_do_something(some arguments) - #]========================================] - macro(xxx_do_something) - <code> - endmacro() - -Test the documentation formatting by running -``cmake --help-module <module-name>``, and also by enabling the -``SPHINX_HTML`` and ``SPHINX_MAN`` options to build the documentation. -Edit the comments until generated documentation looks satisfactory. To -have a .cmake file in this directory NOT show up in the modules -documentation, simply leave out the ``Help/module/<module-name>.rst`` -file and the ``Help/manual/cmake-modules.7.rst`` toctree entry. +CMake upstream. It includes links to contribution instructions, which +in turn link to developer guides for CMake itself. .. _`Find Modules`: Find Modules ------------- +============ -A "find module" is a ``Modules/Find<PackageName>.cmake`` file to be loaded +A "find module" is a ``Find<PackageName>.cmake`` file to be loaded by the :command:`find_package` command when invoked for ``<PackageName>``. The primary task of a find module is to determine whether a package @@ -641,16 +82,11 @@ and required is up to the find module, but should be documented. For internal implementation, it is a generally accepted convention that variables starting with underscore are for temporary use only. -Like all modules, find modules should be properly documented. To add a -module to the CMake documentation, follow the steps in the `Module -Documentation`_ section above. - - .. _`CMake Developer Standard Variable Names`: Standard Variable Names -^^^^^^^^^^^^^^^^^^^^^^^ +----------------------- For a ``FindXxx.cmake`` module that takes the approach of setting variables (either instead of or in addition to creating imported @@ -757,9 +193,8 @@ Make sure you comment them as deprecated, so that no-one starts using them. - A Sample Find Module -^^^^^^^^^^^^^^^^^^^^ +-------------------- We will describe how to create a simple find module for a library ``Foo``. @@ -802,8 +237,7 @@ variables and imported targets are set by the module, such as # Foo::Foo - The Foo library If the package provides any macros, they should be listed here, but can -be documented where they are defined. See the `Module -Documentation`_ section above for more details. +be documented where they are defined. Now the actual libraries and so on have to be found. The code here will obviously vary from module to module (dealing with that, after all, is the |