C, update documentation for info-fields

doc/usage/restructuredtext/domains.rst

@@ -677,12 +677,55 @@ The C domain (name **c**) is suited for documentation of C API.
    Note that you don't have to backslash-escape asterisks in the signature, as
    it is not parsed by the reST inliner.
 
+   In the description of a function you can use the following info-fields
+   (see also :ref:`info-field-lists`).
+
+   * ``param``, ``parameter``, ``arg``, ``argument``,
+     Description of a parameter.
+   * ``type``: Type of a parameter,
+     written as if passed to the :rst:role:`c:expr` role.
+   * ``returns``, ``return``: Description of the return value.
+   * ``rtype``: Return type,
+     written as if passed to the :rst:role:`c:expr` role.
+   * ``retval``, ``retvals``: An alternative to ``returns`` for describing
+     the result of the function.
+
+   .. versionadded:: 4.3
+      The ``retval`` field type.
+
+   For example::
+
+      .. c:function:: PyObject *PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
+
+         :param type: description of the first parameter.
+         :param nitems: description of the second parameter.
+         :returns: a result.
+         :retval NULL: under some conditions.
+         :retval NULL: under some other conditions as well.
+
+   which renders as
+
+   .. c:function:: PyObject *PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)
+
+      ..
+         ** for some editors (e.g., vim) to stop bold-highlighting the source
+
+      :param type: description of the first parameter.
+      :param nitems: description of the second parameter.
+      :returns: a result.
+      :retval NULL: under some conditions.
+      :retval NULL: under some other conditions as well.
+
+
 .. rst:directive:: .. c:macro:: name
                    .. c:macro:: name(arg list)
 
    Describes a C macro, i.e., a C-language ``#define``, without the replacement
    text.
 
+   In the description of a macro you can use the same info-fields as for the
+   :rst:dir:`c:function` directive.
+
    .. versionadded:: 3.0
       The function style variant.