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[docs][LLVM-style RTTI] Add a mention of multiple inheritance.

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llvm-svn: 228479
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Sean Silva 2015-02-07 01:16:26 +00:00
parent 79a2edfa80
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docs/HowToSetUpLLVMStyleRTTI.rst
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@ -377,6 +377,20 @@ contract for ``classof`` is "return ``true`` if the dynamic type of the
argument is-a ``C``". As long as your implementation fulfills this argument is-a ``C``". As long as your implementation fulfills this
contract, you can tweak and optimize it as much as you want. contract, you can tweak and optimize it as much as you want.
For example, LLVM-style RTTI can work fine in the presence of
multiple-inheritance by defining an appropriate ``classof``.
An example of this in practice is
`Decl <http://clang.llvm.org/doxygen/classclang_1_1Decl.html>`_ vs.
`DeclContext <http://clang.llvm.org/doxygen/classclang_1_1DeclContext.html>`_
inside Clang.
The ``Decl`` hierarchy is done very similarly to the example setup
demonstrated in this tutorial.
The key part is how to then incorporate ``DeclContext``: all that is needed
is in ``bool DeclContext::classof(const Decl *)``, which asks the question
"Given a ``Decl``, how can I determine if it is-a ``DeclContext``?".
It answers this with a simple switch over the set of ``Decl`` "kinds", and
returning true for ones that are known to be ``DeclContext``'s.
.. TODO:: .. TODO::
Touch on some of the more advanced features, like ``isa_impl`` and Touch on some of the more advanced features, like ``isa_impl`` and