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doc: Add note about casting from None to T* (#1760)

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* doc: Add note about casting from `None` to `T*`

* doc: reword 'none-to-pointer' note message

* doc: mention opaque types in 'none-to-pointer' note message
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Sergei Izmailov 2019-06-10 22:03:17 +03:00 committed by Wenzel Jakob
parent 30c0352348
commit 979d75de23
1 changed files with 9 additions and 0 deletions
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docs/advanced/functions.rst
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@ -467,6 +467,15 @@ dog)"``, while attempting to call ``meow(None)`` will raise a ``TypeError``:
The default behaviour when the tag is unspecified is to allow ``None``. The default behaviour when the tag is unspecified is to allow ``None``.
.. note::
Even when ``.none(true)`` is specified for an argument, ``None`` will be converted to a
``nullptr`` *only* for custom and :ref:`opaque <opaque>` types. Pointers to built-in types
(``double *``, ``int *``, ...) and STL types (``std::vector<T> *``, ...; if ``pybind11/stl.h``
is included) are copied when converted to C++ (see :doc:`/advanced/cast/overview`) and will
not allow ``None`` as argument. To pass optional argument of these copied types consider
using ``std::optional<T>``
Overload resolution order Overload resolution order
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