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put notes in a ..note section

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Benjamin Peterson 2014-01-20 00:10:23 -05:00
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Doc/library/ctypes.rst
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@ -1022,18 +1022,18 @@ As we can easily check, our array is sorted now::
1 5 7 33 99
>>>
**Important notes for callback functions:**
.. note::
Make sure you keep references to :func:`CFUNCTYPE` objects as long as they are
used from C code. :mod:`ctypes` doesn't, and if you don't, they may be garbage
collected, crashing your program when a callback is made.
Make sure you keep references to :func:`CFUNCTYPE` objects as long as they
are used from C code. :mod:`ctypes` doesn't, and if you don't, they may be
garbage collected, crashing your program when a callback is made.
Also, note that if the callback function is called in a thread created outside
of Python's control (e.g. by the foreign code that calls the callback), ctypes
creates a new dummy Python thread on every invocation. This behavior is correct
for most purposes, but it means that values stored with `threading.local` will
*not* survive across different callbacks, even when those calls are made from
the same C thread.
Also, note that if the callback function is called in a thread created
outside of Python's control (e.g. by the foreign code that calls the
callback), ctypes creates a new dummy Python thread on every invocation. This
behavior is correct for most purposes, but it means that values stored with
`threading.local` will *not* survive across different callbacks, even when
those calls are made from the same C thread.
.. _ctypes-accessing-values-exported-from-dlls: