Pauli Virtanen <p...@iki.fi> added the comment:
@skrah:
Ahh, this always happens when I don't run it :) But my point stands -- the
reason why it does not crash with Numpy is that Numpy calls
PyMemoryView_FromObject to obtain a new memoryview and then uses
PyMemoryView_GET_BUFFER. Along this code path the refcount of self->mbuf gets
properly incremented, as it's explicitly done in PyMemoryView_FromObject.
However, if you have a custom object Foo which just calls `PyObject_GetBuffer`,
and then do the same sequence
a = memoryview(whatever)
b = Foo(a) # --> only grabs the buffer with PyObject_GetBuffer
a.release() # --> will invalidate the buffer
b.mogrify_buffer_contents() # --> boom
Here, the buffer is released too early, as the refcount of `self->mbuf` is not
incremented during the `PyObject_GetBuffer` call.
> Is there anything stopping us just storing the flags on
> PyManagedBuffer?
Slicing memoryviews can invalidate the contiguity flags, and no-strides flags,
so some checks are still probably needed in `memory_getbuf`.
> It's OK if the construction API requires the flag
> information in addition to the Py_buffer struct.
This would be useful, yes.
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<http://bugs.python.org/issue10181>
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