[Python-Dev] Undocumented view==NULL argument in PyObject_GetBuffer()

[Stefan Krah]

Hello,

PyObject_GetBuffer() had an undocumented variant that was used internally:

    PyObject_GetBuffer(obj, NULL, flags)


view==NULL has never been allowed by either PEP-3118 or the documentation:

PEP: "The first variable is the "exporting" object. The second argument 
      is the address to a bufferinfo structure. Both arguments must never 
      be NULL."

3.2 docs: "view must point to an existing Py_buffer structure
           allocated by the caller."



The internal use was to bump up the export count of e.g. a bytearray
without bothering to have it fill in a complete Py_buffer. The increased
export count would then prevent the bytearray from being resized.


However, this feature appears to be unused in the source tree. The last
traces of a middle NULL argument that I found are here:

http://hg.python.org/cpython/file/df3b2b5db900/Modules/posixmodule.c#l561



So, currently the checks for NULL just slow down bytearray_getbuffer()
and a couple of other getbufferprocs. Also, due to the absence of a use
case it takes some VCS history digging to find out why the feature was
there in the first place.


The obvious question is: Will anyone need view==NULL in the future or
can we remove the special case?


Stefan Krah