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bpo-35199: Add an internal _PyTuple_ITEMS() macro #10434

Merged
merged 1 commit into from
Nov 9, 2018
Merged

bpo-35199: Add an internal _PyTuple_ITEMS() macro #10434

merged 1 commit into from
Nov 9, 2018

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vstinner
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@vstinner vstinner commented Nov 9, 2018 •
edited by bedevere-bot
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  • _PyTuple_ITEMS() gives access to the tuple->ob_item field; cast the
    first argument to PyTupleObject*. The macro is only usable if
    Py_BUILD_CORE is defined.
  • Replace &PyTuple_GET_ITEM(ob, 0) with _PyTuple_ITEMS(ob)
  • Replace PyTuple_GET_ITEM(op, 1) with &_PyTuple_ITEMS(ob)[1]

https://bugs.python.org/issue35199

@vstinner
bpo-35199: Add an internal _PyTuple_ITEMS() macro
fc01f8d 
* _PyTuple_ITEMS() gives access to the tuple->ob_item field; cast the
  first argument to PyTupleObject*. The macro is only usable if
  Py_BUILD_CORE is defined.
* Replace &PyTuple_GET_ITEM(ob, 0) with _PyTuple_ITEMS(ob)
* Replace PyTuple_GET_ITEM(op, 1) with &_PyTuple_ITEMS(ob)[1]
@vstinner vstinner merged commit d17a693 into python:master Nov 9, 2018
@vstinner vstinner deleted the tuple_items branch November 9, 2018 15:56
@jdemeyer
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@rhettinger I am confused here... the bpo issue was closed saying that it wouldn't be merged but the PR was merged anyway.

@vstinner
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@rhettinger I am confused here... the bpo issue was closed saying that it wouldn't be merged but the PR was merged anyway.

I rejected my experimental PR #10435. See https://bugs.python.org/issue35199#msg329577

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I rejected my experimental PR #10435. See https://bugs.python.org/issue35199#msg329577

So then what is the purpose of this PR? Apart from just adding a new way to do something which can already be done using PyTuple_GET_ITEM?

Asking from the point of view of a CPython developer: when should I use PyTuple_GET_ITEM and when _PyTuple_ITEMS?

@vstinner
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So then what is the purpose of this PR?

This change allows me to experiment changes on PyTuple_GET_ITEM() like https://bugs.python.org/issue35337

It's also related to my more long-term plan to making type structures like PyTupleObject opaque: https://pythoncapi.readthedocs.io/bad_api.html#c-structures

@vstinner
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Asking from the point of view of a CPython developer: when should I use PyTuple_GET_ITEM and when _PyTuple_ITEMS?

_PyTuple_ITEMS is used for direct access to the internal PyObject** array, whereas PyTuple_GET_ITEM() is used to get a single item.

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@rhettinger rhettinger Awaiting requested review from rhettinger

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@vstinner @jdemeyer @the-knights-who-say-ni @bedevere-bot