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For the record: I care. Generally speaking CPython is a lovingly
crafted source tree, and the choices its architects made are nearly
always sensible and well-reasoned. When I see things like this, things
that seem kind of dumb on first glance, I worry that we're missing
something.
It could be that it did have a sensible reason fifteen years ago, like
some bone-headed compiler generated awful code--and the macros *are*
used everywhere, so maybe performance genuinely suffered. Or maybe
the macros were originally intended to be usable as rvalues; it looks
like Py_INCREF still permits that, and changing it to be a statement
could be considered a breaking API change.
But we can't let ourselves become hidebound and superstitious. I see
no reason why a local temporary variable shouldn't be fine here, and
perhaps in all the macros Mark cites. So don't get me wrong, I'm +1.
(The documentation on Py_INCREF makes no mention of whether it's legal
as an rvalue, and all the examples use it as a statement. Perhaps we
should document it explicitly so for 3.4.)