untrackable objects are not tracked by the garbage collector. This can
reduce the size of collections and therefore the garbage collection overhead
on long-running programs, depending on their particular use of datatypes.
(trivia: this makes the "binary_trees" benchmark from the Computer Language
Shootout 40% faster)
in Object/ are named ``free_list``, the counter ``numfree`` and the upper
limit is a macro ``PyName_MAXFREELIST`` inside an #ifndef block.
The chances should make it easier to adjust Python for platforms with
less memory, e.g. mobile phones.
Python code; but it is possible from C. object.__str__ had the issue of not
expecting a type to doing something within it's tp_str implementation that
could trigger an infinite recursion, but it could in C code.. Both found
thanks to BaseException and how it handles its repr.
Closes issue #1686386. Thanks to Thomas Herve for taking an initial stab at
coming up with a solution.
- Specialcase extended slices that amount to a shallow copy the same way as
is done for simple slices, in the tuple, string and unicode case.
- Specialcase step-1 extended slices to optimize the common case for all
involved types.
- For lists, allow extended slice assignment of differing lengths as long
as the step is 1. (Previously, 'l[:2:1] = []' failed even though
'l[:2] = []' and 'l[:2:None] = []' do not.)
- Implement extended slicing for buffer, array, structseq, mmap and
UserString.UserString.
- Implement slice-object support (but not non-step-1 slice assignment) for
UserString.MutableString.
- Add tests for all new functionality.
