#13896: Fix cython's gc_track and gc_untrack
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Reporter: nbruin |
Owner: rlm
Type: defect |
Status: new
Priority: blocker |
Milestone: sage-5.6
Component: memleak |
Resolution:
Keywords: | Work
issues:
Report Upstream: Reported upstream. Developers acknowledge bug. |
Reviewers:
Authors: | Merged
in:
Dependencies: |
Stopgaps:
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Comment (by robertwb):
I think it helps to look at the generated code. Suppose one has
{{{
cdef class A: ...
cdef class B(A): ...
cdef class C(B): ...
...
}}}
In this case one has, roughly,
{{{
tp_dealloc_A(self) {
[optional untrack]
bodyA
[optional track]
PY_TYPE(self)->tp_free(self)
}
tp_dealloc_B(self) {
[optional untrack]
bodyB
[optional track]
tp_dealloc_A(self)
}
tp_dealloc_C(self) {
[optional untrack]
bodyC
[optional track]
tp_dealloc_B(self)
}
...
}}}
bodyX consists of decrefing Python members, traversing weakrefs, and (if
present)
{{{
PyRef(self)++;
X.__dealloc__(self);
PyRef(self)--;
}}}
The track/untrack markers are added exactly when Python/weakref members
are present, which is where a garbage collection might happen. (When
executing __dealloc__ the refcount is incremented, also preventing garbage
collection.)
What could be an issue is a non-gc-tracked container class that is
subclassed by a gc-tracked class, but we don't have those in Cython.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13896#comment:20>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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