#13447: Make libsingular multivariate polynomial rings collectable
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Reporter: nbruin | Owner: rlm
Type: defect | Status:
needs_info
Priority: major | Milestone:
sage-5.4
Component: memleak | Resolution:
Keywords: | Work issues: Input
from libsingular experts
Report Upstream: Reported upstream. No feedback yet. | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
Printing messages to stderr, it seems to me that the error occurs during
deallocation of a polynomial template, namely in
sage/rings/polynomial/polynomial_template.pxi:
{{{
def __dealloc__(self):
"""
EXAMPLE::
sage: P.<x> = GF(2)[]
sage: del x
"""
celement_destruct(&self.x,
get_cparent((<Polynomial_template>self)._parent))
}}}
Is the cparent of self deallocated too early (perhaps because the
refcounting is still not accurate)?
Or is it a nasty race condition? Namely:
* A polynomial p in a polynomial ring R is about to be garbage collected.
* All python stuff is deleted first. In particular, p's reference to its
parent R is gone.
* Incidentally, because the reference from p to R is gone, R can now be
collected as well.
* When R gets deleted, its underlying libsingular ring is deallocated.
* Now, `p.__dealloc__` is finally called, and tries to access the
underlying libsingular ring - but it is too late.
Question: If a polynomial is created, will the reference counter to the
underlying libsingular ring be incremented?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13447#comment:26>
Sage <http://www.sagemath.org>
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