#5839: [with patch, needs review] MPolynomialRing_libsingular __dealloc__ is
buggy, can lead to crash
---------------------------------+------------------------------------------
Reporter: cwitty | Owner: cwitty
Type: defect | Status: new
Priority: critical | Milestone: sage-3.4.1
Component: commutative algebra | Keywords:
---------------------------------+------------------------------------------
In {{{__dealloc__}}}, if currRing is NULL on entry, then currRing will be
the ring we just deleted on exit. The patch fixes this bug, so that
currRing never points to freed memory.
It took me quite a while to come up with a small reproducible test case
for the problem; here it is. (This test case is also in the patch, as a
doctest.)
{{{
import gc
from sage.rings.polynomial.multi_polynomial_libsingular import
MPolynomialRing_libsingular
R1 = MPolynomialRing_libsingular(GF(5), 2, ('x', 'y'),
TermOrder('degrevlex', 2))
R2 = MPolynomialRing_libsingular(GF(11), 2, ('x', 'y'),
TermOrder('degrevlex', 2))
R3 = MPolynomialRing_libsingular(GF(13), 2, ('x', 'y'),
TermOrder('degrevlex', 2))
gc.collect()
foo = R1.gen(0)
del foo
del R1
gc.collect()
del R2
gc.collect()
del R3
gc.collect()
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5839>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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